Phase Shifting Capacity of the Circadian Pacemaker Determined by the SCN Neuronal Network Organization

PubMed Central

vanderLeest, Henk Tjebbe; Rohling, Jos H. T.; Michel, Stephan; Meijer, Johanna H.

2009-01-01

Background In mammals, a major circadian pacemaker that drives daily rhythms is located in the suprachiasmatic nuclei (SCN), at the base of the hypothalamus. The SCN receive direct light input via the retino-hypothalamic tract. Light during the early night induces phase delays of circadian rhythms while during the late night it leads to phase advances. The effects of light on the circadian system are strongly dependent on the photoperiod to which animals are exposed. An explanation for this phenomenon is currently lacking. Methodology and Principal Findings We recorded running wheel activity in C57 mice and observed large amplitude phase shifts in short photoperiods and small shifts in long photoperiods. We investigated whether these different light responses under short and long days are expressed within the SCN by electrophysiological recordings of electrical impulse frequency in SCN slices. Application of N-methyl-D-aspartate (NMDA) induced sustained increments in electrical activity that were not significantly different in the slices from long and short photoperiods. These responses led to large phase shifts in slices from short days and small phase shifts in slices from long days. An analysis of neuronal subpopulation activity revealed that in short days the amplitude of the rhythm was larger than in long days. Conclusions The data indicate that the photoperiodic dependent phase responses are intrinsic to the SCN. In contrast to earlier predictions from limit cycle theory, we observed large phase shifting responses in high amplitude rhythms in slices from short days, and small shifts in low amplitude rhythms in slices from long days. We conclude that the photoperiodic dependent phase responses are determined by the SCN and propose that synchronization among SCN neurons enhances the phase shifting capacity of the circadian system. PMID:19305510

A Mathematical Model of the Circadian Phase-Shifting Effects of Exogenous Melatonin

PubMed Central

Breslow, Emily R.; Phillips, Andrew J.K.; Huang, Jean M.; St. Hilaire, Melissa A.; Klerman, Elizabeth B.

2013-01-01

Melatonin is endogenously produced and released in humans during nighttime darkness and is suppressed by ocular light exposure. Exogenous melatonin is used to induce circadian phase shifts and sleep. The circadian phase-shifting ability of a stimulus (e.g., melatonin or light) relative to its timing may be displayed as a phase response curve (PRC). Published PRCs to exogenous melatonin show a transition from phase advances to delays approximately 1 h after dim light melatonin onset. A previously developed mathematical model simulates endogenous production and clearance of melatonin as a function of circadian phase, light-induced suppression, and resetting of circadian phase by light. We extend this model to include the pharmacokinetics of oral exogenous melatonin and phase-shifting effects via melatonin receptors in the suprachiasmatic nucleus of the mammalian hypothalamus. Model parameters are fit using 2 data sets: (1) blood melatonin concentration following a 0.3- or 5.0-mg dose, and (2) a PRC to a 3.0-mg dose of melatonin. After fitting to the 3.0-mg PRC, the model correctly predicts that, by comparison, the 0.5-mg PRC is slightly decreased in amplitude and shifted to a later circadian phase. This model also reproduces blood concentration profiles of various melatonin preparations that differ only in absorption rate and percentage degradation by first-pass hepatic metabolism. This model can simulate experimental protocols using oral melatonin, with potential application to guide dose size and timing to optimally shift and entrain circadian rhythms. PMID:23382594

Phase shift in atom interferometry due to spacetime curvature

NASA Astrophysics Data System (ADS)

Overstreet, Chris; Asenbaum, Peter; Kovachy, Tim; Brown, Daniel; Hogan, Jason; Kasevich, Mark

2017-04-01

In previous matter wave interferometers, the interferometer arm separation was small enough that gravitational tidal forces across the arms can be neglected. Gravitationally-induced phase shifts in such experiments arise from the acceleration of the interfering particles with respect to the interferometer beam splitters and mirrors. By increasing the interferometer arm separation, we enter a new regime in which the arms experience resolvably different gravitational forces. Using a single-source gravity gradiometer, we measure a phase shift associated with the tidal forces induced by a nearby test mass. This is the first observation of spacetime curvature across the spatial extent of a single quantum system. CO acknowledges funding from the Stanford Graduate Fellowship.

Compensating temperature-induced ultrasonic phase and amplitude changes

NASA Astrophysics Data System (ADS)

Gong, Peng; Hay, Thomas R.; Greve, David W.; Junker, Warren R.; Oppenheim, Irving J.

2016-04-01

In ultrasonic structural health monitoring (SHM), environmental and operational conditions, especially temperature, can significantly affect the propagation of ultrasonic waves and thus degrade damage detection. Typically, temperature effects are compensated using optimal baseline selection (OBS) or optimal signal stretch (OSS). The OSS method achieves compensation by adjusting phase shifts caused by temperature, but it does not fully compensate phase shifts and it does not compensate for accompanying signal amplitude changes. In this paper, we develop a new temperature compensation strategy to address both phase shifts and amplitude changes. In this strategy, OSS is first used to compensate some of the phase shifts and to quantify the temperature effects by stretching factors. Based on stretching factors, empirical adjusting factors for a damage indicator are then applied to compensate for the temperature induced remaining phase shifts and amplitude changes. The empirical adjusting factors can be trained from baseline data with temperature variations in the absence of incremental damage. We applied this temperature compensation approach to detect volume loss in a thick wall aluminum tube with multiple damage levels and temperature variations. Our specimen is a thick-walled short tube, with dimensions closely comparable to the outlet region of a frac iron elbow where flow-induced erosion produces the volume loss that governs the service life of that component, and our experimental sequence simulates the erosion process by removing material in small damage steps. Our results show that damage detection is greatly improved when this new temperature compensation strategy, termed modified-OSS, is implemented.

Cross-phase modulation spectral shifting: nonlinear phase contrast in a pump-probe microscope

PubMed Central

Wilson, Jesse W.; Samineni, Prathyush; Warren, Warren S.; Fischer, Martin C.

2012-01-01

Microscopy with nonlinear phase contrast is achieved by a simple modification to a nonlinear pump-probe microscope. The technique measures cross-phase modulation by detecting a pump-induced spectral shift in the probe pulse. Images with nonlinear phase contrast are acquired both in transparent and absorptive media. In paraffin-embedded biopsy sections, cross-phase modulation complements the chemically-specific pump-probe images with structural context. PMID:22567580

Towards the control of the modal energy transfer in transverse mode instabilities

NASA Astrophysics Data System (ADS)

Stihler, Christoph; Jauregui, Cesar; Tünnermann, Andreas; Limpert, Jens

2018-02-01

Thermally-induced refractive index gratings (RIG) in high-power fiber laser systems lead to transverse mode instabilities (TMI) above a certain average power threshold. The effect of TMI is currently the main limitation for the further average power scaling of fiber lasers and amplifiers with nearly diffraction-limited beam quality. In this work we experimentally investigate, for the first time, the growth of the RIG strength by introducing a phase-shift between the RIG and the modal interference pattern in a fiber amplifier. The experiments reveal that the RIG is strong enough to couple energy between different transverse modes even at powers significantly below the TMI threshold, provided that the introduced phase-shift is high enough. This indicates that, as the strength of the RIG further increases with increasing average output power, the RIG becomes more and more sensitive to even small noise-induced phase-shifts, which ultimately trigger TMI. Furthermore, it is shown that a beam cleaning also occurs when a positive phase-shift is introduced, even above the TMI threshold. This finding will pave the way for the development of a new class of mitigation strategies for TMI, which key feature is the control of the introduced phase-shift.

The Phase Shift in the Jumping Ring

NASA Astrophysics Data System (ADS)

Jeffery, Rondo N.; Amiri, Farhang

2008-09-01

The popular physics demonstration experiment known as Thomson's Jumping Ring (JR) has been variously explained as a simple example of Lenz's law, or as the result of a phase shift of the ring current relative to the induced emf. The failure of the first-quadrant Lenz's law explanation is shown by the time the ring takes to jump and by levitation. A method is given for measuring the phase shift with results for aluminum and brass rings.

Phase shifting interferometry based on a vibration sensor - feasibility study on elimination of the depth degeneracy

NASA Astrophysics Data System (ADS)

Lee, Seung Seok; Kim, Ju Ha; Choi, Eun Seo

2017-04-01

We proposed novel phase-shifting interferometry using a fiber-optic vibration sensor. The Doppler shift in the coiled fiber caused by vibrations can be used to detect the vibrations by using a fiber-optic interferometer. The principle can be applied to induce phase shifts. While applying vibrations to the coiled fiber at various vibration frequencies, we recorded the variations in the interference fringes. The interference fringe moved to longer wavelengths when a vibration frequency was increased from 38.00 to 38.40 kHz. Phase variations of 3.59 rad/kHz were obtained. The ability to accurately control the phase by using the vibrations in the coiled fiber was demonstrated by the elimination of the depth degeneracy using the complex signal generated by the phase-shifted interference fringes. Using vibrations to control phase shifting can be an acceptable alternative to conventional methods and can be applied to resolve the depth ambiguity in Fourier domain optical coherence tomography.

Retrieval-Induced vs. Context-Induced Forgetting: Does Retrieval-Induced Forgetting Depend on Context Shifts?

PubMed Central

Soares, Julia S.; Polack, Cody W.; Miller, Ralph R.

2015-01-01

Retrieval-induced forgetting (RIF) is the observation that retrieval of target information causes forgetting of related non-target information. A number of accounts of this phenomenon have been proposed, including a context-shift based account (Jonker, Seli, & Macleod, 2013). This account proposes that RIF occurs due to the context shift from study to retrieval practice, provided there is little context shift between retrieval practice and test phases. We tested both claims put forth by this context account. In Experiment 1, we degraded the context shift between study and retrieval practice by implementing a generative study condition that was highly similar to retrieval practice. We observed no degradation of RIF for these generated exemplars relative to a conventional study control. In Experiment 2, we conceptually replicated the finding of RIF following generative study, and tested whether context differences between each of the three phases affected the size of RIF. Our findings were again contrary to the predictions of the context account. Conjointly, the two experiments refute arguments about the potential inadequacy of our context shifts that could be used to explain either result alone. Overall, our results are most consistent with an inhibitory account of RIF (e.g., Anderson, 2003). PMID:26389628

A Rodent Model of Night-Shift Work Induces Short-Term and Enduring Sleep and Electroencephalographic Disturbances.

PubMed

Grønli, Janne; Meerlo, Peter; Pedersen, Torhild T; Pallesen, Ståle; Skrede, Silje; Marti, Andrea R; Wisor, Jonathan P; Murison, Robert; Henriksen, Tone E G; Rempe, Michael J; Mrdalj, Jelena

2017-02-01

Millions of people worldwide are working at times that overlap with the normal time for sleep. Sleep problems related to the work schedule may mediate the well-established relationship between shift work and increased risk for disease, occupational errors and accidents. Yet, our understanding of causality and the underlying mechanisms that explain this relationship is limited. We aimed to assess the consequences of night-shift work for sleep and to examine whether night-shift work-induced sleep disturbances may yield electrophysiological markers of impaired maintenance of the waking brain state. An experimental model developed in rats simulated a 4-day protocol of night-work in humans. Two groups of rats underwent 8-h sessions of enforced ambulation, either at the circadian time when the animal was physiologically primed for wakefulness (active-workers, mimicking day-shift) or for sleep (rest-workers, mimicking night-shift). The 4-day rest-work schedule induced a pronounced redistribution of sleep to the endogenous active phase. Rest-work also led to higher electroencephalogram (EEG) slow-wave (1-4 Hz) energy in quiet wakefulness during work-sessions, suggesting a degraded waking state. After the daily work-sessions, being in their endogenous active phase, rest-workers slept less and had higher gamma (80-90 Hz) activity during wake than active-workers. Finally, rest-work induced an enduring shift in the main sleep period and attenuated the accumulation of slow-wave energy during NREM sleep. A comparison of recovery data from 12:12 LD and constant dark conditions suggests that reduced time in NREM sleep throughout the recorded 7-day recovery phase induced by rest-work may be modulated by circadian factors. Our data in rats show that enforced night-work-like activity during the normal resting phase has pronounced acute and persistent effects on sleep and waking behavior. The study also underscores the potential importance of animal models for future studies on the health consequences of night-shift work and the mechanisms underlying increased risk for diseases.

Dynamical manifestation of an evolving Berry phase as a frequency shift of the resonance transition between two eigenstates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Toriyama, Koichi; Oguchi, Akihide; Morinaga, Atsuo

2011-12-15

We investigate the phenomenon that a Berry phase evolving linearly in time induces a frequency shift of the resonance transition between two eigenstates, regardless of whether or not they are superposed. Using the magnetic-field-insensitive two-photon microwave--radio-frequency transition, which is free of any other dynamical frequency shift, we demonstrate that the frequency shift caused by a uniform rotation of the magnetic field corresponds to the derivative of the Berry phase with respect to time and depends on the direction of rotation of the magnetic field.

Neurotransmitters of the retino-hypothalamic tract.

PubMed

Hannibal, Jens

2002-07-01

The brain's biological clock, which, in mammals, is located in the suprachiasmatic nucleus (SCN), generates circadian rhythms in behaviour and physiology. These biological rhythms are adjusted daily (entrained) to the environmental light/dark cycle via a monosynaptic retinofugal pathway, the retinohypothalamic tract (RHT). In this review, the anatomical and physiological evidence for glutamate and pituitary adenylate cyclase-activating polypeptide (PACAP) as principal transmitters of the RHT will be considered. A combination of immunohistochemistry at both the light- and electron-microscopic levels and tract-tracing studies have revealed that these two transmitters are co-stored in a subpopulation of retinal ganglion cells projecting to the retino-recipient zone of the ventral SCN. The PACAP/glutamate-containing cells, which constitute the RHT, also contain a recently identified photoreceptor protein, melanopsin, which may function as a "circadian photopigment". In vivo and in vitro studies have shown that glutamate and glutamate agonists such as N-methyl- D-aspartate mimic light-induced phase shifts and that application of glutamate antagonists blocks light-induced phase shifts at subjective night indicating that glutamate mediates light signalling to the clock. PACAP in nanomolar concentrations has similar phase-shifting capacity as light and glutamate, whereas PACAP in micromolar concentrations modulates glutamate-induced phase shifts. Possible targets for PACAP and glutamate are the recently identified clock genes Per1 and Per2, which are induced in the SCN by light, glutamate and PACAP at night.

Optical π phase shift created with a single-photon pulse.

PubMed

Tiarks, Daniel; Schmidt, Steffen; Rempe, Gerhard; Dürr, Stephan

2016-04-01

A deterministic photon-photon quantum logic gate is a long-standing goal. Building such a gate becomes possible if a light pulse containing only one photon imprints a phase shift of π onto another light field. We experimentally demonstrate the generation of such a π phase shift with a single-photon pulse. A first light pulse containing less than one photon on average is stored in an atomic gas. Rydberg blockade combined with electromagnetically induced transparency creates a phase shift for a second light pulse, which propagates through the medium. We measure the π phase shift of the second pulse when we postselect the data upon the detection of a retrieved photon from the first pulse. This demonstrates a crucial step toward a photon-photon gate and offers a variety of applications in the field of quantum information processing.

Mutants with Altered Sensitivity to a Calmodulin Antagonist Affect the Circadian Clock in Neurospora Crassa

PubMed Central

Suzuki, S.; Katagiri, S.; Nakashima, H.

1996-01-01

Two newly isolated mutant strains of Neurospora crassa, cpz-1 and cpz-2, were hypersensitive to chlorpromazine with respect to mycelial growth but responded differently to the drug with respect to the circadian conidiation rhythm. In the wild type, chlorpromazine caused shortening of the period length of the conidiation rhythm. Pulse treatment with the drug shifted the phase and inhibited light-induced phase shifting in Neurospora. By contrast to the wild type, the cpz-2 strain was resistant to these inhibitory effects of chlorpromazine. Inhibition of cpz-2 function by chlorpromazine affected three different parameters of circadian conidiation rhythm, namely, period length, phase and light-induced phase shifting. These results indicate that the cpz-2 gene must be involved in or related closely to the clock mechanism of Neurospora. By contrast, the cpz-1 strain was hypersensitive to chlorpromazine with respect to the circadian conidiation rhythm. PMID:8807291

Analytical results for a conditional phase shift between single-photon pulses in a nonlocal nonlinear medium

NASA Astrophysics Data System (ADS)

Viswanathan, Balakrishnan; Gea-Banacloche, Julio

2017-04-01

We analyze a recent scheme proposed by Xia et al. to induce a conditional phase shift between two single-photon pulses by having them propagate at different speeds through a nonlinear medium with a nonlocal response. We have obtained an analytical solution for the case they considered, which supports their claim that a π phase shift with unit fidelity is possible in principle. We discuss the conditions that have to be met and the challenges and opportunities that this might present to the realization of a single-photon conditional phase gate.

Frequency-dependent polarization-angle-phase-shift in the microwave-induced magnetoresistance oscillations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Han-Chun; Ye, Tianyu; Mani, R. G.

2015-02-14

Linear polarization angle, θ, dependent measurements of the microwave radiation-induced oscillatory magnetoresistance, R{sub xx}, in high mobility GaAs/AlGaAs 2D electron devices have shown a θ dependence in the oscillatory amplitude along with magnetic field, frequency, and extrema-dependent phase shifts, θ{sub 0}. Here, we suggest a microwave frequency dependence of θ{sub 0}(f) using an analysis that averages over other smaller contributions, when those contributions are smaller than estimates of the experimental uncertainty.

Phase Misalignment between Suprachiasmatic Neuronal Oscillators Impairs Photic Behavioral Phase Shifts but not Photic Induction of Gene Expression

PubMed Central

Schwartz, Michael D.; Congdon, Seth; de la Iglesia, Horacio O.

2010-01-01

The ability of the circadian pacemaker within the suprachiasmatic nucleus (SCN) to respond to light stimulation in a phase-specific manner constitutes the basis for photic entrainment of circadian rhythms. The neural basis for this phase-specificity is unclear. We asked whether a lack of synchrony between SCN neurons, as reflected in phase misalignment between dorsomedial (dmSCN) and ventrolateral (vlSCN) neuronal oscillators in the rat, would impact the pacemaker’s ability to respond to phase-resetting light pulses. Light pulses delivered at maximal phase-misalignment between the vl-and dmSCN oscillators increased expression of Per1 mRNA, irrespective of the circadian phase of the dmSCN. However, phase shifts of locomotor activity were only observed when the vl-and dmSCN were phase-aligned at the time of stimulation. Our results fit a model in which a vlSCN oscillator phase-gates its own response to light and in turn relays light information to a dmSCN oscillator. This model predicts that the phase misalignment that results from circadian internal desynchronization could preserve the ability of light to induce gene expression within the master circadian clock but impair its ability to induce behavioral phase shifts. PMID:20881133

Time-Restricted Feeding Shifts the Skin Circadian Clock and Alters UVB-Induced DNA Damage.

PubMed

Wang, Hong; van Spyk, Elyse; Liu, Qiang; Geyfman, Mikhail; Salmans, Michael L; Kumar, Vivek; Ihler, Alexander; Li, Ning; Takahashi, Joseph S; Andersen, Bogi

2017-08-01

The epidermis is a highly regenerative barrier protecting organisms from environmental insults, including UV radiation, the main cause of skin cancer and skin aging. Here, we show that time-restricted feeding (RF) shifts the phase and alters the amplitude of the skin circadian clock and affects the expression of approximately 10% of the skin transcriptome. Furthermore, a large number of skin-expressed genes are acutely regulated by food intake. Although the circadian clock is required for daily rhythms in DNA synthesis in epidermal progenitor cells, RF-induced shifts in clock phase do not alter the phase of DNA synthesis. However, RF alters both diurnal sensitivity to UVB-induced DNA damage and expression of the key DNA repair gene, Xpa. Together, our findings indicate regulation of skin function by time of feeding and emphasize a link between circadian rhythm, food intake, and skin health. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

Proprioceptive influence on the optokinetic nystagmus.

PubMed

Botti, F; Anastasopoulos, D; Kostadima, V; Bambagioni, D; Pettorossi, V E

2001-01-01

The influence of neck and leg proprioceptive inputs on optokinetic-induced quick phases was studied in humans. Ten subjects received unidirectional horizontal optokinetic stimulation (10-20%/s) during sinusoidal neck, leg and combined neck + leg proprioceptive stimulation. The optokinetic reflex was measured by electro-oculography. Neck stimulation induced a shift in the nystagmus beating field in the opposite direction to body movement (gain 0.3 0.4, phase 140-180 degrees). The beating field shift resulted totally from the amplitude and frequency modulation of optokinetic quick phases, as slow phases were not affected. Leg proprioceptive stimulation induced a similar effect, but the phase of the response lagged by approximately 90 degrees compared with that of neck response. With combined neck + leg stimulation, the amplitude of the effect was a sum of the separate effects, but the phase coincided with that of the leg response. This suggests that neck and leg proprioceptive signals do not add linearly and that the leg signal determines the time of the response.

LY2033298, a positive allosteric modulator at muscarinic M₄ receptors, enhances inhibition by oxotremorine of light-induced phase shifts in hamster circadian activity rhythms.

PubMed

Gannon, Robert L; Millan, Mark J

2012-11-01

Entrainment of circadian rhythms to the light-dark cycle is essential for restorative sleep, and abnormal sleep timing is implicated in central nervous system (CNS) disorders like depression, schizophrenia, and Alzheimer's disease. Many transmitters, including acetylcholine, that exerts its actions via muscarinic receptors modulate the suprachiasmatic nucleus, the master pacemaker. Since positive allosteric modulators of muscarinic M(4) receptors are candidates for treatment of mood and cognitive deficits of CNS disorders, it is important to evaluate their circadian actions. The effects of intraperitoneally applied muscarinic agents on circadian wheel-running rhythms were measured employing hamsters, a model organism for studying activity rhythms. Systemic administration of the muscarinic receptor agonist oxotremorine (0.01-0.04 mg/kg) inhibited light-induced phase delays and advances of hamster circadian wheel-running rhythms. The M₄ positive allosteric modulator, LY2033298 (10-40 mg/kg), had no effect on light-induced phase shifts when administered alone, yet significantly enhanced (at 20 mg/kg) the inhibitory influence of oxotremorine on light-induced phase delays. In addition, the muscarinic receptor antagonist, scopolamine, which was without effect on light-induced phase shifts when administered alone (0.001-0.1 mg/kg), antagonized (at 0.1 mg/kg) the inhibitory effect of oxotremorine and LY2033298 on light-induced phase delays. These results are the first to demonstrate that systemically applied muscarinic receptor agonists modulate circadian activity rhythms, and they also reveal a specific role for M₄ receptors. It will be of importance to evaluate circadian actions of psychotropic drugs acting via M₄ receptors, since they may display beneficial properties under pathological conditions.

Mechanism of Pressure-Induced Phase Transitions, Amorphization, and Absorption-Edge Shift in Photovoltaic Methylammonium Lead Iodide.

PubMed

Szafrański, Marek; Katrusiak, Andrzej

2016-09-01

Our single-crystal X-ray diffraction study of methylammonium lead triiodide, MAPbI3, provides the first comprehensive structural information on the tetragonal phase II in the pressure range to 0.35 GPa, on the cubic phase IV stable between 0.35 and 2.5 GPa, and on the isostructural cubic phase V observed above 2.5 GPa, which undergoes a gradual amorphization. The optical absorption study confirms that up to 0.35 GPa, the absorption edge of MAPbI3 is red-shifted, allowing an extension of spectral absorption. The transitions to phases IV and V are associated with the abrupt blue shifts of the absorption edge. The strong increase of the energy gap in phase V result in a spectacular color change of the crystal from black to red around 3.5 GPa. The optical changes have been correlated with the pressure-induced strain of the MAPbI3 inorganic framework and its frustration, triggered by methylammonium cations trapped at random orientations in the squeezed voids.

A Control Allocation Technique to Recover From Pilot-Induced Oscillations (CAPIO) Due to Actuator Rate Limiting

NASA Technical Reports Server (NTRS)

Yildiz, Yildiray; Kolmanovsky, Ilya V.

2010-01-01

This paper proposes a control allocation technique that can help pilots recover from pilot induced oscillations (PIO). When actuators are rate-saturated due to aggressive pilot commands, high gain flight control systems or some anomaly in the system, the effective delay in the control loop may increase depending on the nature of the cause. This effective delay increase manifests itself as a phase shift between the commanded and actual system signals and can instigate PIOs. The proposed control allocator reduces the effective time delay by minimizing the phase shift between the commanded and the actual attitude accelerations. Simulation results are reported, which demonstrate phase shift minimization and recovery from PIOs. Conversion of the objective function to be minimized and constraints to a form that is suitable for implementation is given.

Role of Inflammatory Signaling in the Differential Effects of Saturated and Poly-unsaturated Fatty Acids on Peripheral Circadian Clocks.

PubMed

Kim, Sam-Moon; Neuendorff, Nichole; Chapkin, Robert S; Earnest, David J

2016-05-01

Inflammatory signaling may play a role in high-fat diet (HFD)-related circadian clock disturbances that contribute to systemic metabolic dysregulation. Therefore, palmitate, the prevalent proinflammatory saturated fatty acid (SFA) in HFD and the anti-inflammatory, poly-unsaturated fatty acid (PUFA), docosahexaenoic acid (DHA), were analyzed for effects on circadian timekeeping and inflammatory responses in peripheral clocks. Prolonged palmitate, but not DHA, exposure increased the period of fibroblast Bmal1-dLuc rhythms. Acute palmitate treatment produced phase shifts of the Bmal1-dLuc rhythm that were larger in amplitude as compared to DHA. These phase-shifting effects were time-dependent and contemporaneous with rhythmic changes in palmitate-induced inflammatory responses. Fibroblast and differentiated adipocyte clocks exhibited cell-specific differences in the time-dependent nature of palmitate-induced shifts and inflammation. DHA and other inhibitors of inflammatory signaling (AICAR, cardamonin) repressed palmitate-induced proinflammatory responses and phase shifts of the fibroblast clock, suggesting that SFA-mediated inflammatory signaling may feed back to modulate circadian timekeeping in peripheral clocks. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Cross-phase modulation-induced spectral broadening in silicon waveguides.

PubMed

Zhang, Yanbing; Husko, Chad; Lefrancois, Simon; Rey, Isabella H; Krauss, Thomas F; Schröder, Jochen; Eggleton, Benjamin J

2016-01-11

We analytically and experimentally investigate cross-phase modulation (XPM) in silicon waveguides. In contrast to the well known result in pure Kerr media, the spectral broadening ratio of XPM to self-phase modulation is not two in the presence of either two-photon absorption (TPA) or free carriers. The physical origin of this change is different for each effect. In the case of TPA, this nonlinear absorption attenuates and slightly modifies the pulse shape due to differential absorption in the pulse peak and wings. When free carriers are present two different mechanisms modify the dynamics. First, free-carrier absorption performs a similar role to TPA, but is additionally asymmetric due to the delayed free-carrier response. Second, free-carrier dispersion induces an asymmetric blue phase shift which competes directly with the symmetric Kerr-induced XPM red shift. We confirm this analysis with pump-probe experiments in a silicon photonic crystal waveguide.

Ps laser pulse induced stimulated Raman scattering of ammonium nitrate dissolved in water

NASA Astrophysics Data System (ADS)

Kumar, V. Rakesh; Kiran, P. Prem

2018-04-01

An intense picosecond laser pulse focused into a liquid medium generates a shock wave in the focal region. This shock wave while propagating into the medium varies the pressure and temperature of the liquid locally leading to the appearance of novel phases which are manifested by the appearance of Raman peaks. We present the phase changes of ammonium nitrate (AN) dissolved in water by studying the forward and backward stimulated Raman Scattering (FSRS and BSRS) signals due to propagation of 30 ps laser pulse induced shockwaves. The dominant peak corresponding to the NO3- symmetric stretching mode is observed with a Raman shift of 1045 cm-1 which represents phase IV of AN with an orthogonal crystalline structure. Apart from this peak, the dominant mode of liquid phase of water with a Raman shift of 3400 cm-1 and an ice VII peak at a Raman shift of 3050 cm-1 confirming the pressure of 10 GPa is observed. The effect of the concentration and input energy on the appearance of the phases will be presented.

A Control Allocation System for Automatic Detection and Compensation of Phase Shift Due to Actuator Rate Limiting

NASA Technical Reports Server (NTRS)

Yildiz, Yidiray; Kolmanovsky, Ilya V.; Acosta, Diana

2011-01-01

This paper proposes a control allocation system that can detect and compensate the phase shift between the desired and the actual total control effort due to rate limiting of the actuators. Phase shifting is an important problem in control system applications since it effectively introduces a time delay which may destabilize the closed loop dynamics. A relevant example comes from flight control where aggressive pilot commands, high gain of the flight control system or some anomaly in the system may cause actuator rate limiting and effective time delay introduction. This time delay can instigate Pilot Induced Oscillations (PIO), which is an abnormal coupling between the pilot and the aircraft resulting in unintentional and undesired oscillations. The proposed control allocation system reduces the effective time delay by first detecting the phase shift and then minimizing it using constrained optimization techniques. Flight control simulation results for an unstable aircraft with inertial cross coupling are reported, which demonstrate phase shift minimization and recovery from a PIO event.

The Phase Shift in the Jumping Ring

ERIC Educational Resources Information Center

Jeffery, Rondo N.; Amiri, Farhang

2008-01-01

The popular physics demonstration experiment known as Thomson's Jumping Ring (JR) has been variously explained as a simple example of Lenz's law, or as the result of a phase shift of the ring current relative to the induced emf. The failure of the first-quadrant Lenz's law explanation is shown by the time the ring takes to jump and by levitation.…

Phase-shift detection in a Fourier-transform method for temperature sensing using a tapered fiber microknot resonator.

PubMed

Larocque, Hugo; Lu, Ping; Bao, Xiaoyi

2016-04-01

Phase-shift detection in a fast-Fourier-transform (FFT)-based spectrum analysis technique for temperature sensing using a tapered fiber microknot resonator is proposed and demonstrated. Multiple transmission peaks in the FFT spectrum of the device were identified as optical modes having completed different amounts of round trips within the ring structure. Temperature variation induced phase shifts for each set of peaks were characterized, and experimental results show that different peaks have distinct temperature sensitivities reaching values up to -0.542  rad/°C, which is about 10 times greater than that of a regular adiabatic taper Mach-Zehnder interferometer when using similar phase-tracking schemes.

Wave-mixing-induced transparency with zero phase shift in atomic vapors

NASA Astrophysics Data System (ADS)

Zhou, F.; Zhu, C. J.; Li, Y.

2017-12-01

We present a wave-mixing induced transparency that can lead to a hyper-Raman gain-clamping effect. This new type of transparency is originated from a dynamic gain cancellation effect in a multiphoton process where a highly efficient light field of new frequency is generated and amplified. We further show that this novel dynamic gain cancellation effect not only makes the medium transparent to a probe light field at appropriate frequency but also eliminates the probe field propagation phase shift. This gain-cancellation-based induced transparency holds for many potential applications on optical communication and may lead to effective suppression of parasitic Raman/hyper-Raman noise field generated in high intensity optical fiber transmissions.

Angular phase shift in polarization-angle dependence of microwave-induced magnetoresistance oscillations

NASA Astrophysics Data System (ADS)

Liu, Han-Chun; Samaraweera, Rasanga L.; Mani, R. G.; Reichl, C.; Wegscheider, W.

2016-12-01

We examine the microwave frequency (f ) variation of the angular phase shift, θ0, observed in the polarization-angle dependence of microwave-induced magnetoresistance oscillations in a high-mobility GaAs/AlGaAs two-dimensional electron system. By fitting the diagonal resistance Rx x versus θ plots to an empirical cosine square law, we extract θ0 and trace its quasicontinuous variation with f . The results suggest that the overall average of θ0 extracted from Hall bar device sections with length-to-width ratios of L /W =1 and 2 is the same. We compare the observations with expectations arising from the "ponderomotive force" theory for microwave radiation-induced transport phenomena.

Electromagnetically-induced-transparency-based cross-phase-modulation at attojoule levels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lo, Hsiang-Yu; Chen, Yen-Chun; Su, Po-Ching

2011-04-15

We report the experimental demonstration of electromagnetically-induced-transparency-based cross-phase-modulation at attojoule or, equivalently, few-hundred-photon levels. A phase shift of 0.005 rad of a probe pulse modulated by a signal pulse with an energy of {approx}100 aJ, equivalent to {approx}400 photons, was observed in a four-level system of cold {sup 87}Rb atoms.

Two mechanisms of rephasal of circadian rhythms in response to a 180 deg phase shift /simulated 12-hr time zone change/

NASA Technical Reports Server (NTRS)

Deroshia, C. W.; Winget, C. M.; Bond, G. H.

1976-01-01

A model developed by Wever (1966) is considered. The model describes the behavior of circadian rhythms in response to photoperiod phase shifts simulating time zone changes, as a function of endogenous periodicity, light intensity, and direction of phase shift. A description is given of an investigation conducted to test the model upon the deep body temperature rhythm in unrestrained subhuman primates. An evaluation is conducted regarding the applicability of the model in predicting the type and duration of desynchronization induced by simulated time zone changes as a function of endogenous periodicity.

The timing of the human circadian clock is accurately represented by the core body temperature rhythm following phase shifts to a three-cycle light stimulus near the critical zone

NASA Technical Reports Server (NTRS)

Jewett, M. E.; Duffy, J. F.; Czeisler, C. A.

2000-01-01

A double-stimulus experiment was conducted to evaluate the phase of the underlying circadian clock following light-induced phase shifts of the human circadian system. Circadian phase was assayed by constant routine from the rhythm in core body temperature before and after a three-cycle bright-light stimulus applied near the estimated minimum of the core body temperature rhythm. An identical, consecutive three-cycle light stimulus was then applied, and phase was reassessed. Phase shifts to these consecutive stimuli were no different from those obtained in a previous study following light stimuli applied under steady-state conditions over a range of circadian phases similar to those at which the consecutive stimuli were applied. These data suggest that circadian phase shifts of the core body temperature rhythm in response to a three-cycle stimulus occur within 24 h following the end of the 3-day light stimulus and that this poststimulus temperature rhythm accurately reflects the timing of the underlying circadian clock.

Spectroscopic Doppler analysis for visible-light optical coherence tomography

NASA Astrophysics Data System (ADS)

Shu, Xiao; Liu, Wenzhong; Duan, Lian; Zhang, Hao F.

2017-12-01

Retinal oxygen metabolic rate can be effectively measured by visible-light optical coherence tomography (vis-OCT), which simultaneously quantifies oxygen saturation and blood flow rate in retinal vessels through spectroscopic analysis and Doppler measurement, respectively. Doppler OCT relates phase variation between sequential A-lines to the axial flow velocity of the scattering medium. The detectable phase shift is between -π and π due to its periodicity, which limits the maximum measurable unambiguous velocity without phase unwrapping. Using shorter wavelengths, vis-OCT is more vulnerable to phase ambiguity since flow induced phase variation is linearly related to the center wavenumber of the probing light. We eliminated the need for phase unwrapping using spectroscopic Doppler analysis. We split the whole vis-OCT spectrum into a series of narrow subbands and reconstructed vis-OCT images to extract corresponding Doppler phase shifts in all the subbands. Then, we quantified flow velocity by analyzing subband-dependent phase shift using linear regression. In the phantom experiment, we showed that spectroscopic Doppler analysis extended the measurable absolute phase shift range without conducting phase unwrapping. We also tested this method to quantify retinal blood flow in rodents in vivo.

Coma measurement by transmission image sensor with a PSM

NASA Astrophysics Data System (ADS)

Wang, Fan; Wang, Xiangzhao; Ma, Mingying; Zhang, Dongqing; Shi, Weijie; Hu, Jianming

2005-01-01

As feature size decreases, especially with the use of resolution enhancement technique such as off axis illumination and phase shifting mask, fast and accurate in-situ measurement of coma has become very important in improving the performance of modern lithographic tools. The measurement of coma can be achieved by the transmission image sensor, which is an aerial image measurement device. The coma can be determined by measuring the positions of the aerial image at multiple illumination settings. In the present paper, we improve the measurement accuracy of the above technique with an alternating phase shifting mask. Using the scalar diffraction theory, we analyze the effect of coma on the aerial image. To analyze the effect of the alternating phase shifting mask, we compare the pupil filling of the mark used in the above technique with that of the phase-shifted mark used in the new technique. We calculate the coma-induced image displacements of the marks at multiple partial coherence and NA settings, using the PROLITH simulation program. The simulation results show that the accuracy of coma measurement can increase approximately 20 percent using the alternating phase shifting mask.

Carbachol Induces Phase-dependent Phase Shifts of Per1 Transcription Rhythms in Cultured Suprachiasmatic Nucleus Slices.

PubMed

Dojo, Kumiko; Yamaguchi, Yoshiaki; Fustin, Jean-Michel; Doi, Masao; Kobayashi, Masaki; Okamura, Hitoshi

2017-04-01

Among nonphotic stimulants, a classic cholinergic agonist, carbachol, is known to have a strong and unique phase-resetting effect on the circadian clock: Intracerebroventricular carbachol treatment causes phase delays during the subjective early night and phase advances in the subjective late night, but the effects of this drug on the suprachiasmatic nucleus (SCN) in vivo and in vitro are still controversial. In the present study, we succeeded in reproducing the biphasic phase-shifting effect of carbachol on clock gene expression in organotypic SCN slices prepared from mice carrying a Per1-promoter fused luciferase gene ( Per1-luc). Since this biphasic effect of carbachol in Per1-luc SCN was prevented by atropine but not by mecamylamine, we concluded that these phase shifts were muscarinic receptor-dependent. Next, we analyzed the expression of muscarinic receptors in the SCN by in situ hybridization and found that M3 and M4 subtypes were expressed in SCN cells. These signals appeared neonatally and reached adult levels at postnatal day 10. Together, these findings suggest that carbachol has a phase-dependent phase-shifting effect on the SCN clock through muscarinic receptor subtypes expressed in the SCN.

Nonlinear nature of composite structure induced by the interaction of nonplanar solitons in a nonextensive plasma

NASA Astrophysics Data System (ADS)

Han, Jiu-Ning; Luo, Jun-Hua; Liu, Zhen-Lai; Shi, Jun; Xiang, Gen-Xiang; Li, Jun-Xiu

2015-06-01

The nonlinear properties of composite structure induced by the head-on collision of electron-acoustic solitons in a general plasma composed of cold fluid electrons, hot nonextensive distributed electron, and stationary ions are studied. We have made a detailed investigation on the time-evolution process of this merged wave structure. It is found that the structure survives during some time interval, and there are obviously different for the properties of the composite structures which are induced in cylindrical and spherical geometries. Moreover, it is shown that there are both positive and negative phase shifts for each colliding soliton after the interaction. For fixed plasma parameters, the soliton received the largest phase shift in spherical geometry, followed by the cylindrical and one-dimensional planar geometries.

Recurrent noise-induced phase singularities in drifting patterns.

PubMed

Clerc, M G; Coulibaly, S; del Campo, F; Garcia-Nustes, M A; Louvergneaux, E; Wilson, M

2015-11-01

We show that the key ingredients for creating recurrent traveling spatial phase defects in drifting patterns are a noise-sustained structure regime together with the vicinity of a phase transition, that is, a spatial region where the control parameter lies close to the threshold for pattern formation. They both generate specific favorable initial conditions for local spatial gradients, phase, and/or amplitude. Predictions from the stochastic convective Ginzburg-Landau equation with real coefficients agree quite well with experiments carried out on a Kerr medium submitted to shifted optical feedback that evidence noise-induced traveling phase slips and vortex phase-singularities.

Warming-induced upward migration of the alpine treeline in the Changbai Mountains, northeast China.

PubMed

Du, Haibo; Liu, Jie; Li, Mai-He; Büntgen, Ulf; Yang, Yue; Wang, Lei; Wu, Zhengfang; He, Hong S

2018-03-01

Treeline responses to environmental changes describe an important phenomenon in global change research. Often conflicting results and generally too short observations are, however, still challenging our understanding of climate-induced treeline dynamics. Here, we use a state-of-the-art dendroecological approach to reconstruct long-term changes in the position of the alpine treeline in relation to air temperature at two sides in the Changbai Mountains in northeast China. Over the past 160 years, the treeline increased by around 80 m, a process that can be divided into three phases of different rates and drives. The first phase was mainly influenced by vegetation recovery after an eruption of the Tianchi volcano in 1702. The slowly upward shift in the second phase was consistent with the slowly increasing temperature. The last phase coincided with rapid warming since 1985, and shows with 33 m per 1°C, the most intense upward shift. The spatial distribution and age structure of trees beyond the current treeline confirm the latest, warming-induced upward shift. Our results suggest that the alpine treeline will continue to rise, and that the alpine tundra may disappear if temperatures will increase further. This study not only enhances mechanistic understanding of long-term treeline dynamics, but also highlights the effects of rising temperatures on high-elevation vegetation dynamics. © 2017 John Wiley & Sons Ltd.

Unwrapping eddy current compensation: improved compensation of eddy current induced baseline shifts in high-resolution phase-contrast MRI at 9.4 Tesla.

PubMed

Espe, Emil K S; Zhang, Lili; Sjaastad, Ivar

2014-10-01

Phase-contrast MRI (PC-MRI) is a versatile tool allowing evaluation of in vivo motion, but is sensitive to eddy current induced phase offsets, causing errors in the measured velocities. In high-resolution PC-MRI, these offsets can be sufficiently large to cause wrapping in the baseline phase, rendering conventional eddy current compensation (ECC) inadequate. The purpose of this study was to develop an improved ECC technique (unwrapping ECC) able to handle baseline phase discontinuities. Baseline phase discontinuities are unwrapped by minimizing the spatiotemporal standard deviation of the static-tissue phase. Computer simulations were used for demonstrating the theoretical foundation of the proposed technique. The presence of baseline wrapping was confirmed in high-resolution myocardial PC-MRI of a normal rat heart at 9.4 Tesla (T), and the performance of unwrapping ECC was compared with conventional ECC. Areas of phase wrapping in static regions were clearly evident in high-resolution PC-MRI. The proposed technique successfully eliminated discontinuities in the baseline, and resulted in significantly better ECC than the conventional approach. We report the occurrence of baseline phase wrapping in PC-MRI, and provide an improved ECC technique capable of handling its presence. Unwrapping ECC offers improved correction of eddy current induced baseline shifts in high-resolution PC-MRI. Copyright © 2013 Wiley Periodicals, Inc.

Interaction of Phase Singularities on Spiral Wave Tail: Reconsideration of Capturing the Excitable Gap.

PubMed

Tomii, Naoki; Yamazaki, Masatoshi; Arafune, Tatsuhiko; Kamiya, Kaichiro; Nakazawa, Kazuo; Honjo, Haruo; Shibata, Nitaro; Sakuma, Ichiro

2018-03-09

The action mechanism of stimulation toward spiral waves (SWs) owing to the complex excitation patterns that occur just after point stimulation has not yet been experimentally clarified. This study sought to test our hypothesis that the effect of capturing excitable gap of SW by stimulation can also be explained as the interaction of original phase singularity (PS) and PSs induced by the stimulation on the wave tail (WT) of the original SW. Phase variance analysis was used to quantitatively analyze the post-shock PS trajectories. In a two-dimensional subepicardial layer of Langendorff-perfused rabbit hearts, optical mapping was utilized to record the excitation pattern during stimulation. After SW was induced by S1-S2 shock, single biphasic point stimulation S3 was applied. In 70 of the S1-S2-S3 stimulation episodes applied on six hearts, the original PS was clearly observed just before the S3 point stimulation in 37 episodes. Pairwise PSs were newly induced by the S3 in 20 episodes. The original PS collided with the newly-induced PSs in 16 episodes; otherwise, they did not interact with the original PS. SW shift occurred most efficiently when the S3 shock was applied at the relative refractory period, and PS shifted in the direction of WT. Quantitative tracking of PS clarified that stimulation in desirable conditions induces pairwise PSs on WT and that the collision of PSs causes SW shift along the WT. Results of this study indicate the importance of the interaction of shock-induced excitation with the WT for effective stimulation.

Reduction of the Nonlinear Phase Shift Induced by Stimulated Brillouin Scattering for Bi-Directional Pumping Configuration System Using Particle Swarm Optimization Algorithm

NASA Astrophysics Data System (ADS)

Al-Asadi, H. A.

2013-02-01

We present a theoretical analysis of an additional nonlinear phase shift of backward Stokes wave based on stimulated Brillouin scattering in the system with a bi-directional pumping scheme. We optimize three parameters of the system: the numerical aperture, the optical loss and the pumping wavelength to minimize an additional nonlinear phase shift of backward Stokes waves due to stimulated Brillouin scattering. The optimization is performed with various Brillouin pump powers and the optical reflectivity values are based on the modern, global evolutionary computation algorithm, particle swarm optimization. It is shown that the additional nonlinear phase shift of backward Stokes wave varies with different optical fiber lengths, and can be minimized to less than 0.07 rad according to the particle swarm optimization algorithm for 5 km. The bi-directional pumping configuration system is shown to be efficient when it is possible to transmit the power output to advanced when frequency detuning is negative and delayed when it is positive, with the optimum values of the three parameters to achieve the reduction of an additional nonlinear phase shift.

A Liquid Optical Phase Shifter with an Embedded Electrowetting Actuator

PubMed Central

Ashtiani, Alireza Ousati; Jiang, Hongrui

2017-01-01

We demonstrate an electrowetting-based liquid optical phase shifter. The phase shifter consists of two immiscible liquid layers with different refractive indices. Sandwiched between the two liquids is a rigid membrane that moves freely along the optical axis and supported by a compliant surround. When applied with a pressure, the thicknesses of both liquid layers change, which induces a difference in optical path, resulting in a phase shift. A miniaturized electrowetting-based actuator is used to produce hydraulic pressure. A multi-layered SU8 bonded structure was fabricated. A phase shift of 171° was observed when the device was incorporated in a Mach-Zehnder interferometer and driven with 100 V. PMID:29038640

The dressed atom as binary phase modulator: towards attojoule/edge optical phase-shift keying.

PubMed

Kerckhoff, Joseph; Armen, Michael A; Pavlichin, Dmitri S; Mabuchi, Hideo

2011-03-28

We use a single 133Cs atom strongly coupled to an optical resonator to induce random binary phase modulation of a near infra-red, ∼ 500 pW laser beam, with each modulation edge caused by the dissipation of a single photon (≈ 0.23 aJ) by the atom. While our ability to deterministically induce phase edges with an additional optical control beam is limited thus far, theoretical analysis of an analogous, solid-state system indicates that efficient external control should be achievable in demonstrated nanophotonic systems.

Direct observation of dopant distribution in GaAs compound semiconductors using phase-shifting electron holography and Lorentz microscopy.

PubMed

Sasaki, Hirokazu; Otomo, Shinya; Minato, Ryuichiro; Yamamoto, Kazuo; Hirayama, Tsukasa

2014-06-01

Phase-shifting electron holography and Lorentz microscopy were used to map dopant distributions in GaAs compound semiconductors with step-like dopant concentration. Transmission electron microscope specimens were prepared using a triple beam focused ion beam (FIB) system, which combines a Ga ion beam, a scanning electron microscope, and an Ar ion beam to remove the FIB damaged layers. The p-n junctions were clearly observed in both under-focused and over-focused Lorentz microscopy images. A phase image was obtained by using a phase-shifting reconstruction method to simultaneously achieve high sensitivity and high spatial resolution. Differences in dopant concentrations between 1 × 10(19) cm(-3) and 1 × 10(18) cm(-3) regions were clearly observed by using phase-shifting electron holography. We also interpreted phase profiles quantitatively by considering inactive layers induced by ion implantation during the FIB process. The thickness of an inactive layer at different dopant concentration area can be measured from the phase image. © The Author 2014. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

NOLM-based all-optical 40 Gbit/s format conversion through sum-frequency generation (SFG) in a PPLN waveguide

NASA Astrophysics Data System (ADS)

Wang, Jian; Sun, Junqiang

2005-11-01

A novel all-optical format conversion scheme from NRZ to RZ based on sum-frequency generation (SFG) in a periodically poled LiNbO 3 (PPLN) waveguide is proposed, using a nonlinear optical loop mirror (NOLM). The conversion mechanism relies on the combination of attenuation and nonlinear phase shift induced on the clockwise signal field during the SFG process. The SFG between pump, and co- and counter- propagating signals in the PPLN waveguide are numerically studied, showing that counter-propagating SFG can be ignored when quasi-phase matching (QPM) for SFG during co-propagating interaction. The nonlinear phase shift induced on the clockwise signal field is analyzed in detail, showing that it is more effective to yield large values for nonlinear phase shift when appropriately phase mismatched for the SFG process. Two tuning schemes are proposed depend on whether the sum-frequency wavelength is variable or fixed. It is found that the latter has a rather wide 3dB signal conversion bandwidth approximately 154nm. Finally, the influence of reversible process of SFG is discussed and the optimum arrangement of pump and signal peak powers is theoretically demonstrated. The result shows that proper power arrangement, pump width, and waveguide length are necessary for achieving a good conversion effect.

Does calcium influx regulate melatonin production through the circadian pacemaker in chick pineal cells? Effects of nitrendipine, Bay K 8644, Co2+, Mn2+, and low external Ca2+.

PubMed

Zatz, M; Mullen, D A

1988-11-01

We have recently described a system, using dispersed chick pineal cells in static culture, which displays a persistent, photosensitive, circadian rhythm of melatonin production and release. Here, we describe the effects of nitrendipine (NTR) (a dihydropyridine 'antagonist' of L-type calcium channels), Bay K 8644 (BK) (a dihydropyridine calcium channel 'agonist'), cobalt and manganese ions (both inorganic calcium channel blockers), and low external calcium concentrations, on the melatonin rhythm. NTR inhibited and BK stimulated melatonin output; they were potent and effective. Co2+, Mn2+, and low external Ca2+ markedly inhibited melatonin output. These results support a role for calcium influx through voltage-dependent calcium channels (L-type) in the regulation of melatonin production. Four or 8 h pulses of white light or darkness, in otherwise constant red light, cause, in addition to acute effects, phase-dependent phase shifts of the melatonin rhythm in subsequent cycles. Such phase shifts indicate an effect on (proximal to) the pacemaker generating the rhythm. Four or 8 h pulses of NTR, BK, Co2+, or low Ca2+, however, did not appreciably alter the phase of subsequent melatonin cycles. Neither did BK interfere with phase shifts induced by light pulses. Mn2+ pulses did induce phase-dependent phase shifts, but, unlike those evoked by light or dark pulses, these were all delays. Such effects of Mn2+ in other systems have been attributed to, and are characteristic of, 'metabolic inhibitors'. On balance, the results fail to support a prominent role for calcium influx in regulating the pacemaker underlying the circadian rhythm in chick pineal cells. Rather, calcium influx appears to regulate melatonin production primarily by acting on the melatonin-synthesizing apparatus, distal to the pacemaker.

Efficient green light generation by Q-switched Nd: YAG laser in periodically poled potassium titanyl phosphate crystal

NASA Astrophysics Data System (ADS)

Zhang, Shuanggen; Guo, Wengang; Lv, Fuyun

2014-07-01

A PPKTP crystal was used to efficient green emission. Spectrum characteristics of FF and SH wave was analyzed, and phase-matching wavelength shift results from thermally-induced poling period shift. A conversion efficiency of 26.1% can be achieved.

Rebound spiking in layer II medial entorhinal cortex stellate cells: Possible mechanism of grid cell function

PubMed Central

Shay, Christopher F.; Ferrante, Michele; Chapman, G. William; Hasselmo, Michael E.

2015-01-01

Rebound spiking properties of medial entorhinal cortex (mEC) stellate cells induced by inhibition may underlie their functional properties in awake behaving rats, including the temporal phase separation of distinct grid cells and differences in grid cell firing properties. We investigated rebound spiking properties using whole cell patch recording in entorhinal slices, holding cells near spiking threshold and delivering sinusoidal inputs, superimposed with realistic inhibitory synaptic inputs to test the capacity of cells to selectively respond to specific phases of inhibitory input. Stellate cells showed a specific phase range of hyperpolarizing inputs that elicited spiking, but non-stellate cells did not show phase specificity. In both cell types, the phase range of spiking output occurred between the peak and subsequent descending zero crossing of the sinusoid. The phases of inhibitory inputs that induced spikes shifted earlier as the baseline sinusoid frequency increased, while spiking output shifted to later phases. Increases in magnitude of the inhibitory inputs shifted the spiking output to earlier phases. Pharmacological blockade of h-current abolished the phase selectivity of hyperpolarizing inputs eliciting spikes. A network computational model using cells possessing similar rebound properties as found in vitro produces spatially periodic firing properties resembling grid cell firing when a simulated animal moves along a linear track. These results suggest that the ability of mEC stellate cells to fire rebound spikes in response to a specific range of phases of inhibition could support complex attractor dynamics that provide completion and separation to maintain spiking activity of specific grid cell populations. PMID:26385258

Assessing the high frequency behavior of non-polarizable electrodes for spectral induced polarization measurements

NASA Astrophysics Data System (ADS)

Abdulsamad, Feras; Florsch, Nicolas; Schmutz, Myriam; Camerlynck, Christian

2016-12-01

During the last decades, the usage of spectral induced polarization (SIP) measurements in hydrogeology and detecting environmental problems has been extensively increased. However, the physical mechanisms which are responsible for the induced polarization response over the usual frequency range (typically 1 mHz to 10-20 kHz) require better understanding. The phase shift observed at high frequencies is sometimes attributed to the so-called Maxwell-Wagner polarization which takes place when charges cross an interface. However, SIP measurements of tap water show a phase shift at frequencies higher than 1 kHz, where no Maxwell-Wagner polarization may occur. In this paper, we enlighten the possible origin of this phase shift and deduce its likely relationship with the types of the measuring electrodes. SIP Laboratory measurements of tap water using different types of measuring electrodes (polarizable and non-polarizable electrodes) are carried out to detect the origin of the phase shift at high frequencies and the influence of the measuring electrodes types on the observed complex resistivity. Sodium chloride is used to change the conductivity of the medium in order to quantify the solution conductivity role. The results of these measurements are clearly showing the impact of the measuring electrodes type on the measured phase spectrum while the influence on the amplitude spectrum is negligible. The phenomenon appearing on the phase spectrum at high frequency (> 1 kHz) whatever the electrode type is, the phase shows an increase compared to the theoretical response, and the discrepancy (at least in absolute value) increases with frequency, but it is less severe when medium conductivity is larger. Additionally, the frequency corner is shifted upward in frequency. The dependence of this phenomenon on the conductivity and the measuring electrodes type (electrode-electrolyte interface) seems to be due to some dielectric effects (as an electrical double layer of small relaxation time formed at the electrodes interface). Therefore, this dielectric response should be taken into account at high frequency to better analytically separate the medium own response from that linked to the measuring electrodes used. We modeled this effect by adding a capacitance connected in parallel with the traditional equivalent electric circuit used to describe the dielectric response of medium.

Autobalanced Ramsey Spectroscopy

NASA Astrophysics Data System (ADS)

Sanner, Christian; Huntemann, Nils; Lange, Richard; Tamm, Christian; Peik, Ekkehard

2018-01-01

We devise a perturbation-immune version of Ramsey's method of separated oscillatory fields. Spectroscopy of an atomic clock transition without compromising the clock's accuracy is accomplished by actively balancing the spectroscopic responses from phase-congruent Ramsey probe cycles of unequal durations. Our simple and universal approach eliminates a wide variety of interrogation-induced line shifts often encountered in high precision spectroscopy, among them, in particular, light shifts, phase chirps, and transient Zeeman shifts. We experimentally demonstrate autobalanced Ramsey spectroscopy on the light shift prone Yb+ 171 electric octupole optical clock transition and show that interrogation defects are not turned into clock errors. This opens up frequency accuracy perspectives below the 10-18 level for the Yb+ system and for other types of optical clocks.

Shift in Food Intake and Changes in Metabolic Regulation and Gene Expression during Simulated Night-Shift Work: A Rat Model.

PubMed

Marti, Andrea Rørvik; Meerlo, Peter; Grønli, Janne; van Hasselt, Sjoerd Johan; Mrdalj, Jelena; Pallesen, Ståle; Pedersen, Torhild Thue; Henriksen, Tone Elise Gjøtterud; Skrede, Silje

2016-11-08

Night-shift work is linked to a shift in food intake toward the normal sleeping period, and to metabolic disturbance. We applied a rat model of night-shift work to assess the immediate effects of such a shift in food intake on metabolism. Male Wistar rats were subjected to 8 h of forced activity during their rest (ZT2-10) or active (ZT14-22) phase. Food intake, body weight, and body temperature were monitored across four work days and eight recovery days. Food intake gradually shifted toward rest-work hours, stabilizing on work day three. A subgroup of animals was euthanized after the third work session for analysis of metabolic gene expression in the liver by real-time polymerase chain reaction (PCR). Results show that work in the rest phase shifted food intake to rest-work hours. Moreover, liver genes related to energy storage and insulin metabolism were upregulated, and genes related to energy breakdown were downregulated compared to non-working time-matched controls. Both working groups lost weight during the protocol and regained weight during recovery, but animals that worked in the rest phase did not fully recover, even after eight days of recovery. In conclusion, three to four days of work in the rest phase is sufficient to induce disruption of several metabolic parameters, which requires more than eight days for full recovery.

On-chip tunable dispersion in a ring laser gyroscope for enhanced rotation sensing

NASA Astrophysics Data System (ADS)

Zhang, Hao; Liu, Jiaming; Lin, Jian; Li, Wenxiu; Xue, Xia; Huang, Anping; Xiao, Zhisong

2016-05-01

A gyroscope structure with tailored local dispersion profile to enhance sensitivity is proposed, which uses lithium niobate (LiNbO3) thin film as the on-chip material of gyroscope's resonator. A Mach-Zehnder interferometer (MZI) structure as a coupler, which induces a different reference phase shift in each arm, is inserted into the position between ring resonator and output bus waveguide. Through modulating reference phase shift in MZI, theoretical rotation sensitivity enhancement as large as one order of magnitude is presented.

Time-dependent phase shift of a retrieved pulse in off-resonant electromagnetically-induced-transparency-based light storage

NASA Astrophysics Data System (ADS)

Maynard, M.-A.; Bouchez, R.; Lugani, J.; Bretenaker, F.; Goldfarb, F.; Brion, E.

2015-11-01

We report measurements of the time-dependent phases of the leak and retrieved pulses obtained in electromagnetically-induced-transparency storage experiments with metastable helium vapor at room temperature. In particular, we investigate the influence of the optical detuning at two-photon resonance and provide numerical simulations of the full dynamical Maxwell-Bloch equations, which allow us to account for the experimental results.

Rapid Adjustment of Circadian Clocks to Simulated Travel to Time Zones across the Globe.

PubMed

Harrison, Elizabeth M; Gorman, Michael R

2015-12-01

Daily rhythms in mammalian physiology and behavior are generated by a central pacemaker located in the hypothalamic suprachiasmatic nuclei (SCN), the timing of which is set by light from the environment. When the ambient light-dark cycle is shifted, as occurs with travel across time zones, the SCN and its output rhythms must reset or re-entrain their phases to match the new schedule-a sluggish process requiring about 1 day per hour shift. Using a global assay of circadian resetting to 6 equidistant time-zone meridians, we document this characteristically slow and distance-dependent resetting of Syrian hamsters under typical laboratory lighting conditions, which mimic summer day lengths. The circadian pacemaker, however, is additionally entrainable with respect to its waveform (i.e., the shape of the 24-h oscillation) allowing for tracking of seasonally varying day lengths. We here demonstrate an unprecedented, light exposure-based acceleration in phase resetting following 2 manipulations of circadian waveform. Adaptation of circadian waveforms to long winter nights (8 h light, 16 h dark) doubled the shift response in the first 3 days after the shift. Moreover, a bifurcated waveform induced by exposure to a novel 24-h light-dark-light-dark cycle permitted nearly instant resetting to phase shifts from 4 to 12 h in magnitude, representing a 71% reduction in the mismatch between the activity rhythm and the new photocycle. Thus, a marked enhancement of phase shifting can be induced via nonpharmacological, noninvasive manipulation of the circadian pacemaker waveform in a model species for mammalian circadian rhythmicity. Given the evidence of conserved flexibility in the human pacemaker waveform, these findings raise the promise of flexible resetting applicable to circadian disruption in shift workers, frequent time-zone travelers, and any individual forced to adjust to challenging schedules. © 2015 The Author(s).

Phase delaying the human circadian clock with a single light pulse and moderate delay of the sleep/dark episode: no influence of iris color.

PubMed

Canton, Jillian L; Smith, Mark R; Choi, Ho-Sun; Eastman, Charmane I

2009-07-17

Light exposure in the late evening and nighttime and a delay of the sleep/dark episode can phase delay the circadian clock. This study assessed the size of the phase delay produced by a single light pulse combined with a moderate delay of the sleep/dark episode for one day. Because iris color or race has been reported to influence light-induced melatonin suppression, and we have recently reported racial differences in free-running circadian period and circadian phase shifting in response to light pulses, we also tested for differences in the magnitude of the phase delay in subjects with blue and brown irises. Subjects (blue-eyed n = 7; brown eyed n = 6) maintained a regular sleep schedule for 1 week before coming to the laboratory for a baseline phase assessment, during which saliva was collected every 30 minutes to determine the time of the dim light melatonin onset (DLMO). Immediately following the baseline phase assessment, which ended 2 hours after baseline bedtime, subjects received a 2-hour bright light pulse (~4,000 lux). An 8-hour sleep episode followed the light pulse (i.e. was delayed 4 hours from baseline). A final phase assessment was conducted the subsequent night to determine the phase shift of the DLMO from the baseline to final phase assessment.Phase delays of the DLMO were compared in subjects with blue and brown irises. Iris color was also quantified from photographs using the three dimensions of red-green-blue color axes, as well as a lightness scale. These variables were correlated with phase shift of the DLMO, with the hypothesis that subjects with lighter irises would have larger phase delays. The average phase delay of the DLMO was -1.3 +/- 0.6 h, with a maximum delay of ~2 hours, and was similar for subjects with blue and brown irises. There were no significant correlations between any of the iris color variables and the magnitude of the phase delay. A single 2-hour bright light pulse combined with a moderate delay of the sleep/dark episode delayed the circadian clock an average of ~1.5 hours. There was no evidence that iris color influenced the magnitude of the phase shift. Future studies are needed to replicate our findings that iris color does not impact the magnitude of light-induced circadian phase shifts, and that the previously reported differences may be due to race.

Analytical results for a conditional phase shift between single-photon pulses in a nonlocal nonlinear medium

NASA Astrophysics Data System (ADS)

Viswanathan, Balakrishnan; Gea-Banacloche, Julio

2018-03-01

It has been suggested that second-order nonlinearities could be used for quantum logic at the single-photon level. Specifically, successive two-photon processes in principle could accomplish the phase shift (conditioned on the presence of two photons in the low-frequency modes) |011 〉→i |100 〉→-|011 〉 . We have analyzed a recent scheme proposed by Xia et al. [Phys. Rev. Lett. 116, 023601 (2016)], 10.1103/PhysRevLett.116.023601 to induce such a conditional phase shift between two single-photon pulses propagating at different speeds through a nonlinear medium with a nonlocal response. We present here an analytical solution for the most general case, i.e., for an arbitrary response function, initial state, and pulse velocity, which supports their numerical observation that a π phase shift with unit fidelity is possible, in principle, in an appropriate limit. We also discuss why this is possible in this system, despite the theoretical objections to the possibility of conditional phase shifts on single photons that were raised some time ago by Shapiro [Phys. Rev. A 73, 062305 (2006)], 10.1103/PhysRevA.73.062305 and by Gea-Banacloche [Phys. Rev. A 81, 043823 (2010)], 10.1103/PhysRevA.81.043823 one of us.

Retrieving plasmonic near-field information: A quantum-mechanical model for streaking photoelectron spectroscopy of gold nanospheres

NASA Astrophysics Data System (ADS)

Li, Jianxiong; Saydanzad, Erfan; Thumm, Uwe

2016-11-01

Streaked photoemission from nanostructures is characterized by size- and material-dependent nanometer-scale variations of the induced nanoplasmonic response to the electronic field of the streaking pulse and thus holds promise of allowing photoelectron imaging with both subfemtosecond temporal and nanometer spatial resolution. In order to scrutinize the driven collective electronic dynamics in 10-200-nm-diameter gold nanospheres, we calculated the plasmonic field induced by streaking pulses in the infrared and visible spectral range and developed a quantum-mechanical model for streaked photoemission by extreme ultraviolet pulses. Our simulated photoelectron spectra reveal a significant amplitude enhancement and phase shift of the photoelectron streaking trace relative to calculations that exclude the induced plasmonic field. Both are most pronounced for streaking pulses tuned to the plasmon frequency and retrace the plasmonic electromagnetic field enhancement and phase shift near the nanosphere surface.

Terahertz artificial birefringence and tunable phase shifter based on dielectric metasurface with compound lattice.

PubMed

Ji, Yun-Yun; Fan, Fei; Chen, Meng; Yang, Lei; Chang, Sheng-Jiang

2017-05-15

A dielectric metasurface with line-square compound lattice structure has been fabricated and demonstrated in the terahertz (THz) regime by the THz time-domain spectroscopy and numerical simulation. A polarization dependent electromagnetically induced transparency (EIT) effect is achieved in this metasurface due to the mode coupling and interference between the resonance modes in line and square subunits of the metasurface. Accompany with the EIT effect, a large artificial birefringence effect between two orthogonal polarization states is also observed in this compound metasurface, of which birefringence is over 0.6. Furthermore, the liquid crystals are filled on the surface of this dielectric metasurface to fabricate an electrically tunable THz LC phase shifter. The experimental results show that its tunable phase shift under the biased electric field reaches 0.33π, 1.8 times higher than the bare silicon, which confirms the enhancement role of THz microstructure on the LC phase shift in the THz regime. The large birefringence phase shift of this compound metasurface and its LC tunable phase shifter will be of great significance for potential applications in THz polarization and phase devices.

Optical DC overlay measurement in the 2nd level process of 65 nm alternating phase shift mask

NASA Astrophysics Data System (ADS)

Ma, Jian; Han, Ke; Lee, Kyung; Korobko, Yulia; Silva, Mary; Chavez, Joas; Irvine, Brian; Henrichs, Sven; Chakravorty, Kishore; Olshausen, Robert; Chandramouli, Mahesh; Mammen, Bobby; Padmanaban, Ramaswamy

2005-11-01

Alternating phase shift mask (APSM) techniques help bridge the significant gap between the lithography wavelength and the patterning of minimum features, specifically, the poly line of 35 nm gate length (1x) in Intel's 65 nm technology. One of key steps in making APSM mask is to pattern to within the design tolerances the 2nd level resist so that the zero-phase apertures will be protected by the resist and the pi-phase apertures will be wide open for quartz etch. The ability to align the 2nd level to the 1st level binary pattern, i.e. the 2nd level overlay capability is very important, so is the capability of measuring the overlay accurately. Poor overlay could cause so-called the encroachment after quartz etch, producing undesired quartz bumps in the pi-apertures or quartz pits in the zero-apertures. In this paper, a simple, low-cost optical setup for the 2nd level DC (develop check) overlay measurements in the high volume manufacturing (HVM) of APSM masks is presented. By removing systematic errors in overlay associated with TIS and MIS (tool-induced shift and Mask-process induced shift), it is shown that this setup is capable of supporting the measurement of DC overlay with a tolerance as small as +/- 25 nm. The outstanding issues, such as DC overlay error component analysis, DC - FC (final check) overlay correlation and the overlay linearity (periphery vs. indie), are discussed.

Filter-Based Phase Shifts Distort Neuronal Timing Information.

PubMed

Yael, Dorin; Vecht, Jacob J; Bar-Gad, Izhar

2018-01-01

Filters are widely used for the modulation, typically attenuation, of amplitudes of different frequencies within neurophysiological signals. Filters, however, also induce changes in the phases of different frequencies whose amplitude is unmodulated. These phase shifts cause time lags in the filtered signals, leading to a disruption of the timing information between different frequencies within the same signal and between different signals. The emerging time lags can be either constant in the case of linear phase (LP) filters or vary as a function of the frequency in the more common case of non-LP (NLP) filters. Since filters are used ubiquitously online in the early stages of data acquisition, the vast majority of neurophysiological signals thus suffer from distortion of the timing information even prior to their sampling. This distortion is often exacerbated by further multiple offline filtering stages of the sampled signal. The distortion of timing information may cause misinterpretation of the results and lead to erroneous conclusions. Here we present a variety of typical examples of filter-induced phase distortions and discuss the evaluation and restoration of the timing information underlying the original signal.

Filter-Based Phase Shifts Distort Neuronal Timing Information

PubMed Central

Yael, Dorin; Vecht, Jacob J.

2018-01-01

Filters are widely used for the modulation, typically attenuation, of amplitudes of different frequencies within neurophysiological signals. Filters, however, also induce changes in the phases of different frequencies whose amplitude is unmodulated. These phase shifts cause time lags in the filtered signals, leading to a disruption of the timing information between different frequencies within the same signal and between different signals. The emerging time lags can be either constant in the case of linear phase (LP) filters or vary as a function of the frequency in the more common case of non-LP (NLP) filters. Since filters are used ubiquitously online in the early stages of data acquisition, the vast majority of neurophysiological signals thus suffer from distortion of the timing information even prior to their sampling. This distortion is often exacerbated by further multiple offline filtering stages of the sampled signal. The distortion of timing information may cause misinterpretation of the results and lead to erroneous conclusions. Here we present a variety of typical examples of filter-induced phase distortions and discuss the evaluation and restoration of the timing information underlying the original signal. PMID:29766044

Can short-wavelength depleted bright light during single simulated night shifts prevent circadian phase shifts?

PubMed

Regente, J; de Zeeuw, J; Bes, F; Nowozin, C; Appelhoff, S; Wahnschaffe, A; Münch, M; Kunz, D

2017-05-01

In single night shifts, extending habitual wake episodes leads to sleep deprivation induced decrements of performance during the shift and re-adaptation effects the next day. We investigated whether short-wavelength depleted (=filtered) bright light (FBL) during a simulated night shift would counteract such effects. Twenty-four participants underwent a simulated night shift in dim light (DL) and in FBL. Reaction times, subjective sleepiness and salivary melatonin concentrations were assessed during both nights. Daytime sleep was recorded after both simulated night shifts. During FBL, we found no melatonin suppression compared to DL, but slightly faster reaction times in the second half of the night. Daytime sleep was not statistically different between both lighting conditions (n = 24) and there was no significant phase shift after FBL (n = 11). To conclude, our results showed positive effects from FBL during simulated single night shifts which need to be further tested with larger groups, in more applied studies and compared to standard lighting. Copyright © 2016 Elsevier Ltd. All rights reserved.

Multimode excitation-induced phase shifts in intrinsic Fabry-Perot interferometric fiber sensor spectra.

PubMed

Ma, Cheng; Wang, Anbo

2010-09-01

We report the modal analysis of optical fiber single-mode-multimode-single-mode intrinsic Fabry-Perot interferometer sensors. The multimode nature of the Fabry-Perot cavity gives rise to an additional phase term in the spectrogram due to intermodal dispersion-induced wavefront distortion, which could significantly affect the cavity length demodulation accuracy. By using an exact model to analyze the modal behavior, this phase term is explained by employing a rotating vector approach. Comparison of the theoretical analysis with experimental results is presented.

A method searching for optimum fractional order and its application in self-phase modulation induced nonlinear phase noise estimation in coherent optical fiber transmission systems

NASA Astrophysics Data System (ADS)

Huang, Chuan; Guo, Peng; Yang, Aiying; Qiao, Yaojun

2018-07-01

In single channel systems, the nonlinear phase noise only comes from the channel itself through self-phase modulation (SPM). In this paper, a fast-nonlinear effect estimation method is proposed based on fractional Fourier transformation (FrFT). The nonlinear phase noise caused by Self-phase modulation effect is accurately estimated for single model 10Gbaud OOK and RZ-QPSK signals with the fiber length range of 0-200 km and the launch power range of 1-10 mW. The pulse windowing is adopted to search the optimum fractional order for the OOK and RZ-QPSK signals. Since the nonlinear phase shift caused by the SPM effect is very small, the accurate optimum fractional order of the signal cannot be found based on the traditional method. In this paper, a new method magnifying the phase shift is proposed to get the accurate optimum order and thus the nonlinear phase shift is calculated. The simulation results agree with the theoretical analysis and the method is applicable to signals whose pulse type has the similar characteristics with Gaussian pulse.

Shift in Food Intake and Changes in Metabolic Regulation and Gene Expression during Simulated Night-Shift Work: A Rat Model

PubMed Central

Marti, Andrea Rørvik; Meerlo, Peter; Grønli, Janne; van Hasselt, Sjoerd Johan; Mrdalj, Jelena; Pallesen, Ståle; Pedersen, Torhild Thue; Henriksen, Tone Elise Gjøtterud; Skrede, Silje

2016-01-01

Night-shift work is linked to a shift in food intake toward the normal sleeping period, and to metabolic disturbance. We applied a rat model of night-shift work to assess the immediate effects of such a shift in food intake on metabolism. Male Wistar rats were subjected to 8 h of forced activity during their rest (ZT2-10) or active (ZT14-22) phase. Food intake, body weight, and body temperature were monitored across four work days and eight recovery days. Food intake gradually shifted toward rest-work hours, stabilizing on work day three. A subgroup of animals was euthanized after the third work session for analysis of metabolic gene expression in the liver by real-time polymerase chain reaction (PCR). Results show that work in the rest phase shifted food intake to rest-work hours. Moreover, liver genes related to energy storage and insulin metabolism were upregulated, and genes related to energy breakdown were downregulated compared to non-working time-matched controls. Both working groups lost weight during the protocol and regained weight during recovery, but animals that worked in the rest phase did not fully recover, even after eight days of recovery. In conclusion, three to four days of work in the rest phase is sufficient to induce disruption of several metabolic parameters, which requires more than eight days for full recovery. PMID:27834804

Application of constrained equilibrium thermodynamics to irradiated alloy systems

NASA Astrophysics Data System (ADS)

Holloway, James Paul; Stubbins, James F.

1984-05-01

Equilibrium thermodynamics are applied to systems with an excess of point defects to calculate the relative stability of phases. It is possible to model systems with supersaturation levels of vacancies and interstitials, such as those found under irradiation. The calculations reveal the extent to which phase compositional boundaries could shift when one phase or both in a two phase system contain an excess of point defects. Phase boundary shifts in the Ni-Si, Fe-Ni, Ni-Cr, and Fe-Cr systems are examined as a function of the number of excess defects in each phase. It is also found that the critical temperature of the sigma phase in the Fe-Cr system and the fcc-bcc transition in the Fe-Ni are sensitive to excess defect concentrations. These results may apply to local irradiation-induced phase transformations in the presence of solute segregation.

Collisional phase shifts of ring dark solitons in inhomogeneous Bose Einstein condensates

NASA Astrophysics Data System (ADS)

Peng, Ping; Li, Guan-Qiang; Xue, Ju-Kui

2007-06-01

The head-on collisions of two ring dark solitons in inhomogeneous Bose Einstein condensates (BECs) with thin disk-shaped potential are studied by the extended Poincaré Lighthill Kuo (PLK) perturbation method. The result shows that the system admits a solution with two concentric ring solitons, one moving inwards and the other moving outwards, which in small-amplitude limit, are described by two modified cylindrical KdV equations in the respective reference frames. In particular, the analytical phase shifts induced by the head-on collisions between two ring dark solitary waves are derived, and the result shows that the phase shifts change with the radial coordinate r according to the (1+σr)r law (where σ˜ωr2/ωz2), which are quite different with the homogeneous case.

Tuning the frequency of ultrashort laser pulses by a cross-phase-modulation-induced shift in a photonic crystal fiber.

PubMed

Konorov, S O; Akimov, D A; Zheltikov, A M; Ivanov, A A; Alfimov, M V; Scalora, M

2005-06-15

Femtosecond pulses of fundamental Cr:forsterite laser radiation are used as a pump field to tune the frequency of copropagating second-harmonic pulses of the same laser through cross-phase modulation in a photonic crystal fiber. Sub-100-kW femtosecond pump pulses coupled into a photonic crystal fiber with an appropriate dispersion profile can shift the central frequency of the probe field by more than 100 nm, suggesting a convenient way to control propagation and spectral transformations of ultrashort laser pulses.

Blood flow velocity measurement by endovascular Doppler optical coherence tomography

NASA Astrophysics Data System (ADS)

Sun, Cuiru; Nolte, Felix; Vuong, Barry; Cheng, Kyle H. Y.; Lee, Kenneth K. C.; Standish, Beau A.; Courtney, Brian; Marotta, Tom R.; Yang, Victor X. D.

2013-03-01

Blood flow velocity and volumetric flow measurements are important parameters for assessment of the severity of stenosis and the outcome of interventional therapy. However, feasibility of intravascular flow measurement using a rotational catheter based phase resolved Doppler optical coherence tomography (DOCT) is difficult. Motion artefacts induced by the rotating optical imaging catheter, and the radially dependent noise background of measured Doppler signals are the main challenges encountered. In this study, a custom-made data acquisition system and developed algorithms to remove non-uniform rotational distortion (NURD) induced phase shift artefact by tracking the phase shift observed on catheter sheath. The flow velocity is calculated from Doppler shift obtained by Kasai autocorrelation after motion artefact removal. Blood flow velocity profiles in porcine carotid arteries in vivo were obtained at 100 frames/s with 500 A-lines/frame and DOCT images were taken at 20 frames/s with 2500 A-lines/frame. Time-varying velocity profiles were obtained at an artery branch. Furthermore, the identification of a vein adjacent to the catheterized vessel based on the color Doppler signal was also observed. The absolute measurement of intravascular flow using a rotating fiber catheter can provide insights to different stages of interventional treatment of stenosis in carotid artery.

Modulation of cochlear responses in the guinea pig by low-frequency, phase-shifted maskers following noise trauma.

PubMed

Hoehmann, D; Müller, S; Dornhoffer, J L

1995-01-01

Low-frequency acoustic biasing using an intensive phase-shifted, low-frequency masker was studied according to its ability to determine disorders of cochlear micromechanics following noise trauma in the guinea pig as animal model. Statistical analyses proved that this technique allowed electrophysiological differentiation of controls versus groups with different degrees of experimentally induced threshold shifts. To substantiate group differences an intensity of at least 70 dB SPL was required for the 52 Hz masker and the difference in relation to the test-tone intensity had to be +/- 10 or +/- 20 dB SPL. The noise-traumatized cochlea could be identified by means of a threshold shift for the 5 microV pseudothreshold, a low modulation span of the compound action potential amplitude (< 25-50 microV frequency dependent), and reduced positive summating potential amplitude with negative non-modulating values within the different measurement phases for 1 and 2 kHz stimulation.

Retrieving plasmonic field information from metallic nanospheres using attosecond photoelectron streaking spectroscopy

NASA Astrophysics Data System (ADS)

Li, Jianxiong; Saydanzad, Erfan; Thumm, Uwe

2017-04-01

Streaked photoemission by attosecond extreme ultraviolet (XUV) pulses into an infrared (IR) or visible streaking pulse, holds promise for imaging with sub-fs time resolution the dielectric plasmonic response of metallic nanoparticles to the IR or visible streaking pulse. We calculated the plasmonic field induced by streaking pulses for 10 to 200 nm diameter Au, Ag, and Cu nanospheres and obtained streaked photoelectron spectra by employing our quantum-mechanical model. Our simulated spectra show significant oscillation-amplitude enhancements and phase shifts for all three metals (relative to spectra that are calculated without including the induced plasmonic field) and allow the reconstruction of the plasmonic field enhancements and phase shifts for each material. Supported by the US NSD-EPSCoR program, NSF, and DoE.

Influence of Pressure on Physical Property of Ammonia Borane and its Re-hydrogenation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Jiuhua

The project systematically studied the high pressure behavior of ammonia borane and its derivative lithium amidoborane. Phase transitions in these materials are investigated in the pressure range up to 20 GPa and temperature range from 80 K to 400K. A number of new phase transitions are discovered in this pressure and temperature range including a second order transformation at 5 GPa and a first order transformation at 12 GPa at room temperature, and four new transitions at high pressure and low temperatures. The Clapeyron slopes for both pressure-induce tetragonal (I4mm) phase to orthorhombic (Cmc21) phase and temperature-induce tetragonal (I4mm) phasemore » to orthorhombic (Pmn21) phase are determined to be positive, indicating these phase transitions are exothermic. This result demonstrates that the high pressure orthorhombic phase of ammonia borane has lower enthalpy than that of tetragonal phase at ambient conditions. If we assume decomposition from the orthorhombic phase yields the same products as that from the tetragonal phase, the decomposition of the orthorhombic phase will be less exothermic. Therefore rehydrogenation from the decomposed product into the orthorhombic phase at high pressure may become easier. The project also studied the influences of nanoconfinement on the phase transitions. Comparative study using Raman spectroscopy indicates that the temperature induced I4mm to Pmn21 transition is suppressed from 217 K to 195 K when the sample is confined in SBA15 (7-9 nm pore size). When the pore size is reduced from 7-9 nm to 3-4 nm, this transition is totally suppressed in the temperature down to 80 K. A similar influence of the nanoconfiement on pressure induced phase transitions is also observed using Raman spectroscopy. The phase boundary between the I4mm phase and high pressure Cmc21 phase at ambient temperature shifts from 0.9 GPa to 0.5 GPa; and that between the Cmc21 phase and higher pressure P21 phase shifts from 10.2 GPa to 9.7 GPa.« less

Laser-induced separation of hydrogen isotopes in the liquid phase

DOEpatents

Freund, Samuel M.; Maier, II, William B.; Beattie, Willard H.; Holland, Redus F.

1980-01-01

Hydrogen isotope separation is achieved by either (a) dissolving a hydrogen-bearing feedstock compound in a liquid solvent, or (b) liquefying a hydrogen-bearing feedstock compound, the liquid phase thus resulting being kept at a temperature at which spectral features of the feedstock relating to a particular hydrogen isotope are resolved, i.e., a clear-cut isotope shift is delineated, irradiating the liquid phase with monochromatic radiation of a wavelength which at least preferentially excites those molecules of the feedstock containing a first hydrogen isotope, inducing photochemical reaction in the excited molecules, and separating the reaction product containing the first isotope from the liquid phase.

Two-phase charge-coupled device

NASA Technical Reports Server (NTRS)

Kosonocky, W. F.; Carnes, J. E.

1973-01-01

A charge-transfer efficiency of 99.99% per stage was achieved in the fat-zero mode of operation of 64- and 128-stage two-phase charge-coupled shift registers at 1.0-MHz clock frequency. The experimental two-phase charge-coupled shift registers were constructed in the form of polysilicon gates overlapped by aluminum gates. The unidirectional signal flow was accomplished by using n-type substrates with 0.5 to 1.0 ohm-cm resistivity in conjunction with a channel oxide thickness of 1000 A for the polysilicon gates and 3000 A for the aluminum gates. The operation of the tested shift registers with fat zero is in good agreement with the free-charge transfer characteristics expected for the tested structures. The charge-transfer losses observed when operating the experimental shift registers without the fat zero are attributed to fast interface state trapping. The analytical part of the report contains a review backed up by an extensive appendix of the free-charge transfer characteristics of CCD's in terms of thermal diffusion, self-induced drift, and fringing field drift. Also, a model was developed for the charge-transfer losses resulting from charge trapping by fast interface states. The proposed model was verified by the operation of the experimental two-phase charge-coupled shift registers.

Influence of Oil Saturation Upon Spectral Induced Polarization of Oil Bearing Sands

EPA Science Inventory

The presence of oil in an unconsolidated granular porous material such as sand changes both the resistivity of the material and the value of the phase shift between the low-frequency current and the voltage. The resistivity and the phase angle can be written as a complex-valued r...

Relativistic Quark Model Based Description of Low Energy NN Scattering

NASA Astrophysics Data System (ADS)

Antalik, R.; Lyubovitskij, V. E.

A model describing the NN scattering phase shifts is developed. Two nucleon interactions induced by meson exchange forces are constructed starting from π, η, η‧ pseudoscalar-, the ρ, ϕ, ω vector-, and the ɛ(600), a0, f0(1400) scalar — meson-nucleon coupling constants, which we obtained within a relativistic quantum field theory based quark model. Working within the Blankenbecler-Sugar-Logunov-Tavkhelidze quasipotential dynamics, we describe the NN phase shifts in a relativistically invariant way. In this procedure we use phenomenological form factor cutoff masses and effective ɛ and ω meson-nucleon coupling constants, only. Resulting NN phase shifts are in a good agreement with both, the empirical data, and the entirely phenomenological Bonn OBEP model fit. While the quality of our description, evaluated as a ratio of our results to the Bonn OBEP model χ2 ones is about 1.2, other existing (semi)microscopic results gave qualitative results only.

Cross-phase-modulation-induced instability in photonic-crystal fibers.

PubMed

Serebryannikov, E E; Konorov, S O; Ivanov, A A; Alfimov, M V; Scalora, M; Zheltikov, A M

2005-08-01

Cross-phase-modulation-induced instability is identified as a significant mechanism for efficient parametric four-wave-mixing frequency conversion in photonic-crystal fibers. Fundamental-wavelength femtosecond pulses of a Cr, forsterite laser are used in our experiments to transform the spectrum of copropagating second-harmonic pulses of the same laser in a photonic-crystal fiber. Efficient generation of sidebands shifted by more than 80 THz with respect to the central frequency of the second harmonic is observed in the output spectrum of the probe field.

Circadian waveform bifurcation, but not phase-shifting, leaves cued fear memory intact.

PubMed

Harrison, E M; Carmack, S A; Block, C L; Sun, J; Anagnostaras, S G; Gorman, M R

2017-02-01

In mammals, memory acquisition and retrieval can be affected by time of day, as well as by manipulations of the light/dark cycle. Under bifurcation, a manipulation of circadian waveform, two subjective days and nights are experimentally induced in rodents. We examined the effect of bifurcation on Pavlovian fear conditioning, a prominent model of learning and memory. Here we demonstrate that bifurcation of the circadian waveform produces a small deficit in acquisition, but not on retrieval of fear memory. In contrast, repeated phase-shifting in a simulated jet-lag protocol impairs retrieval of memory for cued fear. The results have implications for those attempting to adjust to shift-work or other challenging schedules. Copyright © 2016 Elsevier Inc. All rights reserved.

Performance improvement of coherent free-space optical communication with quadrature phase-shift keying modulation using digital phase estimation.

PubMed

Li, Xueliang; Geng, Tianwen; Ma, Shuang; Li, Yatian; Gao, Shijie; Wu, Zhiyong

2017-06-01

The performance of coherent free-space optical (CFSO) communication with phase modulation is limited by both phase fluctuations and intensity scintillations induced by atmospheric turbulence. To improve the system performance, one effective way is to use digital phase estimation. In this paper, a CFSO communication system with quadrature phase-shift keying modulation is studied. With consideration of the effects of log-normal amplitude fluctuations and Gauss phase fluctuations, a two-stage Mth power carrier phase estimation (CPE) scheme is proposed. The simulation results show that the phase noise can be suppressed greatly by this scheme, and the system symbol error rate performance with the two-stage Mth power CPE can be three orders lower than that of the single-stage Mth power CPE. Therefore, the two-stage CPE we proposed can contribute to the performance improvements of the CFSO communication system and has determinate guidance sense to its actual application.

ac Stark-mediated quantum control with femtosecond two-color laser pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Serrat, Carles

2005-11-15

A critical dependence of the quantum interference on the optical Stark spectral shift produced when two-color laser pulses interact with a two-level medium is observed. The four-wave mixing of two ultrashort phase-locked {omega}-3{omega} laser pulses propagating coherently in a two-level system depends on the pulses' relative phase. The phase dominating the efficiency of the coupling to the anti-Stokes Raman component is found to be determined by the sign of the total ac Stark shift induced in the system, in such a way that the phase sensitivity disappears precisely where the ac Stark effect due to both pulses is compensated. Amore » coherent control scheme based on this phenomenon can be contemplated as the basis for nonlinear optical spectroscopy techniques.« less

Effect of gravitational focusing on annual modulation in dark-matter direct-detection experiments.

PubMed

Lee, Samuel K; Lisanti, Mariangela; Peter, Annika H G; Safdi, Benjamin R

2014-01-10

The scattering rate in dark-matter direct-detection experiments should modulate annually due to Earth's orbit around the Sun. The rate is typically thought to be extremized around June 1, when the relative velocity of Earth with respect to the dark-matter wind is maximal. We point out that gravitational focusing can alter this modulation phase. Unbound dark-matter particles are focused by the Sun's gravitational potential, affecting their phase-space density in the lab frame. Gravitational focusing can result in a significant overall shift in the annual-modulation phase, which is most relevant for dark matter with low scattering speeds. The induced phase shift for light O(10)  GeV dark matter may also be significant, depending on the threshold energy of the experiment.

Carrier-separating demodulation of phase shifting self-mixing interferometry

NASA Astrophysics Data System (ADS)

Tao, Yufeng; Wang, Ming; Xia, Wei

2017-03-01

A carrier separating method associated with noise-elimination had been introduced into a sinusoidal phase-shifting self-mixing interferometer. The conventional sinusoidal phase shifting self-mixing interferometry was developed into a more competitive instrument with high computing efficiency and nanometer accuracy of λ / 100 in dynamical vibration measurement. The high slew rate electro-optic modulator induced a sinusoidal phase carrier with ultralow insertion loss in this paper. In order to extract phase-shift quickly and precisely, this paper employed the carrier-separating to directly generate quadrature signals without complicated frequency domain transforms. Moreover, most noises were evaluated and suppressed by a noise-elimination technology synthesizing empirical mode decomposition with wavelet transform. The overall laser system was described and inherent advantages such as high computational efficiency and decreased nonlinear errors of the established system were demonstrated. The experiment implemented on a high precision PZT (positioning accuracy was better than 1 nm) and compared with laser Doppler velocity meter. The good agreement of two instruments shown that the short-term resolution had improved from 10 nm to 1.5 nm in dynamic vibration measurement with reduced time expense. This was useful in precision measurement to improve the SMI with same sampling rate. The proposed signal processing was performed in pure time-domain requiring no preprocessing electronic circuits.

Stability Properties and Cross Coupling Performance of the Control Allocation Scheme CAPIO

NASA Technical Reports Server (NTRS)

Yildiz, Yildiray; Kolmanovsky, Ilya V.

2010-01-01

This paper presents a stability analysis and an application of a recently developed Control Allocator for recovery from Pilot Induced Oscillations (CAPIO). When actuators are rate-saturated due to either aggressive pilot commands, high gain ight control systems or some anomaly in the system, the effective delay in the control loop may increase. This effective delay increase manifests itself as a phase shift between the commanded and actual system signals and can instigate Pilot induced Oscillations (PIO). CAPIO reduces the e ective time delay by minimizing the phase shift between the commanded and the actual attitude accelerations. We present a stability analysis of CAPIO for a scalar system. In addition, we present simulation results for aircraft with cross-coupling which demonstrates the potential of CAPIO serving as an effective PIO handler in adverse conditions.

Combination of light and melatonin time cues for phase advancing the human circadian clock.

PubMed

Burke, Tina M; Markwald, Rachel R; Chinoy, Evan D; Snider, Jesse A; Bessman, Sara C; Jung, Christopher M; Wright, Kenneth P

2013-11-01

Photic and non-photic stimuli have been shown to shift the phase of the human circadian clock. We examined how photic and non-photic time cues may be combined by the human circadian system by assessing the phase advancing effects of one evening dose of exogenous melatonin, alone and in combination with one session of morning bright light exposure. Randomized placebo-controlled double-blind circadian protocol. The effects of four conditions, dim light (∼1.9 lux, ∼0.6 Watts/m(2))-placebo, dim light-melatonin (5 mg), bright light (∼3000 lux, ∼7 Watts/m(2))-placebo, and bright light-melatonin on circadian phase was assessed by the change in the salivary dim light melatonin onset (DLMO) prior to and following treatment under constant routine conditions. Melatonin or placebo was administered 5.75 h prior to habitual bedtime and 3 h of bright light exposure started 1 h prior to habitual wake time. Sleep and chronobiology laboratory environment free of time cues. Thirty-six healthy participants (18 females) aged 22 ± 4 y (mean ± SD). Morning bright light combined with early evening exogenous melatonin induced a greater phase advance of the DLMO than either treatment alone. Bright light alone and melatonin alone induced similar phase advances. Information from light and melatonin appear to be combined by the human circadian clock. The ability to combine circadian time cues has important implications for understanding fundamental physiological principles of the human circadian timing system. Knowledge of such principles is important for designing effective countermeasures for phase-shifting the human circadian clock to adapt to jet lag, shift work, and for designing effective treatments for circadian sleep-wakefulness disorders.

Hand held phase-shifting diffraction moire interferometer

DOEpatents

Deason, Vance A.; Ward, Michael B.

1994-01-01

An interferometer in which a coherent beam of light is generated within a remote case and transmitted to a hand held unit tethered to said remote case, said hand held unit having optical elements for directing a pair of mutually coherent collimated laser beams at a diffraction grating. Data from the secondary or diffracted beams are then transmitted to a separate video and data acquisition system for recording and analysis for load induced deformation or for identification purposes. Means are also provided for shifting the phase of one incident beam relative to the other incident beam and being controlled from within said remote case.

Suprachiasmatic astrocytes modulate the circadian clock in response to TNF-α1

PubMed Central

Duhart, José M.; Leone, María Juliana; Paladino, Natalia; Evans, Jennifer A.; Castanon-Cervantes, Oscar; Davidson, Alec J.; Golombek, Diego A.

2013-01-01

The immune and the circadian systems interact in a bidirectional fashion. The master circadian oscillator, located in the suprachiasmatic nuclei of the hypothalamus (SCN), responds to peripheral and local immune stimuli, such as proinflammatory cytokines and bacterial endotoxin. Astrocytes exert several immune functions in the central nervous system and there is growing evidence that points towards a role of these cells in the regulation of circadian rhythms. The aim of this work was to assess the response of SCN astrocytes to immune stimuli, particularly to the proinflammatory cytokine TNF-α. TNF-α applied to cultures of SCN astrocytes from Per2luc knock in mice altered both the phase and amplitude of PER2 expression rhythms, in a phase dependent manner. Furthermore, conditioned media from SCN astrocytes cultures transiently challenged with TNF-α induced an increase in Per1 expression in NIH 3T3 cells, that was blocked by TNF-α antagonism. In addition, these conditioned media could induce phase shifts in SCN PER2 rhythms and, when administered intracerebroventricularly, induced phase delays in behavioral circadian rhythms and SCN activation in control mice, but not in TNF-Receptor-1 mutants. In summary, our results show that TNF-α modulates the molecular clock of SCN astrocytes in vitro and also that, in response to this molecule, SCN astrocytes can modulate clock gene expression in other cells and tissues, and induce phase shifts in a circadian behavioral output in vivo. These findings suggest a role for astroglial cells in the alteration of circadian timing by immune activation. PMID:24062487

Surface characterization of hydrogen charged and uncharged alpha-2 and gamma titanium aluminide alloys using AES and REELS

NASA Technical Reports Server (NTRS)

Shanabarger, M. R.

1990-01-01

The surfaces of selected uncharged and hydrogen charged alpha-2 and gamma titanium aluminide alloys with Nb additions were characterized by Auger electron (AES) and reflected electron energy loss (REELS) spectroscopy. The alloy surfaces were cleaned before analysis at room temperature by ion sputtering. The low energy (500 eV) ion sputtering process preferentially sputtered the surface concentration. The surface concentrations were determined by comparing AES data from the alloys with corresponding data from elemental references. No differences were observed in the Ti or Nb Auger spectra for the uncharged and hydrogen charged alloys, even though the alpha-2 alloy had 33.4 atomic percent dissolved hydrogen. Also, no differences were observed in the AES spectra when hydrogen was adsorbed from the gas phase. Bulk plasmon energy shifts were observed in all alloys. The energy shifts were induced either by dissolved hydrogen (alpha-2 alloy) or hydrogen adsorbed from the gas phase (alpha-2 and gamma alloys). The adsorption induced plasmon energy shifts were greatest for the gamma alloy and cp-Ti metal.

Circadian Periods of Sensitivity for Ramelteon on the onset of Running-wheel Activity and the Peak of Suprachiasmatic Nucleus Neuronal Firing Rhythms in C3H/HeN Mice

PubMed Central

Rawashdeh, Oliver; Hudson, Randall L.; Stepien, Iwona; Dubocovich, Margarita L.

2016-01-01

Ramelteon, an MT1/MT2 melatonin receptor agonist, is used for the treatment of sleep-onset insomnia and circadian sleep disorders. Ramelteon phase shifts circadian rhythms in rodents and humans when given at the end of the subjective day; however, its efficacy at other circadian times is not known. Here, the authors determined in C3H/ HeN mice the maximal circadian sensitivity for ramelteon in vivo on the onset of circadian running-wheel activity rhythms, and in vitro on the peak of circadian rhythm of neuronal firing in suprachiasmatic nucleus (SCN) brain slices. The phase response curve (PRC) for ramelteon (90 μg/mouse, subcutaneous [sc]) on circadian wheel-activity rhythms shows maximal sensitivity during the late mid to end of the subjective day, between CT8 and CT12 (phase advance), and late subjective night and early subjective day, between CT20 and CT2 (phase delay), using a 3-day-pulse treatment regimen in C3H/HeN mice. The PRC for ramelteon resembles that for melatonin in C3H/ HeN mice, showing the same magnitude of maximal shifts at CT10 and CT2, except that the range of sensitivity for ramelteon (CT8–CT12) during the subjective day is broader. Furthermore, in SCN brain slices in vitro, ramelteon (10 pM) administered at CT10 phase advances (5.6 ± 0.29 h, n = 3) and at CT2 phase delays (−3.2 ± 0.12 h, n = 6) the peak of circadian rhythm of neuronal firing, with the shifts being significantly larger than those induced by melatonin (10 pM) at the same circadian times (CT10: 2.7 ± 0.15 h, n = 4, p < .05; CT2: −1.13 ± 0.08 h, n = 6, p < .001, respectively). The phase shifts induced by both melatonin and ramelteon in the SCN brain slice at either CT10 or CT2 corresponded with the period of sensitivity observed in vivo. In conclusion, melatonin and ramelteon showed identical periods of circadian sensitivity at CT10 (advance) and CT2 (delay) to shift the onset of circadian activity rhythms in vivo and the peak of SCN neuronal firing rhythms in vitro. PMID:21182402

Polymorphism of POPE/cholesterol system: a 2H nuclear magnetic resonance and infrared spectroscopic investigation.

PubMed Central

Paré, C; Lafleur, M

1998-01-01

It is well established that cholesterol induces the formation of a liquid-ordered phase in phosphatidylcholine (PC) bilayers. The goal of this work is to examine the influence of cholesterol on phosphatidylethanolamine polymorphism. The behavior of 1-palmitoyl-2-oleoyl-phosphatidylethanolamine (POPE)/cholesterol mixtures was characterized using infrared and 2H nuclear magnetic resonance (NMR) spectroscopy (using POPE bearing a perdeuterated palmitoyl chain in the latter case). Our results reveal that cholesterol induces the formation of a liquid-ordered phase in POPE membranes, similar to those observed for various PC/cholesterol systems. However, the coexistence region of the gel and the liquid-ordered phases is different from that proposed for PC/cholesterol systems. The results indicate a progressive broadening of the gel-to-fluid phase transition, suggesting the absence of an eutectic. In addition, there is a progressive downshift of the end of the transition for cholesterol content higher than 10 mol %. Cholesterol has an ordering effect on the acyl chains of POPE, but it is less pronounced than for the PC equivalent. This study also shows that the cholesterol effect on the lamellar-to-hexagonal (L(alpha)-H(II)) phase transition is not monotonous. It shifts the transition toward the low temperatures between 0 and 30 mol % cholesterol but shifts it toward the high temperatures when cholesterol content is higher than 30 mol %. The change in conformational order of the lipid acyl chains, as probed by the shift of the symmetric methylene C-H stretching, shows concerted variations. Finally, we show that cholesterol maintains its chain ordering effect in the hexagonal phase. PMID:9533701

Simple and robust referencing system enables identification of dissolved-phase xenon spectral frequencies.

PubMed

Antonacci, Michael A; Zhang, Le; Burant, Alex; McCallister, Drew; Branca, Rosa T

2018-08-01

To assess the effect of macroscopic susceptibility gradients on the gas-phase referenced dissolved-phase 129 Xe (DPXe) chemical shift (CS) and to establish the robustness of a water-based referencing system for in vivo DPXe spectra. Frequency shifts induced by spatially varying magnetic susceptibility are calculated by finite-element analysis for the human head and chest. Their effect on traditional gas-phase referenced DPXe CS is then assessed theoretically and experimentally. A water-based referencing system for the DPXe resonances that uses the local water protons as reference is proposed and demonstrated in vivo in rats. Across the human brain, macroscopic susceptibility gradients can induce an apparent variation in the DPXe CS of up to 2.5 ppm. An additional frequency shift as large as 6.5 ppm can exist between DPXe and gas-phase resonances. By using nearby water protons as reference for the DPXe CS, the effect of macroscopic susceptibility gradients is eliminated and consistent CS values are obtained in vivo, regardless of shimming conditions, region of interest analyzed, animal orientation, or lung inflation. Combining in vitro and in vivo spectroscopic measurements finally enables confident assignment of some of the DPXe peaks observed in vivo. To use hyperpolarized xenon as a biological probe in tissues, the DPXe CS in specific organs/tissues must be reliably measured. When the gas-phase is used as reference, variable CS values are obtained for DPXe resonances. Reliable peak assignments in DPXe spectra can be obtained by using local water protons as reference. Magn Reson Med 80:431-441, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Behavioral transitions induced by speed and noise in animal aggregates

NASA Astrophysics Data System (ADS)

Cambui, Dorílson S.; Iliass, Tarras

2017-04-01

In this paper, we used a self-propelled particle model to study the transition between phases of collective behavior observed in animal aggregates. In these systems, transitions occur when individuals shift from one collective state to another. We investigated transitions induced by both the speed and the noise. Statistical quantities that characterize the phase transition driven by noise, such as order parameter, the Binder cumulant and the susceptibility were analyzed, and we used the finite-size scaling theory to estimate the critical exponent ratios β/ν and γ/ν.

Frequency modulation of high-order harmonic generation in an orthogonally polarized two-color laser field.

PubMed

Li, Guicun; Zheng, Yinghui; Ge, Xiaochun; Zeng, Zhinan; Li, Ruxin

2016-08-08

We have experimentally investigated the frequency modulation of high-order harmonics in an orthogonally polarized two-color laser field consisting of a mid-infrared 1800nm fundamental pulse and its second harmonic pulse. It is demonstrated that the high harmonic spectra can be fine-tuned as we slightly change the relative delay of the two-color laser pulses. By analyzing the relative frequency shift of each harmonic at different two-color delays, the nonadiabatic spectral shift induced by the rapid variation of the intensity-dependent intrinsic dipole phase can be distinguished from the blueshift induced by the change of the refractive index during self-phase modulation (SPM). Our comprehensive analysis shows that the frequency modulation pattern is a reflection of the average emission time of high-order harmonic generation (HHG), thus offering a simple method to fine-tune the spectra of the harmonics on a sub-cycle time scale.

Analysis of all-optical temporal integrator employing phased-shifted DFB-SOA.

PubMed

Jia, Xin-Hong; Ji, Xiao-Ling; Xu, Cong; Wang, Zi-Nan; Zhang, Wei-Li

2014-11-17

All-optical temporal integrator using phase-shifted distributed-feedback semiconductor optical amplifier (DFB-SOA) is investigated. The influences of system parameters on its energy transmittance and integration error are explored in detail. The numerical analysis shows that, enhanced energy transmittance and integration time window can be simultaneously achieved by increased injected current in the vicinity of lasing threshold. We find that the range of input pulse-width with lower integration error is highly sensitive to the injected optical power, due to gain saturation and induced detuning deviation mechanism. The initial frequency detuning should also be carefully chosen to suppress the integration deviation with ideal waveform output.

Hand held phase-shifting diffraction Moire interferometer

DOEpatents

Deason, V.A.; Ward, M.B.

1994-09-20

An interferometer is described in which a coherent beam of light is generated within a remote case and transmitted to a hand held unit tethered to said remote case, said hand held unit having optical elements for directing a pair of mutually coherent collimated laser beams at a diffraction grating. Data from the secondary or diffracted beams are then transmitted to a separate video and data acquisition system for recording and analysis for load induced deformation or for identification purposes. Means are also provided for shifting the phase of one incident beam relative to the other incident beam and being controlled from within said remote case. 4 figs.

Laboratory-based x-ray phase-contrast tomography enables 3D virtual histology

NASA Astrophysics Data System (ADS)

Töpperwien, Mareike; Krenkel, Martin; Quade, Felix; Salditt, Tim

2016-09-01

Due to the large penetration depth and small wavelength hard x-rays offer a unique potential for 3D biomedical and biological imaging, combining capabilities of high resolution and large sample volume. However, in classical absorption-based computed tomography, soft tissue only shows a weak contrast, limiting the actual resolution. With the advent of phase-contrast methods, the much stronger phase shift induced by the sample can now be exploited. For high resolution, free space propagation behind the sample is particularly well suited to make the phase shift visible. Contrast formation is based on the self-interference of the transmitted beam, resulting in object-induced intensity modulations in the detector plane. As this method requires a sufficiently high degree of spatial coherence, it was since long perceived as a synchrotron-based imaging technique. In this contribution we show that by combination of high brightness liquid-metal jet microfocus sources and suitable sample preparation techniques, as well as optimized geometry, detection and phase retrieval, excellent three-dimensional image quality can be obtained, revealing the anatomy of a cobweb spider in high detail. This opens up new opportunities for 3D virtual histology of small organisms. Importantly, the image quality is finally augmented to a level accessible to automatic 3D segmentation.

Entrainment and phase-shifting by centrifugation abolished in mice lacking functional vestibular input

NASA Astrophysics Data System (ADS)

Fuller, Charles; Ringgold, Kristyn

The circadian pacemaker can be phase shifted and entrained by appropriately timed locomotor activity, however the mechanism(s) involved remain poorly understood. Recent work in our lab has suggested the involvement of the vestibular otolith organs in activity-induced changes within the circadian timing system (CTS). For example, we have shown that changes in circa-dian period and phase in response to locomotion (wheel running) require functional macular gravity receptors. We believe the neurovestibular system is responsible for the transduction of gravitoinertial input associated with the types of locomotor activity that are known to af-fect the pacemaker. This study investigated the hypothesis that daily, timed gravitoinertial stimuli, as applied by centrifugation. would induce entrainment of circadian rhythms in only those animals with functional afferent vestibular input. To test this hypothesis, , chemically labyrinthectomized (Labx) mice, mice lacking macular vestibular input (head tilt or hets) and wildtype (WT) littermates were implanted i.p. with biotelemetry and individually housed in a 4-meter diameter centrifuge in constant darkness (DD). After 2 weeks in DD, the mice were exposed daily to 2G via centrifugation from 1000-1200 for 9 weeks. Only WT mice showed entrainment to the daily 2G pulse. The 2G pulse was then re-set to occur at 1200-1400 for 4 weeks. Only WT mice demonstrated a phase shift in response to the re-setting of the 2G pulse and subsequent re-entrainment to the new centrifugation schedule. These results provide further evidence that gravitoinertial stimuli require a functional vestibular system to both en-train and phase shift the CTS. Entrainment among only WT mice supports the role of macular gravity receptive cells in modulation of the CTS while also providing a functional mechanism by which gravitoinertial stimuli, including locomotor activity, may affect the pacemaker.

Inducing jet-lag in older people: directional asymmetry

NASA Technical Reports Server (NTRS)

Monk, T. H.; Buysse, D. J.; Carrier, J.; Kupfer, D. J.

2000-01-01

Twenty healthy elderly subjects (12 female, 8 male; mean age 81 years, range 67-87 years) each experienced a 15-day time isolation protocol in which they lived individually in a special laboratory apartment in which sleep and circadian rhythm measures could be taken. There were two experiments: one (6 females, 4 males) involved a 6-h phase advance of the sleep/wake cycle, and the other (6 females, 4 males) a 6-h phase delay. Each started with 5 baseline days, immediately followed by the phase shift. The subject was then held to the phase shifted routine for the remainder of the study. Rectal temperatures were recorded minute-by-minute throughout the entire experiment and each night of sleep was recorded using polysomnography. A directional asymmetry in phase-shift effects was apparent, with significantly more sleep disruption and circadian rhythm amplitude disruption after the phase advance than after the phase delay. Sleep disruption was reflected in reduced time spent asleep, and in changed REM latency, which increased in the phase advance direction but decreased in the phase delay direction. Although the phase advance led to a significant increase in wakefulness in the first half of the night, the phase delay did not lead to an equivalent increase in wakefulness during the second half of the night. Examination of both raw and 'demasked' circadian rectal temperature rhythms confirmed that phase adjustment was slow in both directions, but was less slow (and more monotonic) after the phase delay than after the phase advance. Subjective alertness suffered more disruption after the phase advance than after the phase delay.

The detection of chronic cerebral hemorrhage in rabbits with magnetic induction

NASA Astrophysics Data System (ADS)

Sun, Jian; Jin, Gui; Qin, Mingxin; Wan, Zibing; Wang, Jinbao; ChaoWang; Guo, Wanyou; Xu, Lin; Ning, Xu; Xu, Jia; Pu, Xianjie; Chen, Mingsheng; Zhao, Hongmei

2012-12-01

Chronic cerebral hemorrhage (CCH) in the brain is an important clinical problem that is often monitored and studied with expensive devices such as MRI and PET, which are not readily available in low economical resource parts of the world. We have developed a less expensive tool for non-contact monitoring of CCH in the brain. The system measures the phase shift between the electromagnetic signals on the two coils. CCH was induced in the brain of rabbits by stereotactic method. Intracranial pressure (ICP) and Electrocardiograph (ECG) of subjects were monitored for 1.5h. Signals were continuously monitored up to t=1.5h at exciting frequency 10.7MHz. From 0.8 to 2.4 ml of autologous blood was injected (each injection quantity of 0.8 ml, the interval time for 30 minutes). The results show significant phase shifts increase as a function of injection volume. ICP and phase shift were directly proportional to the related, while HRV were stable around 200beats*min-1. Our system has high sensitivity that even 0.8 ml can also be detected. In this study, the curves of inductive phase shift are significantly related to ICP. This observation suggests that the method could be valuable, in addition to continuous monitoring, also for early warning in emergency medicine and critical care units.

Cortico-pontine theta carrier frequency phase shift across sleep/wake states following monoaminergic lesion in rat.

PubMed

Kalauzi, Aleksandar; Spasic, Sladjana; Petrovic, Jelena; Ciric, Jelena; Saponjic, Jelena

2012-06-01

This study was aimed to explore the sleep/wake states related cortico-pontine theta carrier frequency phase shift following a systemically induced chemical axotomy of the monoaminergic afferents within a brain of the freely moving rats. Our experiments were performed in 14 adult, male Sprague Dawley rats, chronically implanted for sleep recording. We recorded sleep during baseline condition, following sham injection (saline i.p. 1 ml/kg), and every week for 5 weeks following injection of the systemic neurotoxins (DSP-4 or PCA; 1 ml/kg, i.p.) for chemical axotomy of the locus coeruleus (LC) and dorsal raphe (DR) axon terminals. After sleep/wake states identification, FFT analysis was performed on 5 s epochs. Theta carrier frequency phase shift (∆Φ) was calculated for each epoch by averaging theta Fourier component phase shifts, and the ∆Φ values were plotted for each rat in control condition and 28 days following the monoaminergic lesions, as a time for permanently established DR or LC chemical axotomy. Calculated group averages have shown that ∆Φ increased between pons and cortex significantly in all sleep/wake states (Wake, NREM and REM) following the monoaminergic lesions, with respect to controls. Monoaminergic lesions established the pontine leading role in the brain theta oscillations during all sleep/wake states.

Repeated light-dark phase shifts modulate voluntary ethanol intake in male and female high alcohol-drinking (HAD1) rats.

PubMed

Clark, James W; Fixaris, Michael C; Belanger, Gabriel V; Rosenwasser, Alan M

2007-10-01

Chronic disruption of sleep and other circadian biological rhythms, such as occurs in shift work or in frequent transmeridian travel, appears to represent a significant source of allostatic load, leading to the emergence of stress-related physical and psychological illness. Recent animal experiments have shown that these negative health effects may be effectively modeled by exposure to repeated phase shifts of the daily light-dark (LD) cycle. As chronobiological disturbances are thought to promote relapse in abstinent alcoholics, and may also be associated with increased risk of subsequent alcohol abuse in nonalcoholic populations, the present experiment was designed to examine the effects of repeated LD phase shifts on voluntary ethanol intake in rats. A selectively bred, high alcohol-drinking (HAD1) rat line was utilized to increase the likelihood of excessive alcoholic-like drinking. Male and female rats of the selectively bred HAD1 rat line were maintained individually under a LD 12:12 cycle with both ethanol (10% v/v) and water available continuously. Animals in the experimental group were subjected to repeated 6-hour LD phase advances at 3 to 4 week intervals, while control rats were maintained under a stable LD cycle throughout the study. Contact-sensing drinkometers were used to monitor circadian lick patterns, and ethanol and water intakes were recorded weekly. Control males showed progressively increasing ethanol intake and ethanol preference over the course of the study, but males exposed to chronic LD phase shifts exhibited gradual decreases in ethanol drinking. In contrast, control females displayed decreasing ethanol intake and ethanol preference over the course of the experiment, while females exposed to experimental LD phase shifts exhibited a slight increase in ethanol drinking. Chronic circadian desynchrony induced by repeated LD phase shifts resulted in sex-specific modulation of voluntary ethanol intake, reducing ethanol intake in males while slightly increasing intake in females. While partially contrary to initial predictions, these results are consistent with extensive prior research showing that chronic stress may either increase or decrease ethanol intake, depending on strain, sex, stressor type, and experimental history. Thus, repeated LD phase shifts may provide a novel chronobiological model for the analysis of stress effects on alcohol intake.

Combination of Light and Melatonin Time Cues for Phase Advancing the Human Circadian Clock

PubMed Central

Burke, Tina M.; Markwald, Rachel R.; Chinoy, Evan D.; Snider, Jesse A.; Bessman, Sara C.; Jung, Christopher M.; Wright, Kenneth P.

2013-01-01

Study Objectives: Photic and non-photic stimuli have been shown to shift the phase of the human circadian clock. We examined how photic and non-photic time cues may be combined by the human circadian system by assessing the phase advancing effects of one evening dose of exogenous melatonin, alone and in combination with one session of morning bright light exposure. Design: Randomized placebo-controlled double-blind circadian protocol. The effects of four conditions, dim light (∼1.9 lux, ∼0.6 Watts/m2)-placebo, dim light-melatonin (5 mg), bright light (∼3000 lux, ∼7 Watts/m2)-placebo, and bright light-melatonin on circadian phase was assessed by the change in the salivary dim light melatonin onset (DLMO) prior to and following treatment under constant routine conditions. Melatonin or placebo was administered 5.75 h prior to habitual bedtime and 3 h of bright light exposure started 1 h prior to habitual wake time. Setting: Sleep and chronobiology laboratory environment free of time cues. Participants: Thirty-six healthy participants (18 females) aged 22 ± 4 y (mean ± SD). Results: Morning bright light combined with early evening exogenous melatonin induced a greater phase advance of the DLMO than either treatment alone. Bright light alone and melatonin alone induced similar phase advances. Conclusion: Information from light and melatonin appear to be combined by the human circadian clock. The ability to combine circadian time cues has important implications for understanding fundamental physiological principles of the human circadian timing system. Knowledge of such principles is important for designing effective countermeasures for phase-shifting the human circadian clock to adapt to jet lag, shift work, and for designing effective treatments for circadian sleep-wakefulness disorders. Citation: Burke TM; Markwald RR; Chinoy ED; Snider JA; Bessman SC; Jung CM; Wright Jr KP. Combination of light and melatonin time cues for phase advancing the human circadian clock. SLEEP 2013;36(11):1617-1624. PMID:24179293

Phase segregation due to simultaneous migration and coalescence

NASA Technical Reports Server (NTRS)

Davis, Robert H.; Wang, Hua; Hawker, Debra

1994-01-01

Ground-based modeling and experiments have been performed on the interaction and coalescence of drops leading to macroscopic phase separation. The focus has been on gravity-induced motion, with research also initiated on thermocapillary motion of drops. The drop size distribution initially shifts toward larger drops with time due to coalescence, and then a back towards smaller drops due to the larger preferentially settling out. As a consequence, the phase separation rate initially increases with time and then decreases.

High-speed single-pixel digital holography

NASA Astrophysics Data System (ADS)

González, Humberto; Martínez-León, Lluís.; Soldevila, Fernando; Araiza-Esquivel, Ma.; Tajahuerce, Enrique; Lancis, Jesús

2017-06-01

The complete phase and amplitude information of biological specimens can be easily determined by phase-shifting digital holography. Spatial light modulators (SLMs) based on liquid crystal technology, with a frame-rate around 60 Hz, have been employed in digital holography. In contrast, digital micro-mirror devices (DMDs) can reach frame rates up to 22 kHz. A method proposed by Lee to design computer generated holograms (CGHs) permits the use of such binary amplitude modulators as phase-modulation devices. Single-pixel imaging techniques record images by sampling the object with a sequence of micro-structured light patterns and using a simple photodetector. Our group has reported some approaches combining single-pixel imaging and phase-shifting digital holography. In this communication, we review these techniques and present the possibility of a high-speed single-pixel phase-shifting digital holography system with phase-encoded illumination. This system is based on a Mach-Zehnder interferometer, with a DMD acting as the modulator for projecting the sampling patterns on the object and also being used for phase-shifting. The proposed sampling functions are phaseencoded Hadamard patterns generated through a Lee hologram approach. The method allows the recording of the complex amplitude distribution of an object at high speed on account of the high frame rates of the DMD. Reconstruction may take just a few seconds. Besides, the optical setup is envisaged as a true adaptive system, which is able to measure the aberration induced by the optical system in the absence of a sample object, and then to compensate the wavefront in the phasemodulation stage.

A Balanced Diet Is Necessary for Proper Entrainment Signals of the Mouse Liver Clock

PubMed Central

Hirao, Akiko; Tahara, Yu; Kimura, Ichiro; Shibata, Shigenobu

2009-01-01

Background The peripheral circadian clock in mice is entrained not only by light-dark cycles but also by daily restricted feeding schedules. Behavioral and cell culture experiments suggest an increase in glucose level as a factor in such feeding-induced entrainment. For application of feeding-induced entrainment in humans, nutrient content and dietary variations should be considered. Principal Finding To elucidate the food composition necessary for dietary entrainment, we examined whether complete or partial substitution of dietary nutrients affected phase shifts in liver clocks of mice. Compared with fasting mice or ad libitum fed mice, the liver bioluminescence rhythm advanced by 3–4 h on the middle day in Per2::luciferase knock-in mice that were administered a standard mouse diet, i.e. AIN-93M formula [0.6–0.85 g/10 g mouse BW] (composition: 14% casein, 47% cornstarch, 15% gelatinized cornstarch, 10% sugar, 4% soybean oil, and 10% other [fiber, vitamins, minerals, etc.]), for 2 days. When each nutrient was tested alone (100% nutrient), an insignificant weak phase advance was found to be induced by cornstarch and soybean oil, but almost no phase advance was induced by gelatinized cornstarch, high-amylose cornstarch, glucose, sucrose, or casein. A combination of glucose and casein without oil, vitamin, or fiber caused a significant phase advance. When cornstarch in AIN-93M was substituted with glucose, sucrose, fructose, polydextrose, high-amylose cornstarch, or gelatinized cornstarch, the amplitude of phase advance paralleled the increase in blood glucose concentration. Conclusions Our results strongly suggest the following: (1) balanced diets containing carbohydrates/sugars and proteins are good for restricted feeding-induced entrainment of the peripheral circadian clock and (2) a balanced diet that increases blood glucose, but not by sugar alone, is suitable for entrainment. These findings may assist in the development of dietary recommendations for on-board meals served to air travelers and shift workers to reduce jet lag-like symptoms. PMID:19738906

Majorana ϕ0-junction in a disordered spin-orbit coupling nanowire with tilted magnetic field

NASA Astrophysics Data System (ADS)

Huang, Hong; Liang, Qi-Feng; Yao, Dao-Xin; Wang, Zhi

2017-12-01

Majorana Josephson junctions in nanowire systems exhibit a pseudo-4π period current-phase relation in the clean limit. In this work, we study how this current-phase relation responds to a tilted magnetic field in a disordered Majorana Josephson junction within the Bogoliubov-de Gennes approach. We show that the tilted magnetic field induces a ϕ0 phase shift to the current-phase relation. Most importantly, we find that this ϕ0-junction behavior is robust even in the presence of disorders.

Attention during adaptation weakens negative afterimages of perceptually colour-spread surfaces.

PubMed

Lak, Armin

2008-06-01

The visual system can complete coloured surfaces from stimulus fragments, inducing the subjective perception of a colour-spread figure. Negative afterimages of these induced colours were first reported by S. Shimojo, Y. Kamitani, and S. Nishida (2001). Two experiments were conducted to examine the effect of attention on the duration of these afterimages. The results showed that shifting attention to the colour-spread figure during the adaptation phase weakened the subsequent afterimage. On the basis of previous findings that the duration of these afterimages is correlated with the strength of perceptual filling-in (grouping) among local inducers during the adaptation phase, it is proposed that attention weakens perceptual filling-in during the adaptation phase and thereby prevents the stimulus from being segmented into an illusory figure. (PsycINFO Database Record (c) 2008 APA, all rights reserved).

Dimorphism in Histoplasma capsulatum: a model for the study of cell differentiation in pathogenic fungi.

PubMed Central

Maresca, B; Kobayashi, G S

1989-01-01

Several fungi can assume either a filamentous or a unicellular morphology in response to changes in environmental conditions. This process, known as dimorphism, is a characteristic of several pathogenic fungi, e.g., Histoplasma capsulatum, Blastomyces dermatitidis, and Paracoccidioides brasiliensis, and appears to be directly related to adaptation from a saprobic to a parasitic existence. H. capsulatum is the most extensively studied of the dimorphic fungi, with a parasitic phase consisting of yeast cells and a saprobic mycelial phase. In culture, the transition of H. capsulatum from one phase to the other can be triggered reversibly by shifting the temperature of incubation between 25 degrees C (mycelia) and 37 degrees C (yeast phase). Mycelia are found in soil and never in infected tissue, in contrast to the yeast phase, which is the only form present in patients. The temperature-induced phase transition and the events in establishment of the disease state are very likely to be intimately related. Furthermore, the temperature-induced phase transition implies that each growth phase is an adaptation to two critically different environments. A fundamental question concerning dimorphism is the nature of the signal(s) that responds to temperature shifts. So far, both the responding cell component(s) and the mechanism(s) remain unclear. This review describes the work done in the last several years at the biochemical and molecular levels on the mechanisms involved in the mycelium to yeast phase transition and speculates on possible models of regulation of morphogenesis in dimorphic pathogenic fungi. Images PMID:2666842

Mechanically-induced disorder in CaFe 2As 2: A 57Fe Mössbauer study

DOE PAGES

Ma, Xiaoming; Ran, Sheng; Canfield, Paul C.; ...

2015-10-17

57Fe Mössbauer spectroscopy was used to perform a microscopic study on the extremely pressure and strain sensitive compound, CaFe 2As 2, with different degrees of strain introduced by grinding and annealing. At the base temperature, in the antiferromagnetic/orthorhombic phase, compared to a sharp sextet Mössbauer spectrum of single crystal CaFe 2As 2, which is taken as an un-strained sample, an obviously broadened sextet and an extra doublet were observed for ground CaFe 2As 2 powders with different degrees of strain. The Mössbauer results suggest that the magnetic phase transition of CaFe 2As 2 can be inhomogeneously suppressed by the grindingmore » induced strain to such an extent that the antiferromagnetic order in parts of the grains forming the powdered sample remain absent all the way down to 4.6 K. However, strain has almost no effect on the temperature dependent hyperfine magnetic field in the grains with magnetic order. Additional electronic and asymmetry information was obtained from the isomer shift and quadrupole splitting. Similar isomer shift values in the magnetic phase for samples with different degrees of strain, indicate that the stain does not bring any significant variation of the electronic density at 57Fe nucleus position. As a result, the absolute values of quadrupole shift in the magnetic phase decrease and approach zero with increasing degrees of strain, indicating that the strain reduces the average lattice asymmetry at Fe atom position.« less

Effect of Al/Ga substitution on the structural and luminescence properties of Y3(Al1-xGax)5O12: Ce3+ phosphors

NASA Astrophysics Data System (ADS)

Fu, Sheng; Tan, Jin; Bai, Xin; Yang, Shanjie; You, Lei; Du, Zhengkang

2018-01-01

As candidates for display and lighting materials, a series of gallium-substituted cerium-doped yttrium aluminum garnet (Y3(GaxAl1-x)5O12: Ce3+) phosphors were synthesized by high temperature solid-state reaction. The phases, morphology, luminescence spectra and thermal stability of the phosphors were investigated. The volatilization of Ga2O3 induces the constituents out of stoichiometric ratio and different impurities in the system. The excitation and emission spectra occur red shift (339 nm - 351 nm) and blue shift (465 nm - 437 nm), and blue shift (541 nm - 517 nm), respectively. The spectra have no further blue shift and the luminescence intensity decrease with x over 0.4. Combining crystal structure with PL spectrum, the distortion of dodecahedron and crystal field splitting of 5d level of Ce3+ are influenced by Ga3+ in octahedral coordination polyhedron rather than tetrahedron. The crystalline perfection and Ga3+ occupying the tetrahedron induce less garnet phase formation, more impurities and the 5d level located in the conductive bands, thus accounting for the x = 0.4 turning points of the PL and PLE intensity. Based on the thermal quenching and CIE, the Y3(GaxAl1-x)5O12: Ce3+0.06 phosphors have great potential for use on the w-LED.

Phase Transformation and Creep Behavior in Ti50Pd30Ni20 High Temperature Shape Memory Alloy in Compression

NASA Technical Reports Server (NTRS)

Kumar, Parikshith K.; Desai, Uri; Monroe, James; Lagoudas, Dimitris C.; Karaman, Ibrahim; Noebe, Ron; Bigelow, Glenn

2010-01-01

The creep behavior and the phase transformation of Ti50Pd30Ni20 High Temperature Shape Memory Alloy (HTSMA) is investigated by standard creep tests and thermomechanical tests. Ingots of the alloy are induction melted, extruded at high temperature, from which cylindrical specimens are cut and surface polished. A custom high temperature test setup is assembled to conduct the thermomechanical tests. Following preliminary monotonic tests, standard creep tests and thermally induced phase transformation tests are conducted on the specimen. The creep test results suggest that over the operating temperatures and stresses of this alloy, the microstructural mechanisms responsible for creep change. At lower stresses and temperatures, the primary creep mechanism is a mixture of dislocation glide and dislocation creep. As the stress and temperature increase, the mechanism shifts to predominantly dislocation creep. If the operational stress or temperature is raised even further, the mechanism shifts to diffusion creep. The thermally induced phase transformation tests show that actuator performance can be affected by rate independent irrecoverable strain (transformation induced plasticity + retained martensite) as well as creep. The rate of heating and cooling can adversely impact the actuators performance. While the rate independent irrecoverable strain is readily apparent early in the actuators life, viscoplastic strain continues to accumulate over the lifespan of the HTSMA. Thus, in order to get full actuation out of the HTSMA, the heating and cooling rates must be sufficiently high enough to avoid creep.

Redshifted and blueshifted photoluminescence emission of InAs/InP quantum dots upon amorphization of phase change material.

PubMed

Humam, Nurrul Syafawati Binti; Sato, Yu; Takahashi, Motoki; Kanazawa, Shohei; Tsumori, Nobuhiro; Regreny, Philippe; Gendry, Michel; Saiki, Toshiharu

2014-06-16

We present the mechanisms underlying the redshifted and blueshifted photoluminescence (PL) of quantum dots (QDs) upon amorphization of phase change material (PCM). We calculated the stress and energy shift distribution induced by volume expansion using finite element method. Simulation result reveals that redshift is obtained beneath the flat part of amorphous mark, while blueshift is obtained beneath the edge region of amorphous mark. Simulation result is accompanied by two experimental studies; two-dimensional PL intensity mapping of InAs/InP QD sample deposited by a layer of PCM, and an analysis on the relationship between PL intensity ratio and energy shift were performed.

A microprocessor based portable bolt tension monitor

NASA Technical Reports Server (NTRS)

Perey, D. F.

1991-01-01

A bolt tension monitor (BTM) which uses ultrasonics and a pulsed phase locked loop circuit to measure load-induced acoustic phase shifts which are independent of friction is described. The BTM makes it possible to measure the load in a bolt that was tightened at some time in the past. This capability to recertify a load after-the-fact will help to insure the integrity of a bolted joint.

Coherent detection of THz-induced sideband emission from excitons in the nonperturbative regime

NASA Astrophysics Data System (ADS)

Uchida, K.; Otobe, T.; Mochizuki, T.; Kim, C.; Yoshita, M.; Tanaka, K.; Akiyama, H.; Pfeiffer, L. N.; West, K. W.; Hirori, H.

2018-04-01

Strong interaction of a terahertz (THz) wave with excitons induces nonperturbative optical effects such as Rabi splitting and high-order sideband generation. Here, we investigated coherent properties of THz-induced sideband emissions from GaAs/AlGaAs multiquantum wells. With increasing THz electric field, optical susceptibility of the THz-dressed exciton shows a redshift with spectral broadening and extraordinary phase shift. This implies that the field ionization of the 1 s exciton modifies the THz-dressed exciton in the nonperturbative regime.

Geoelectrical Response of Surfactant Solutions in a Quartzitic Sand Analog Aquifer

EPA Science Inventory

In this project, the resistivity and phase shift of ten surfactant aqueous solutions in a sand matrix were measured using spectral induced polarization (SIP). In addition, specific conductivity, pH, dissolved oxygen, and dielectric constant measurements of the solutions were also...

Cocrystal formation in solution: Inducing phase transition by manipulating the amount of cocrystallizing agent

NASA Astrophysics Data System (ADS)

Gagniere, Emilie; Mangin, Denis; Puel, François; Valour, Jean-Pierre; Klein, Jean-Paul; Monnier, Olivier

2011-02-01

The purpose of this work was to assess the possibility of inducing solution mediated phase transition (SMPT) by manipulating the amount of the cocrystallizing agent. The cocrystal, composed of an active pharmaceutical ingredient (carbamazepine, CBZ) and its cocrystallizing agent (a vitamin—nicotinamide, NCT), was selected as a model compound. Batch experiments were performed in a stirred vessel. The solute concentrations of both CBZ and NCT were monitored using in situ ATR-FTIR spectroscopy. The introduction of NCT in dry form allowed a shift in the phase diagram, leading to an SMPT from CBZ crystals toward cocrystals. The concentration profiles gave information on the phase transition kinetics, i.e., the kinetics of nucleation, growth and dissolution mechanisms of the solid phases involved. Several situations were analyzed. This procedure could also be used to correct a process deviation that led to CBZ crystals instead of cocrystals.

Resonant tidal excitation of oscillation modes in merging binary neutron stars: Inertial-gravity modes

NASA Astrophysics Data System (ADS)

Xu, Wenrui; Lai, Dong

2017-10-01

In coalescing neutron star (NS) binaries, tidal force can resonantly excite low-frequency (≲500 Hz ) oscillation modes in the NS, transferring energy between the orbit and the NS. This resonant tide can induce phase shift in the gravitational waveforms, and potentially provide a new window of studying NS interior using gravitational waves. Previous works have considered tidal excitations of pure g-modes (due to stable stratification of the star) and pure inertial modes (due to Coriolis force), with the rotational effect treated in an approximate manner. However, for realistic NSs, the buoyancy and rotational effects can be comparable, giving rise to mixed inertial-gravity modes. We develop a nonperturbative numerical spectral code to compute the frequencies and tidal coupling coefficients of these modes. We then calculate the phase shift in the gravitational waveform due to each resonance during binary inspiral. Given the uncertainties in the NS equation of state and stratification property, we adopt polytropic NS models with a parametrized stratification. We derive relevant scaling relations and survey how the phase shift depends on various properties of the NS. We find that for canonical NSs (with mass M =1.4 M⊙ and radius R =10 km ) and modest rotation rates (≲300 Hz ), the gravitational wave phase shift due to a resonance is generally less than 0.01 radian. But the phase shift is a strong function of R and M , and can reach a radian or more for low-mass NSs with larger radii (R ≳15 km ). Significant phase shift can also be produced when the combination of stratification and rotation gives rise to a very low frequency (≲20 Hz in the inertial frame) modified g-mode. As a by-product of our precise calculation of oscillation modes in rotating NSs, we find that some inertial modes can be strongly affected by stratification; we also find that the m =1 r -mode, previously identified to have a small but finite inertial-frame frequency based on the Cowling approximation, in fact has essentially zero frequency, and therefore cannot be excited during the inspiral phase of NS binaries.

Shifting the Phase Boundary with Electric Fields to Jump In and Out of the Phase Diagram at Constant Temperature

NASA Astrophysics Data System (ADS)

Roth, Connie B.; Kriisa, Annika

Understanding the phase behavior of polymer blends and block copolymers under the presence of electric fields is important for advanced applications containing electrodes such as organic photovoltaics and batteries, as well as for field-directed assembly and alignment of domains. We have recently demonstrated that electric fields enhance the miscibility of polystyrene (PS) / poly(vinyl methyl ether blends) (PVME) blends, shifting the phase separation temperature Ts(E) up by 13.5 +/- 1.4 K for electric field strengths of E = 1.7 MV/m. Experimentally this effect is much larger than the traditional predictions from adding the standard electrostatic energy term for mixtures to the free energy of mixing. However, accounting for the energy penalty of dielectric interfaces between domains created during phase separation, the primary factor that drives alignment of domains, may also be responsible for the change in miscibility. Here we investigate the dynamics of repeatedly jumping the system from the one-phase to the two-phase region and demonstrate that this can be done at a constant temperature simply by turning the electric field on and off, illustrating electric-field-induced remixing in the two-phase region.

NPY-Induced Phase Shifts of PER2::LUC Rhythms are Mediated by Long-Term Suppression of Neuronal Excitability in a Phase-Specific Manner

PubMed Central

Besing, Rachel C.; Hablitz, Lauren M.; Paul, Jodi R.; Johnson, Russell L.; Prosser, Rebecca A.; Gamble, Karen L.

2013-01-01

Endogenous circadian rhythms are entrained to the 24-h light/dark cycle by both light and nonphotic stimuli. During the day, nonphotic stimuli, such as novel-wheel induced exercise, produce large phase advances. Neuropeptide Y (NPY) release from the thalamus onto suprachiasmatic nucleus (SCN) neurons at least partially mediates this nonphotic signal. We examined the hypothesis that NPY-induced phase advances are accompanied by suppression of PER2 and are mediated by long-term depression of neuronal excitability in a phase-specific manner. First, we found that NPY-induced phase advances in PER2::LUC SCN cultures are largest when NPY (2.35 µM) is given in the early part of the day (circadian time [CT] 0–6). In addition, PER2::LUC levels in NPY-treated (compared to vehicle-treated) samples were suppressed beginning 6–7 h after treatment. Similar NPY application to organotypic Per1::GFP SCN cultures resulted in long-term suppression of spike rate of GFP+ cells when slices were treated with NPY during the early or middle of the day (zeitgeber time [ZT] 2 or 6), but not during the late day (ZT 10). Furthermore, 1-h bath application of NPY to acute SCN brain slices decreased general neuronal activity measured through extracellular recordings. Finally, NPY-induced phase advances of PER2::LUC rhythms were blocked by latent depolarization with 34.5 mM [K+] 3 h after NPY application. These results suggest that NPY-induced phase advances may be mediated by long-term depression of neuronal excitability. This model is consistent with findings in other brain regions that NPY-induced persistent hyperpolarization underlies mechanisms of energy homeostasis, anxiety-related behavior, and thalamocortical synchronous firing. PMID:22324550

cGMP-Phosphodiesterase Inhibition Enhances Photic Responses and Synchronization of the Biological Circadian Clock in Rodents

PubMed Central

Plano, Santiago A.; Agostino, Patricia V.; de la Iglesia, Horacio O.; Golombek, Diego A.

2012-01-01

The master circadian clock in mammals is located in the hypothalamic suprachiasmatic nuclei (SCN) and is synchronized by several environmental stimuli, mainly the light-dark (LD) cycle. Light pulses in the late subjective night induce phase advances in locomotor circadian rhythms and the expression of clock genes (such as Per1-2). The mechanism responsible for light-induced phase advances involves the activation of guanylyl cyclase (GC), cGMP and its related protein kinase (PKG). Pharmacological manipulation of cGMP by phosphodiesterase (PDE) inhibition (e.g., sildenafil) increases low-intensity light-induced circadian responses, which could reflect the ability of the cGMP-dependent pathway to directly affect the photic sensitivity of the master circadian clock within the SCN. Indeed, sildenafil is also able to increase the phase-shifting effect of saturating (1200 lux) light pulses leading to phase advances of about 9 hours, as well as in C57 a mouse strain that shows reduced phase advances. In addition, sildenafil was effective in both male and female hamsters, as well as after oral administration. Other PDE inhibitors (such as vardenafil and tadalafil) also increased light-induced phase advances of locomotor activity rhythms and accelerated reentrainment after a phase advance in the LD cycle. Pharmacological inhibition of the main downstream target of cGMP, PKG, blocked light-induced expression of Per1. Our results indicate that the cGMP-dependent pathway can directly modulate the light-induced expression of clock-genes within the SCN and the magnitude of light-induced phase advances of overt rhythms, and provide promising tools to design treatments for human circadian disruptions. PMID:22590651

Influence of Temperature on Fatigue-Induced Martensitic Phase Transformation in a Metastable CrMnNi-Steel

NASA Astrophysics Data System (ADS)

Biermann, Horst; Glage, Alexander; Droste, Matthias

2016-01-01

Metastable austenitic steels can exhibit a fatigue-induced martensitic phase transformation during cyclic loading. It is generally agreed that a certain strain amplitude and a threshold of the cumulated plastic strain must be exceeded to trigger martensitic phase transformation under cyclic loading. With respect to monotonic loading, the martensitic phase transformation takes place up to a critical temperature—the so-called M d temperature. The goal of the present investigation is to determine an M d,c temperature which would be the highest temperature at which a fatigue-induced martensitic phase transformation can take place. For this purpose, fatigue tests controlled by the total strain were performed at different temperatures. The material investigated was a high-alloy metastable austenitic steel X3CrMnNi16.7.7 (16.3Cr-7.2Mn-6.6Ni-0.03C-0.09N-1.0Si) produced using the hot pressing technique. The temperatures were set in the range of 283 K (10 °C) ≤ T ≤ 473 K (200 °C). Depending on the temperature and strain amplitude, the onset of the martensitic phase transformation shifted to different values of the cumulated plastic strain, or was inhibited completely. Moreover, it is known that metastable austenitic CrMnNi steels with higher nickel contents can exhibit the deformation-induced twinning effect. Thus, at higher temperatures and strain amplitudes, a transition from the deformation-induced martensitic transformation to deformation-induced twinning takes place. The fatigue-induced martensitic phase transformation was monitored during cyclic loading using a ferrite sensor. The microstructure after the fatigue tests was examined using the back-scattered electrons, the electron channeling contrast imaging and the electron backscatter diffraction techniques to study the temperature-dependent dislocation structures and phase transformations.

Ab initio calculation of the electronic absorption spectrum of liquid water

NASA Astrophysics Data System (ADS)

Martiniano, Hugo F. M. C.; Galamba, Nuno; Cabral, Benedito J. Costa

2014-04-01

The electronic absorption spectrum of liquid water was investigated by coupling a one-body energy decomposition scheme to configurations generated by classical and Born-Oppenheimer Molecular Dynamics (BOMD). A Frenkel exciton Hamiltonian formalism was adopted and the excitation energies in the liquid phase were calculated with the equation of motion coupled cluster with single and double excitations method. Molecular dynamics configurations were generated by different approaches. Classical MD were carried out with the TIP4P-Ew and AMOEBA force fields. The BLYP and BLYP-D3 exchange-correlation functionals were used in BOMD. Theoretical and experimental results for the electronic absorption spectrum of liquid water are in good agreement. Emphasis is placed on the relationship between the structure of liquid water predicted by the different models and the electronic absorption spectrum. The theoretical gas to liquid phase blue-shift of the peak positions of the electronic absorption spectrum is in good agreement with experiment. The overall shift is determined by a competition between the O-H stretching of the water monomer in liquid water that leads to a red-shift and polarization effects that induce a blue-shift. The results illustrate the importance of coupling many-body energy decomposition schemes to molecular dynamics configurations to carry out ab initio calculations of the electronic properties in liquid phase.

Isothermal lipid phase transitions.

PubMed

Cevc, G

1991-03-01

In liotropic lipid systems phase transitions can be induced isothermally by changing the solvent concentration or composition; alternatively, lipid composition can be modified by (bio)chemical means. The probability for isothermal phase transitions increases with the decreasing transition entropy; it is proportional to the magnitude of the transition temperature shift caused by transformation-inducing system variation. Manipulations causing large thermodynamic effects, such as lipid (de)hydration, binding of protons or divalent ions and macromolecular adsorption, but also close bilayer approach are, therefore, likely to cause structural lipid change(s) at a constant temperature. Net lipid charges enhance the membrane susceptibility to salt-induced isothermal phase transitions; a large proportion of this effect is due to the bilayer dehydration, however, rather than being a consequence of the decreased Coulombic electrostatic interactions. Membrane propensity for isothermal phase transitions, consequently, always increases with the hydrophilicity of the lipid heads, as well as with the desaturation and shortening of the lipid chains. Upon a phase change at a constant temperature, some of the interfacially bound solutes (e.g. protons or calcium) are released in the solution. Membrane permeability and fusogenicity simultaneously increase. In mixed systems, isothermal phase transitions, moreover, may result in lateral phase separation. All this opens up ways for the involvement of isothermal phase transitions in the regulation of biological processes.

Light-driven changes in energy metabolism directly entrain the cyanobacterial circadian oscillator

PubMed Central

Rust, Michael J.; Golden, Susan S.; O'Shea, Erin K.

2012-01-01

Circadian clocks are self-sustained biological oscillators that can be entrained by environmental cues. Though this phenomenon has been studied in many organisms, the molecular mechanisms of entrainment remain unclear. Three cyanobacterial proteins and ATP are sufficient to generate oscillations in phosphorylation in vitro. We show that changes in illumination that induce a phase shift in cultured cyanobacteria also cause changes in the ATP/ADP ratio. When these nucleotide changes are simulated in the in vitro oscillator, they cause phase shifts similar to those observed in vivo. Physiological concentrations of ADP inhibit kinase activity in the oscillator and a mathematical model constrained by data shows that this effect is sufficient to quantitatively explain entrainment of the cyanobacterial circadian clock. PMID:21233390

The role of the endocrine system in feeding-induced tissue-specific circadian entrainment.

PubMed

Sato, Miho; Murakami, Mariko; Node, Koichi; Matsumura, Ritsuko; Akashi, Makoto

2014-07-24

The circadian clock is entrained to environmental cycles by external cue-mediated phase adjustment. Although the light input pathway has been well defined, the mechanism of feeding-induced phase resetting remains unclear. The tissue-specific sensitivity of peripheral entrainment to feeding suggests the involvement of multiple pathways, including humoral and neuronal signals. Previous in vitro studies with cultured cells indicate that endocrine factors may function as entrainment cues for peripheral clocks. However, blood-borne factors that are well characterized in actual feeding-induced resetting have yet to be identified. Here, we report that insulin may be involved in feeding-induced tissue-type-dependent entrainment in vivo. In ex vivo culture experiments, insulin-induced phase shift in peripheral clocks was dependent on tissue type, which was consistent with tissue-specific insulin sensitivity, and peripheral entrainment in insulin-sensitive tissues involved PI3K- and MAPK-mediated signaling pathways. These results suggest that insulin may be an immediate early factor in feeding-mediated tissue-specific entrainment. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

[Hair growth effect of minoxidil].

PubMed

Otomo, Susumu

2002-03-01

The length and size of hair are depend on the anagen term in its hair cycle. It has been reported that the some cell growth factors, such as VEGF, FGF-5S, IGF-1 and KGF, induce the proliferation of cells in the matrix, dermal papilla and dermal papillary vascular system and increase the amount of extra cellular matrix in dermal papilla and then maintain follicles in the anagen phase. On the other hand, negative factors, like FGF-5, thrombospondin, or still unknown ones, terminate the anagen phase. If the negative factors become dominant against cell proliferation factors according to fulfilling some time set by the biological clock for hair follicles, TGF beta induced in the matrix tissues evokes apoptosis of matrix cells and shifts the follicles from anagen to catagen. Androgenetic alopecia is caused by miniaturizing of hair follicles located in the frontal or crown part of scalp and are hereditarily more sensitive to androgen. In their hair cycles, the androgen shortens the anagen phase of follicles and shifts them to the catagen phase earlier than usual. The mode of action of hair growth effect of minoxidil is not completely elucidated, but the most plausible explanation proposed here is that minoxidil works as a sulfonylurea receptor (SUR) activator and prolongs the anagen phase of hair follicles in the following manner: minoxidil (1) induces cell growth factors such as VEGF, HGF, IGF-1 and potentiates HGF and IGF-1 actions by the activation of uncoupled SUR on the plasma membrane of dermal papilla cells, (2) inhibits of TGF beta induced apoptosis of hair matrix cells by opening the Kir 6.0 channel pore coupled with SUR on the mitochondrial inner membrane, and (3) dilates hair follicle arteries and increases blood flow in dermal papilla by opening the Kir 6.0 channel pore coupled with SUR on the plasma membrane of vascular smooth muscle cells.

Double-image storage optimized by cross-phase modulation in a cold atomic system

NASA Astrophysics Data System (ADS)

Qiu, Tianhui; Xie, Min

2017-09-01

A tripod-type cold atomic system driven by double-probe fields and a coupling field is explored to store double images based on the electromagnetically induced transparency (EIT). During the storage time, an intensity-dependent signal field is applied further to extend the system with the fifth level involved, then the cross-phase modulation is introduced for coherently manipulating the stored images. Both analytical analysis and numerical simulation clearly demonstrate a tunable phase shift with low nonlinear absorption can be imprinted on the stored images, which effectively can improve the visibility of the reconstructed images. The phase shift and the energy retrieving rate of the probe fields are immune to the coupling intensity and the atomic optical density. The proposed scheme can easily be extended to the simultaneous storage of multiple images. This work may be exploited toward the end of EIT-based multiple-image storage devices for all-optical classical and quantum information processings.

Neonatal monosodium glutamate treatment counteracts circadian arrhythmicity induced by phase shifts of the light-dark cycle in female and male Siberian hamsters

PubMed Central

Prendergast, Brian J.; Onishi, Kenneth G.; Zucker, Irving

2013-01-01

Studies of rats and voles suggest that distinct pathways emanating from the anterior hypothalamic-retrochiasmatic area and the mediobasal hypothalamic arcuate nucleus independently generate ultradian rhythms (URs) in hormone secretion and behavior. We evaluated the hypothesis that destruction of arcuate nucleus (ARC) neurons, in concert with dampening of suprachiasmatic nucleus (SCN) circadian rhythmicity, would compromise the generation of ultradian rhythms (URs) of locomotor activity. Siberian hamsters of both sexes treated neonatally with monosodium glutamate (MSG) that destroys ARC neurons were subjected in adulthood to a circadian disrupting phase-shift protocol (DPS) that produces SCN arrhythmia. MSG treatments induced hypogonadism and obesity, and markedly reduced the size of the optic chiasm and primary optic tracts. MSG-treated hamsters exhibited normal entrainment to the light-dark cycle, but MSG treatment counteracted the circadian arrhythmicity induced by the DPS protocol: only 6% of MSG-treated hamsters exhibited circadian arrhythmia, whereas 50% of control hamsters were circadian disrupted. In MSG-treated hamsters that retained circadian rhythmicity after DPS treatment, quantitative parameters of URs appeared normal, but in the 2 MSG-treated hamsters that became circadian arrhythmic after DPS, both dark-phase and light-phase URs were abolished. Although preliminary, these data are consistent with reports in voles suggesting that the combined disruption of SCN and ARC function impairs the expression of behavioral URs. The data also suggest that light thresholds for entrainment of circadian rhythms may be lower than those required to disrupt circadian organization. PMID:23701725

Pressure-magnetic field induced phase transformation in Ni{sub 46}Mn{sub 41}In{sub 13} Heusler alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rama Rao, N. V., E-mail: nvrrao@dmrl.drdo.in; Manivel Raja, M.; Pandian, S.

2014-12-14

The effect of hydrostatic pressure and magnetic field on the magnetic properties and phase transformation in Ni{sub 46}Mn{sub 41}In{sub 13} Heusler alloy was investigated. Pressure (P)-magnetic field (H)-temperature (T) phase diagram has been constructed from experimental results. In the P–T contour of the phase diagram, the slope of the austenite-martensite phase boundary line appears positive (dT/dP > 0), while it appears negative (dT/dH < 0) in the H–T contour. The results revealed that pressure and magnetic field have opposite effect on phase stabilization. The combined effect of pressure and magnetic field on martensitic transition has led to two important findings: (i) pressure dependent shiftmore » of austenite start temperature (A{sub s}) is higher when larger field is applied, and (ii) field dependent shift of A{sub s} is lowered when a higher pressure is applied. The pressure and magnetic field dependent shift observed in the martensitic transformation has been explained on the basis of thermodynamic calculations. Curie temperature of the phases was found to increase with pressure at a rate of 0.6 K/kbar.« less

Thermoresponsive Polymers and Inverse Opal Hydrogels for the Detection of Diols.

PubMed

Couturier, Jean-Philippe; Wischerhoff, Erik; Bernin, Robert; Hettrich, Cornelia; Koetz, Joachim; Sütterlin, Martin; Tiersch, Brigitte; Laschewsky, André

2016-05-03

Responsive inverse opal hydrogels functionalized by boroxole moieties were synthesized and explored as sensor platforms for various low molar mass as well as polymeric diols and polyols, including saccharides, glycopolymers and catechols, by exploiting the diol induced modulation of their structural color. The underlying thermoresponsive water-soluble copolymers and hydrogels exhibit a coil-to-globule or volume phase transition, respectively, of the LCST-type. They were prepared from oligoethylene oxide methacrylate (macro)monomers and functionalized via copolymerization to bear benzoboroxole moieties. The resulting copolymers represent weak polyacids, which can bind specifically to diols within an appropriate pH window. Due to the resulting modulation of the overall hydrophilicity of the systems and the consequent shift of their phase transition temperature, the usefulness of such systems for indicating the presence of catechols, saccharides, and glycopolymers was studied, exploiting the diol/polyol induced shifts of the soluble polymers' cloud point, or the induced changes of the hydrogels' swelling. In particular, the increased acidity of benzoboroxoles compared to standard phenylboronic acids allowed performing the studies in PBS buffer (phosphate buffered saline) at the physiologically relevant pH of 7.4. The inverse opals constructed of these thermo- and analyte-responsive hydrogels enabled following the binding of specific diols by the induced shift of the optical stop band. Their highly porous structure enabled the facile and specific optical detection of not only low molar mass but also of high molar mass diol/polyol analytes such as glycopolymers. Accordingly, such thermoresponsive inverse opal systems functionalized with recognition units represent attractive and promising platforms for the facile sensing of even rather big analytes by simple optical means, or even by the bare eye.

Validation of a noninvasive test routinely used in otology for the diagnosis of cerebrospinal fluid shunt malfunction in patients with normal pressure hydrocephalus.

PubMed

Sakka, Laurent; Chomicki, Alexandre; Gabrillargues, Jean; Khalil, Toufic; Chazal, Jean; Avan, Paul

2016-02-01

Ventriculoperitoneal shunting is the first-line treatment for normal pressure hydrocephalus. Noninvasive auditory tests based on recorded otoacoustic emissions were assessed, as currently used for universal neonatal hearing screenings, for the diagnosis of cerebrospinal fluid shunt malfunction. The test was designed based on previous works, which demonstrated that an intracranial pressure change induces a proportional, characteristic, otoacoustic-emission phase shift. Forty-four patients with normal pressure hydrocephalus (23 idiopathic and 21 secondary cases) were included in this prospective observational study. The male:female sex ratio was 1.44, the age range was 21-87 years (mean age 64.3 years), and the range of the follow-up period was 1-3 years (mean 20 months). Patients were implanted with a Sophy SU8 adjustable-pressure valve as the ventriculoperitoneal shunt. The phase shifts of otoacoustic emissions in response to body tilt were measured preoperatively, immediately postoperatively, and at 3-6 months, 7-15 months, 16-24 months, and more than 24 months postoperatively. Three groups were enrolled: Group 1, 19 patients who required no valve opening-pressure adjustment; Group 2, 18 patients who required valve opening-pressure adjustments; and Group 3, 7 patients who required valve replacement. In Group 1, phase shift, which was positive before surgery, became steadily negative after surgery and during the follow-up. In Group 2, phase shift, which was positive before surgery, became negative immediately after surgery and increasingly negative after a decrease in the valve-opening pressure. In Group 3, phase shift was positive in 6 cases and slightly negative in 1 case before revision, but after revision phase shift became significantly negative in all cases. Otoacoustic emissions noninvasively reflect cerebrospinal fluid shunt function and are impacted by valve-opening pressure adjustments. Otoacoustic emissions consistently diagnosed shunt malfunction and predicted the need for surgical revision. The authors' diagnostic test, which can be repeated without risk or discomfort by an unskilled operator, may address the crucial need of detecting valve dysfunction in patients with poor clinical outcome after shunt surgery.

Macroalgal Extracts Induce Bacterial Assemblage Shifts and Sublethal Tissue Stress in Caribbean Corals

PubMed Central

Morrow, Kathleen M.; Ritson-Williams, Raphael; Ross, Cliff; Liles, Mark R.; Paul, Valerie J.

2012-01-01

Benthic macroalgae can be abundant on present-day coral reefs, especially where rates of herbivory are low and/or dissolved nutrients are high. This study investigated the impact of macroalgal extracts on both coral-associated bacterial assemblages and sublethal stress response of corals. Crude extracts and live algal thalli from common Caribbean macroalgae were applied onto the surface of Montastraea faveolata and Porites astreoides corals on reefs in both Florida and Belize. Denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene amplicons was used to examine changes in the surface mucus layer (SML) bacteria in both coral species. Some of the extracts and live algae induced detectable shifts in coral-associated bacterial assemblages. However, one aqueous extract caused the bacterial assemblages to shift to an entirely new state (Lobophora variegata), whereas other organic extracts had little to no impact (e.g. Dictyota sp.). Macroalgal extracts more frequently induced sublethal stress responses in M. faveolata than in P. astreoides corals, suggesting that cellular integrity can be negatively impacted in selected corals when comparing co-occurring species. As modern reefs experience phase-shifts to a higher abundance of macroalgae with potent chemical defenses, these macroalgae are likely impacting the composition of microbial assemblages associated with corals and affecting overall reef health in unpredicted and unprecedented ways. PMID:23028648

Macroalgal extracts induce bacterial assemblage shifts and sublethal tissue stress in Caribbean corals.

PubMed

Morrow, Kathleen M; Ritson-Williams, Raphael; Ross, Cliff; Liles, Mark R; Paul, Valerie J

2012-01-01

Benthic macroalgae can be abundant on present-day coral reefs, especially where rates of herbivory are low and/or dissolved nutrients are high. This study investigated the impact of macroalgal extracts on both coral-associated bacterial assemblages and sublethal stress response of corals. Crude extracts and live algal thalli from common Caribbean macroalgae were applied onto the surface of Montastraea faveolata and Porites astreoides corals on reefs in both Florida and Belize. Denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene amplicons was used to examine changes in the surface mucus layer (SML) bacteria in both coral species. Some of the extracts and live algae induced detectable shifts in coral-associated bacterial assemblages. However, one aqueous extract caused the bacterial assemblages to shift to an entirely new state (Lobophora variegata), whereas other organic extracts had little to no impact (e.g. Dictyota sp.). Macroalgal extracts more frequently induced sublethal stress responses in M. faveolata than in P. astreoides corals, suggesting that cellular integrity can be negatively impacted in selected corals when comparing co-occurring species. As modern reefs experience phase-shifts to a higher abundance of macroalgae with potent chemical defenses, these macroalgae are likely impacting the composition of microbial assemblages associated with corals and affecting overall reef health in unpredicted and unprecedented ways.

Transient coherence of media under strong phase modulation exploiting electromagnetically induced transparency

NASA Astrophysics Data System (ADS)

Shwa, David; Katz, Nadav

2014-08-01

When quantum systems are shifted faster than their transition and coupling time scales, their susceptibility is dramatically modified. We measure the optical susceptibility of a strongly modulated electromagnetically induced transparency system. Time vs detuning plots for different pump modulation frequencies reveal a transition between an adiabatic regime where a series of smooth pulses are created and a nonadiabatic regime where a strong transient oscillating response is added. Applying a magnetic field lifts the hyperfine level degeneracy, revealing an interference effect between the different magnetic level transients. We explore the dynamics of the magnetic and nonmagnetic cases and discuss their coherent nature. We finally combine the global phase of the transmitted pulses with the transient interference to achieve broadband magnetic sensing without losing the sensitivity of a single electromagnetically induced transparency line.

Modelling the work to be done by Escherichia coli to adapt to sudden temperature upshifts.

PubMed

Swinnen, I A M; Bernaerts, K; Van Impe, J F

2006-05-01

This paper studies and models the effect of the amplitude of a sudden temperature upshift DeltaT on the adaptation period of Escherichia coli, in terms of the work to be done by the cells during the subsequent lag phase (i.e., the product of growth rate mumax and lag phase duration lambda). Experimental data are obtained from bioreactor experiments with E. coli K12 MG1655. At a predetermined time instant during the exponential growth phase, a sudden temperature upshift is applied (no other environmental changes take place). The length of the (possibly) induced lag phase and the specific growth rate after the shift are quantified with the growth model of Baranyi and Roberts (Int J Food Microbiol 23, 1994, 277). Different models to describe the evolution of the product lambda x mumax as a function of the amplitude of the temperature shift are statistically compared. The evolution of lambda x mumax is influenced by the amplitude of the temperature shift DeltaT and by the normal physiological temperature range. As some cut-off is observed, the linear model with translation is preferred to describe this evolution. This work contributes to the characterization of microbial lag phenomena, in this case for E. coli K12 MG1655, in view of accurate predictive model building.

Relative phase noise induced impairment in CO-OFDM optical communication system with distributed fiber Raman amplifier.

PubMed

Wu, Jiadi; Cheng, Jingchi; Tang, Ming; Deng, Lei; Songnian, Fu; Shum, Perry Ping; Liu, Deming

2014-05-15

In this Letter, we demonstrate that the interplay between Raman pump relative intensity noise and cross-phase modulation leads to a relative phase noise (RPN) that brings non-negligible performance degradation to coherent optical orthogonal frequency-division multiplexing (CO-OFDM) transmission systems with co-pumped Raman amplification. By theoretical analysis and numerical simulation, we proved that RPN brings more system impairment in terms of Q-factor penalty than the single carrier system, and relatively larger walk-off between pump and signal helps to suppress the RPN induced impairment. A higher-order modulated signal is less tolerant to RPN than a lower-order signal. With the same spectral efficiency, the quadrature-amplitude modulation format shows better tolerance to RPN than phase-shift keying. The reported findings will be useful for the design and optimization of Raman amplified CO-OFDM multi-carrier transmission systems.

Low-power, ultrafast, and dynamic all-optical tunable plasmon induced transparency in two stub resonators side-coupled with a plasmonic waveguide system

NASA Astrophysics Data System (ADS)

Wang, Boyun; Zeng, Qingdong; Xiao, Shuyuan; Xu, Chen; Xiong, Liangbin; Lv, Hao; Du, Jun; Yu, Huaqing

2017-11-01

We theoretically and numerically investigate a low-power, ultrafast, and dynamic all-optical tunable plasmon induced transparency (PIT) in two stub resonators side-coupled with a metal-dielectric-metal (MDM) plasmonic waveguide system. The optical Kerr effect is enhanced by the local electromagnetic field of surface plasmon polaritons (SPPs) and the plasmonic waveguide based on graphene-Ag composite material structures with large effective Kerr nonlinear coefficient. An ultrafast response time of the order of 1 ps is reached because of ultrafast carrier relaxation dynamics of graphene. With dynamically tuning the propagation phase of the plasmonic waveguide, π-phase shift of the transmission spectrum in the PIT system is achieved under excitation of a pump light with an intensity as low as 5.8 MW cm-2. The group delay is controlled between 0.14 and 0.67 ps. Moreover, the tunable bandwidth of about 42 nm is obtained. For the indirect coupling between two stub cavities or the phase coupling scheme, the phase shift multiplication effect of the PIT effect is found. All observed schemes are analyzed rigorously through finite-difference time-domain simulations and coupled-mode formalism. This work not only paves the way towards the realization of on-chip integrated nanophotonic devices but also opens the possibility of the construction of ultrahigh-speed information processing chips based on plasmonic circuits.

Equivalence principle for quantum systems: dephasing and phase shift of free-falling particles

NASA Astrophysics Data System (ADS)

Anastopoulos, C.; Hu, B. L.

2018-02-01

We ask the question of how the (weak) equivalence principle established in classical gravitational physics should be reformulated and interpreted for massive quantum objects that may also have internal degrees of freedom (dof). This inquiry is necessary because even elementary concepts like a classical trajectory are not well defined in quantum physics—trajectories originating from quantum histories become viable entities only under stringent decoherence conditions. From this investigation we posit two logically and operationally distinct statements of the equivalence principle for quantum systems. Version A: the probability distribution of position for a free-falling particle is the same as the probability distribution of a free particle, modulo a mass-independent shift of its mean. Version B: any two particles with the same velocity wave-function behave identically in free fall, irrespective of their masses. Both statements apply to all quantum states, including those without a classical correspondence, and also for composite particles with quantum internal dof. We also investigate the consequences of the interaction between internal and external dof induced by free fall. For a class of initial states, we find dephasing occurs for the translational dof, namely, the suppression of the off-diagonal terms of the density matrix, in the position basis. We also find a gravitational phase shift in the reduced density matrix of the internal dof that does not depend on the particle’s mass. For classical states, the phase shift has a natural classical interpretation in terms of gravitational red-shift and special relativistic time-dilation.

Adsorption of hydrogen on stable and metastable Ir(100) surfaces

NASA Astrophysics Data System (ADS)

Arman, Mohammad Alif; Klein, Andreas; Ferstl, Pascal; Valookaran, Abhilash; Gustafson, Johan; Schulte, Karina; Lundgren, Edvin; Heinz, Klaus; Schneider, Alexander; Mittendorfer, Florian; Hammer, Lutz; Knudsen, Jan

2017-02-01

Using the combination of high resolution core level spectroscopy and density functional theory we present a detailed spectroscopic study for all clean and hydrogen covered phases of Ir(100). The results are complemented by an investigation of the hydrogen desorption process from various phases using temperature programmed desorption spectroscopy and scanning tunneling microscopy. In total, all experimentally determined core level shifts match very well with those predicted by density functional theory based on established structural models. In particular, we find for the (bridge site) adsorption on the unreconstructed 1×1 phase that the initial core level shift of surface Ir atoms is altered by +0.17 eV for each Ir-H bond formed. In the submonolayer regime we find evidence for island formation at low temperatures. For the H-induced deconstructed 5×1-H phase we identify four different surface core level shifts with two of them being degenerate. Finally, for the reconstructed 5×1-hex phase also four surface components are identified, which undergo a rather rigid core level shift of +0.15 eV upon hydrogen adsorption suggesting a similarly homogeneous charge transfer to all Ir surface atoms. Thermodesorption experiments for the 5×1-H phase reveal two different binding states for hydrogen independent of the total coverage. We conclude that the surface always separates into patches of fully covered deconstructed and uncovered reconstructed phases. We could also show by tunneling microscopy that with the desorption of the last hydrogen atom from the deconstructed unit cell the surface instantaneously reverts into the reconstructed state. Eventually, we could determine the saturation coverage upon molecular adsorption for all phases to be θmax1 × 1 - H = 1.0 ML , θmax5 × 1 - H = 0.8 ML , and θmax5 × 1 - hex - H ≥ 1.0 ML .

Positive and negative modulation of circadian activity rhythms by mGluR5 and mGluR2/3 metabotropic glutamate receptors.

PubMed

Gannon, Robert L; Millan, Mark J

2011-01-01

Glutamate released from retinal ganglion cells conveys information about the daily light:dark cycle to master circadian pacemaker neurons within the suprachiasmatic nucleus that then synchronize internal circadian rhythms with the external day-length. Glutamate activation of ionotropic glutamate receptors in the suprachiasmatic nucleus is well established, but the function of the metabotropic glutamate receptors that are also located in this nucleus is not known. Therefore, in this study we evaluated agonists and antagonists acting at orthosteric or allosteric sites for mGluR5 and mGluR2/3 metabotropic glutamate receptors for their ability to modulate light-induced phase advances and delays of hamster circadian activity rhythms. mGluR5 allosteric antagonists fenobam, MPEP and MTEP, each 10 mg/kg, potentiated light-induced phase advances of hamster circadian activity rhythms, while the mGluR5 agonists CHPG, (S)-3,5-DHPG or positive allosteric modulator CDPPB had no effect. Neither mGluR5 agonists nor antagonists had any effect on light-induced phase delays of activity rhythms. The competitive mGluR2/3 antagonist LY341495, 10 mg/kg, also potentiated light-induced phase advances, but inhibited light-induced phase delays. The mGluR2/3 agonists LY354740 and LY404039 were without effect on phase advances while a third agonist LY379268, 10 mg/kg, inhibited both light-induced advances and delays. Finally, mGluR2/3 agonists LY379268 and LY404039 also inhibited light-induced phase delays of activity rhythms. These results suggest that during light-induced phase advances, mGluR2/3 and mGluR5 receptors act to negatively modulate the effects of light on the circadian pacemaker or its output(s). mGluR5 receptors do not appear to be involved during light-induced phase delays. In contrast, the role for mGluR2/3 receptors during phase delays is more complicated as both agonists and antagonists inhibit light-induced phase delays. Dysfunctions in human circadian rhythms have been implicated in some forms of depression, and metabotropic glutamate receptor ligands, which are also being evaluated for antidepressant activity, are shown here to be capable of modifying light-induced phase shifts of circadian activity rhythms. Copyright © 2010 Elsevier Ltd. All rights reserved.

Quantitative phase imaging using four interferograms with special phase shifts by dual-wavelength in-line phase-shifting interferometry

NASA Astrophysics Data System (ADS)

Xu, Xiaoqing; Wang, Yawei; Ji, Ying; Xu, Yuanyuan; Xie, Ming; Han, Hao

2018-05-01

A new approach of quantitative phase imaging using four interferograms with special phase shifts in dual-wavelength in-line phase-shifting interferometry is presented. In this method, positive negative 2π phase shifts are employed to easily separate the incoherent addition of two single-wavelength interferograms by combining the phase-shifting technique with the subtraction procedure, then the quantitative phase at one of both wavelengths can be achieved based on two intensities without the corresponding dc terms by the use of the character of the trigonometric function. The quantitative phase of the other wavelength can be retrieved from two dc-term suppressed intensities obtained by employing the two-step phase-shifting technique or the filtering technique in the frequency domain. The proposed method is illustrated with theory, and its effectiveness is demonstrated by simulation experiments of the spherical cap and the HeLa cell, respectively.

Laser-ablative engineering of phase singularities in plasmonic metamaterial arrays for biosensing applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aristov, Andrey I.; Kabashin, Andrei V., E-mail: kabashin@lp3.univ-mrs.fr; Zywietz, Urs

2014-02-17

By using methods of laser-induced transfer combined with nanoparticle lithography, we design and fabricate large-area gold nanoparticle-based metamaterial arrays exhibiting extreme Heaviside-like phase jumps in reflected light due to a strong diffractive coupling of localized plasmons. When employed in sensing schemes, these phase singularities provide the sensitivity of 5 × 10{sup 4} deg. of phase shift per refractive index unit change that is comparable with best values reported for plasmonic biosensors. The implementation of sensor platforms on the basis of such metamaterial arrays promises a drastic improvement of sensitivity and cost efficiency of plasmonic biosensing devices.

High-speed optical phase-shifting apparatus

DOEpatents

Zortman, William A.

2016-11-08

An optical phase shifter includes an optical waveguide, a plurality of partial phase shifting elements arranged sequentially, and control circuitry electrically coupled to the partial phase shifting elements. The control circuitry is adapted to provide an activating signal to each of the N partial phase shifting elements such that the signal is delayed by a clock cycle between adjacent partial phase shifting elements in the sequence. The transit time for a guided optical pulse train between the input edges of consecutive partial phase shifting elements in the sequence is arranged to be equal to a clock cycle, thereby enabling pipelined processing of the optical pulses.

Beam shuttering interferometer and method

DOEpatents

Deason, V.A.; Lassahn, G.D.

1993-07-27

A method and apparatus resulting in the simplification of phase shifting interferometry by eliminating the requirement to know the phase shift between interferograms or to keep the phase shift between interferograms constant. The present invention provides a simple, inexpensive means to shutter each independent beam of the interferometer in order to facilitate the data acquisition requirements for optical interferometry and phase shifting interferometry. By eliminating the requirement to know the phase shift between interferograms or to keep the phase shift constant, a simple, economical means and apparatus for performing the technique of phase shifting interferometry is provide which, by thermally expanding a fiber optical cable changes the optical path distance of one incident beam relative to another.

Beam shuttering interferometer and method

DOEpatents

Deason, Vance A.; Lassahn, Gordon D.

1993-01-01

A method and apparatus resulting in the simplification of phase shifting interferometry by eliminating the requirement to know the phase shift between interferograms or to keep the phase shift between interferograms constant. The present invention provides a simple, inexpensive means to shutter each independent beam of the interferometer in order to facilitate the data acquisition requirements for optical interferometry and phase shifting interferometry. By eliminating the requirement to know the phase shift between interferograms or to keep the phase shift constant, a simple, economical means and apparatus for performing the technique of phase shifting interferometry is provide which, by thermally expanding a fiber optical cable changes the optical path distance of one incident beam relative to another.

Locomotor activity and non-photic influences on circadian clocks.

PubMed

Mrosovsky, N

1996-08-01

Some of the main themes in this review are as follows. 1. The notion that non-photic zeitgebers are weak needs re-examining. Phase-shifts to some non-photic manipulations can be as large as those to light pulses. 2. As well as being able to phase-shift and entrain free-running rhythms, non-photic events have a number of other effects: these include after-effects of entrainment, period changes, and promotion of splitting. 3. The critical variable for non-photic shifting is unknown. Locomotor activity is more likely to be an index of some other necessary state rather than being causal itself. This index may be better when tendencies to move are channelled into easily measured behaviours like wheel-running. 4. Given ignorance about the critical variable, quantification of activity may be the best presently available measure of zeitgeber intensity. Therefore, the behaviour during non-photic manipulations must be examined as carefully as the shifts themselves. When no phase-shifting follows manipulations such as IGL lesions or serotonin depletion, if the animals are inactive, then little can be inferred. 5. Lack of information on the critical variable(s) for non-photic shifting makes it problematic to compare data from studies using different non-photic manipulations. However, the presence of locomotor activity (or its correlate) does appear to be necessary for triazolam to produce shifts. 6. Novelty-induced wheel-running in hamsters depends on the NPY projection from the IGL to SCN. It remains to be determined how important NPY is in other species or in clock-resetting by other manipulations, but methods are now available to study this. 7. Interactions between photic and non-photic zeitgebers remain virtually unexplored, but it is evident that photic and non-photic stimuli can attenuate the phase-shifting effects of each other. Interactions are not purely additive or predictable from PRCs. 8. The circadian system does more than synchronize free-running rhythms to the solar day. Its non-photic functions and their interactions with photic inputs probably account for some of the anatomical complexity of circadian circuitry.

Light-induced suppression of endogenous circadian amplitude in humans

NASA Technical Reports Server (NTRS)

Jewett, Megan; Czeisler, Charles A.; Kronauer, Richard E.

1991-01-01

A recent demonstration that the phase of the human circadian pacemaker could be inverted using an unconventional three-cycle stimulus has led to an investigation of whether critically timed exposure to a more moderate stimulus could drive that oscillator toward its singularity, a phaseless position at which the amplitude of circadian oscillation is zero. It is reported here that exposure of humans to fewer cycles of bright light, centered around the time at which the human circadian pacemaker is most sensitive to light-induced phase shifts, can markedly attenuate endogenous cicadian amplitude. In some cases this results in an apparent loss of rhythmicity, as expected to occur in the region of singularity.

Input Source and Strength Influences Overall Firing Phase of Model Hippocampal CA1 Pyramidal Cells During Theta: Relevance to REM Sleep Reactivation and Memory Consolidation

PubMed Central

Booth, Victoria; Poe, Gina R.

2005-01-01

In simulation studies using a realistic model CA1 pyramidal cell, we accounted for the shift in mean firing phase from theta cycle peaks to theta cycle troughs during REM sleep reactivation of hippocampal CA1 place cells over several days of growing familiarization with an environment (Poe et al., 2000). Changes in the theta drive between proximal and distal dendritic regions of the cell modulated the theta phase of firing when stimuli were presented at proximal and distal dendritic locations. Stimuli at proximal dendritic sites (proximal to 100 μm from the soma) invoked firing with a significant phase preference at the depolarizing theta peaks, while distal stimuli (> 290 μm from the soma) invoked firing at hyperpolarizing theta troughs. The location-related phase preference depended on active dendritic conductances, a sufficient electrotonic separation between input sites and theta-induced subthreshold membrane potential oscillations in the cell. The simulation results predict that the shift in mean theta phase during REM sleep cellular reactivation could occur through potentiation of distal dendritic (temporo-ammonic) synapses and depotentiation of proximal dendritic (Schaffer collateral) synapses over the course of familiarization. PMID:16411243

Study of nanometer-level precise phase-shift system used in electronic speckle shearography and phase-shift pattern interferometry

NASA Astrophysics Data System (ADS)

Jing, Chao; Liu, Zhongling; Zhou, Ge; Zhang, Yimo

2011-11-01

The nanometer-level precise phase-shift system is designed to realize the phase-shift interferometry in electronic speckle shearography pattern interferometry. The PZT is used as driving component of phase-shift system and translation component of flexure hinge is developed to realize micro displacement of non-friction and non-clearance. Closed-loop control system is designed for high-precision micro displacement, in which embedded digital control system is developed for completing control algorithm and capacitive sensor is used as feedback part for measuring micro displacement in real time. Dynamic model and control model of the nanometer-level precise phase-shift system is analyzed, and high-precision micro displacement is realized with digital PID control algorithm on this basis. It is proved with experiments that the location precision of the precise phase-shift system to step signal of displacement is less than 2nm and the location precision to continuous signal of displacement is less than 5nm, which is satisfied with the request of the electronic speckle shearography and phase-shift pattern interferometry. The stripe images of four-step phase-shift interferometry and the final phase distributed image correlated with distortion of objects are listed in this paper to prove the validity of nanometer-level precise phase-shift system.

Ab initio calculation of the electronic absorption spectrum of liquid water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martiniano, Hugo F. M. C.; Galamba, Nuno; Cabral, Benedito J. Costa, E-mail: ben@cii.fc.ul.pt

2014-04-28

The electronic absorption spectrum of liquid water was investigated by coupling a one-body energy decomposition scheme to configurations generated by classical and Born-Oppenheimer Molecular Dynamics (BOMD). A Frenkel exciton Hamiltonian formalism was adopted and the excitation energies in the liquid phase were calculated with the equation of motion coupled cluster with single and double excitations method. Molecular dynamics configurations were generated by different approaches. Classical MD were carried out with the TIP4P-Ew and AMOEBA force fields. The BLYP and BLYP-D3 exchange-correlation functionals were used in BOMD. Theoretical and experimental results for the electronic absorption spectrum of liquid water are inmore » good agreement. Emphasis is placed on the relationship between the structure of liquid water predicted by the different models and the electronic absorption spectrum. The theoretical gas to liquid phase blue-shift of the peak positions of the electronic absorption spectrum is in good agreement with experiment. The overall shift is determined by a competition between the O–H stretching of the water monomer in liquid water that leads to a red-shift and polarization effects that induce a blue-shift. The results illustrate the importance of coupling many-body energy decomposition schemes to molecular dynamics configurations to carry out ab initio calculations of the electronic properties in liquid phase.« less

Possible daily and seasonal variations in quantum interference induced by Chern-Simons gravity.

PubMed

Okawara, Hiroki; Yamada, Kei; Asada, Hideki

2012-12-07

Possible effects of Chern-Simons (CS) gravity on a quantum interferometer turn out to be dependent on the latitude and direction of the interferometer on Earth in orbital motion around the Sun. Daily and seasonal variations in phase shifts are predicted with an estimate of the size of the effects, wherefore neutron interferometry with ~5 m arm length and ~10(-4) phase measurement accuracy would place a bound on a CS parameter comparable to the Gravity Probe B satellite.

Tungsten-incorporation induced red-shift in the bandgap of gallium oxide thin films

NASA Astrophysics Data System (ADS)

Rubio, E. J.; Ramana, C. V.

2013-05-01

Tungsten (W) incorporated Ga2O3 films were produced by co-sputter deposition. W-concentration was varied by the applied sputtering-power. The structure and optical properties of W-incorporated Ga2O3 films were evaluated using X-ray diffraction, scanning electron microscopy, and spectrophotometric measurements. No secondary phase formation was observed in W-incorporated Ga2O3 films. W-induced effects were significant on the structure and optical properties of Ga2O3 films. The bandgap of Ga2O3 films without W-incorporation was ˜5 eV. Red-shift in the bandgap was noted with increasing W-concentration indicating the electronic structure changes in W-Ga2O3 films. A functional relationship between W-concentration and optical property is discussed.

Temporal dynamics of circadian phase shifting response to consecutive night shifts in healthcare workers: role of light-dark exposure.

PubMed

Stone, Julia E; Sletten, Tracey L; Magee, Michelle; Ganesan, Saranea; Mulhall, Megan D; Collins, Allison; Howard, Mark; Lockley, Steven W; Rajaratnam, Shantha M W

2018-06-01

Shift work is highly prevalent and is associated with significant adverse health impacts. There is substantial inter-individual variability in the way the circadian clock responds to changing shift cycles. The mechanisms underlying this variability are not well understood. We tested the hypothesis that light-dark exposure is a significant contributor to this variability; when combined with diurnal preference, the relative timing of light exposure accounted for 71% of individual variability in circadian phase response to night shift work. These results will drive development of personalised approaches to manage circadian disruption among shift workers and other vulnerable populations to potentially reduce the increased risk of disease in these populations. Night shift workers show highly variable rates of circadian adaptation. This study examined the relationship between light exposure patterns and the magnitude of circadian phase resetting in response to night shift work. In 21 participants (nursing and medical staff in an intensive care unit) circadian phase was measured using 6-sulphatoxymelatonin at baseline (day/evening shifts or days off) and after 3-4 consecutive night shifts. Daily light exposure was examined relative to individual circadian phase to quantify light intensity in the phase delay and phase advance portions of the light phase response curve (PRC). There was substantial inter-individual variability in the direction and magnitude of phase shift after three or four consecutive night shifts (mean phase delay -1:08 ± 1:31 h; range -3:43 h delay to +3:07 h phase advance). The relative difference in the distribution of light relative to the PRC combined with diurnal preference accounted for 71% of the variability in phase shift. Regression analysis incorporating these factors estimated phase shift to within ±60 min in 85% of participants. No participants met criteria for partial adaptation to night work after three or four consecutive night shifts. Our findings provide evidence that the phase resetting that does occur is based on individual light exposure patterns relative to an individual's baseline circadian phase. Thus, a 'one size fits all' approach to promoting adaptation to shift work using light therapy, implemented without knowledge of circadian phase, may not be efficacious for all individuals. © 2018 Monash University. The Journal of Physiology © 2018 The Physiological Society.

Effects of sensorineural hearing loss on temporal coding of harmonic and inharmonic tone complexes in the auditory nerve

PubMed Central

Kale, Sushrut; Micheyl, Christophe; Heinz, Michael G.

2013-01-01

Listeners with sensorineural hearing loss (SNHL) often show poorer thresholds for fundamental-frequency (F0) discrimination, and poorer discrimination between harmonic and frequency-shifted (inharmonic) complex tones, than normal-hearing (NH) listeners—especially when these tones contain resolved or partially resolved components. It has been suggested that these perceptual deficits reflect reduced access to temporal-fine-structure (TFS) information, and could be due to degraded phase-locking in the auditory nerve (AN) with SNHL. In the present study, TFS and temporal-envelope (ENV) cues in single AN-fiber responses to bandpass-filtered harmonic and inharmonic complex tones were measured in chinchillas with either normal hearing or noise-induced SNHL. The stimuli were comparable to those used in recent psychophysical studies of F0 and harmonic/inharmonic discrimination. As in those studies, the rank of the center component was manipulated to produce different resolvability conditions, different phase relationships (cosine and random phase) were tested, and background noise was present. Neural TFS and ENV cues were quantified using cross-correlation coefficients computed using shuffled cross-correlograms between neural responses to REF (harmonic) and TEST (F0- or frequency-shifted) stimuli. In animals with SNHL, AN-fiber tuning curves showed elevated thresholds, broadened tuning, best-frequency shifts, and downward shifts in the dominant TFS response component; however, no significant degradation in the ability of AN fibers to encode TFS or ENV cues was found. Consistent with optimal-observer analyses, the results indicate that TFS and ENV cues depended only on the relevant frequency shift in Hz and thus were not degraded because phase-locking remained intact. These results suggest that perceptual “TFS-processing” deficits do not simply reflect degraded phase-locking at the level of the AN. To the extent that performance in F0 and harmonic/inharmonic discrimination tasks depend on TFS cues, it is likely through a more complicated (sub-optimal) decoding mechanism, which may involve “spatiotemporal” (place-time) neural representations. PMID:23716215

Electric Field-Induced Large Strain in Ni/Sb-co Doped (Bi0.5Na0.5) TiO3-Based Lead-Free Ceramics

NASA Astrophysics Data System (ADS)

Li, Liangliang; Hao, Jigong; Xu, Zhijun; Li, Wei; Chu, Ruiqing

2018-02-01

Lead-free piezoelectric ceramics (Bi0.5Na0.5)0.935Ba0.065Ti1- x (Ni0.5Sb0.5) x O3 (BNBT6.5- xNS) have been fabricated using conventional solid sintering technique. The effect of (Ni, Sb) doping on the phase structure and electrical properties of BNBT6.5 ceramics were systematically investigated. Results show that the addition of (Ni, Sb) destroyed the ferroelectric long-range order of BNBT6.5 and shifted the ferroelectric-relaxor transition temperature ( T F-R) down to room temperature. Thus, this process induced an ergodic relaxor phase at zero field in samples with x = 0.005. Under the electric field, the ergodic relaxor phase could reversibly transform to ferroelectric phase, which promotes the strain response with peak value of 0.38% (at 80 kV/cm, corresponding to d 33 * = 479 pm/V) at x = 0.005. Temperature-dependent measurements of both polarization and strain confirmed that the large strain originated from a reversible field-induced ergodic relaxor to ferroelectric phase transformation. The proposed material exhibits potential for nonlinear actuators.

Indications for an inducible component of error-prone DNA repair in yeast.

PubMed

Siede, W; Eckardt, F

1984-01-01

In a thermoconditional mutant of mutagenic DNA repair (rev 2ts = rad 5-8) of Saccharomyces cerevisiae recovery of survival and mutation frequencies can be monitored by incubating UV-irradiated cells in growth medium at a permissive temperature (23 degrees C) before plating and a shift to restrictive temperature (36 degrees C). Inhibition of protein synthesis with cycloheximide during incubation at permissive conditions blocks this REV 2 dependent recovery process in stationary phase rev 2ts cells, whereas it can be reduced but not totally abolished in exponentially growing cells. These results indicate a strict dependence on post-irradiation protein synthesis in stationary phase cells and argue for a considerable constitutive level and only limited inducibility in logarithmic phase cells. The UV inducibility of the REV 2 coded function in stationary phase cells could be confirmed by analysis of the dose-response pattern of the his 5-2 reversion: in stationary phase rev 2ts cells, the quadratic component of the biphasic linear-quadratic induction kinetics found at 23 degrees C, which is interpreted as the consequence of induction of mutagenic repair, is eliminated at 36 degrees C.

In-line phase shift tomosynthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hammonds, Jeffrey C.; Price, Ronald R.; Pickens, David R.

2013-08-15

Purpose: The purpose of this work is to (1) demonstrate laboratory measurements of phase shift images derived from in-line phase-contrast radiographs using the attenuation-partition based algorithm (APBA) of Yan et al.[Opt. Express 18(15), 16074–16089 (2010)], (2) verify that the APBA reconstructed images obey the linearity principle, and (3) reconstruct tomosynthesis phase shift images from a collection of angularly sampled planar phase shift images.Methods: An unmodified, commercially available cabinet x-ray system (Faxitron LX-60) was used in this experiment. This system contains a tungsten anode x-ray tube with a nominal focal spot size of 10 μm. The digital detector uses CsI/CMOS withmore » a pixel size of 50 × 50 μm. The phantoms used consisted of one acrylic plate, two polystyrene plates, and a habanero pepper. Tomosynthesis images were reconstructed from 51 images acquired over a ±25° arc. All phase shift images were reconstructed using the APBA.Results: Image contrast derived from the planar phase shift image of an acrylic plate of uniform thickness exceeded the contrast of the traditional attenuation image by an approximate factor of two. Comparison of the planar phase shift images from a single, uniform thickness polystyrene plate with two polystyrene plates demonstrated an approximate linearity of the estimated phase shift with plate thickness (−1600 rad vs −2970 rad). Tomographic phase shift images of the habanero pepper exhibited acceptable spatial resolution and contrast comparable to the corresponding attenuation image.Conclusions: This work demonstrated the feasibility of laboratory-based phase shift tomosynthesis and suggests that phase shift imaging could potentially provide a new imaging biomarker. Further investigation will be needed to determine if phase shift contrast will be able to provide new tissue contrast information or improved clinical performance.« less

Overfishing reduces resilience of kelp beds to climate-driven catastrophic phase shift.

PubMed

Ling, S D; Johnson, C R; Frusher, S D; Ridgway, K R

2009-12-29

A key consideration in assessing impacts of climate change is the possibility of synergistic effects with other human-induced stressors. In the ocean realm, climate change and overfishing pose two of the greatest challenges to the structure and functioning of marine ecosystems. In eastern Tasmania, temperate coastal waters are warming at approximately four times the global ocean warming average, representing the fastest rate of warming in the Southern Hemisphere. This has driven range extension of the ecologically important long-spined sea urchin (Centrostephanus rodgersii), which has now commenced catastrophic overgrazing of productive Tasmanian kelp beds leading to loss of biodiversity and important rocky reef ecosystem services. Coincident with the overgrazing is heavy fishing of reef-based predators including the spiny lobster Jasus edwardsii. By conducting experiments inside and outside Marine Protected Areas we show that fishing, by removing large predatory lobsters, has reduced the resilience of kelp beds against the climate-driven threat of the sea urchin and thus increased risk of catastrophic shift to widespread sea urchin barrens. This shows that interactions between multiple human-induced stressors can exacerbate nonlinear responses of ecosystems to climate change and limit the adaptive capacity of these systems. Management actions focused on reducing the risk of catastrophic phase shift in ecosystems are particularly urgent in the face of ongoing warming and unprecedented levels of predator removal from the world's oceans.

Overfishing reduces resilience of kelp beds to climate-driven catastrophic phase shift

PubMed Central

Ling, S. D.; Johnson, C. R.; Frusher, S. D.; Ridgway, K. R.

2009-01-01

A key consideration in assessing impacts of climate change is the possibility of synergistic effects with other human-induced stressors. In the ocean realm, climate change and overfishing pose two of the greatest challenges to the structure and functioning of marine ecosystems. In eastern Tasmania, temperate coastal waters are warming at approximately four times the global ocean warming average, representing the fastest rate of warming in the Southern Hemisphere. This has driven range extension of the ecologically important long-spined sea urchin (Centrostephanus rodgersii), which has now commenced catastrophic overgrazing of productive Tasmanian kelp beds leading to loss of biodiversity and important rocky reef ecosystem services. Coincident with the overgrazing is heavy fishing of reef-based predators including the spiny lobster Jasus edwardsii. By conducting experiments inside and outside Marine Protected Areas we show that fishing, by removing large predatory lobsters, has reduced the resilience of kelp beds against the climate-driven threat of the sea urchin and thus increased risk of catastrophic shift to widespread sea urchin barrens. This shows that interactions between multiple human-induced stressors can exacerbate nonlinear responses of ecosystems to climate change and limit the adaptive capacity of these systems. Management actions focused on reducing the risk of catastrophic phase shift in ecosystems are particularly urgent in the face of ongoing warming and unprecedented levels of predator removal from the world's oceans. PMID:20018706

Gas-Phase Dopant-Induced Conformational Changes Monitored with Transversal Modulation Ion Mobility Spectrometry.

PubMed

Meyer, Nicole Andrea; Root, Katharina; Zenobi, Renato; Vidal-de-Miguel, Guillermo

2016-02-16

The potential of a Transversal Modulation Ion Mobility Spectrometry (TMIMS) instrument for protein analysis applications has been evaluated. The Collision Cross Section (CCS) of cytochrome c measured with the TMIMS is in agreement with values reported in the literature. Additionally, it enables tandem IMS-IMS prefiltration in dry gas and in vapor doped gas. The chemical specificity of the different dopants enables interesting studies on the structure of proteins as CCS changed strongly depending on the specific dopant. Hexane produced an unexpectedly high CCS shift, which can be utilized to evaluate the exposure of hydrophobic parts of the protein. Alcohols produced higher shifts with a dual behavior: an increase in CCS due to vapor uptake at specific absorption sites, followed by a linear shift typical for unspecific and unstable vapor uptake. The molten globule +8 shows a very specific transition. Initially, its CCS follows the trend of the compact folded states, and then it rapidly increases to the levels of the unfolded states. This strong variation suggests that the +8 charge state undergoes a dopant-induced conformational change. Interestingly, more sterically demanding alcohols seem to unfold the protein more effectively also in the gas phase. This study shows the capabilities of the TMIMS device for protein analysis and how tandem IMS-IMS with dopants could provide better understanding of the conformational changes of proteins.

Different hydraulic responses to the 2008 Wenchuan and 2011 Tohoku earthquakes in two adjacent far-field wells: the effect of shales on aquifer lithology

NASA Astrophysics Data System (ADS)

Zhang, Yan; Fu, Li-Yun; Ma, Yuchuan; Hu, Junhua

2016-11-01

Zuojiazhuang and Baodi are two adjacent wells ( 50 km apart) in northern China. The large 2008 M w 7.9 Wenchuan and 2011 M w 9.1 Tohoku earthquakes induced different co-seismic water-level responses in these far-field (>1000 km) wells. The co-seismic water-level changes in the Zuojiazhuang well exhibited large amplitudes ( 2 m), whereas those in the Baodi well were small and unclear ( 0.05 m). The mechanism of the different co-seismic hydraulic responses in the two wells needs to be revealed. In this study, we used the barometric responses in different frequency domains and the phase shifts and amplitude ratios of the tidal responses (M2 wave), together with the well logs, to explain this inconformity. Our calculations show that the co-seismic phase shifts of the M2 wave decreased or remained unchanged in the Baodi well, which was quite different from the Zuojiazhuang well and from the commonly accepted phenomena. According to the well logs, the lithology of the Baodi well is characterized by the presence of a significant amount of shale. The low porosity/permeability of shale in the Baodi well could be the cause for the unchanged and decreased phase shifts and tiny co-seismic water-level responses. In addition, shale is one of the causes of positive phase shifts and indicates a vertical water-level flow, which may be due to a semi-confined aquifer or the complex and anisotropic fracturing of shale.

PSK Shift Timing Information Detection Using Image Processing and a Matched Filter

DTIC Science & Technology

2009-09-01

phase shifts are enhanced.  Develop, design, and test the resulting phase shift identification scheme. xx  Develop, design, and test an optional...and the resulting phase shift identification algorithm is investigated for SNR levels in the range -2dB to 12 dB. Detection performances are derived...test the resulting phase shift identification scheme.  Develop, design, and test an optional analysis window overlapping technique to improve phase

Alternating phase-shifted mask for logic gate levels, design, and mask manufacturing

NASA Astrophysics Data System (ADS)

Liebmann, Lars W.; Graur, Ioana C.; Leipold, William C.; Oberschmidt, James M.; O'Grady, David S.; Regaill, Denis

1999-07-01

While the benefits of alternating phase shifted masks in improving lithographic process windows at increased resolution are well known throughout the lithography community, broad implementation of this potentially powerful technique has been slow due to the inherent complexity of the layout design and mask manufacturing process. This paper will review a project undertaken at IBM's Semiconductor Research and Development Center and Mask Manufacturing and Development facility to understand the technical and logistical issues associated with the application of alternating phase shifted mask technology to the gate level of a full microprocessor chip. The work presented here depicts an important milestone toward integration of alternating phase shifted masks into the manufacturing process by demonstrating an automated design solution and yielding a functional alternating phase shifted mask. The design conversion of the microprocessor gate level to a conjugate twin shifter alternating phase shift layout was accomplished with IBM's internal design system that automatically scaled the design, added required phase regions, and resolved phase conflicts. The subsequent fabrication of a nearly defect free phase shifted mask, as verified by SEM based die to die inspection, highlights the maturity of the alternating phase shifted mask manufacturing process in IBM's internal mask facility. Well defined and recognized challenges in mask inspection and repair remain and the layout of alternating phase shifted masks present a design and data preparation overhead, but the data presented here demonstrate the feasibility of designing and building manufacturing quality alternating phase shifted masks for the gate level of a microprocessor.

Effect of Phase Shift from Corals to Zoantharia on Reef Fish Assemblages

PubMed Central

Cruz, Igor C. S.; Loiola, Miguel; Albuquerque, Tiago; Reis, Rodrigo; de Anchieta C. C. Nunes, José; Reimer, James D.; Mizuyama, Masaru; Kikuchi, Ruy K. P.; Creed, Joel C.

2015-01-01

Consequences of reef phase shifts on fish communities remain poorly understood. Studies on the causes, effects and consequences of phase shifts on reef fish communities have only been considered for coral-to-macroalgae shifts. Therefore, there is a large information gap regarding the consequences of novel phase shifts and how these kinds of phase shifts impact on fish assemblages. This study aimed to compare the fish assemblages on reefs under normal conditions (relatively high cover of corals) to those which have shifted to a dominance of the zoantharian Palythoa cf. variabilis on coral reefs in Todos os Santos Bay (TSB), Brazilian eastern coast. We examined eight reefs, where we estimated cover of corals and P. cf. variabilis and coral reef fish richness, abundance and body size. Fish richness differed significantly between normal reefs (48 species) and phase-shift reefs (38 species), a 20% reduction in species. However there was no difference in fish abundance between normal and phase shift reefs. One fish species, Chaetodon striatus, was significantly less abundant on normal reefs. The differences in fish assemblages between different reef phases was due to differences in trophic groups of fish; on normal reefs carnivorous fishes were more abundant, while on phase shift reefs mobile invertivores dominated. PMID:25629532

Photonic band-gap modulation of blue phase liquid crystal (Presentation Recording)

NASA Astrophysics Data System (ADS)

Lin, Tsung-Hsien

2015-10-01

Blue phase liquid crystals (BPLCs) are self-assembled 3D photonic crystals exhibiting high susceptibility to external stimuli. Two methods for the photonic bandgap tuning of BPs were demonstrated in this work. Introducing a chiral azobenzene into a cholesteric liquid crystal could formulate a photoresponsive BPLC. Under violet irradiation, the azo dye experiences trans-cis isomerization, which leads to lattice swelling as well as phase transition in different stages of the process. Ultrawide reversible tuning of the BP photonic bandgap from ultraviolet to near infrared has been achieved. The tuning is reversible and nonvolatile. We will then demonstract the electric field-induced bandgap tuning in polymer-stabilized BPLCs. Under different BPLCs material preparation conditions, both red-shift and broadening of the photonic bandgaps have been achieved respectively. The stop band can be shifted over 100 nm. The bandwidth can be expanded from ~ 30 nm to ~ 250 nm covering nearly the full visible range. It is believed that the developed approaches could strongly promote the use of BPLC in photonic applications.

Apparatus and method for monitoring the presence of a conductive media

DOEpatents

DuVall, Bruce W.; Valentine, James W.; Morey, Kenneth O.

1979-01-01

An inductive level sensor has inductively coupled primary and secondary windings. Circuitry drives the primary with an AC signal of constant current magnitude and selected frequency f to induce in the secondary, a voltage signal V of magnitude .vertline.V.vertline., frequency f and phase difference .phi. from the driving signal. Circuitry operates to generate a voltage output signal proportional to .vertline.V.vertline. cos (.phi.-.theta.), where .theta. is a selectively set phase shift factor. By properly and selectively adjusting the frequency f and phase shift factor .theta., an output signal .vertline.V.vertline. cos (.phi.-.theta.) can be provided which self-compensates for changes in mutual inductance caused by operating temperature variations so that an output signal is produced which is substantially linearly proportional to changes in the level of a pool of liquid metal being monitored. Disclosed also is calibration circuitry and circuitry for converting the voltage signal .vertline.V.vertline. cos (.phi.-.theta.) into a current signal.

Magnetosonic waves interactions in a spin-1/2 degenerate quantum plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Sheng-Chang, E-mail: lsc1128lsc@126.com; Han, Jiu-Ning

2014-03-15

We investigate the magnetosonic waves and their interactions in a spin-1/2 degenerate quantum plasma. With the help of the extended Poincaré-Lighthill-Kuo perturbation method, we derive two Korteweg-de Vries-Burgers equations to describe the magnetosonic waves. The parameter region where exists magnetosonic waves and the phase diagram of the compressive and rarefactive solitary waves with different plasma parameters are shown. We further explore the effects of quantum diffraction, quantum statistics, and electron spin magnetization on the head-on collisions of magnetosonic solitary waves. We obtain the collision-induced phase shifts (trajectory changes) analytically. Both for the compressive and rarefactive solitary waves, it is foundmore » that the collisions only lead to negative phase shifts. Our present study should be useful to understand the collective phenomena related to the magnetosonic wave collisions in degenerate plasmas like those in the outer shell of massive white dwarfs as well as to the potential applications of plasmas.« less

Study of thermospheric and ionospheric tidal responses to the 2009 stratospheric sudden warming by an assimilative atmosphere-ionosphere coupled TIME-GCM with FORMOSAT-3/COSMIC observations

NASA Astrophysics Data System (ADS)

Lin, Jia-Ting; Liu, Hanli; Liu, Jann-Yenq; Lin, Charles C. H.; Chen, Chia-Hung; Chang, Loren; Chen, Wei-Han

In this study, ionospheric peak densities obtained from radio occultation soundings of FORMOSAT-3/COSMIC are decomposed into their various constituent tidal components for studying the stratospheric sudden warming (SSW) effects on the tidal responses during the 2008/2009. The observations are further compared with the results from an atmosphere-ionosphere coupled model, TIME-GCM. The model assimilates MERRA 3D meteorological data between the lower-boundary (~30km) and 0.1h Pa (~62km) by a nudging method. The comparison shows general agreement in the major features of decrease of migrating tidal signatures (DW1, SW2 and TW3) in ionosphere around the growth phase of SSW, with phase/time shifts in the daily time of maximum around EIA and middle latitudes. Both the observation and simulation indicate a pronounced enhancement of the ionospheric SW2 signatures after the stratospheric temperature increase. The model suggest that the typical morning enhancement/afternoon reduction of electron density variation is mainly caused by modification of the ionospheric migrating tidal signatures. The model shows that the thermospheric SW2 tide variation is similar to ionosphere as well as the phase shift. These phases shift of migrating tides are highly related to the present of induced secondary planetary wave 1 in the E region.

Frequency Invariability of (Pb,La)(Zr,Ti)O₃ Antiferroelectric Thick-Film Micro-Cantilevers.

PubMed

An, Kun; Jin, Xuechen; Meng, Jiang; Li, Xiao; Ren, Yifeng

2018-05-13

Micro-electromechanical systems comprising antiferroelectric layers can offer both actuation and transduction to integrated technologies. Micro-cantilevers based on the (Pb 0.97 La 0.02 )(Zr 0.95 Ti 0.05 )O₃ (PLZT) antiferroelectric thick film are fabricated by the micro-nano manufacturing process, to utilize the effect of phase transition induced strain and sharp phase switch of antiferroelectric materials. When micro-cantilevers made of antiferroelectric thick films were driven by sweep voltages, there were two resonant peaks corresponding to the natural frequency shift from 27.8 to 27.0 kHz, before and after phase transition. This is the compensation principle for the PLZT micro-cantilever to tune the natural frequency by the amplitude modulation of driving voltage, rather than of frequency modulation. Considering the natural frequency shift about 0.8 kHz and the frequency tuning ability about 156 Hz/V before the phase transition, this can compensate the frequency shift caused by increasing temperature by tuning only the amplitude of driving voltage, when the ultrasonic micro-transducer made of antiferroelectric thick films works for such a long period. Therefore, antiferroelectric thick films with hetero-structures incorporated into PLZT micro-cantilevers not only require a lower driving voltage (no more than 40 V) than rival bulk piezoelectric ceramics, but also exhibit better performance of frequency invariability, based on the amplitude modulation.

Circular carrier squeezing interferometry: Suppressing phase shift error in simultaneous phase-shifting point-diffraction interferometer

NASA Astrophysics Data System (ADS)

Zheng, Donghui; Chen, Lei; Li, Jinpeng; Sun, Qinyuan; Zhu, Wenhua; Anderson, James; Zhao, Jian; Schülzgen, Axel

2018-03-01

Circular carrier squeezing interferometry (CCSI) is proposed and applied to suppress phase shift error in simultaneous phase-shifting point-diffraction interferometer (SPSPDI). By introducing a defocus, four phase-shifting point-diffraction interferograms with circular carrier are acquired, and then converted into linear carrier interferograms by a coordinate transform. Rearranging the transformed interferograms into a spatial-temporal fringe (STF), so the error lobe will be separated from the phase lobe in the Fourier spectrum of the STF, and filtering the phase lobe to calculate the extended phase, when combined with the corresponding inverse coordinate transform, exactly retrieves the initial phase. Both simulations and experiments validate the ability of CCSI to suppress the ripple error generated by the phase shift error. Compared with carrier squeezing interferometry (CSI), CCSI is effective on some occasions in which a linear carrier is difficult to introduce, and with the added benefit of eliminating retrace error.

Hyper-Ramsey spectroscopy of optical clock transitions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yudin, V. I.; Taichenachev, A. V.; Oates, C. W.

2010-07-15

We present nonstandard optical Ramsey schemes that use pulses individually tailored in duration, phase, and frequency to cancel spurious frequency shifts related to the excitation itself. In particular, the field shifts and their uncertainties can be radically suppressed (by two to four orders of magnitude) in comparison with the usual Ramsey method (using two equal pulses) as well as with single-pulse Rabi spectroscopy. Atom interferometers and optical clocks based on two-photon transitions, heavily forbidden transitions, or magnetically induced spectroscopy could significantly benefit from this method. In the latter case, these frequency shifts can be suppressed considerably below a fractional levelmore » of 10{sup -17}. Moreover, our approach opens the door for high-precision optical clocks based on direct frequency comb spectroscopy.« less

Moiré deflectometry using the Talbot-Lau interferometer as refraction diagnostic for High Energy Density plasmas at energies below 10 keV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Valdivia, M. P.; Stutman, D.; Finkenthal, M.

2014-07-15

The highly localized density gradients expected in High Energy Density (HED) plasma experiments can be characterized by x-ray phase-contrast imaging in addition to conventional attenuation radiography. Moiré deflectometry using the Talbot-Lau grating interferometer setup is an attractive HED diagnostic due to its high sensitivity to refraction induced phase shifts. We report on the adaptation of such a system for operation in the sub-10 keV range by using a combination of free standing and ultrathin Talbot gratings. This new x-ray energy explored matches well the current x-ray backlighters used for HED experiments, while also enhancing phase effects at lower electron densities.more » We studied the performance of the high magnification, low energy Talbot-Lau interferometer, for single image phase retrieval using Moiré fringe deflectometry. Our laboratory and simulation studies indicate that such a device is able to retrieve object electron densities from phase shift measurements. Using laboratory x-ray sources from 7 to 15 μm size we obtained accurate simultaneous measurements of refraction and attenuation for both sharp and mild electron density gradients.« less

Moiré deflectometry using the Talbot-Lau interferometer as refraction diagnostic for high energy density plasmas at energies below 10 keV.

PubMed

Valdivia, M P; Stutman, D; Finkenthal, M

2014-07-01

The highly localized density gradients expected in High Energy Density (HED) plasma experiments can be characterized by x-ray phase-contrast imaging in addition to conventional attenuation radiography. Moiré deflectometry using the Talbot-Lau grating interferometer setup is an attractive HED diagnostic due to its high sensitivity to refraction induced phase shifts. We report on the adaptation of such a system for operation in the sub-10 keV range by using a combination of free standing and ultrathin Talbot gratings. This new x-ray energy explored matches well the current x-ray backlighters used for HED experiments, while also enhancing phase effects at lower electron densities. We studied the performance of the high magnification, low energy Talbot-Lau interferometer, for single image phase retrieval using Moiré fringe deflectometry. Our laboratory and simulation studies indicate that such a device is able to retrieve object electron densities from phase shift measurements. Using laboratory x-ray sources from 7 to 15 μm size we obtained accurate simultaneous measurements of refraction and attenuation for both sharp and mild electron density gradients.

REVIEW OF SIGNAL DISTORTION THROUGH METAL MICROELECTRODE RECORDING CIRCUITS AND FILTERS

PubMed Central

NELSON, Matthew J.; POUGET, Pierre; NILSEN, Erik A.; PATTEN, Craig D.; SCHALL, Jeffrey D.

2008-01-01

Interest in local field potentials (LFPs) and action potential shape has increased markedly. The present work describes distortions of these signals that occur for two reasons. First, the microelectrode recording circuit operates as a voltage divider producing frequency-dependent attenuation and phase-shifts when electrode impedance is not negligible relative to amplifier input impedance. Because of the much higher electrode impedance at low frequencies, this occurred over frequency ranges of LFPs measured by neurophysiologists for one head-stage tested. Second, frequency-dependent phase shifts are induced by subsequent filters. Thus, we report these effects and the resulting amplitude envelope delays and distortion of waveforms recorded through a commercial data acquisition system and a range of tungsten microelectrodes. These distortions can be corrected, but must be accounted for when interpreting field potential and spike shape data. PMID:18242715

Review of signal distortion through metal microelectrode recording circuits and filters.

PubMed

Nelson, Matthew J; Pouget, Pierre; Nilsen, Erik A; Patten, Craig D; Schall, Jeffrey D

2008-03-30

Interest in local field potentials (LFPs) and action potential shape has increased markedly. The present work describes distortions of these signals that occur for two reasons. First, the microelectrode recording circuit operates as a voltage divider producing frequency-dependent attenuation and phase shifts when electrode impedance is not negligible relative to amplifier input impedance. Because of the much higher electrode impedance at low frequencies, this occurred over frequency ranges of LFPs measured by neurophysiologists for one head-stage tested. Second, frequency-dependent phase shifts are induced by subsequent filters. Thus, we report these effects and the resulting amplitude envelope delays and distortion of waveforms recorded through a commercial data acquisition system and a range of tungsten microelectrodes. These distortions can be corrected, but must be accounted for when interpreting field potential and spike shape data.

Geometric phase and o -mode blueshift in a chiral anisotropic medium inside a Fabry-Pérot cavity

NASA Astrophysics Data System (ADS)

Timofeev, Ivan V.; Gunyakov, Vladimir A.; Sutormin, Vitaly S.; Myslivets, Sergey A.; Arkhipkin, Vasily G.; Vetrov, Stepan Ya.; Lee, Wei; Zyryanov, Victor Ya.

2015-11-01

Anomalous spectral shift of transmission peaks is observed in a Fabry-Pérot cavity filled with a chiral anisotropic medium. The effective refractive index value resides out of the interval between the ordinary and the extraordinary refractive indices. The spectral shift is explained by contribution of a geometric phase. The problem is solved analytically using the approximate Jones matrix method, numerically using the accurate Berreman method, and geometrically using the generalized Mauguin-Poincaré rolling cone method. The o -mode blueshift is measured for a 4-methoxybenzylidene-4 '-n -butylaniline twisted-nematic layer inside the Fabry-Pérot cavity. The twist is electrically induced due to the homeoplanar-twisted configuration transition in an ionic-surfactant-doped liquid crystal layer. Experimental evidence confirms the validity of the theoretical model.

Performance of synchronous optical receivers using atmospheric compensation techniques.

PubMed

Belmonte, Aniceto; Khan, Joseph

2008-09-01

We model the impact of atmospheric turbulence-induced phase and amplitude fluctuations on free-space optical links using synchronous detection. We derive exact expressions for the probability density function of the signal-to-noise ratio in the presence of turbulence. We consider the effects of log-normal amplitude fluctuations and Gaussian phase fluctuations, in addition to local oscillator shot noise, for both passive receivers and those employing active modal compensation of wave-front phase distortion. We compute error probabilities for M-ary phase-shift keying, and evaluate the impact of various parameters, including the ratio of receiver aperture diameter to the wave-front coherence diameter, and the number of modes compensated.

Time-resolved coherent Raman spectroscopy by high-speed pump-probe delay scanning.

PubMed

Domingue, S R; Winters, D G; Bartels, R A

2014-07-15

Using a spinning window pump-probe delay scanner, we demonstrate a means of acquiring time-resolved vibrational spectra at rates up to 700 Hz. The time-dependent phase shift accumulated by the probe pulse in the presence of a coherently vibrating sample gives rise to a Raman-induced frequency shifting readily detectable in a balanced detector. This rapid delay scanning system represents a 23-fold increase in averaging speed and is >10× faster than state-of-the-art voice coil delay lines. These advancements make pump-probe spectroscopy a more practical means of imaging complex media.

Investigation of advanced phase-shifting projected fringe profilometry techniques

NASA Astrophysics Data System (ADS)

Liu, Hongyu

1999-11-01

The phase-shifting projected fringe profilometry (PSPFP) technique is a powerful tool in the profile measurements of rough engineering surfaces. Compared with other competing techniques, this technique is notable for its full-field measurement capacity, system simplicity, high measurement speed, and low environmental vulnerability. The main purpose of this dissertation is to tackle three important problems, which severely limit the capability and the accuracy of the PSPFP technique, with some new approaches. Chapter 1 provides some background information of the PSPFP technique including the measurement principles, basic features, and related techniques is briefly introduced. The objectives and organization of the thesis are also outlined. Chapter 2 gives a theoretical treatment to the absolute PSPFP measurement. The mathematical formulations and basic requirements of the absolute PSPFP measurement and its supporting techniques are discussed in detail. Chapter 3 introduces the experimental verification of the proposed absolute PSPFP technique. Some design details of a prototype system are discussed as supplements to the previous theoretical analysis. Various fundamental experiments performed for concept verification and accuracy evaluation are introduced together with some brief comments. Chapter 4 presents the theoretical study of speckle- induced phase measurement errors. In this analysis, the expression for speckle-induced phase errors is first derived based on the multiplicative noise model of image- plane speckles. The statistics and the system dependence of speckle-induced phase errors are then thoroughly studied through numerical simulations and analytical derivations. Based on the analysis, some suggestions on the system design are given to improve measurement accuracy. Chapter 5 discusses a new technique combating surface reflectivity variations. The formula used for error compensation is first derived based on a simplified model of the detection process. The techniques coping with two major effects of surface reflectivity variations are then introduced. Some fundamental problems in the proposed technique are studied through simulations. Chapter 6 briefly summarizes the major contributions of the current work and provides some suggestions for the future research.

Spatial Shifts in Tidal-Fluvial Environments

NASA Astrophysics Data System (ADS)

Dykstra, S. L.; Dzwonkowski, B.

2017-12-01

Fresh water discharge damps tidal propagation and increases the phase lag, which has important impacts on system-wide sediment transport process and ecological structure. Here, the role of discharge on spatial variability in the dynamics of tidal rivers is investigated in Mobile Bay and Delta, a microtidal diurnal system where discharge ranges multiple orders of magnitude. Long-term observations at 7 velocity stations and 20 water level stations, ranging over 260km along the system, were analyzed. Observations of the tidal extinguishing point in both velocity and water level were highly variable with significant shifts in location covering a distance over 140km. The velocity stations also allowed for measuring the extent of flood (i.e. point where tidal flow is arrested by discharge) shifting 100km. With increased discharge, flow characteristics at station locations can transition from an estuary (i.e. bidirectional tidal flow) to a tidal river to a traditional fluvial environment. This revealed systematic discharge induced damping and an increase in phase lag. Interestingly, before damping occurs, the tide amplifies ( 15%) seaward of the extent of flood. Another consistent pattern is the higher sensitivity of the velocity signal to discharge than water level. This causes the velocity to lag more and create progressive tides. In a microtidal diurnal system, the signal propagates further inland than a semidiurnal tide due to its lower frequency but is easily damped due to the small amplitude, creating large shifts. Previous research has focused on environments dominated by semidiurnal tides with similar magnitudes to discharge using water level observations. For example, the well studied Columbia and the St. Lawrence rivers have small shifts in their tidal extinguishing point O(10km) (Jay 2016, Matte 2014). These shifts are not large enough to observe process like discharge-induced amplification and damping at the same site like in the Mobile system, but they may indicate a decoupling of the water level and velocity signal by discharge. Throughout the world, shifts in tidal rivers are created by seasonal discharge patterns, but large storms can quickly disrupt a system and move it over 140km in a few days.

Responses of the circadian system of rats to conditioned and unconditioned stimuli.

PubMed

de Groot, M H; Rusak, B

2000-08-01

The circadian systems of rodents respond to light pulses presented during the subjective night with phase shifts and altered cellular activity in the suprachiasmatic nuclei (SCN), including expression of immediate-early genes (IEGs) such as c-fos. A recent study showed that a nonphotic stimulus (an air disturbance generated by a fan) that does not normally induce the expression of c-fos-like immunoreactivity in the SCN of rats can be made to do so after being paired repeatedly with a light pulse in a Pavlovian conditioning paradigm. Furthermore, after conditioning (but not after noncontingent exposure to these stimuli), the fan also induced phase shifts in activity and body temperature rhythms comparable to those produced by light. The authors performed three experiments designed to replicate and extend these findings in rats. In experiment 1, rats were tested for conditioning effects of repeated pairings of a light pulse with a neutral air disturbance under a full photoperiod. In experiment 2, a modified conditioning paradigm was used in which a skeleton photoperiod served as both the entraining zeitgeber and the unconditioned stimulus. Animals in the paired and unpaired training conditions were exposed to both the light pulse and the air disturbance, but the air disturbance signaled the onset of light in the paired condition only. Phase shifts of wheel-running activity rhythms and gene expression in the SCN, intergeniculate leaflet, and paraventricular nucleus of the thalamus were assessed in animals following either of the training conditions or the control procedures. Experiment 3 assessed whether the air disturbance could entrain the circadian activity rhythms of rats with or without previous pairing with light in a classical conditioning paradigm. No evidence for classical conditioning, nor for unconditioned effects of the air disturbance on the circadian system, was found in these studies.

Quantitative phase imaging of human red blood cells using phase-shifting white light interference microscopy with colour fringe analysis

NASA Astrophysics Data System (ADS)

Singh Mehta, Dalip; Srivastava, Vishal

2012-11-01

We report quantitative phase imaging of human red blood cells (RBCs) using phase-shifting interference microscopy. Five phase-shifted white light interferograms are recorded using colour charge coupled device camera. White light interferograms were decomposed into red, green, and blue colour components. The phase-shifted interferograms of each colour were then processed by phase-shifting analysis and phase maps for red, green, and blue colours were reconstructed. Wavelength dependent refractive index profiles of RBCs were computed from the single set of white light interferogram. The present technique has great potential for non-invasive determination of refractive index variation and morphological features of cells and tissues.

Detection of ionized gas molecules in air by graphene and carbon nanotube networks

NASA Astrophysics Data System (ADS)

Hao, Ji; Li, Bo; Yung, Hyun Young; Liu, Fangze; Hong, Sanghyung; Jung, Yung Joon; Kar, Swastik

The liquid phase ions sensing by graphene and carbon nanotube has been demonstrated in many publications due to the minimum gate voltage easily shift induced by ionic gating effect, but it is still unclear for vapor phase ions sensing. Here we want to report that the ionized gas molecules in air can be also very sensitively detected by graphene and carbon nanotube networks under very low applied voltage, which shows the very high charge to current amplification factor, the value can be up to 108 A/C, and the direction of current-change can be used to differentiate the positive and negative ions. In further, the field effect of graphene device induced by vapor phase ions was discussed. NSF ECCS 1202376, NSF ECCS CAREER 1351424 and NSF DMREF 1434824, a Northeastern University Provost's Tier-1 seed Grant for interdisciplinary research, Technology Innovation Program (10050481) from Ministry of Trade, Industry & Energy of Republic of Korea.

Origin of bias-stress induced instability in organic thin-film transistors with semiconducting small-molecule/insulating polymer blend channel.

PubMed

Park, Ji Hoon; Lee, Young Tack; Lee, Hee Sung; Lee, Jun Young; Lee, Kimoon; Lee, Gyu Baek; Han, Jiwon; Kim, Tae Woong; Im, Seongil

2013-03-13

The stabilities of a blending type organic thin-film transistor with phase-separated TIPS-pentacene channel layer were characterized under the conditions of negative-bias-stress (NBS) and positive-bias-stress (PBS). During NBS, threshold voltage (Vth) shifts noticeably. NBS-imposed devices revealed interfacial trap density-of-states (DOS) at 1.56 and 1.66 eV, whereas initial device showed the DOS at only 1.56 eV, as measured by photoexcited charge-collection spectroscopy (PECCS) method. Possible origin of this newly created defect is related to ester group in PMMA, which induces some hole traps at the TIPS-pentacene/i-PMMA interface. PBS-imposed device showed little Vth shift but visible off-current increase as "back-channel" effect, which is attributed to the water molecules trapped on the TFT surface.

Homodyne locking of a squeezer.

PubMed

Heurs, M; Petersen, I R; James, M R; Huntington, E H

2009-08-15

We report on the successful implementation of an approach to locking the frequencies of an optical parametric oscillator (OPO)-based squeezed-vacuum source and its driving laser. The technique allows the simultaneous measurement of the phase shifts induced by a cavity, which may be used for the purposes of frequency locking, as well as the simultaneous measurement of the sub-quantum-noise-limited (sub-QNL) phase quadrature output of the OPO. The homodyne locking technique is cheap, easy to implement, and has the distinct advantage that subsequent homodyne measurements are automatically phase locked. The homodyne locking technique is also unique in that it is a sub-QNL frequency discriminator.

Phase shifts in the Fourier spectra of phase gratings and phase grids: an application for one-shot phase-shifting interferometry.

PubMed

Toto-Arellano, Noel-Ivan; Rodriguez-Zurita, Gustavo; Meneses-Fabian, Cruz; Vazquez-Castillo, Jose F

2008-11-10

Among several techniques, phase shifting interferometry can be implemented with a grating used as a beam divider to attain several interference patterns around each diffraction order. Because each pattern has to show a different phase-shift, a suitable shifting technique must be employed. Phase gratings are attractive to perform the former task due to their higher diffraction efficiencies. But as is very well known, the Fourier coefficients of only-phase gratings are integer order Bessel functions of the first kind. The values of these real-valued functions oscillate around zero, so they can adopt negative values, thereby introducing phase shifts of pi at certain diffraction orders. Because this almost trivial fact seems to have been overlooked in the literature regarding its practical implications, in this communication such phase shifts are stressed in the description of interference patterns obtained with grating interferometers. These patterns are obtained by placing two windows in the object plane of a 4f system with a sinusoidal grating/grid in the Fourier plane. It is shown that the corresponding experimental observations of the fringe modulation, as well as the corresponding phase measurements, are all in agreement with the proposed description. A one-shot phase shifting interferometer is finally proposed taking into account these properties after proper incorporation of modulation of polarization.

ACUTE ETHANOL DISRUPTS PHOTIC AND SEROTONERGIC CIRCADIAN CLOCK PHASE-RESETTING IN THE MOUSE

PubMed Central

Brager, Allison J.; Ruby, Christina L.; Prosser, Rebecca A.; Glass, J. David

2011-01-01

Background Alcohol abuse is associated with impaired circadian rhythms and sleep. Ethanol administration disrupts circadian clock phase-resetting, suggesting a mode for the disruptive effect of alcohol abuse on the circadian timing system. In this study, we extend previous work in C57BL/6J mice to: 1) characterize the SCN pharmacokinetics of acute systemic ethanol administration; 2) explore the effects of acute ethanol on photic and non-photic phase-resetting; and 2) determine if the SCN is a direct target for photic effects. Methods First, microdialysis was used to characterize the pharmacokinetics of acute i.p. injections of 3 doses of ethanol (0.5, 1.0 and 2.0 g/kg) in the mouse suprachiasmatic (SCN) circadian clock. Second, the effects of acute i.p. ethanol administration on photic phase-delays and serotonergic ([+]8-OH-DPAT-induced) phase-advances of the circadian activity rhythm were assessed. Third, the effects of reverse-microdialysis ethanol perfusion of the SCN on photic phase-resetting were characterized. Results Peak ethanol levels from the 3 doses of ethanol in the SCN occurred within 20–40 min post-injection with half-lives for clearance ranging from 0.6–1.8 hr. Systemic ethanol treatment dose-dependently attenuated photic and serotonergic phase-resetting. This treatment also did not affect basal SCN neuronal activity as assessed by Fos expression. Intra-SCN perfusion with ethanol markedly reduced photic phase-delays. Conclusions These results confirm that acute ethanol attenuates photic phase-delay shifts and serotonergic phase-advance shifts in the mouse. This dual effect could disrupt photic and non-photic entrainment mechanisms governing circadian clock timing. It is also significant that the SCN clock is a direct target for disruptive effects of ethanol on photic shifting. Such actions by ethanol could underlie the disruptive effects of alcohol abuse on behavioral, physiological, and endocrine rhythms associated with alcoholism. PMID:21463340

Visual experience and subsequent sleep induce sequential plastic changes in putative inhibitory and excitatory cortical neurons

PubMed Central

Aton, Sara J.; Broussard, Christopher; Dumoulin, Michelle; Seibt, Julie; Watson, Adam; Coleman, Tammi; Frank, Marcos G.

2013-01-01

Ocular dominance plasticity in the developing primary visual cortex is initiated by monocular deprivation (MD) and consolidated during subsequent sleep. To clarify how visual experience and sleep affect neuronal activity and plasticity, we continuously recorded extragranular visual cortex fast-spiking (FS) interneurons and putative principal (i.e., excitatory) neurons in freely behaving cats across periods of waking MD and post-MD sleep. Consistent with previous reports in mice, MD induces two related changes in FS interneurons: a response shift in favor of the closed eye and depression of firing. Spike-timing–dependent depression of open-eye–biased principal neuron inputs to FS interneurons may mediate these effects. During post-MD nonrapid eye movement sleep, principal neuron firing increases and becomes more phase-locked to slow wave and spindle oscillations. Ocular dominance (OD) shifts in favor of open-eye stimulation—evident only after post-MD sleep—are proportional to MD-induced changes in FS interneuron activity and to subsequent sleep-associated changes in principal neuron activity. OD shifts are greatest in principal neurons that fire 40–300 ms after neighboring FS interneurons during post-MD slow waves. Based on these data, we propose that MD-induced changes in FS interneurons play an instructive role in ocular dominance plasticity, causing disinhibition among open-eye–biased principal neurons, which drive plasticity throughout the visual cortex during subsequent sleep. PMID:23300282

Complex conductivity response to microbial growth and biofilm formation on phenanthrene spiked medium

NASA Astrophysics Data System (ADS)

Albrecht, Remy; Gourry, Jean Christophe; Simonnot, Marie-Odile; Leyval, Corinne

2011-11-01

Several laboratory studies have recently demonstrated the utility of geophysical methods for the investigation of microbial-induced changes over contaminated sites. However, it remains difficult to distinguish the effects due to the new physical properties imparted by microbial processes, to bacterial growth, or to the development of bacterial biofilm. We chose to study the influence of biofilm formation on geophysical response using complex conductivity measurements (0.1-1000 Hz) in phenanthrene-contaminated media. Biotic assays were conducted with two phenanthrene (PHE) degrading bacterial strains: Burkholderia sp (NAH1), which produced biofilm and Stenophomonas maltophilia (MATE10), which did not, and an abiotic control. Results showed that bacterial densities for NAH1 and MATE10 strains continuously increased at the same rate during the experiment. However, the complex conductivity signature showed noticeable differences between the two bacteria, with a phase shift of 50 mrad at 4 Hz for NAH1, which produced biofilm. Biofilm volume was quantified by Scanning Confocal Laser Microscopy (SCLM). Significant correlations were established between phase shift decrease and biofilm volume for NAH1 assays. Results suggest that complex conductivity measurements, specifically phase shift, can be a useful indicator of biofilm formation inside the overall signal of microbial activity on contaminated sites.

Rapid resetting of human peripheral clocks by phototherapy during simulated night shift work.

PubMed

Cuesta, Marc; Boudreau, Philippe; Cermakian, Nicolas; Boivin, Diane B

2017-11-24

A majority of night shift workers have their circadian rhythms misaligned to their atypical schedule. While bright light exposure at night is known to reset the human central circadian clock, the behavior of peripheral clocks under conditions of shift work is more elusive. The aim of the present study was to quantify the resetting effects of bright light exposure on both central (plasma cortisol and melatonin) and peripheral clocks markers (clock gene expression in peripheral blood mononuclear cells, PBMCs) in subjects living at night. Eighteen healthy subjects were enrolled to either a control (dim light) or a bright light group. Blood was sampled at baseline and on the 4 th day of simulated night shift. In response to a night-oriented schedule, the phase of PER1 and BMAL1 rhythms in PBMCs was delayed by ~2.5-3 h (P < 0.05), while no shift was observed for the other clock genes and the central markers. Three cycles of 8-h bright light induced significant phase delays (P < 0.05) of ~7-9 h for central and peripheral markers, except BMAL1 (advanced by +5h29; P < 0.05). Here, we demonstrate in humans a lack of peripheral clock adaptation under a night-oriented schedule and a rapid resetting effect of nocturnal bright light exposure on peripheral clocks.

Investigation of direct integrated optics modulators. [applicable to data preprocessors

NASA Technical Reports Server (NTRS)

Batchman, T. E.

1980-01-01

Direct modulation techniques applicable to integrated optics data preprocessors were investigated. Several methods of modulating a coherent optical beam by interaction with an incoherent beam were studied. It was decided to investigate photon induced conductivity changes in thin semiconductor cladding layers on optical waveguides. Preliminary calculations indicate significant changes can be produced in the phase shift in a propagating wave when the conductivity is changed by ten percent or more. Experimental devices to verify these predicted phase changes and experiments designed to prove the concept are described.

Parallel-quadrature phase-shifting digital holographic microscopy using polarization beam splitter

PubMed Central

Das, Bhargab; Yelleswarapu, Chandra S; Rao, DVGLN

2012-01-01

We present a digital holography microscopy technique based on parallel-quadrature phase-shifting method. Two π/2 phase-shifted holograms are recorded simultaneously using polarization phase-shifting principle, slightly off-axis recording geometry, and two identical CCD sensors. The parallel phase-shifting is realized by combining circularly polarized object beam with a 45° degree polarized reference beam through a polarizing beam splitter. DC term is eliminated by subtracting the two holograms from each other and the object information is reconstructed after selecting the frequency spectrum of the real image. Both amplitude and phase object reconstruction results are presented. Simultaneous recording eliminates phase errors caused by mechanical vibrations and air turbulences. The slightly off-axis recording geometry with phase-shifting allows a much larger dimension of the spatial filter for reconstruction of the object information. This leads to better reconstruction capability than traditional off-axis holography. PMID:23109732

Silicon RFIC Techniques for Reconfigurable Military Applications

DTIC Science & Technology

2008-12-01

21 3.2.1 Motivation ...2008-295 21 3.2 Distributed Cascode LNAs at 20 GHz 3.2.1 Motivation Millimetrewave integrated circuits are traditionally implemented using...ZRef=50. Ohm Phase=-45. PhaseShiftSML PS4 ZRef=50. Ohm Phase=-22.5 PhaseShiftSML PS7 ZRef=50. Ohm Phase=-180 PhaseShiftSML PS8 ZRef=50. Ohm Phase=-180

Ultra narrow flat-top filter based on multiple equivalent phase shifts

NASA Astrophysics Data System (ADS)

Wang, Fei; Zou, Xihua; Yin, Zuowei; Chen, Xiangfei; Shen, Haisong

2008-11-01

Instead of real phase shifts, equivalent phase shifts (EPS) are adopted to construct ultra narrow phase-shifted band-pass filer in sampled Bragg gratings (SBG). Two optimized distributions of multiple equivalent phase shifts, using 2 and 5 EPSs respectively, are given in this paper to realize flat-top and ripple-free transmission characteristics simultaneously. Also two demonstrations with 5 EPSs both on hydrogen-loaded and photosensitive fibers are presented and their spectrums are examined by an optical vector analyzer (OVA). Given only ordinary phase mask and sub-micrometer precision control, ultra-narrowband flat-top filters with expected performance can be achieved flexibly and cost-effectively.

Metallization of a Rashba wire by a superconducting layer in the strong-proximity regime

NASA Astrophysics Data System (ADS)

Reeg, Christopher; Loss, Daniel; Klinovaja, Jelena

2018-04-01

Semiconducting quantum wires defined within two-dimensional electron gases and strongly coupled to thin superconducting layers have been extensively explored in recent experiments as promising platforms to host Majorana bound states. We study numerically such a geometry, consisting of a quasi-one-dimensional wire coupled to a disordered three-dimensional superconducting layer. We find that, in the strong-coupling limit of a sizable proximity-induced superconducting gap, all transverse subbands of the wire are significantly shifted in energy relative to the chemical potential of the wire. For the lowest subband, this band shift is comparable in magnitude to the spacing between quantized levels that arises due to the finite thickness of the superconductor (which typically is ˜500 meV for a 10-nm-thick layer of aluminum); in higher subbands, the band shift is much larger. Additionally, we show that the width of the system, which is usually much larger than the thickness, and moderate disorder within the superconductor have almost no impact on the induced gap or band shift. We provide a detailed discussion of the ramifications of our results, arguing that a huge band shift and significant renormalization of semiconducting material parameters in the strong-coupling limit make it challenging to realize a topological phase in such a setup, as the strong coupling to the superconductor essentially metallizes the semiconductor. This metallization of the semiconductor can be tested experimentally through the measurement of the band shift.

Dark goggles and bright light improve circadian rhythm adaptation to night-shift work.

PubMed

Eastman, C I; Stewart, K T; Mahoney, M P; Liu, L; Fogg, L F

1994-09-01

We compared the contributions of bright light during the night shift and dark goggles during daylight for phase shifting the circadian rhythm of temperature to realign with a 12-hour shift of sleep. After 10 baseline days there were 8 night-work/day-sleep days. Temperature was continuously recorded from 50 subjects. There were four groups in a 2 x 2 design: light (bright, dim), goggles (yes, no). Subjects were exposed to bright light (about 5,000 lux) for 6 hours on the first 2 night shifts. Dim light was < 500 lux. Both bright light and goggles were significant factors for producing circadian rhythm phase shifts. The combination of bright light plus goggles was the most effective, whereas the combination of dim light and no goggles was the least effective. The temperature rhythm either phase advanced or phase delayed when it aligned with daytime sleep. However, when subjects did not have goggles only phase advances occurred. Goggles were necessary for producing phase delays. The most likely explanation is that daylight during the travel-home window after a night shift inhibits phase-delay shifts, and goggles can prevent this inhibition. Larger temperature-rhythm phase shifts were associated with better subjective daytime sleep, less subjective fatigue and better mood.

DISREGULATION OF INFLAMMATORY RESPONSES BY CHRONIC CIRCADIAN DISRUPTION

PubMed Central

Castanon-Cervantes, Oscar; Wu, Mingwei; Ehlen, J. Christopher; Paul, Ketema; Gamble, Karen L.; Johnson, Russell L.; Besing, Rachel C.; Menaker, Michael; Gewirtz, Andrew T.; Davidson, Alec J.

2010-01-01

Circadian rhythms modulate nearly every mammalian physiological process. Chronic disruption of circadian timing in shift work or during chronic jet lag in animal models leads to a higher risk of several pathologies. Many of these conditions in both shift workers and experimental models share the common risk factor of inflammation. Here we show that experimentally-induced circadian disruption altered innate immune responses. Endotoxemic shock induced by LPS was magnified leading to hypothermia and death after 4 consecutive weekly 6h phase-advances of the light-dark schedule, with 89% mortality compared with 21% in unshifted control mice. This may be due to a heightened release of pro-inflammatory cytokines in response to LPS treatment in shifted animals. Isolated peritoneal macrophages harvested from shifted mice exhibited a similarly heightened response to LPS in vitro, indicating that these cells are a target for jet lag. Sleep deprivation and stress are known to alter immune function and are potential mediators of the effects we describe. However polysomnographic recording in mice exposed to the shifting schedule revealed no sleep loss, and stress measures were not altered in shifted mice. In contrast, we observed altered or abolished rhythms in the expression of clock genes in the central clock, liver, thymus and peritoneal macrophages in mice after chronic jet lag. We conclude that circadian disruption, but not sleep loss or stress, are associated with jet lag-related disregulation of the innate immune system. Such immune changes might be a common mechanism for the myriad negative health effects of shift work. PMID:20944004

Light-driven liquid microlenses

NASA Astrophysics Data System (ADS)

Angelini, A.; Pirani, F.; Frascella, F.; Ricciardi, S.; Descrovi, E.

2017-02-01

We propose a liquid polymeric compound based on photo-responsive azo-polymers to be used as light-activated optical element with tunable and reversible functionalities. The interaction of a laser beam locally modifies the liquid density thus producing a refractive index gradient. The laser induced refractive index profiles are observed along the optical axis of the microscope to evaluate the total phase shift induced and along the orthogonal direction to provide the axial distribution of the refractive index variation. The focusing and imaging properties of the liquid lenses as functions of the light intensity are illustrated.

Theta–gamma coordination between anterior cingulate and prefrontal cortex indexes correct attention shifts

PubMed Central

Voloh, Benjamin; Valiante, Taufik A.; Everling, Stefan; Womelsdorf, Thilo

2015-01-01

Anterior cingulate and lateral prefrontal cortex (ACC/PFC) are believed to coordinate activity to flexibly prioritize the processing of goal-relevant over irrelevant information. This between-area coordination may be realized by common low-frequency excitability changes synchronizing segregated high-frequency activations. We tested this coordination hypothesis by recording in macaque ACC/PFC during the covert utilization of attention cues. We found robust increases of 5–10 Hz (theta) to 35–55 Hz (gamma) phase–amplitude correlation between ACC and PFC during successful attention shifts but not before errors. Cortical sites providing theta phases (i) showed a prominent cue-induced phase reset, (ii) were more likely in ACC than PFC, and (iii) hosted neurons with burst firing events that synchronized to distant gamma activity. These findings suggest that interareal theta–gamma correlations could follow mechanistically from a cue-triggered reactivation of rule memory that synchronizes theta across ACC/PFC. PMID:26100868

Phase-shifted Solc-type filter based on thin periodically poled lithium niobate in a reflective geometry.

PubMed

Ding, Tingting; Zheng, Yuanlin; Chen, Xianfeng

2018-04-30

Configurable narrow bandwidth filters are indispensable components in optical communication networks. Here, we present an easily-integrated compact tunable filtering based on polarization-coupling process in a thin periodically poled lithium niobate (PPLN) in a reflective geometry via the transverse electro-optic (EO) effect. The structure, composed of an in-line polarizer and a thinned PPLN chip, forms a phase-shift Solc-type filter with similar mechanism to defected Bragg gratings. The filtering effect can be dynamically switched on and off by a transverse electric filed. Analogy of electromagnetically induced transparency (EIT) transmission spectrum and electrically controllable group delay is experimentally observed. The mechanism features tunable center wavelength in a wide range with respect to temperature and tunable optical delay to the applied voltage, which may offer another way for optical tunable filters or delay lines.

Nonlinear optical modulation in a plasmonic Bi:YIG Mach-Zehnder interferometer

NASA Astrophysics Data System (ADS)

Firby, C. J.; Elezzabi, A. Y.

2017-02-01

In this work, we propose a magnetoplasmonic modulator for nonlinear radio-frequency (RF) modulation of an integrated optical signal. The modulator consists of a plasmonic Mach-Zehnder interferometer (MZI), constructed of the ferrimagnetic garnet, bismuth-substituted yttrium iron garnet (Bi:YIG). The transverse component of the Bi:YIG magnetization induces a nonreciprocal phase shift (NRPS) onto the guided optical mode, which can be actively modulated through external magnetic fields. In an MZI, the modulated phase shift in turn modulates the output optical intensity. Due to the highly nonlinear evolution of the Bi:YIG magnetization, we show that the spectrum of the output modulated intensity signal can contain harmonics of the driving RF field, frequency splitting around the driving frequency, down-conversion, or mixing of multiple RF signals. This device provides a unique mechanism of simultaneously generating a number of modulation frequencies within a single device.

Alternative stable states and phase shifts in coral reefs under anthropogenic stress.

PubMed

Fung, Tak; Seymour, Robert M; Johnson, Craig R

2011-04-01

Ecosystems with alternative stable states (ASS) may shift discontinuously from one stable state to another as environmental parameters cross a threshold. Reversal can then be difficult due to hysteresis effects. This contrasts with continuous state changes in response to changing environmental parameters, which are less difficult to reverse. Worldwide degradation of coral reefs, involving "phase shifts" from coral to algal dominance, highlights the pressing need to determine the likelihood of discontinuous phase shifts in coral reefs, in contrast to continuous shifts with no ASS. However, there is little evidence either for or against the existence of ASS for coral reefs. We use dynamic models to investigate the likelihood of continuous and discontinuous phase shifts in coral reefs subject to sustained environmental perturbation by fishing, nutrification, and sedimentation. Our modeling results suggest that coral reefs with or without anthropogenic stress can exhibit ASS, such that discontinuous phase shifts can occur. We also find evidence to support the view that high macroalgal growth rates and low grazing rates on macroalgae favor ASS in coral reefs. Further, our results suggest that the three stressors studied, either alone or in combination, can increase the likelihood of both continuous and discontinuous phase shifts by altering the competitive balance between corals and algae. However, in contrast to continuous phase shifts, we find that discontinuous shifts occur only in model coral reefs with parameter values near the extremes of their empirically determined ranges. This suggests that continuous shifts are more likely than discontinuous shifts in coral reefs. Our results also suggest that, for ecosystems in general, tackling multiple human stressors simultaneously maximizes resilience to phase shifts, ASS, and hysteresis, leading to improvements in ecosystem health and functioning.

Concentration-dependent effect of melatonin on DSPC membrane

NASA Astrophysics Data System (ADS)

Sahin, Ipek; Bilge, Duygu; Kazanci, Nadide; Severcan, Feride

2013-11-01

The concentration-induced effects of melatonin on distearoyl phosphatidylcholine (DSPC) model membranes were investigated by using two different non-invasive techniques, namely Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). An investigation of the Csbnd H, Cdbnd O and PO2- double bond stretching mode in FTIR spectra and DSC studies reveals that the inclusion of melatonin changes the physical properties of the DSPC multilamellar liposomes (MLVs) by shifting the main phase transition to lower temperatures, abolishing the pretransition, ordering the system in the gel phase and slightly disordering the system in the liquid crystalline phase, increasing the dynamics both in the gel phase and liquid crystalline phases. Melatonin also causes strong hydrogen bonding between Cdbnd O and PO2- groups of lipids and the water molecules around.

EUV phase-shifting masks and aberration monitors

NASA Astrophysics Data System (ADS)

Deng, Yunfei; Neureuther, Andrew R.

2002-07-01

Rigorous electromagnetic simulation with TEMPEST is used to examine the use of phase-shifting masks in EUV lithography. The effects of oblique incident illumination and mask patterning by ion-mixing of multilayers are analyzed. Oblique incident illumination causes streamers at absorber edges and causes position shifting in aerial images. The diffraction waves between ion-mixed and pristine multilayers are observed. The phase-shifting caused by stepped substrates is simulated and images show that it succeeds in creation of phase-shifting effects. The diffraction process at the phase boundary is also analyzed. As an example of EUV phase-shifting masks, a coma pattern and probe based aberration monitor is simulated and aerial images are formed under different levels of coma aberration. The probe signal rises quickly as coma increases as designed.

Predicted Role of NAD Utilization in the Control of Circadian Rhythms during DNA Damage Response

PubMed Central

Luna, Augustin; McFadden, Geoffrey B.; Aladjem, Mirit I.; Kohn, Kurt W.

2015-01-01

The circadian clock is a set of regulatory steps that oscillate with a period of approximately 24 hours influencing many biological processes. These oscillations are robust to external stresses, and in the case of genotoxic stress (i.e. DNA damage), the circadian clock responds through phase shifting with primarily phase advancements. The effect of DNA damage on the circadian clock and the mechanism through which this effect operates remains to be thoroughly investigated. Here we build an in silico model to examine damage-induced circadian phase shifts by investigating a possible mechanism linking circadian rhythms to metabolism. The proposed model involves two DNA damage response proteins, SIRT1 and PARP1, that are each consumers of nicotinamide adenine dinucleotide (NAD), a metabolite involved in oxidation-reduction reactions and in ATP synthesis. This model builds on two key findings: 1) that SIRT1 (a protein deacetylase) is involved in both the positive (i.e. transcriptional activation) and negative (i.e. transcriptional repression) arms of the circadian regulation and 2) that PARP1 is a major consumer of NAD during the DNA damage response. In our simulations, we observe that increased PARP1 activity may be able to trigger SIRT1-induced circadian phase advancements by decreasing SIRT1 activity through competition for NAD supplies. We show how this competitive inhibition may operate through protein acetylation in conjunction with phosphorylation, consistent with reported observations. These findings suggest a possible mechanism through which multiple perturbations, each dominant during different points of the circadian cycle, may result in the phase advancement of the circadian clock seen during DNA damage. PMID:26020938

Effects of Housing on Methamphetamine-Induced Neurotoxicity and Spatial Learning and Memory.

PubMed

Gutierrez, Arnold; Jablonski, Sarah A; Amos-Kroohs, Robyn M; Barnes, Anna C; Williams, Michael T; Vorhees, Charles V

2017-07-19

Severe stress potentiates methamphetamine (MA) neurotoxicity. However, whether moderate stress increases or decreases the neurotoxic effects of MA is unknown. We assessed the effects of MA (4 × 10 mg/kg at 2 h intervals) in combination with prior barren-cage housing in adult male Sprague-Dawley rats on monoamines and glial fibrillary acid protein (GFAP) in one cohort and spatial learning and memory in the Morris water maze in another cohort. MA reduced dopamine (DA) and serotonin (5-HT) in the neostriatum and nucleus accumbens, 5-HT in the hippocampus, and increased GFAP in neostriatum and nucleus accumbens compared with saline controls. In neostriatum, barren-cage housing protected against MA-induced increases in GFAP, but it did not prevent DA and 5-HT reductions, although it did increase hippocampal norepinephrine. MA impaired spatial learning during acquisition, reversal, and shift phases and impaired reference memory on reversal and shift probe trials. Barren-cage housing enhanced performance during acquisition but not during reversal or shift or on probe trials. The data indicate that prior barren-cage housing moderates MA-induced neostriatal astrogliosis and initial spatial learning, but has no protective effect when the platform is smaller and relocated and therefore requires cognitive flexibility in relearning.

Frequency stabilization in nonlinear MEMS and NEMS oscillators

DOEpatents

Lopez, Omar Daniel; Antonio, Dario

2014-09-16

An illustrative system includes an amplifier operably connected to a phase shifter. The amplifier is configured to amplify a voltage from an oscillator. The phase shifter is operably connected to a driving amplitude control, wherein the phase shifter is configured to phase shift the amplified voltage and is configured to set an amplitude of the phase shifted voltage. The oscillator is operably connected to the driving amplitude control. The phase shifted voltage drives the oscillator. The oscillator is at an internal resonance condition, based at least on the amplitude of the phase shifted voltage, that stabilizes frequency oscillations in the oscillator.

Direct Measurement of Large, Diffuse, Optical Structures

NASA Technical Reports Server (NTRS)

Saif, Babak N.; Keski-Kuha, Ritva; Feinberg, Lee; Wyant, J. C.; Atkinson, C.

2004-01-01

Digital Speckle Pattern Interferometry (DSPI) is a well-established method for the measurement of diffuse objects in experimental mechanics. DSPIs are phase shifting interferometers. Three or four bucket temporal phase shifting algorithms are commonly used to provide phase shifting. These algorithms are sensitive to vibrations and can not be used to measure large optical structures far away from the interferometer. In this research a simultaneous phase shifted interferometer, PhaseCam product of 4D Technology Corporation in Tucson Arizona, is modified to be a Simultaneous phase shifted Digital Speckle Pattern Interferometer (SDSPI). Repeatability, dynamic range, and accuracy of the SDSPI are characterized by measuring a 5 cm x 5 cm carbon fiber coupon.

Molecular aspect ratio and anchoring strength effects in a confined Gay-Berne liquid crystal

NASA Astrophysics Data System (ADS)

Cañeda-Guzmán, E.; Moreno-Razo, J. A.; Díaz-Herrera, E.; Sambriski, E. J.

2014-04-01

Phase diagrams for Gay-Berne (GB) fluids were obtained from molecular dynamics simulations for GB(2, 5, 1, 2) (i.e. short mesogens) and GB(3, 5, 1, 2) (i.e. long mesogens), which yield isotropic, nematic, and smectic-B phases. The long-mesogen fluid also yields the smectic-A phase. Ordered phases of the long-mesogen fluid form at higher temperatures and lower densities when compared to those of the short-mesogen fluid. The effect of confinement under weak and strong substrate couplings in slab geometry was investigated. Compared to the bulk, the isotropic-nematic transition does not shift in temprature significantly for the weakly coupled substrate in either mesogen fluid. However, the strongly coupled substrate shifts the transition to lower temperature. Confinement induces marked stratification in the short-mesogen fluid. This effect diminishes with distance from the substrate, yielding bulk-like behaviour in the slab central region. Fluid stratification is very weak for the long-mesogen fluid, but the strongly coupled substrate induces 'smectisation', an ordering effect that decays with distance. Orientation of the fluid on the substrate depends on the mesogen. There is no preferred orientation in a plane parallel to the substrate for the weakly coupled case. In the strongly coupled case, the mesogen orientation mimics that of adjacent fluid layers. Planar anchoring is observed with a broad distribution of orientations in the weakly coupled case. In the strongly coupled case, the distribution leans toward planar orientations for the short-mesogen fluid, while a marginal preference for tilting persists in the long-mesogen fluid.

Effect of different glucose concentrations on proteome of Saccharomyces cerevisiae.

PubMed

Guidi, Francesca; Francesca, Guidi; Magherini, Francesca; Francesca, Magherini; Gamberi, Tania; Tania, Gamberi; Borro, Marina; Marina, Borro; Simmaco, Maurizio; Maurizio, Simmaco; Modesti, Alessandra; Alessandra, Modesti

2010-07-01

We performed a proteomic study to understand how Saccharomyces cerevisiae adapts its metabolism during the exponential growth on three different concentrations of glucose; this information will be necessary to understand yeast carbon metabolism in different environments. We induced a natural diauxic shift by growing yeast cells in glucose restriction thus having a fast and complete glucose exhaustion. We noticed differential expressions of groups of proteins. Cells in high glucose have a decreased growth rate during the initial phase of fermentation; in glucose restriction and in high glucose we found an over-expression of a protein (Peroxiredoxin) involved in protection against oxidative stress insult. The information obtained in our study validates the application of a proteomic approach for the identification of the molecular bases of environmental variations such as fermentation in high glucose and during a naturally induced diauxic shift. Copyright (c) 2010 Elsevier B.V. All rights reserved.

A novel phase retrieval method from three-wavelength in-line phase-shifting interferograms based on positive negative 2π phase shifts

NASA Astrophysics Data System (ADS)

Xu, Xiaoqing; Wang, Yawei; Ji, Ying; Xu, Yuanyuan; Xie, Ming

2018-01-01

A new method to extract quantitative phases for each wavelength from three-wavelength in-line phase-shifting interferograms is proposed. Firstly, seven interferograms with positive negative 2π phase shifts are sequentially captured by using the phase-shifting technique. Secondly, six dc-term suppressed intensities can be achieved by the use of the algebraic algorithm. Finally, the wrapped phases at the three wavelengths can be acquired simultaneously from these six interferograms add-subtracting by employing the trigonometric function method. The surface morphology with increased ambiguity-free range at synthetic beat wavelength can be obtained, while maintaining the low noise precision of the single wavelength measurement, by combining this method with three-wavelength phase unwrapping method. We illustrate the principle of this algorithm, and the simulated experiments of the spherical cap and the HeLa cell are conducted to prove our proposed method, respectively.

3D measurement using combined Gray code and dual-frequency phase-shifting approach

NASA Astrophysics Data System (ADS)

Yu, Shuang; Zhang, Jing; Yu, Xiaoyang; Sun, Xiaoming; Wu, Haibin; Liu, Xin

2018-04-01

The combined Gray code and phase-shifting approach is a commonly used 3D measurement technique. In this technique, an error that equals integer multiples of the phase-shifted fringe period, i.e. period jump error, often exists in the absolute analog code, which can lead to gross measurement errors. To overcome this problem, the present paper proposes 3D measurement using a combined Gray code and dual-frequency phase-shifting approach. Based on 3D measurement using the combined Gray code and phase-shifting approach, one set of low-frequency phase-shifted fringe patterns with an odd-numbered multiple of the original phase-shifted fringe period is added. Thus, the absolute analog code measured value can be obtained by the combined Gray code and phase-shifting approach, and the low-frequency absolute analog code measured value can also be obtained by adding low-frequency phase-shifted fringe patterns. Then, the corrected absolute analog code measured value can be obtained by correcting the former by the latter, and the period jump errors can be eliminated, resulting in reliable analog code unwrapping. For the proposed approach, we established its measurement model, analyzed its measurement principle, expounded the mechanism of eliminating period jump errors by error analysis, and determined its applicable conditions. Theoretical analysis and experimental results show that the proposed approach can effectively eliminate period jump errors, reliably perform analog code unwrapping, and improve the measurement accuracy.

Tamoxifen-model membrane interactions: an FT-IR study

NASA Astrophysics Data System (ADS)

Boyar, Handan; Severcan, Feride

1997-06-01

The temperature- and concentration-induced effects of tamoxifen (TAM) on dipalmitoyl phosphatidylcholine (DPPC) model membranes were investigated by the Fourier transform-infrared (FT-IR) spectroscopic technique. An investigation of the C-H stretching region and the CO mode reveals that the inclusion of TAM changes the physical properties of the DPPC multibilayers by (i) shifting the main phase transition to lower temperatures; (ii) broadening the transition profile slightly; (iii) disordering the system in the gel and in the liquid crystalline phases; (iv) increasing the dynamics in the gel phase and decreasing the dynamics of the acyl chains in the liquid crystalline phase; (v) increasing the mobility of the terminal methyl group region of the bilayer in the gel phase and decreasing it in the liquid crystalline phase; (vi) increasing the frequency of the CO stretching mode both in the gel and in the liquid crystalline phases, i.e. non-bonding with carbonyl groups.

Imaging of cochlear tissue with a grating interferometer and hard X-rays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richter, Claus-Peter; Shintani-Smith, Stephanie; Fishman, Andrew

This article addresses an important current development in medical and biological imaging: the possibility of imaging soft tissue at resolutions in the micron range using hard X-rays. Challenging environments, including the cochlea, require the imaging of soft tissue structure surrounded by bone. We demonstrate that cochlear soft tissue structures can be imaged with hard X-ray phase contrast. Furthermore, we show that only a thin slice of the tissue is required to introduce a large phase shift. It is likely that the phase contrast image of the soft tissue structures is sufficient to image the structures even if surrounded by bone.more » For the present set of experiments, structures with low-absorption contrast have been visualized using in-line phase contrast imaging and a grating interferometer. The experiments have been performed at the Advanced Photon Source at Argonne National Laboratories, a third generation source of synchrotron radiation. The source provides highly coherent X-ray radiation with high-photon flux (>10{sup 12} photons/s) at high-photon energies (5-70 keV). Radiographic and light microscopy images of the gerbil cochlear slice samples were compared. It has been determined that a 20-{micro}m thick tissue slice induces a phase shift between 1/3{pi} and 2/3{pi}.« less

Etched-multilayer phase shifting masks for EUV lithography

DOEpatents

Chapman, Henry N.; Taylor, John S.

2005-04-05

A method is disclosed for the implementation of phase shifting masks for EUV lithography. The method involves directly etching material away from the multilayer coating of the mask, to cause a refractive phase shift in the mask. By etching into the multilayer (for example, by reactive ion etching), rather than depositing extra material on the top of the multilayer, there will be minimal absorption loss associated with the phase shift.

Constant frequency pulsed phase-locked loop measuring device

NASA Technical Reports Server (NTRS)

Yost, William T. (Inventor); Kushnick, Peter W. (Inventor); Cantrell, John H. (Inventor)

1993-01-01

A measuring apparatus is presented that uses a fixed frequency oscillator to measure small changes in the phase velocity ultrasonic sound when a sample is exposed to environmental changes such as changes in pressure, temperature, etc. The invention automatically balances electrical phase shifts against the acoustical phase shifts in order to obtain an accurate measurement of electrical phase shifts.

Alternating phase-shifting masks: phase determination and impact of quartz defects--theoretical and experimental results

NASA Astrophysics Data System (ADS)

Griesinger, Uwe A.; Dettmann, Wolfgang; Hennig, Mario; Heumann, Jan P.; Koehle, Roderick; Ludwig, Ralf; Verbeek, Martin; Zarrabian, Mardjan

2002-07-01

In optical lithography balancing the aerial image of an alternating phase shifting mask (alt. PSM) is a major challenge. For the exposure wavelengths (currently 248nm and 193nm) an optimum etching method is necessary to overcome imbalance effects. Defects play an important role in the imbalances of the aerial image. In this contribution defects will be discussed by using the methodology of global phase imbalance control also for local imbalances which are a result of quartz defects. The effective phase error can be determined with an AIMS-system by measuring the CD width between the images of deep- and shallow trenches at different focus settings. The AIMS results are analyzed in comparison to the simulated and lithographic print results of the alternating structures. For the analysis of local aerial image imbalances it is necessary to investigate the capability of detecting these phase defects with state of the art inspection systems. Alternating PSMs containing programmed defects were inspected with different algorithms to investigate the capture rate of special phase defects in dependence on the defect size. Besides inspection also repair of phase defects is an important task. In this contribution we show the effect of repair on the optical behavior of phase defects. Due to the limited accuracy of the repair tools the repaired area still shows a certain local phase error. This error can be caused either by residual quartz material or a substrate damage. The influence of such repair induced phase errors on the aerial image were investigated.

Absolute Definition of Phase Shift in the Elastic Scattering of a Particle from Compound Systems

NASA Technical Reports Server (NTRS)

Temkin, A.

1961-01-01

The projection of the target wave function on the total wave function of a scattered particle interacting with the target system is used to define an absolute phase shift including any multiples of pi. With this definition of the absolute phase shift, one can prove rigorously in the limit of zero energy for s-wave electrons scattered from atomic hydrogen that the triplet phase shift must approach a nonzero multiple of pi. One can further show that at least one pi of this phase shift is not connected with the existence of a bound state of the H- ion.

Phase-contrast scanning transmission electron microscopy.

PubMed

Minoda, Hiroki; Tamai, Takayuki; Iijima, Hirofumi; Hosokawa, Fumio; Kondo, Yukihito

2015-06-01

This report introduces the first results obtained using phase-contrast scanning transmission electron microscopy (P-STEM). A carbon-film phase plate (PP) with a small center hole is placed in the condenser aperture plane so that a phase shift is introduced in the incident electron waves except those passing through the center hole. A cosine-type phase-contrast transfer function emerges when the phase-shifted scattered waves interfere with the non-phase-shifted unscattered waves, which passed through the center hole before incidence onto the specimen. The phase contrast resulting in P-STEM is optically identical to that in phase-contrast transmission electron microscopy that is used to provide high contrast for weak phase objects. Therefore, the use of PPs can enhance the phase contrast of the STEM images of specimens in principle. The phase shift resulting from the PP, whose thickness corresponds to a phase shift of π, has been confirmed using interference fringes displayed in the Ronchigram of a silicon single crystal specimen. The interference fringes were found to abruptly shift at the edge of the PP hole by π. © The Author 2015. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Electro-optic study of PZT ferroelectric ceramics using modulation of reflected light

NASA Astrophysics Data System (ADS)

Kniazkov, A. V.

2016-04-01

Electro-optic coefficients of variations in the refractive index of PZT and PLZT ceramic materials induced by ac electric field are estimated using modulation of reflected light. The electro-optic coefficients of PLZT ceramics measured with the aid of conventional birefringence using the phase shift of transmitted radiation and the proposed method of birefringence using the modulation of reflected light are compared.

Preparation and enhanced daylight-induced photocatalytic activity of C,N,S-tridoped titanium dioxide powders.

PubMed

Zhou, Minghua; Yu, Jiaguo

2008-04-15

A simple method for preparing highly daylight-induced photoactive nanocrystalline C,N,S-tridoped TiO2 powders was developed by a solid-phase reaction. The as-prepared TiO2 powders were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectra, N2 adsorption-desorption measurements and transmission electron microscopy (TEM). The photocatalytic activity was evaluated by the photocatalytic oxidation of formaldehyde under daylight irradiation in air. The results show that daylight-induced photocatalytic activities of the as-prepared TiO2 powders were improved by C,N,S-tridoping. The C,N,S-tridoped TiO2 powders exhibited stronger absorption in the near UV and visible-light region with red shift in the band-gap transition. When the molar ratio of CS(NH2)2 to xerogel TiO2 powders (prepared by hydrolysis of Ti(OC4H9)4 in distilled water) (R) was kept in 3, the daylight-induced photocatalytic activities of the as-prepared C,N,S-tridoped TiO2 powders were about more than six times greater than that of Degussa P25 and un-doped TiO2 powders. The high activities of the C,N,S-tridoped TiO2 can be attributed to the results of the synergetic effects of strong absorption in the near UV and visible-light region, red shift in adsorption edge and two phase structures of un-doped TiO2 and C,N,S-tridoped TiO2.

Influence of OPD in wavelength-shifting interferometry

NASA Astrophysics Data System (ADS)

Wang, Hongjun; Tian, Ailing; Liu, Bingcai; Dang, Juanjuan

2009-12-01

Phase-shifting interferometry is a powerful tool for high accuracy optical measurement. It operates by change the optical path length in the reference arm or test arm. This method practices by move optical device. So it has much problem when the optical device is very large and heavy. For solve this problem, the wavelength-shifting interferometry was put forwarded. In wavelength-shifting interferometry, the phase shifting angle was achieved by change the wavelength of optical source. The phase shifting angle was decided by wavelength and OPD (Optical Path Difference) between test and reference wavefront. So the OPD is an important factor to measure results. But in measurement, because the positional error and profile error of under testing optical element is exist, the phase shifting angle is different in different test point when wavelength scanning, it will introduce phase shifting angle error, so it will introduce optical surface measure error. For analysis influence of OPD on optical surface error, the relation between surface error and OPD was researched. By simulation, the relation between phase shifting error and OPD was established. By analysis, the error compensation method was put forward. After error compensation, the measure results can be improved to great extend.

Influence of OPD in wavelength-shifting interferometry

NASA Astrophysics Data System (ADS)

Wang, Hongjun; Tian, Ailing; Liu, Bingcai; Dang, Juanjuan

2010-03-01

Phase-shifting interferometry is a powerful tool for high accuracy optical measurement. It operates by change the optical path length in the reference arm or test arm. This method practices by move optical device. So it has much problem when the optical device is very large and heavy. For solve this problem, the wavelength-shifting interferometry was put forwarded. In wavelength-shifting interferometry, the phase shifting angle was achieved by change the wavelength of optical source. The phase shifting angle was decided by wavelength and OPD (Optical Path Difference) between test and reference wavefront. So the OPD is an important factor to measure results. But in measurement, because the positional error and profile error of under testing optical element is exist, the phase shifting angle is different in different test point when wavelength scanning, it will introduce phase shifting angle error, so it will introduce optical surface measure error. For analysis influence of OPD on optical surface error, the relation between surface error and OPD was researched. By simulation, the relation between phase shifting error and OPD was established. By analysis, the error compensation method was put forward. After error compensation, the measure results can be improved to great extend.

Quantitative refractive index distribution of single cell by combining phase-shifting interferometry and AFM imaging.

PubMed

Zhang, Qinnan; Zhong, Liyun; Tang, Ping; Yuan, Yingjie; Liu, Shengde; Tian, Jindong; Lu, Xiaoxu

2017-05-31

Cell refractive index, an intrinsic optical parameter, is closely correlated with the intracellular mass and concentration. By combining optical phase-shifting interferometry (PSI) and atomic force microscope (AFM) imaging, we constructed a label free, non-invasive and quantitative refractive index of single cell measurement system, in which the accurate phase map of single cell was retrieved with PSI technique and the cell morphology with nanoscale resolution was achieved with AFM imaging. Based on the proposed AFM/PSI system, we achieved quantitative refractive index distributions of single red blood cell and Jurkat cell, respectively. Further, the quantitative change of refractive index distribution during Daunorubicin (DNR)-induced Jurkat cell apoptosis was presented, and then the content changes of intracellular biochemical components were achieved. Importantly, these results were consistent with Raman spectral analysis, indicating that the proposed PSI/AFM based refractive index system is likely to become a useful tool for intracellular biochemical components analysis measurement, and this will facilitate its application for revealing cell structure and pathological state from a new perspective.

Two-phase SLIPI for instantaneous LIF and Mie imaging of transient fuel sprays.

PubMed

Storch, Michael; Mishra, Yogeshwar Nath; Koegl, Matthias; Kristensson, Elias; Will, Stefan; Zigan, Lars; Berrocal, Edouard

2016-12-01

We report in this Letter a two-phase structured laser illumination planar imaging [two-pulse SLIPI (2p-SLIPI)] optical setup where the "lines structure" is spatially shifted by exploiting the birefringence property of a calcite crystal. By using this optical component and two cross-polarized laser pulses, the shift of the modulated pattern is not "time-limited" anymore. Consequently, two sub-images with spatially mismatched phases can be recorded within a few hundred of nanoseconds only, freezing the motion of the illuminated transient flow. In comparison with previous setups for instantaneous imaging based on structured illumination, the current optical design presents the advantage of having a single optical path, greatly simplifying its complexity. Due to its virtue of suppressing the effects from multiple light scattering, the 2p-SLIPI technique is applied here in an optically dense multi-jet direct-injection spark-ignition (DISI) ethanol spray. The fast formation of polydispersed droplets and appearance of voids after fuel injection are investigated by simultaneous detection of Mie scattering and liquid laser-induced fluorescence. The results allow for significantly improved analysis of the spray structure.

Stabilization of the Activated hERG Channel Voltage Sensor by Depolarization Involves the S4-S5 Linker.

PubMed

Thouta, Samrat; Hull, Christina M; Shi, Yu Patrick; Sergeev, Valentine; Young, James; Cheng, Yen M; Claydon, Thomas W

2017-01-24

Slow deactivation of hERG channels is critical for preventing cardiac arrhythmia yet the mechanistic basis for the slow gating transition is unclear. Here, we characterized the temporal sequence of events leading to voltage sensor stabilization upon membrane depolarization. Progressive increase in step depolarization duration slowed voltage-sensor return in a biphasic manner (τ fast = 34 ms, τ slow  = 2.5 s). The faster phase of voltage-sensor return slowing correlated with the kinetics of pore opening. The slower component occurred over durations that exceeded channel activation and was consistent with voltage sensor relaxation. The S4-S5 linker mutation, G546L, impeded the faster phase of voltage sensor stabilization without attenuating the slower phase, suggesting that the S4-S5 linker is important for communications between the pore gate and the voltage sensor during deactivation. These data also demonstrate that the mechanisms of pore gate-opening-induced and relaxation-induced voltage-sensor stabilization are separable. Deletion of the distal N-terminus (Δ2-135) accelerated off-gating current, but did not influence the relative contribution of either mechanism of stabilization of the voltage sensor. Lastly, we characterized mode-shift behavior in hERG channels, which results from stabilization of activated channel states. The apparent mode-shift depended greatly on recording conditions. By measuring slow activation and deactivation at steady state we found the "true" mode-shift to be ∼15 mV. Interestingly, the "true" mode-shift of gating currents was ∼40 mV, much greater than that of the pore gate. This demonstrates that voltage sensor return is less energetically favorable upon repolarization than pore gate closure. We interpret this to indicate that stabilization of the activated voltage sensor limits the return of hERG channels to rest. The data suggest that this stabilization occurs as a result of reconfiguration of the pore gate upon opening by a mechanism that is influenced by the S4-S5 linker, and by a separable voltage-sensor intrinsic relaxation mechanism. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Correcting spherical aberrations induced by an unknown medium through determination of its refractive index and thickness.

PubMed

Iwaniuk, Daniel; Rastogi, Pramod; Hack, Erwin

2011-09-26

In imaging and focusing applications, spherical aberration induces axial broadening of the point spread function (PSF). A transparent medium between lens and object of interest induces spherical aberration. We propose a method that first obtains both the physical thickness and the refractive index of the aberration inducing medium in situ by measuring the induced focal shifts for paraxial and large angle rays. Then, the fourth order angle dependence of the optical path difference inside the medium is used to correct the spherical aberration using a phase-only spatial light modulator. The obtained measurement accuracy of 3% is sufficient for a complete compensation as demonstrated in a model microscope with NA 0.3 with glass plate induced axial broadening of the PSF by a factor of 5. © 2011 Optical Society of America

Analytical estimation of laser phase noise induced BER floor in coherent receiver with digital signal processing.

PubMed

Vanin, Evgeny; Jacobsen, Gunnar

2010-03-01

The Bit-Error-Ratio (BER) floor caused by the laser phase noise in the optical fiber communication system with differential quadrature phase shift keying (DQPSK) and coherent detection followed by digital signal processing (DSP) is analytically evaluated. An in-phase and quadrature (I&Q) receiver with a carrier phase recovery using DSP is considered. The carrier phase recovery is based on a phase estimation of a finite sum (block) of the signal samples raised to the power of four and the phase unwrapping at transitions between blocks. It is demonstrated that errors generated at block transitions cause the dominating contribution to the system BER floor when the impact of the additive noise is negligibly small in comparison with the effect of the laser phase noise. Even the BER floor in the case when the phase unwrapping is omitted is analytically derived and applied to emphasize the crucial importance of this signal processing operation. The analytical results are verified by full Monte Carlo simulations. The BER for another type of DQPSK receiver operation, which is based on differential phase detection, is also obtained in the analytical form using the principle of conditional probability. The principle of conditional probability is justified in the case of differential phase detection due to statistical independency of the laser phase noise induced signal phase error and the additive noise contributions. Based on the achieved analytical results the laser linewidth tolerance is calculated for different system cases.

Phase retrieval from the phase-shift moiré fringe patterns in simultaneous dual-wavelength interferometry

NASA Astrophysics Data System (ADS)

Cheng, Jinlong; Gao, Zhishan; Bie, Shuyou; Dou, Yimeng; Ni, Ruihu; Yuan, Qun

2018-02-01

Simultaneous dual-wavelength interferometry (SDWI) could extend the measured range of each single-wavelength interferometry. The moiré fringe generated in SDWI indirectly represents the information of the measured long synthetic-wavelength ({λ }{{S}}) phase, thus the phase demodulation is rather arduous. To address this issue, we present a method to convert the moiré fringe pattern into a synthetic-wavelength interferogram (moiré to synthetic-wavelength, MTS). After the square of the moiré fringe pattern in the MTS method, the additive moiré pattern is turned into a multiplicative one. And the synthetic-wavelength interferogram could be obtained by a low-pass filtering in spectrum of the multiplicative moiré fringe pattern. Therefore, when the dual-wavelength interferometer is implemented with the π/2 phase shift at {λ }{{S}}, a sequence of synthetic-wavelength phase-shift interferograms with π/2 phase shift could be obtained after the MTS method processing on the captured moiré fringe patterns. And then the synthetic-wavelength phase could be retrieved by the conventional phase-shift algorithm. Compared with other methods in SDWI, the proposed MTS approach could reduce the restriction of the phase shift and frame numbers for the adoption of the conventional phase-shift algorithm. Following, numerical simulations are executed to evaluate the performance of the MTS method in processing time, frames of interferograms and the phase shift error compensation. And the necessary linear carrier for MTS method is less than 0.11 times of the traditional dual-wavelength spatial-domain Fourier transform method. Finally, the deviations for MTS method in experiment are 0.97% for a step with the height of 7.8 μm and 1.11% for a Fresnel lens with the step height of 6.2328 μm.

Quantum phase transitions in the noncommutative Dirac oscillator

NASA Astrophysics Data System (ADS)

Panella, O.; Roy, P.

2014-10-01

We study the (2 + 1)-dimensional Dirac oscillator in a homogeneous magnetic field in the noncommutative plane. It is shown that the effect of noncommutativity is twofold: (i) momentum noncommuting coordinates simply shift the critical value (Bcr) of the magnetic field at which the well known left-right chiral quantum phase transition takes place (in the commuting phase); (ii) noncommutativity in the space coordinates induces a new critical value of the magnetic field, Bcr*, where there is a second quantum phase transition (right-left): this critical point disappears in the commutative limit. The change in chirality associated with the magnitude of the magnetic field is examined in detail for both critical points. The phase transitions are described in terms of the magnetization of the system. Possible applications to the physics of silicene and graphene are briefly discussed.

Phase of neural excitation relative to basilar membrane motion in the organ of Corti: Theoretical considerations

NASA Astrophysics Data System (ADS)

Andoh, Masayoshi; Nakajima, Chihiro; Wada, Hiroshi

2005-09-01

Although the auditory transduction process is dependent on neural excitation of the auditory nerve in relation to motion of the basilar membrane (BM) in the organ of Corti (OC), specifics of this process are unclear. In this study, therefore, an attempt was made to estimate the phase of the neural excitation relative to the BM motion using a finite-element model of the OC at the basal turn of the gerbil, including the fluid-structure interaction with the lymph fluid. It was found that neural excitation occurs when the BM exhibits a maximum velocity toward the scala vestibuli at 10 Hz and shows a phase delay relative to the BM motion with increasing frequency up to 800 Hz. It then shows a phase advance until the frequency reaches 2 kHz. From 2 kHz, neural excitation again shows a phase delay with increasing frequency. From 800 Hz up to 2 kHz, the phase advances because the dominant force exerted on the hair bundle shifts from a velocity-dependent Couette flow-induced force to a displacement-dependent force induced by the pressure difference. The phase delay that occurs from 2 kHz is caused by the resonance process of the hair bundle of the IHC.

Pressure-induced phase transformation, reversible amorphization, and anomalous visible light response in organolead bromide perovskite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yonggang; Lu, Xujie; Yang, Wenge

Hydrostatic pressure, as an alternative of chemical pressure to tune the crystal structure and physical properties, is a significant technique for novel function material design and fundamental research. In this article, we report the phase stability and visible light response of the organolead bromide perovskite, CH 3NH 3PbBr 3 (MAPbBr 3), under hydrostatic pressure up to 34 GPa at room temperature: Two phase transformations below 2 GPa (from Pm3¯m to Im3¯, then to Pnma) and a reversible amorphization starting from about 2 GPa were observed, which could be attributed to the tilting of PbBr 6 octahedra and destroying of long-rangemore » ordering of MA cations, respectively. The visible light response of MAPbBr 3 to pressure was studied by in situ photoluminescence, electric resistance, photocurrent measurements and first-principle simulations. The anomalous band gap evolution during compression with red-shift followed by blue-shift is explained by the competition between compression effect and pressure-induced amorphization. Along with the amorphization process accomplished around 25 GPa, the resistance increased by 5 orders of magnitude while the system still maintains its semiconductor characteristics and considerable response to the visible light irradiation. Lastly, our results not only show that hydrostatic pressure may provide an applicable tool for the organohalide perovskites based photovoltaic device functioning as switcher or controller, but also shed light on the exploration of more amorphous organometal composites as potential light absorber.« less

Pressure-Induced Phase Transformation, Reversible Amorphization, and Anomalous Visible Light Response in Organolead Bromide Perovskite.

PubMed

Wang, Yonggang; Lü, Xujie; Yang, Wenge; Wen, Ting; Yang, Liuxiang; Ren, Xiangting; Wang, Lin; Lin, Zheshuai; Zhao, Yusheng

2015-09-02

Hydrostatic pressure, as an alternative of chemical pressure to tune the crystal structure and physical properties, is a significant technique for novel function material design and fundamental research. In this article, we report the phase stability and visible light response of the organolead bromide perovskite, CH3NH3PbBr3 (MAPbBr3), under hydrostatic pressure up to 34 GPa at room temperature. Two phase transformations below 2 GPa (from Pm3̅m to Im3̅, then to Pnma) and a reversible amorphization starting from about 2 GPa were observed, which could be attributed to the tilting of PbBr6 octahedra and destroying of long-range ordering of MA cations, respectively. The visible light response of MAPbBr3 to pressure was studied by in situ photoluminescence, electric resistance, photocurrent measurements and first-principle simulations. The anomalous band gap evolution during compression with red-shift followed by blue-shift is explained by the competition between compression effect and pressure-induced amorphization. Along with the amorphization process accomplished around 25 GPa, the resistance increased by 5 orders of magnitude while the system still maintains its semiconductor characteristics and considerable response to the visible light irradiation. Our results not only show that hydrostatic pressure may provide an applicable tool for the organohalide perovskites based photovoltaic device functioning as switcher or controller, but also shed light on the exploration of more amorphous organometal composites as potential light absorber.

Pressure-induced phase transformation, reversible amorphization, and anomalous visible light response in organolead bromide perovskite

DOE PAGES

Wang, Yonggang; Lu, Xujie; Yang, Wenge; ...

2015-08-18

Hydrostatic pressure, as an alternative of chemical pressure to tune the crystal structure and physical properties, is a significant technique for novel function material design and fundamental research. In this article, we report the phase stability and visible light response of the organolead bromide perovskite, CH 3NH 3PbBr 3 (MAPbBr 3), under hydrostatic pressure up to 34 GPa at room temperature: Two phase transformations below 2 GPa (from Pm3¯m to Im3¯, then to Pnma) and a reversible amorphization starting from about 2 GPa were observed, which could be attributed to the tilting of PbBr 6 octahedra and destroying of long-rangemore » ordering of MA cations, respectively. The visible light response of MAPbBr 3 to pressure was studied by in situ photoluminescence, electric resistance, photocurrent measurements and first-principle simulations. The anomalous band gap evolution during compression with red-shift followed by blue-shift is explained by the competition between compression effect and pressure-induced amorphization. Along with the amorphization process accomplished around 25 GPa, the resistance increased by 5 orders of magnitude while the system still maintains its semiconductor characteristics and considerable response to the visible light irradiation. Lastly, our results not only show that hydrostatic pressure may provide an applicable tool for the organohalide perovskites based photovoltaic device functioning as switcher or controller, but also shed light on the exploration of more amorphous organometal composites as potential light absorber.« less

In-line digital holography with phase-shifting Greek-ladder sieves

NASA Astrophysics Data System (ADS)

Xie, Jing; Zhang, Junyong; Zhang, Yanli; Zhou, Shenlei; Zhu, Jianqiang

2018-04-01

Phase shifting is the key technique in in-line digital holography, but traditional phase shifters have their own limitations in short wavelength regions. Here, phase-shifting Greek-ladder sieves with amplitude-only modulation are introduced into in-line digital holography, which are essentially a kind of diffraction lens with three-dimensional array diffraction-limited foci. In the in-line digital holographic experiment, we design two kinds of sieves by lithography and verify the validity of their phase-shifting function by measuring a 1951 U.S. Air Force resolution test target and three-dimensional array foci. With advantages of high resolving power, low cost, and no limitations at shorter wavelengths, phase-shifting Greek-ladder sieves have great potential in X-ray holography or biochemical microscopy for the next generation of synchrotron light sources.

Successive disorder to disorder phase transitions in ionic liquid [HMIM][BF4] under high pressure

NASA Astrophysics Data System (ADS)

Zhu, Xiang; Yuan, Chaosheng; Li, Haining; Zhu, Pinwen; Su, Lei; Yang, Kun; Wu, Jie; Yang, Guoqiang; Liu, Jing

2016-02-01

In situ high-pressure Raman spectroscopy and synchrotron X-ray diffraction have been employed to investigate the phase behavior of ionic liquid, 1-hexyl-3-methylimidazolium tetrafluoroborate ([HMIM][BF4]) under high pressure up to 20 GPa at room temperature. With increasing pressure, some characteristic bands of [HMIM][BF4] disappear, and some characteristic bands of [HMIM][BF4] display non-monotonic pressure-induced frequency shift and non-monotonic variation of full width at half-maximum. Two successive phase transitions at ˜1.7 GPa and 7.3 GPa have been corroborated by the results above. The glass transition pressure (Pg) of [HMIM][BF4] at ˜7.3 GPa has been obtained by ruby R1 line broadening measurements and analysis of synchrotron X-ray diffraction patterns, and its glass transition mechanism is also analyzed in detail. These facts are suggestive of two successive disorder to disorder phase transitions induced by compression, that is, [HMIM][BF4] serves as a superpressurized glass under the pressure above 7.3 GPa, which is similar to the glassy state at low temperature, and a compression-induced liquid to liquid phase transition in [HMIM][BF4] occurs at ˜1.7 GPa. Besides, the conformational equilibrium of the GAAA conformer and AAAA conformer was converted easily in liquid [HMIM][BF4], while it was difficult to be influenced in glassy state.

Several localized waves induced by linear interference between a nonlinear plane wave and bright solitons

NASA Astrophysics Data System (ADS)

Qin, Yan-Hong; Zhao, Li-Chen; Yang, Zhan-Ying; Yang, Wen-Li

2018-01-01

We investigate linear interference effects between a nonlinear plane wave and bright solitons, which are admitted by a pair-transition coupled two-component Bose-Einstein condensate. We demonstrate that the interference effects can induce several localized waves possessing distinctive wave structures, mainly including anti-dark solitons, W-shaped solitons, multi-peak solitons, Kuznetsov-Ma like breathers, and multi-peak breathers. Specifically, the explicit conditions for them are clarified by a phase diagram based on the linear interference properties. Furthermore, the interactions between these localized waves are discussed. The detailed analysis indicates that the soliton-soliton interaction induced phase shift brings the collision between these localized waves which can be inelastic for solitons involving collision and can be elastic for breathers. These characters come from the fact that the profile of solitons depends on the relative phase between bright solitons and a plane wave, and the profile of breathers does not depend on the relative phase. These results would motivate more discussions on linear interference between other nonlinear waves. Specifically, the solitons or breathers obtained here are not related to modulational instability. The underlying reasons are discussed in detail. In addition, possibilities to observe these localized waves are discussed in a two species Bose-Einstein condensate.

Disorder-induced stiffness degradation of highly disordered porous materials

NASA Astrophysics Data System (ADS)

Laubie, Hadrien; Monfared, Siavash; Radjaï, Farhang; Pellenq, Roland; Ulm, Franz-Josef

2017-09-01

The effective mechanical behavior of multiphase solid materials is generally modeled by means of homogenization techniques that account for phase volume fractions and elastic moduli without considering the spatial distribution of the different phases. By means of extensive numerical simulations of randomly generated porous materials using the lattice element method, the role of local textural properties on the effective elastic properties of disordered porous materials is investigated and compared with different continuum micromechanics-based models. It is found that the pronounced disorder-induced stiffness degradation originates from stress concentrations around pore clusters in highly disordered porous materials. We identify a single disorder parameter, φsa, which combines a measure of the spatial disorder of pores (the clustering index, sa) with the pore volume fraction (the porosity, φ) to scale the disorder-induced stiffness degradation. Thus, we conclude that the classical continuum micromechanics models with one spherical pore phase, due to their underlying homogeneity assumption fall short of addressing the clustering effect, unless additional texture information is introduced, e.g. in form of the shift of the percolation threshold with disorder, or other functional relations between volume fractions and spatial disorder; as illustrated herein for a differential scheme model representative of a two-phase (solid-pore) composite model material.

New insights into heat induced structural changes of pectin methylesterase on fluorescence spectroscopy and molecular modeling basis

NASA Astrophysics Data System (ADS)

Nistor, Oana Viorela; Stănciuc, Nicoleta; Aprodu, Iuliana; Botez, Elisabeta

2014-07-01

Heat-induced structural changes of Aspergillus oryzae pectin methylesterase (PME) were studied by means of fluorescence spectroscopy and molecular modeling, whereas the functional enzyme stability was monitored by inactivation studies. The fluorescence spectroscopy experiments were performed at two pH value (4.5 and 7.0). At both pH values, the phase diagrams were linear, indicating the presence of two molecular species induced by thermal treatment. A red shift of 7 nm was observed at neutral pH by increasing temperature up to 60 °C, followed by a blue shift of 4 nm at 70 °C, suggesting significant conformational rearrangements. The quenching experiments using acrylamide and iodide demonstrate a more flexible conformation of enzyme with increasing temperature, especially at neutral pH. The experimental results were complemented with atomic level observations on PME model behavior after performing molecular dynamics simulations at different temperatures. The inactivation kinetics of PME in buffer solutions was fitted using a first-order kinetics model, resulting in activation energy of 241.4 ± 7.51 kJ mol-1.

Phase correction, phase resetting, and phase shifts after subliminal timing perturbations in sensorimotor synchronization.

PubMed

Repp, B H

2001-06-01

Recent studies of synchronized finger tapping have shown that perceptually subliminal phase shifts in an auditory sequence are rapidly compensated for in the motor activity (B. H. Repp, 2000a). Experiment 1 used a continuation-tapping task to confirm that this compensation is indeed a phase correction, not an adjustment of the central timekeeper period. Experiments 2-5 revealed that this phase correction occurs even when there is no ordinary sensorimotor asynchrony--when the finger taps are in antiphase or arbitrary phase relative to the auditory sequence (Experiments 2 and 3) or when the tap coinciding with the sequence phase shift is withheld (Experiments 4 and 5). The phase correction observed in the latter conditions was instantaneous, which suggests that phase resetting occurs when the motor activity is discontinuous. A prolonged phase shift suggestive of overcompensation was observed in some conditions, which poses a challenge to pure phase correction models.

The effect of hydrostatic pressure on model membrane domain composition and lateral compressibility.

PubMed

Barriga, H M G; Law, R V; Seddon, J M; Ces, O; Brooks, N J

2016-01-07

Phase separation in ternary model membranes is known to occur over a range of temperatures and compositions and can be induced by increasing hydrostatic pressure. We have used small angle X-ray scattering (SAXS) to study phase separation along pre-determined tie lines in dioleoylphosphatidylcholine (DOPC), dipalmitoylphosphatidylcholine (DPPC) and cholesterol (CHOL) mixtures. We can unequivocally distinguish the liquid ordered (Lo) and liquid disordered (Ld) phases in diffraction patterns from biphasic mixtures and compare their lateral compressibility. The variation of tie line endpoints with increasing hydrostatic pressure was determined, at atmospheric pressure and up to 100 MPa. We find an extension and shift of the tie lines towards the DOPC rich region of the phase diagram at increased pressure, this behaviour differs slightly from that reported for decreasing temperature.

Computer simulation studies of anisotropic systems. XXXII. Field-induction of a smectic A phase in a Gay-Berne mesogen

NASA Astrophysics Data System (ADS)

Luckhurst, G. R.; Saielli, G.

2000-03-01

Molecular field theory predicts the induction of a smectic A phase by the application of a field, either magnetic or electric, to a nematic phase. This intriguing behavior results from an enhancement of the orientational order which is coupled to the translational order and so shifts the smectic A-nematic transition. To test this prediction we have investigated a system of Gay-Berne mesogenic molecules subject to an applied field of second rank using isothermal-isobaric Monte Carlo simulations. The results of our calculations are compared with the Kventsel-Luckhurst-Zewdie molecular field theory of smectogens, modified to include the effect of an external field. We have also used the simulations to explore the possibility of inducing more ordered smectic phases with stronger fields.

Phase-Shift Interferometry with a Digital Photocamera

ERIC Educational Resources Information Center

Vannoni, Maurizio; Trivi, Marcelo; Molesini, Giuseppe

2007-01-01

A phase-shift interferometry experiment is proposed, working on a Twyman-Green optical configuration with additional polarization components. A guideline is provided to modern phase-shift interferometry, using concepts and laboratory equipment at the level of undergraduate optics courses. (Contains 5 figures.)

Improved detection sensitivity of D-mannitol crystalline phase content using differential spectral phase shift terahertz spectroscopy measurements.

PubMed

Allard, Jean-François; Cornet, Alain; Debacq, Christophe; Meurens, Marc; Houde, Daniel; Morris, Denis

2011-02-28

We report quantitative measurement of the relative proportion of δ- and β-D-mannitol crystalline phases inserted into polyethylene powder pellets, obtained by time-domain terahertz spectroscopy. Nine absorption bands have been identified from 0.2 THz to 2.2 THz. The best quantification of the δ-phase proportion is made using the 1.01 THz absorption band. Coherent detection allows using the spectral phase shift of the transmitted THz waveform to improve the detection sensitivity of the relative δ-phase proportion. We argue that differential phase shift measurements are less sensitive to samples' defects. Using a linear phase shift compensation for pellets of slightly different thicknesses, we were able to distinguish a 0.5% variation in δ-phase proportion.

Effects of light, food, and methamphetamine on the circadian activity rhythm in mice.

PubMed

Pendergast, Julie S; Yamazaki, Shin

2014-04-10

The circadian rhythm of locomotor activity in mice is synchronized to environmental factors such as light and food availability. It is well-known that entrainment of the activity rhythm to the light-dark cycle is attained by the circadian pacemaker in the suprachiasmatic nucleus (SCN). Locomotor activity is also controlled by two extra-SCN oscillators; periodic food availability entrains the food-entrainable oscillator (FEO) and constant consumption of low-dose methamphetamine reveals the output of the methamphetamine-sensitive circadian oscillator (MASCO). In this study, we sought to investigate the relationship between the SCN, FEO, and MASCO by examining the combinatorial effects of light, food restriction, and/or methamphetamine on locomotor activity. To investigate coupling between the SCN and FEO, we tested whether food anticipatory activity, which is the output of the FEO, shifted coordinately with phase shifts of the light-dark cycle. We found that the phase of food anticipatory activity was phase-delayed or phase-advanced symmetrically with the respective shift of the light-dark cycle, suggesting that the FEO is strongly coupled to the SCN and the phase angle between the SCN and FEO is maintained during ad libitum feeding. To examine the effect of methamphetamine on the output of the FEO, we administered methamphetamine to mice undergoing restricted feeding and found that food-entrained activity was delayed by methamphetamine treatment. In addition, restricted feeding induced dissociation of the MASCO and SCN activity rhythms during short-term methamphetamine treatment, when these rhythms are typically integrated. In conclusion, our data suggest that the outputs of the SCN, FEO and MASCO collectively drive locomotor activity. Copyright © 2014 Elsevier Inc. All rights reserved.

Analytical Characterization of SPM Impact on XPM-Induced Degradation in Dispersion-Compensated WDM Systems

NASA Astrophysics Data System (ADS)

Luís, Ruben S.; Cartaxo, Adolfo V. T.

2005-03-01

This paper proposes the definition of a cross-phase modulation (XPM)-induced power penalty for intensity modulation/direct detection (IM-DD) systems as a function of the normalized variance of the XPM-induced IM. This allows the definition of 1-dB power penalty reference values. New expressions of the equivalent linear model transfer functions for the XPM-induced IM and phase modulation (PM) that include the influence of self-phase modulation (SPM) as well as group-velocity dispersion are derived. The new expressions allow a significant extension for higher powers and dispersion parameters of expressions derived in previous papers for single-segment and multisegment fiber systems with dispersion compensation. Good agreement between analytical results and numerical simulations is obtained. Consistency with work performed numerically and experimentally by other authors is shown, validating the proposed model. Using the proposed model, the influence of residual dispersion and SPM on the limitations imposed by XPM on the performance of dispersion-compensated systems is assessed. It is shown that inline residual dispersion may lead to performance improvement for a properly tuned total residual dispersion. The influence of SPM is shown to degrade the system performance when nonzero-dispersion-shifted fiber is used. However, systems using standard single-mode fiber may benefit from the presence of SPM.

Electric-field-induced magnetic domain writing in a Co wire

NASA Astrophysics Data System (ADS)

Tanaka, Yuki; Hirai, Takamasa; Koyama, Tomohiro; Chiba, Daichi

2018-05-01

We have demonstrated that the local magnetization in a Co microwire can be switched by an application of a gate voltage without using any external magnetic fields. The electric-field-induced reversible ferromagnetic phase transition was used to realize this. An internal stray field from a ferromagnetic gate electrode assisted the local domain reversal in the Co wire. This new concept of electrical domain switching may be useful for dramatically reducing the power consumption of writing information in a magnetic racetrack memory, in which a shift of a magnetic domain by electric current is utilized.

Importance of correlation effects in hcp iron revealed by a pressure-induced electronic topological transition.

PubMed

Glazyrin, K; Pourovskii, L V; Dubrovinsky, L; Narygina, O; McCammon, C; Hewener, B; Schünemann, V; Wolny, J; Muffler, K; Chumakov, A I; Crichton, W; Hanfland, M; Prakapenka, V B; Tasnádi, F; Ekholm, M; Aichhorn, M; Vildosola, V; Ruban, A V; Katsnelson, M I; Abrikosov, I A

2013-03-15

We discover that hcp phases of Fe and Fe(0.9)Ni(0.1) undergo an electronic topological transition at pressures of about 40 GPa. This topological change of the Fermi surface manifests itself through anomalous behavior of the Debye sound velocity, c/a lattice parameter ratio, and Mössbauer center shift observed in our experiments. First-principles simulations within the dynamic mean field approach demonstrate that the transition is induced by many-electron effects. It is absent in one-electron calculations and represents a clear signature of correlation effects in hcp Fe.

Probing the limits of the rigid-intensity-shift model in differential-phase-contrast scanning transmission electron microscopy

NASA Astrophysics Data System (ADS)

Clark, L.; Brown, H. G.; Paganin, D. M.; Morgan, M. J.; Matsumoto, T.; Shibata, N.; Petersen, T. C.; Findlay, S. D.

2018-04-01

The rigid-intensity-shift model of differential-phase-contrast imaging assumes that the phase gradient imposed on the transmitted probe by the sample causes the diffraction pattern intensity to shift rigidly by an amount proportional to that phase gradient. This behavior is seldom realized exactly in practice. Through a combination of experimental results, analytical modeling and numerical calculations, using as case studies electron microscope imaging of the built-in electric field in a p-n junction and nanoscale domains in a magnetic alloy, we explore the breakdown of rigid-intensity-shift behavior and how this depends on the magnitude of the phase gradient and the relative scale of features in the phase profile and the probe size. We present guidelines as to when the rigid-intensity-shift model can be applied for quantitative phase reconstruction using segmented detectors, and propose probe-shaping strategies to further improve the accuracy.

Doppler radar with multiphase modulation of transmitted and reflected signal

NASA Technical Reports Server (NTRS)

Shores, Paul W. (Inventor); Griffin, John W. (Inventor); Kobayashi, Herbert S. (Inventor)

1989-01-01

A microwave radar signal is generated and split by a circulator. A phase shifter introduces a series of phase shifts into a first part of the split signal which is then transmitted by antenna. A like number of phase shifts is introduced by the phase shifter into the return signal from the target. The circulator delivers the phase shifted return signal and the leakage signal from the circulator to a mixer which generates an IF signal output at the Doppler frequency. The IF signal is amplified, filtered, counted per unit of time, and the result displayed to provide indications of target sense and range rate. An oscillator controls rate of phase shift in the transmitted and received radar signals and provides a time base for the counter. The phase shift magnitude increases may be continuous and linear or discrete functions of time.

Circadian rhythm phase shifts and endogenous free-running circadian period differ between African-Americans and European-Americans.

PubMed

Eastman, Charmane I; Suh, Christina; Tomaka, Victoria A; Crowley, Stephanie J

2015-02-11

Successful adaptation to modern civilization requires the internal circadian clock to make large phase shifts in response to circumstances (e.g., jet travel and shift work) that were not encountered during most of our evolution. We found that the magnitude and direction of the circadian clock's phase shift after the light/dark and sleep/wake/meal schedule was phase-advanced (made earlier) by 9 hours differed in European-Americans compared to African-Americans. European-Americans had larger phase shifts, but were more likely to phase-delay after the 9-hour advance (to phase shift in the wrong direction). The magnitude and direction of the phase shift was related to the free-running circadian period, and European-Americans had a longer circadian period than African-Americans. Circadian period was related to the percent Sub-Saharan African and European ancestry from DNA samples. We speculate that a short circadian period was advantageous during our evolution in Africa and lengthened with northern migrations out of Africa. The differences in circadian rhythms remaining today are relevant for understanding and treating the modern circadian-rhythm-based disorders which are due to a misalignment between the internal circadian rhythms and the times for sleep, work, school and meals.

Inspection of arterial-induced skin vibration by Moire fringe with two-dimensional continuous wavelet transform

NASA Astrophysics Data System (ADS)

Wang, Chun-Hsiung; Chiu, Shih-Yung; Hsu, Yu-Hsiang; Lee, Shu-Sheng; Lee, Chih-Kung

2017-06-01

A non-contact arterial-induced skin vibration inspection system is implemented. This optical metrology system is constructed with shadow Moiré configuration and the fringe analysis algorithm. Developed with the Region of Interested (ROI) capturing technique and the Two-dimensional Wavelet Transform (2D-CWT) method, this algorithm is able to retrieve the height-correlated phase information from the shadow Moiré fringe patterns. Using a commercial video camera or a CMOS image sensor, this system could monitor the skin-vibration induced by the cyclic deformation of inner layered artery. The cross-sectional variation and the rhythm of heart cycle could be continuously measured for health monitoring purposes. The average vibration amplitude of the artery at the wrist ranges between 20 μm and 50 μm, which is quite subtle comparing with the skin surface structure. Having the non-stationary motion of human body, the traditional phase shifting (PS) technique can be very unstable due to the requirement of several frames of images, especially for case that artery is continuously pumping. To bypass this fundamental issue, the shadow Moiré technique is introduced to enhance the surface deformation characteristic. And the phase information is retrieved by the means of spectrum filtering instead of PS technique, which the phase is calculated from intensity maps of multiple images. The instantaneous surface can therefore be reconstructed individually from each frame, enabling the subtle arterial-induced skin vibration measurement. The comparative results of phase reconstruction between different fringe analysis algorithms will be demonstrated numerically and experimentally. And the electrocardiography (ECG) results will used as the reference for the validity of health monitoring potential of the non-contact arterial-induced skin vibration inspection system.

Volume moiré tomography based on projection extraction by spatial phase shifting of double crossed gratings

NASA Astrophysics Data System (ADS)

Wang, Jia; Guo, Zhenyan; Song, Yang; Han, Jun

2018-01-01

To realize volume moiré tomography (VMT) for the real three-dimensional (3D) diagnosis of combustion fields, according to 3D filtered back projection (FBP) reconstruction algorithm, the radial derivatives of the projected phase should be measured firstly. In this paper, a simple spatial phase-shifting moiré deflectometry with double cross gratings is presented to measure the radial first-order derivative of the projected phase. Based on scalar diffraction theory, the explicit analytical intensity distributions of moiré patterns on different diffracted orders are derived, and the spatial shifting characteristics are analyzed. The results indicate that the first-order derivatives of the projected phase in two mutually perpendicular directions are involved in moiré patterns, which can be combined to compute the radial first-order derivative. And multiple spatial phase-shifted moiré patterns can be simultaneously obtained; the phase-shifted values are determined by the parameters of the system. A four-step phase-shifting algorithm is proposed for phase extraction, and its accuracy is proved by numerical simulations. Finally, the moiré deflectometry is used to measure the radial first-order derivative of projected phase of a propane flame with plane incident wave, and the 3D temperature distribution is reconstructed.

Nonadiabatic conditional geometric phase shift with NMR.

PubMed

Xiang-Bin, W; Keiji, M

2001-08-27

A conditional geometric phase shift gate, which is fault tolerant to certain types of errors due to its geometric nature, was realized recently via nuclear magnetic resonance (NMR) under adiabatic conditions. However, in quantum computation, everything must be completed within the decoherence time. The adiabatic condition makes any fast conditional Berry phase (cyclic adiabatic geometric phase) shift gate impossible. Here we show that by using a newly designed sequence of simple operations with an additional vertical magnetic field, the conditional geometric phase shift gate can be run nonadiabatically. Therefore geometric quantum computation can be done at the same rate as usual quantum computation.

A POSITIONAL DATA SYSTEM

DOEpatents

Forster, G.A.

1963-09-24

between master and slave synchros is described. A threephase a-c power source is connected to the stators of the synchros and an error detector is connected to the rotors of the synchros to measure the phasor difference therebetween. A phase shift network shifts the phase of one of the rotors 90 degrees and a demodulator responsive thereto causes the phasor difference signal of the rotors to shift phase 180 degrees whenever the 90 degree phase shifted signal goes negative. The phase shifted difference signal has a waveform which, with the addition of small values of resistance and capacitance, gives a substantially pure d-c output whose amplitude and polarity is proportional to the magnitude and direction of the difference in the angular positions of the synchro's rotors. (AEC)

Multiwavelength digital holography with wavelength-multiplexed holograms and arbitrary symmetric phase shifts.

PubMed

Tahara, Tatsuki; Otani, Reo; Omae, Kaito; Gotohda, Takuya; Arai, Yasuhiko; Takaki, Yasuhiro

2017-05-15

We propose multiwavelength in-line digital holography with wavelength-multiplexed phase-shifted holograms and arbitrary symmetric phase shifts. We use phase-shifting interferometry selectively extracting wavelength information to reconstruct multiwavelength object waves separately from wavelength-multiplexed monochromatic images. The proposed technique obtains systems of equations for real and imaginary parts of multiwavelength object waves from the holograms by introducing arbitrary symmetric phase shifts. Then, the technique derives each complex amplitude distribution of each object wave selectively and analytically by solving the two systems of equations. We formulate the algorithm in the case of an arbitrary number of wavelengths and confirm its validity numerically and experimentally in the cases where the number of wavelengths is two and three.

RF power recovery feedback circulator

DOEpatents

Sharamentov, Sergey I [Bolingbrook, IL

2011-03-29

A device and method for improving the efficiency of RF systems having a Reflective Load. In the preferred embodiment, Reflected Energy from a superconducting resonator of a particle accelerator is reintroduced to the resonator after the phase of the Reflected Energy is aligned with the phase of the Supply Energy from a RF Energy Source. In one embodiment, a Circulator is used to transfer Reflected Energy from the Reflective Load into a Phase Adjuster which aligns the phase of the Reflected Energy with that of the Supply Energy. The phase-aligned energy is then combined with the Supply Energy, and reintroduced into the Reflective Load. In systems having a constant phase shift, the Phase Adjuster may be designed to shift the phase of the Reflected Energy by a constant amount using a Phase Shifter. In systems having a variety (variable) phase shifts, a Phase Shifter controlled by a phase feedback loop comprising a Phase Detector and a Feedback Controller to account for the various phase shifts is preferable.

One-shot phase-shifting phase-grating interferometry with modulation of polarization: case of four interferograms.

PubMed

Rodriguez-Zurita, Gustavo; Meneses-Fabian, Cruz; Toto-Arellano, Noel-Ivan; Vázquez-Castillo, José F; Robledo-Sánchez, Carlos

2008-05-26

An experimental setup for optical phase extraction from 2-D interferograms using a one-shot phase-shifting technique able to achieve four interferograms with 90 degrees phase shifts in between is presented. The system uses a common-path interferometer consisting of two windows in the input plane and a phase grating in Fourier plane as its pupil. Each window has a birefringent wave plate attached in order to achieve nearly circular polarization of opposite rotations one respect to the other after being illuminated with a 45 degrees linear polarized beam. In the output, interference of the fields associated with replicated windows (diffraction orders) is achieved by a proper choice of the windows spacing with respect to the grating period. The phase shifts to achieve four interferograms simultaneously to perform phase-shifting interferometry can be obtained by placing linear polarizers on each diffraction orders before detection at an appropriate angle. Some experimental results are shown.

Femtosecond-pulse inscription of fiber Bragg gratings with single or multiple phase-shifts in the structure

NASA Astrophysics Data System (ADS)

Wolf, Alexey; Dostovalov, Alexandr; Skvortsov, Mikhail; Raspopin, Kirill; Parygin, Alexandr; Babin, Sergey

2018-05-01

In this work, long high-quality fiber Bragg gratings with phase shifts in the structure are inscribed directly in the optical fiber by point-by-point technique using femtosecond laser pulses. Phase shifts are introduced during the inscription process with a piezoelectric actuator, which rapidly shifts the fiber along the direction of its movement in a chosen point of the grating with a chosen shift value. As examples, single and double π phase shifts are introduced in fiber Bragg gratings with a length up to 34 mm in passive fibers, which provide corresponding transmission peaks with bandwidth less than 1 pm. It is shown that 37 mm π -phase-shifted grating inscribed in an active Er-doped fiber forms high-quality DFB laser cavity generating single-frequency radiation at 1550 nm with bandwidth of 20 kHz and signal-to-noise ratio of >70 dB. The inscription technique has a high degree of performance and flexibility and can be easily implemented in fibers of various types.

Resynchronization of circadian sleep-wake and temperature cycles in the squirrel monkey following phase shifts of the environmental light-dark cycle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wexler, D.B.; Moore-ede, M.C.

1986-12-01

Circadian rhythms in physiological and behavioral functions gradually resynchronize after phase shifts in environmental time cues. In order to characterize the rate of circadian resynchronization in a diurnal primate model, the temperature, locomotor activity, and polygraphically determined sleep-wake states were monitored in squirrel monkeys before and after 8-h phase shifts of an environmental light-dark cycle of 12 h light and 12 h dark (LD 12:12). For the temperature rhythm, resynchronization took 4 d after phase delay shift and 5 d after phase advance shift; for the rest-activity cycle, resynchronization times were 3 d and 6 d, respectively. The activity acrophasemore » shifted more rapidly than the temperature acrophase early in the post-delay shift interval, but this internal desynchronization between rhythms disappeared during the course of resynchronization. Further study of the early resynchronization process requires emphasis on identifying evoked effects and measuring circadian pacemaker function. 13 references.« less

Resynchronization of circadian sleep-wake and temperature cycles in the squirrel monkey following phase shifts of the environmental light-dark cycle

NASA Technical Reports Server (NTRS)

Wexler, D. B.; Moore-Ede, M. C.

1986-01-01

Circadian rhythms in physiological and behavioral functions gradually resynchronize after phase shifts in environmental time cues. In order to characterize the rate of circadian resynchronization in a diurnal primate model, the temperature, locomotor activity, and polygraphically determined sleep-wake states were monitored in squirrel monkeys before and after 8-h phase shifts of an environmental light-dark cycle of 12 h light and 12 h dark (LD 12:12). For the temperature rhythm, resynchronization took 4 d after phase delay shift and 5 d after phase advance shift; for the rest-activity cycle, resynchronization times were 3 d and 6 d, respectively. The activity acrophase shifted more rapidly than the temperature acrophase early in the post-delay shift interval, but this internal desynchronization between rhythms disappeared during the course of resynchronization. Further study of the early resynchronization process requires emphasis on identifying evoked effects and measuring circadian pacemaker function.

Hemiparetic stepping to the beat: asymmetric response to metronome phase shift during treadmill gait.

PubMed

Pelton, Trudy A; Johannsen, Leif; Huiya Chen; Wing, Alan M

2010-06-01

Walking in time with a metronome is associated with improved spatiotemporal parameters in hemiparetic gait; however, the mechanism linking auditory and motor systems is poorly understood. Hemiparetic cadence control with metronome synchronization was examined to determine specific influences of metronome timing on treadmill walking. A within-participant experiment examined correction processes used to maintain heel strike synchrony with the beat by applying perturbations to the timing of a metronome. Eight chronic hemiparetic participants (mean age = 70 years; standard deviation = 12) were required to synchronize heel strikes with metronome pulses set according to each individual's comfortable speed (mean 0.4 m/s). During five 100-pulse trials, a fixed-phase baseline was followed by 4 unpredictable metronome phase shifts (20% of the interpulse interval), which amounted to 10 phase shifts on each foot. Infrared cameras recorded the motion of bilateral heel markers at 120 Hz. Relative asynchrony between heel strike responses and metronome pulses was used to index compensation for metronome phase shifts. Participants demonstrated compensation for phase shifts with convergence back to pre-phase shift asynchrony. This was significantly slower when the error occurred on the nonparetic side (requiring initial correction with the paretic limb) compared with when the error occurred on the paretic side (requiring initial nonparetic correction). Although phase correction of gait is slowed when the phase shift is delivered to the nonparetic side compared with the paretic side, phase correction is still present. This may underlie the utility of rhythmic auditory cueing in hemiparetic gait rehabilitation.

Measurement of Stress Distribution Around a Circular Hole in a Plate Under Bending Moment Using Phase-shifting Method with Reflective Polariscope Arrangement

NASA Astrophysics Data System (ADS)

Baek, Tae Hyun

Photoelasticity is one of the most widely used whole-field optical methods for stress analysis. The technique of birefringent coatings, also called the method of photoelastic coatings, extends the classical procedures of model photoelasticity to the measurement of surface strains in opaque models made of any structural material. Photoelastic phase-shifting method can be used for the determination of the phase values of isochromatics and isoclinics. In this paper, photoelastic phase-shifting technique and conventional Babinet-Soleil compensation method were utilized to analyze a specimen with a triangular hole and a circular hole under bending. Photoelastic phase-shifting technique is whole-field measurement. On the other hand, conventional compensation method is point measurement. Three groups of results were obtained by phase-shifting method with reflective polariscope arrangement, conventional compensation method and FEM simulation, respectively. The results from the first two methods agree with each other relatively well considering experiment error. The advantage of photoelastic phase-shifting method is that it is possible to measure the stress distribution accurately close to the edge of holes.

The benefits of four weeks of melatonin treatment on circadian patterns in resistance-trained athletes.

PubMed

Leonardo-Mendonça, Roberto C; Martinez-Nicolas, Antonio; de Teresa Galván, Carlos; Ocaña-Wilhelmi, Javier; Rusanova, Iryna; Guerra-Hernández, Eduardo; Escames, Germaine; Acuña-Castroviejo, Darío

2015-01-01

Exercise can induce circadian phase shifts depending on the duration, intensity and frequency. These modifications are of special meaning in athletes during training and competition. Melatonin, which is produced by the pineal gland in a circadian manner, behaves as an endogenous rhythms synchronizer, and it is used as a supplement to promote resynchronization of altered circadian rhythms. In this study, we tested the effect of melatonin administration on the circadian system in athletes. Two groups of athletes were treated with 100 mg day(-1) of melatonin or placebo 30 min before bed for four weeks. Daily rhythm of salivary melatonin was measured before and after melatonin administration. Moreover, circadian variables, including wrist temperature (WT), motor activity and body position rhythmicity, were recorded during seven days before and seven days after melatonin or placebo treatment with the aid of specific sensors placed in the wrist and arm of each athlete. Before treatment, the athletes showed a phase-shift delay of the melatonin circadian rhythm, with an acrophase at 05:00 h. Exercise induced a phase advance of the melatonin rhythm, restoring its acrophase accordingly to the chronotype of the athletes. Melatonin, but not placebo treatment, changed daily waveforms of WT, activity and position. These changes included a one-hour phase advance in the WT rhythm before bedtime, with a longer nocturnal steady state and a smaller reduction when arising at morning than the placebo group. Melatonin, but not placebo, also reduced the nocturnal activity and the activity and position during lunch/nap time. Together, these data reflect the beneficial effect of melatonin to modulate the circadian components of the sleep-wake cycle, improving sleep efficiency.

ENSO and East Asian winter monsoon relationship modulation associated with the anomalous northwest Pacific anticyclone

NASA Astrophysics Data System (ADS)

Kim, Ji-Won; An, Soon-Il; Jun, Sang-Yoon; Park, Hey-Jin; Yeh, Sang-Wook

2017-08-01

Using observational datasets and numerical model experiments, the mechanism on the slowly varying change in the relationship between the El Niño-Southern Oscillation (ENSO) and the East Asian winter monsoon (EAWM) is investigated. The decadal-window (11-, 15-, and 21-year) moving correlations show a significant change in the boreal wintertime ENSO-EAWM relationship between two sub-periods of 1976‒1992 and 1997‒2013. Such recent change in ENSO-EAWM relationship is mainly attributed to the changes in the intensity and zonal location of the anomalous lower-tropospheric northwest Pacific anticyclone (NWP-AC). NWP-AC commonly develops near the region of the Philippine Sea during the ENSO's peak phase and plays an important role of bridging the tropical convection and mid-latitude teleconnection. On one hand, the intensity of the NWP-AC is influenced by the interdecadal variation in a linkage between ENSO and the Indian Ocean sea surface temperature (SST) variability, referring that a strong connection between the Pacific and Indian Oceans results in the strengthening of NWP-AC response to ENSO. On the other hand, the zonal displacement of the NWP-AC is associated with the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). That is, the tropical Pacific mean state (i.e., zonal SST gradient between climatologically warm western Pacific and cold eastern Pacific)—strengthened by either the negative PDO phase or the positive AMO phase—drives the anomalous ENSO-induced convection to be shifted to the west. With this westward shift, the zonal center of the NWP-AC also migrates westward over the Philippine Islands and exerts stronger connection between ENSO and EAWM. In contrast, the relaxed zonal SST contrast associated with either the positive PDO phase or the negative AMO phase tends to exhibit weaker ENSO-EAWM relationship via both of eastward shifted zonal centers of the anomalous ENSO-induced convection and the NWP-AC. Finally, a series of the numerical experiments conducted by an atmospheric general circulation model supports the observational findings.

Pituitary adenylyl cyclase-activating peptide: A pivotal modulator of glutamatergic regulation of the suprachiasmatic circadian clock

PubMed Central

Chen, Dong; Buchanan, Gordon F.; Ding, Jian M.; Hannibal, Jens; Gillette, Martha U.

1999-01-01

The circadian clock in the suprachiasmatic nucleus (SCN) of the hypothalamus organizes behavioral rhythms, such as the sleep–wake cycle, on a near 24-h time base and synchronizes them to environmental day and night. Light information is transmitted to the SCN by direct retinal projections via the retinohypothalamic tract (RHT). Both glutamate (Glu) and pituitary adenylyl cyclase-activating peptide (PACAP) are localized within the RHT. Whereas Glu is an established mediator of light entrainment, the role of PACAP is unknown. To understand the functional significance of this colocalization, we assessed the effects of nocturnal Glu and PACAP on phasing of the circadian rhythm of neuronal firing in slices of rat SCN. When coadministered, PACAP blocked the phase advance normally induced by Glu during late night. Surprisingly, blocking PACAP neurotransmission, with either PACAP6–38, a specific PACAP receptor antagonist, or anti-PACAP antibodies, augmented the Glu-induced phase advance. Blocking PACAP in vivo also potentiated the light-induced phase advance of the rhythm of hamster wheel-running activity. Conversely, PACAP enhanced the Glu-induced delay in the early night, whereas PACAP6–38 inhibited it. These results reveal that PACAP is a significant component of the Glu-mediated light-entrainment pathway. When Glu activates the system, PACAP receptor-mediated processes can provide gain control that generates graded phase shifts. The relative strengths of the Glu and PACAP signals together may encode the amplitude of adaptive circadian behavioral responses to the natural range of intensities of nocturnal light. PMID:10557344

Phase demodulation of Fabry-Perot interferometer-based acoustic sensor utilizing tunable filter with two quadrature wavelengths

NASA Astrophysics Data System (ADS)

Liao, Hao; Lu, Ping; Liu, Li; Liu, Deming; Zhang, Jiangshan

2017-02-01

A phase demodulation method for short-cavity extrinsic Fabry-Perot interferometer (EFPI) based on two orthogonal wavelengths via a tunable optical filter is proposed in this paper. A broadband light is launched into the EFPI sensor and two monochromatic beams with 3dB bandwidth of 0.2nm are selected out from the reflected light of the EFPI sensor. A phase bias is induced between the two interferential signals due to the wavelength difference of the two beams. The wavelength difference will have an affect on the sensitivity of demodulated signal, which has been theoretically and experimentally demonstrated. The maximum sensitivity can be obtained when the phase bias is 0.5π corresponding to the wavelength difference of 1/4 FSR of the EFPI spectrum. The acoustic wave induced phase variation can be interrogated through an optimized differential cross multiplication (DCM) method. A normalization process is induced into the traditional DCM method to eliminate the influence of ambient temperature and pressure fluctuation induced spectrum shift on output signal. This means that, once the wavelength difference is fixed, the wavelength variation of each individual beam will have little influence on the amplitude of demodulated signal. The EFPI sensing head is formed by a 3μm-thick aluminum diaphragm, which has a SNR of more than 53dB. Through the proposed demodulation scheme, a large dynamic range and good linearity is acquired and Q-point drift problem of traditional EFPI sensor can be solved. The demodulation scheme can be applied to other kinds of short-cavity EFPI based acoustic sensors.

Multistable orientation in a nematic liquid crystal cell induced by external field and interfacial interaction

NASA Astrophysics Data System (ADS)

Ong, Hiap Liew; Meyer, Robert B.; Hurd, Alan J.

1984-04-01

The effects of a short-range, arbitrary strength interfacial potential on the magnetic field, electric field, and optical field induced Freedericksz transition in a nematic liquid crystal cell are examined and the exact solution is obtained. By generalizing the criterion for the existence of a first-order optical field induced Freedericksz transition that was obtained previously [H. L. Ong, Phys. Rev. A 28, 2393 (1983)], the general criterion for the transition to be first order is obtained. Based on the existing experimental results, the possibility of surface induced first-order transitions is discussed and three simple empirical approaches are suggested for observing multistable orientation. The early results on the magnetic and electric fields induced Freedericksz transition and the inadequacy of the usual experimental observation methods (phase shift and capacitance measurements) are also discussed.

A three pulse phase response curve to three milligrams of melatonin in humans

PubMed Central

Burgess, Helen J; Revell, Victoria L; Eastman, Charmane I

2008-01-01

Exogenous melatonin is increasingly used for its phase shifting and soporific effects. We generated a three pulse phase response curve (PRC) to exogenous melatonin (3 mg) by administering it to free-running subjects. Young healthy subjects (n = 27) participated in two 5 day laboratory sessions, each preceded by at least a week of habitual, but fixed sleep. Each 5 day laboratory session started and ended with a phase assessment to measure the circadian rhythm of endogenous melatonin in dim light using 30 min saliva samples. In between were three days in an ultradian dim light (< 150 lux)–dark cycle (LD 2.5 : 1.5) during which each subject took one pill per day at the same clock time (3 mg melatonin or placebo, double blind, counterbalanced). Each individual's phase shift to exogenous melatonin was corrected by subtracting their phase shift to placebo (a free-run). The resulting PRC has a phase advance portion peaking about 5 h before the dim light melatonin onset, in the afternoon. The phase delay portion peaks about 11 h after the dim light melatonin onset, shortly after the usual time of morning awakening. A dead zone of minimal phase shifts occurred around the first half of habitual sleep. The fitted maximum advance and delay shifts were 1.8 h and 1.3 h, respectively. This new PRC will aid in determining the optimal time to administer exogenous melatonin to achieve desired phase shifts and demonstrates that using exogenous melatonin as a sleep aid at night has minimal phase shifting effects. PMID:18006583

SU-G-JeP3-14: Positioning and Dosimetric Uncertainties in Image-Guided Radiation Therapy with Respiratory Gating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ali, I; Hossain, S; Algan, O

Purpose: To investigate quantitatively positioning and dosimetric uncertainties due to 4D-CT intra-phase motion in the internal-target-volume (ITV) associated with radiation therapy using respiratory-gating for patients setup with image-guidance-radiation-therapy (IGRT) using free-breathing or average-phase CT-images. Methods: A lung phantom with an embedded tissue-equivalent target is imaged with CT while it is stationary and moving. Four-sets of structures are outlined: (a) the actual target on CT-images of the stationary-target, (b) ITV on CT-images for the free-moving phantom, (c) ITV’s from the ten different phases (10–100%) and (d) ITV on the CT-images generated from combining 3 phases: 40%–50%–60%. The variations in volume, lengthmore » and center-position of the ITV’s and their effects on dosimetry during dose delivery for patients setup with image-guidance are investigated. Results: Intra-phase motion due to breathing affects the volume, center position and length of the ITVs from different respiratory-phases. The ITV’s vary by about 10% from one phase to another. The largest ITV is measured on the free breathing CT images and the smallest is on the stationary CT-images. The ITV lengths vary by about 4mm where it may shrink or elongated depending on the motion-phase. The center position of the ITV varies between the different motion-phases which shifts upto 10mm from the stationary-position which is nearly equal to motion-amplitude. This causes systematic shifts during dose delivery with beam gating using certain phases (40%–50%–60%) for patients setup with IGRT using free-breathing or average-phase CT-images. The dose coverage of the ITV depends on the margins used for treatment-planning-volume where margins larger than the motion-amplitudes are needed to ensure dose coverage of the ITV. Conclusion: Volume, length, and center position of the ITV’s change between the different motion phases. Large systematic shifts are induced by respiratory-gating with ITVs on certain phases when patients are setup with IGRT using free-breathing or average-phase CT-images.« less

Microstructure, Corrosion and Magnetic Behavior of an Aged Dual-Phase Stainless Steel

NASA Astrophysics Data System (ADS)

Ziouche, A.; Haddad, A.; Badji, R.; Zergoug, M.; Zoubiri, N.; Bedjaoui, W.; Abaidia, S.

2018-03-01

In the present work, the effect of the precipitation phenomena on corrosion and magnetic behavior of an aged dual-phase stainless steel was investigated. Aging treatment caused the precipitation of the σ phase, chromium carbides and secondary austenite, which was accompanied by the shifting of the δ/γ interfaces inside the δ ferrite grains. Aging between 700 and 850 °C strongly deteriorated the pitting corrosion resistance of the studied material. Magnetic investigation of the aged material using the vibration sample magnetic technique revealed the sensitivity of the intrinsic magnetic properties to the smallest microstructural change. This was confirmed by the Eddy current technique that led also to the evaluation of the aging-induced localized corrosion.

Strong resetting of the mammalian clock by constant light followed by constant darkness

PubMed Central

Chen, Rongmin; Seo, Dong-oh; Bell, Elijah; von Gall, Charlotte; Lee, Choogon

2008-01-01

The mammalian molecular circadian clock in the suprachiasmatic nuclei (SCN) regulates locomotor activity rhythms as well as clocks in peripheral tissues (Reppert and Weaver, 2002; Ko and Takahashi, 2006). Constant light (LL) can induce behavioral and physiological arrhythmicity, by desynchronizing clock cells in the SCN (Ohta et al., 2005). We examined how the disordered clock cells resynchronize by probing the molecular clock and measuring behavior in mice transferred from LL to constant darkness (DD). The circadian locomotor activity rhythms disrupted in LL become robustly rhythmic again from the beginning of DD, and the starting phase of the rhythm in DD is specific, not random, suggesting that the desynchronized clock cells are quickly reset in an unconventional manner by the L:D transition. By measuring mPERIOD protein rhythms, we showed that the SCN and peripheral tissue clocks quickly become rhythmic again in phase with the behavioral rhythms. We propose that this resetting mechanism may be different from conventional phase shifting, which involves light-induction of Period genes (Albrecht et al., 1997; Shearman et al., 1997; Shigeyoshi et al., 1997). Using our functional insights, we could shift the circadian phase of locomotor activity rhythms by 12 hours using a 15-hour LL treatment: essentially producing phase reversal by a single light pulse, a feat that has not been reported previously in wild-type mice and that has potential clinical utility. PMID:19005049

Dual-wavelength phase-shifting digital holography selectively extracting wavelength information from wavelength-multiplexed holograms.

PubMed

Tahara, Tatsuki; Mori, Ryota; Kikunaga, Shuhei; Arai, Yasuhiko; Takaki, Yasuhiro

2015-06-15

Dual-wavelength phase-shifting digital holography that selectively extracts wavelength information from five wavelength-multiplexed holograms is presented. Specific phase shifts for respective wavelengths are introduced to remove the crosstalk components and extract only the object wave at the desired wavelength from the holograms. Object waves in multiple wavelengths are selectively extracted by utilizing 2π ambiguity and the subtraction procedures based on phase-shifting interferometry. Numerical results show the validity of the proposed technique. The proposed technique is also experimentally demonstrated.

Phase-shift, stimuli-responsive drug carriers for targeted delivery

PubMed Central

O’Neill, Brian E; Rapoport, Natalya

2011-01-01

The intersection of particles and directed energy is a rich source of novel and useful technology that is only recently being realized for medicine. One of the most promising applications is directed drug delivery. This review focuses on phase-shift nanoparticles (that is, particles of submicron size) as well as micron-scale particles whose action depends on an external-energy triggered, first-order phase shift from a liquid to gas state of either the particle itself or of the surrounding medium. These particles have tremendous potential for actively disrupting their environment for altering transport properties and unloading drugs. This review covers in detail ultrasound and laser-activated phase-shift nano- and micro-particles and their use in drug delivery. Phase-shift based drug-delivery mechanisms and competing technologies are discussed. PMID:22059114

Phase shift of TE and TM modes in an optical fiber due to axial strain (exact solution)

NASA Technical Reports Server (NTRS)

Egalon, Claudio O.; Rogowski, Robert S.

1992-01-01

Axial strain may be determined by monitoring the phase shift of modes of a variety of optical fiber sensors. In this paper, the exact solution of a circular optical fiber is used to calculate the phase shift of the TE and TM modes. Whenever an optical fiber is stressed, the optical path length, the index of refraction, and the propagation constants of each fiber mode change. In consequence, the modal phase term, beta(ln)z, of the fields is shifted by an amount Delta phi. In certain cases, it is desirable to control the phase shift term in order to make the fiber either more or less sensitive to certain kinds of strain. It is shown that it can be accomplished by choosing appropriate fiber parameters.

Observation of Phase-Filling Singularities in the Optical Dielectric Function of Highly Doped n-Type Ge.

PubMed

Xu, Chi; Fernando, Nalin S; Zollner, Stefan; Kouvetakis, John; Menéndez, José

2017-06-30

Phase-filling singularities in the optical response function of highly doped (>10^{19}  cm^{-3}) germanium are theoretically predicted and experimentally confirmed using spectroscopic ellipsometry. Contrary to direct-gap semiconductors, which display the well-known Burstein-Moss phenomenology upon doping, the critical point in the joint density of electronic states associated with the partially filled conduction band in n-Ge corresponds to the so-called E_{1} and E_{1}+Δ_{1} transitions, which are two-dimensional in character. As a result of this reduced dimensionality, there is no edge shift induced by Pauli blocking. Instead, one observes the "original" critical point (shifted only by band gap renormalization) and an additional feature associated with the level occupation discontinuity at the Fermi level. The experimental observation of this feature is made possible by the recent development of low-temperature, in situ doping techniques that allow the fabrication of highly doped films with exceptionally flat doping profiles.

Stress and selective attention: the interplay of mood, cortisol levels, and emotional information processing.

PubMed

Ellenbogen, Mark A; Schwartzman, Alex E; Stewart, Jane; Walker, Claire-Dominique

2002-11-01

The effects of a stressful challenge on the processing of emotional words were examined in college students. Stress induction was achieved using a competitive computer task, where the individual either repeatedly lost or won against a confederate. Mood, attention, and cortisol were recorded during the study. There were four findings: (1) Participants in the negative stressor condition were faster to shift attention away from negative words than positive or neutral words; (2) attentional shifts away from negative words were associated with stress-induced mood lowering; (3) participants in the negative stress condition with elevated scores on the Beck Depression Inventory were slow to disengage attention from all stimuli; and (4) elevated depression scores were associated with lower cortisol change from baseline during the experimental phase, and with higher cortisol levels during the recovery phase. These findings point to information-processing strategies as a means to regulate emotion, and to atypical features of cognitive and adrenocortical function that may serve as putative risk markers of depression.

Photonic Magnetic Field Sensor

NASA Astrophysics Data System (ADS)

Wyntjes, Geert

2002-02-01

Small, in-line polarization rotators or isolators to reduce feedback in fiber optic links can be the basis for excellent magnetic field sensors. Based on the giant magneto-optical (GMO) or Faraday effect in iron garnets, they with a magnetic field of a few hundred Gauss, (20 mT) for an interaction length for an optical beam of a few millimeters achieve a polarization rotation or phase shift of 45 deg (1/8 cycle). When powered by a small laser diode, with the induced linear phase shift recovered at the shot noise limit, we have demonstrated sensitivities at the 3.3 nT/Hz1/2 level for frequencies from less than 1 Hz to frequencies into the high kHz range. Through further improvements; an increase in interaction length, better materials and by far the greatest factor, the addition of a flux concentrator, sensitivities at the pT/Hz1/2 level appear to be within reach. We will detail such a design and discuss the issues that may limit achieving these goals.

Optimized distortion correction technique for echo planar imaging.

PubMed

Chen , N K; Wyrwicz, A M

2001-03-01

A new phase-shifted EPI pulse sequence is described that encodes EPI phase errors due to all off-resonance factors, including B(o) field inhomogeneity, eddy current effects, and gradient waveform imperfections. Combined with the previously proposed multichannel modulation postprocessing algorithm (Chen and Wyrwicz, MRM 1999;41:1206-1213), the encoded phase error information can be used to effectively remove geometric distortions in subsequent EPI scans. The proposed EPI distortion correction technique has been shown to be effective in removing distortions due to gradient waveform imperfections and phase gradient-induced eddy current effects. In addition, this new method retains advantages of the earlier method, such as simultaneous correction of different off-resonance factors without use of a complicated phase unwrapping procedure. The effectiveness of this technique is illustrated with EPI studies on phantoms and animal subjects. Implementation to different versions of EPI sequences is also described. Magn Reson Med 45:525-528, 2001. Copyright 2001 Wiley-Liss, Inc.

Band gap narrowing in n-type and p-type 3C-, 2H-, 4H-, 6H-SiC, and Si

NASA Astrophysics Data System (ADS)

Persson, C.; Lindefelt, U.; Sernelius, B. E.

1999-10-01

Doping-induced energy shifts of the conduction band minimum and the valence band maximum have been calculated for n-type and p-type 3C-, 2H-, 4H-, 6H-SiC, and Si. The narrowing of the fundamental band gap and of the optical band gap are presented as functions of ionized impurity concentration. The calculations go beyond the common parabolic treatments of the ground state energy dispersion by using energy dispersion and overlap integrals from band structure calculations. The nonparabolic valence band curvatures influence strongly the energy shifts especially in p-type materials. The utilized method is based on a zero-temperature Green's function formalism within the random phase approximation with local field correction according to Hubbard. We have parametrized the shifts of the conduction and the valence bands and made comparisons with recently published results from a semi-empirical model.

Digital phase shifter synchronizes local oscillators

NASA Technical Reports Server (NTRS)

Ali, S. M.

1978-01-01

Digital phase-shifting network is used as synchronous frequency multiplier for applications such as phase-locking two signals that may differ in frequency. Circuit has various phase-shift capability. Possible applications include data-communication systems and hybrid digital/analog phase-locked loops.

On-chip programmable ultra-wideband microwave photonic phase shifter and true time delay unit.

PubMed

Burla, Maurizio; Cortés, Luis Romero; Li, Ming; Wang, Xu; Chrostowski, Lukas; Azaña, José

2014-11-01

We proposed and experimentally demonstrated an ultra-broadband on-chip microwave photonic processor that can operate both as RF phase shifter (PS) and true-time-delay (TTD) line, with continuous tuning. The processor is based on a silicon dual-phase-shifted waveguide Bragg grating (DPS-WBG) realized with a CMOS compatible process. We experimentally demonstrated the generation of delay up to 19.4 ps over 10 GHz instantaneous bandwidth and a phase shift of approximately 160° over the bandwidth 22-29 GHz. The available RF measurement setup ultimately limits the phase shifting demonstration as the device is capable of providing up to 300° phase shift for RF frequencies over a record bandwidth approaching 1 THz.

Development of a novel polymeric fiber-optic magnetostrictive metal detector.

PubMed

Hua, Wei-Shu; Hooks, Joshua Rosenberg; Wu, Wen-Jong; Wang, Wei-Chih

2010-01-01

The purpose this paper is the development a novel polymeric fiber-optic magnetostrictive metal detector, using a fiber-optic Mach-Zehnder interferometer and polymeric magnetostrictive material. Metal detection is based on the strain-induced optical path length change steming from the ferromagnetic material introduced in the magnetic field. Varied optical phase shifts resulted largely from different metal objects. In this paper, the preliminary results on the different metal material detection will be discussed.

Melanopsin (Opn4) requirement for normal light-induced circadian phase shifting.

PubMed

Panda, Satchidananda; Sato, Trey K; Castrucci, Ana Maria; Rollag, Mark D; DeGrip, Willem J; Hogenesch, John B; Provencio, Ignacio; Kay, Steve A

2002-12-13

The master circadian oscillator in the hypothalamic suprachiasmatic nucleus is entrained to the day/night cycle by retinal photoreceptors. Melanopsin (Opn4), an opsin-based photopigment, is a primary candidate for photoreceptor-mediated entrainment. To investigate the functional role of melanopsin in light resetting of the oscillator, we generated melanopsin-null mice (Opn4-/-). These mice entrain to a light/dark cycle and do not exhibit any overt defect in circadian activity rhythms under constant darkness. However, they display severely attenuated phase resetting in response to brief pulses of monochromatic light, highlighting the critical role of melanopsin in circadian photoentrainment in mammals.

l-5-hydroxytryptophan resets the circadian locomotor activity rhythm of the nocturnal Indian pygmy field mouse, Mus terricolor

NASA Astrophysics Data System (ADS)

Basu, Priyoneel; Singaravel, Muniyandi; Haldar, Chandana

2012-03-01

We report that l-5-hydroxytryptophan (5-HTP), a serotonin precursor, resets the overt circadian rhythm in the Indian pygmy field mouse, Mus terricolor, in a phase- and dose-dependent manner. We used wheel running to assess phase shifts in the free-running locomotor activity rhythm. Following entrainment to a 12:12 h light-dark cycle, 5-HTP (100 mg/kg in saline) was intraperitoneally administered in complete darkness at circadian time (CT)s 0, 3, 6, 9, 12, 15, 18, and 21, and the ensuing phase shifts in the locomotor activity rhythm were calculated. The results show that 5-HTP differentially shifts the phase of the rhythm, causing phase advances from CT 0 to CT 12 and phase delays from CT 12 to CT 21. Maximum advance phase shift was at CT 6 (1.18 ± 0.37 h) and maximum delay was at CT 18 (-2.36 ± 0.56 h). No extended dead zone is apparent. Vehicle (saline) at any CT did not evoke a significant phase shift. Investigations with different doses (10, 50, 100, and 200 mg/kg) of 5-HTP revealed that the phase resetting effect is dose-dependent. The shape of the phase-response curve (PRC) has a strong similarity to PRCs obtained using some serotonergic agents. There was no significant increase in wheel-running activity after 5-HTP injection, ruling out behavioral arousal-dependent shifts. This suggests that this phase resetting does not completely depend on feedback of the overt rhythmic behavior on the circadian clock. A mechanistic explanation of these shifts is currently lacking.

Ultrafast transient grating radiation to optical image converter

DOEpatents

Stewart, Richard E; Vernon, Stephen P; Steel, Paul T; Lowry, Mark E

2014-11-04

A high sensitivity transient grating ultrafast radiation to optical image converter is based on a fixed transmission grating adjacent to a semiconductor substrate. X-rays or optical radiation passing through the fixed transmission grating is thereby modulated and produces a small periodic variation of refractive index or transient grating in the semiconductor through carrier induced refractive index shifts. An optical or infrared probe beam tuned just below the semiconductor band gap is reflected off a high reflectivity mirror on the semiconductor so that it double passes therethrough and interacts with the radiation induced phase grating therein. A small portion of the optical beam is diffracted out of the probe beam by the radiation induced transient grating to become the converted signal that is imaged onto a detector.

A self-reference PRF-shift MR thermometry method utilizing the phase gradient

NASA Astrophysics Data System (ADS)

Langley, Jason; Potter, William; Phipps, Corey; Huang, Feng; Zhao, Qun

2011-12-01

In magnetic resonance (MR) imaging, the most widely used and accurate method for measuring temperature is based on the shift in proton resonance frequency (PRF). However, inter-scan motion and bulk magnetic field shifts can lead to inaccurate temperature measurements in the PRF-shift MR thermometry method. The self-reference PRF-shift MR thermometry method was introduced to overcome such problems by deriving a reference image from the heated or treated image, and approximates the reference phase map with low-order polynomial functions. In this note, a new approach is presented to calculate the baseline phase map in self-reference PRF-shift MR thermometry. The proposed method utilizes the phase gradient to remove the phase unwrapping step inherent to other self-reference PRF-shift MR thermometry methods. The performance of the proposed method was evaluated using numerical simulations with temperature distributions following a two-dimensional Gaussian function as well as phantom and in vivo experimental data sets. The results from both the numerical simulations and experimental data show that the proposed method is a promising technique for measuring temperature.

Characterization of un-irradiated MIMAS MOX fuel by Raman spectroscopy and EPMA

NASA Astrophysics Data System (ADS)

Talip, Zeynep; Peuget, Sylvain; Magnin, Magali; Tribet, Magaly; Valot, Christophe; Vauchy, Romain; Jégou, Christophe

2018-02-01

In this study, Raman spectroscopy technique was implemented to characterize un-irradiated MIMAS (MIcronized - MASter blend) MOX fuel samples with average 7 wt.% Pu content and different damage levels, 13 years after fabrication, one year after thermal recovery and soon after annealing, respectively. The impacts of local Pu content, deviation from stoichiometry and self-radiation damage on Raman spectrum of the studied MIMAS MOX samples were assessed. MIMAS MOX fuel has three different phases Pu-rich agglomerate, coating phase and uranium matrix. In order to distinguish these phases, Raman results were associated with Pu content measurements performed by Electron Microprobe Analysis. Raman results show that T2g frequency significantly shifts from 445 to 453 cm-1 for Pu contents increasing from 0.2 to 25 wt.%. These data are satisfactorily consistent with the calculations obtained with Gruneisen parameters. It was concluded that the position of the T2g band is mainly controlled by Pu content and self-radiation damage. Deviation from stoichiometry does not have a significant influence on T2g band position. Self-radiation damage leads to a shift of T2g band towards lower frequency (∼1-2 cm-1 for the UO2 matrix of damaged sample). However, this shift is difficult to quantify for the coating phase and Pu agglomerates given the dispersion of high Pu concentrations. In addition, 525 cm-1 band, which was attributed to sub-stoichiometric structural defects, is presented for the first time for the self-radiation damaged MOX sample. Thanks to the different oxidation resistance of each phase, it was shown that laser induced oxidation could be alternatively used to identify the phases. It is demonstrated that micro-Raman spectroscopy is an efficient technique for the characterization of heterogeneous MOX samples, due to its low spatial resolution.

Comparison between Phase-Shift Full-Bridge Converters with Noncoupled and Coupled Current-Doubler Rectifier

PubMed Central

Tsai, Cheng-Tao; Tseng, Sheng-Yu

2013-01-01

This paper presents comparison between phase-shift full-bridge converters with noncoupled and coupled current-doubler rectifier. In high current capability and high step-down voltage conversion, a phase-shift full-bridge converter with a conventional current-doubler rectifier has the common limitations of extremely low duty ratio and high component stresses. To overcome these limitations, a phase-shift full-bridge converter with a noncoupled current-doubler rectifier (NCDR) or a coupled current-doubler rectifier (CCDR) is, respectively, proposed and implemented. In this study, performance analysis and efficiency obtained from a 500 W phase-shift full-bridge converter with two improved current-doubler rectifiers are presented and compared. From their prototypes, experimental results have verified that the phase-shift full-bridge converter with NCDR has optimal duty ratio, lower component stresses, and output current ripple. In component count and efficiency comparison, CCDR has fewer components and higher efficiency at full load condition. For small size and high efficiency requirements, CCDR is relatively suitable for high step-down voltage and high efficiency applications. PMID:24381521

The detection of brain oedema with frequency-dependent phase shift electromagnetic induction.

PubMed

González, César A; Rubinsky, Boris

2006-06-01

The spectroscopic distribution of inductive phase shift in the brain as a function of the relative volume of oedema was evaluated with theoretical and experimental methods in the frequency range 1 to 8 MHz. The theoretical study employed a simple mathematical model of electromagnetic induction in tissue and brain tissue data available from the literature to calculate the phase shift as a function of oedema in the bulk of the brain. Experimental data were generated from bulk measurements of ex vivo homogenized pig brain tissue mixed with various volumes of physiological saline in a volume sample typical of the human brain. There is good agreement between the analytical and the experimental results. Detectable changes in phase shift begin from a frequency of about 3 MHz to 4 MHz in the tested compositions and volume. The phase shift increases with frequency and fluid content. The results suggest that measuring phase shift in the bulk of the brain has the potential for becoming a robust means for non-contact detection of oedema in the brain.

Comparison between phase-shift full-bridge converters with noncoupled and coupled current-doubler rectifier.

PubMed

Tsai, Cheng-Tao; Su, Jye-Chau; Tseng, Sheng-Yu

2013-01-01

This paper presents comparison between phase-shift full-bridge converters with noncoupled and coupled current-doubler rectifier. In high current capability and high step-down voltage conversion, a phase-shift full-bridge converter with a conventional current-doubler rectifier has the common limitations of extremely low duty ratio and high component stresses. To overcome these limitations, a phase-shift full-bridge converter with a noncoupled current-doubler rectifier (NCDR) or a coupled current-doubler rectifier (CCDR) is, respectively, proposed and implemented. In this study, performance analysis and efficiency obtained from a 500 W phase-shift full-bridge converter with two improved current-doubler rectifiers are presented and compared. From their prototypes, experimental results have verified that the phase-shift full-bridge converter with NCDR has optimal duty ratio, lower component stresses, and output current ripple. In component count and efficiency comparison, CCDR has fewer components and higher efficiency at full load condition. For small size and high efficiency requirements, CCDR is relatively suitable for high step-down voltage and high efficiency applications.

Microfiber Structures for Sensor Applications

NASA Astrophysics Data System (ADS)

Harun, S. W.; Lim, K. S.; Ahmad, H.

Microfiber loop resonator (MLR) and microfiber knot resonator (MKR) are fabricated using melt-stretching method for applications in temperature and current sensor, respectively. The MLR is embedded into low refractive index polymer for robustness. Although the spacing of the transmission comb spectrum of the MLR is unchanged with temperature, the extinction ratio of the spectrum is observed to decrease linearly with temperature due to induced changes in the material's refractive index. The slope of the extinction ratio reduction against temperature is about 0.043dB/°C. With the assistance of a copper wire that is wrapped by the MKR, resonant wavelength can be tuned by varying the electric current delivered to the wire. The resonant wavelength change is based on the thermally induced optical phase shift in the MKR due to the heat produced by the flow of electric current over a short transit length. It is shown that the wavelength shift is linearly proportional to the square of current in the copper wire with a tuning slope of 46 pm/A2.

Response of the microwave-induced cyclotron harmonic resistance spike to an in-plane magnetic field

NASA Astrophysics Data System (ADS)

Dai, Yanhua; Stone, Kristjan; Knez, Ivan; Zhang, Chi; Du, R. R.; Yang, Changli; Pfeiffer, L. N.; West, K. W.

2011-12-01

Microwave-induced resistance oscillations (MIROs) have been commonly observed in high-mobility GaAs/AlGaAs two-dimensional electron systems (2DESs) under microwave irradiation. In ultraclean GaAs/AlGaAs quantum wells, we have recently observed a very large resistance spike at the second harmonic of cyclotron resonance. In order to elucidate its origin, we have studied the response of microwave photoresistances in a two-axis magnetic field configuration, where the perpendicular (Bz) and the in-plane (Bx) components can be independently applied to the sample. The experiments reveal a distinctive response of the spike to the Bx compared with that of the MIROs. While the major MIRO peaks show an increasing phase shift toward a quarter period in increasing Bx, the spike position shows an essentially zero shift. This finding lends additional support for the notion that the spike is a unique effect in the microwave-driven 2DES.

Advanced Receiver For Phase-Shift-Keyed Signals

NASA Technical Reports Server (NTRS)

Hinedi, Sami M.

1992-01-01

ARX II is second "breadboard" version of advanced receiver, a hybrid digital/analog receiving subsystem, extracting symbols and Doppler shifts from weak phase-shift-keyed signals. Useful in terrestrial digital communication systems.

When are night shifts effective for nursing student clinical learning? Findings from a mixed-method study design.

PubMed

Palese, Alvisa; Basso, Felix; Del Negro, Elena; Achil, Illarj; Ferraresi, Annamaria; Morandini, Marzia; Moreale, Renzo; Mansutti, Irene

2017-05-01

Some nursing programmes offer night shifts for students while others do not, mainly due to the lack of evidence regarding their effectiveness on clinical learning. The principal aims of the study were to describe nursing students' perceptions and to explore conditions influencing effectiveness on learning processes during night shifts. An explanatory mixed-method study design composed of a cross-sectional study (primary method, first phase) followed by a descriptive phenomenological study design (secondary method, second phase) in 2015. Two bachelor of nursing degree programmes located in Northern Italy, three years in length and requiring night shifts for students starting in the second semester of the 1st year, were involved. First phase: all nursing students ending their last clinical placement of the academic year attended were eligible; 352 out the 370 participated. Second phase: a purposeful sample of nine students among those included in the first phase and who attended the highest amount of night shifts were interviewed. First phase: a questionnaire composed of closed and open-ended questions was adopted; data was analyzed through descriptive statistical methods. Second phase: an open-ended face-to-face audio-recorded interview was adopted and data was analyzed through content analysis. Findings from the quantitative phase, showed that students who attended night shifts reported satisfaction (44.7%) less frequently than those who attended only day shifts (55.9%). They also reported boredom (23.5%) significantly more often compared to day shift students (p=0001). Understanding of the nursing role and learning competence was significantly inferior among night shift students as compared to day shift students, while the perception of wasting time was significantly higher among night shift students compared to their counterparts. Night shift students performed nursing rounds (288; 98.2%), non-nursing tasks (247; 84.3%) and/or less often managed clinical problems (insomnia 37; 12.6% and disorientation/confusion 32; 10.9%). Findings from the qualitative phase showed night shifts are experienced by students as a "time potentially capable of generating clinical learning": learning is maximized when students play an active role, encounter patients' clinical problems and develop relationships with patients, caregivers and staff. Night shifts remains ambiguous from the students' perspective and their introduction in nursing education should be approached with care, considering the learning aims expected by students in their clinical placements and the education of clinical mentors education who should be capable of effectively involving students in the process of night care by avoiding non-nursing tasks. Copyright © 2017 Elsevier Ltd. All rights reserved.

Phononic Crystal Tunable via Ferroelectric Phase Transition

NASA Astrophysics Data System (ADS)

Xu, Chaowei; Cai, Feiyan; Xie, Shuhong; Li, Fei; Sun, Rong; Fu, Xianzhu; Xiong, Rengen; Zhang, Yi; Zheng, Hairong; Li, Jiangyu

2015-09-01

Phononic crystals (PCs) consisting of periodic materials with different acoustic properties have potential applications in functional devices. To realize more smart functions, it is desirable to actively control the properties of PCs on demand, ideally within the same fabricated system. Here, we report a tunable PC made of Ba0.7Sr0.3Ti O3 (BST) ceramics, wherein a 20-K temperature change near room temperature results in a 20% frequency shift in the transmission spectra induced by a ferroelectric phase transition. The tunability phenomenon is attributed to the structure-induced resonant excitation of A0 and A1 Lamb modes that exist intrinsically in the uniform BST plate, while these Lamb modes are sensitive to the elastic properties of the plate and can be modulated by temperature in a BST plate around the Curie temperature. The study finds opportunities for creating tunable PCs and enables smart temperature-tuned devices such as the Lamb wave filter or sensor.

Absorption and luminescence spectroscopy of mass-selected flavin adenine dinucleotide mono-anions

NASA Astrophysics Data System (ADS)

Giacomozzi, L.; Kjær, C.; Langeland Knudsen, J.; Andersen, L. H.; Brøndsted Nielsen, S.; Stockett, M. H.

2018-06-01

We report the absorption profile of isolated Flavin Adenine Dinucleotide (FAD) mono-anions recorded using photo-induced dissociation action spectroscopy. In this charge state, one of the phosphoric acid groups is deprotonated and the chromophore itself is in its neutral oxidized state. These measurements cover the first four optical transitions of FAD with excitation energies from 2.3 to 6.0 eV (210-550 nm). The S0 → S2 transition is strongly blue shifted relative to aqueous solution, supporting the view that this transition has a significant charge-transfer character. The remaining bands are close to their solution-phase positions. This confirms that the large discrepancy between quantum chemical calculations of vertical transition energies and solution-phase band maxima cannot be explained by solvent effects. We also report the luminescence spectrum of FAD mono-anions in vacuo. The gas-phase Stokes shift for S1 is 3000 cm-1, which is considerably larger than any previously reported for other molecular ions and consistent with a significant displacement of the ground and excited state potential energy surfaces. Consideration of the vibronic structure is thus essential for simulating the absorption and luminescence spectra of flavins.

Directional mass transport in an atmospheric pressure surface barrier discharge.

PubMed

Dickenson, A; Morabit, Y; Hasan, M I; Walsh, J L

2017-10-25

In an atmospheric pressure surface barrier discharge the inherent physical separation between the plasma generation region and downstream point of application reduces the flux of reactive chemical species reaching the sample, potentially limiting application efficacy. This contribution explores the impact of manipulating the phase angle of the applied voltage to exert a level of control over the electrohydrodynamic forces generated by the plasma. As these forces produce a convective flow which is the primary mechanism of species transport, the technique facilitates the targeted delivery of reactive species to a downstream point without compromising the underpinning species generation mechanisms. Particle Imaging Velocimetry measurements are used to demonstrate that a phase shift between sinusoidal voltages applied to adjacent electrodes in a surface barrier discharge results in a significant deviation in the direction of the plasma induced gas flow. Using a two-dimensional numerical air plasma model, it is shown that the phase shift impacts the spatial distribution of the deposited charge on the dielectric surface between the adjacent electrodes. The modified surface charge distribution reduces the propagation length of the discharge ignited on the lagging electrode, causing an imbalance in the generated forces and consequently a variation in the direction of the resulting gas flow.

Dopaminergic Regulation of Circadian Food Anticipatory Activity Rhythms in the Rat

PubMed Central

Smit, Andrea N.; Patton, Danica F.; Michalik, Mateusz; Opiol, Hanna; Mistlberger, Ralph E.

2013-01-01

Circadian activity rhythms are jointly controlled by a master pacemaker in the hypothalamic suprachiasmatic nuclei (SCN) and by food-entrainable circadian oscillators (FEOs) located elsewhere. The SCN mediates synchrony to daily light-dark cycles, whereas FEOs generate activity rhythms synchronized with regular daily mealtimes. The location of FEOs generating food anticipation rhythms, and the pathways that entrain these FEOs, remain to be clarified. To gain insight into entrainment pathways, we developed a protocol for measuring phase shifts of anticipatory activity rhythms in response to pharmacological probes. We used this protocol to examine a role for dopamine signaling in the timing of circadian food anticipation. To generate a stable food anticipation rhythm, rats were fed 3h/day beginning 6-h after lights-on or in constant light for at least 3 weeks. Rats then received the D2 agonist quinpirole (1 mg/kg IP) alone or after pretreatment with the dopamine synthesis inhibitor α-methylparatyrosine (AMPT). By comparison with vehicle injections, quinpirole administered 1-h before lights-off (19h before mealtime) induced a phase delay of activity onset prior to the next meal. Delay shifts were larger in rats pretreated with AMPT, and smaller following quinpirole administered 4-h after lights-on. A significant shift was not observed in response to the D1 agonist SKF81297. These results provide evidence that signaling at D2 receptors is involved in phase control of FEOs responsible for circadian food anticipatory rhythms in rats. PMID:24312417

Circadian rhythm adaptation to simulated night shift work: effect of nocturnal bright-light duration.

PubMed

Eastman, C I; Liu, L; Fogg, L F

1995-07-01

We compared bright-light durations of 6, 3 and 0 hours (i.e. dim light) during simulated night shifts for phase shifting the circadian rectal temperature rhythm to align with a 12-hour shift of the sleep schedule. After 10 baseline days there were 8 consecutive night-work, day-sleep days, with 8-hour sleep (dark) periods. The bright light (about 5,000 lux, around the baseline temperature minimum) was used during all 8 night shifts, and dim light was < 500 lux. This was a field study in which subjects (n = 46) went outside after the night shifts and slept at home. Substantial circadian adaptation (i.e. a large cumulative temperature rhythm phase shift) was produced in many subjects in the bright light groups, but not in the dim light group. Six and 3 hours of bright light were each significantly better than dim light for phase shifting the temperature rhythm, but there was no significant difference between 6 and 3 hours. Thus, durations > 3 hours are probably not necessary in similar shift-work situations. Larger temperature rhythm phase shifts were associated with better subjective daytime sleep, less subjective fatigue and better overall mood.

S-Matrix to potential inversion of low-energy α-12C phase shifts

NASA Astrophysics Data System (ADS)

Cooper, S. G.; Mackintosh, R. S.

1990-10-01

The IP S-matrix to potential inversion procedure is applied to phase shifts for selected partial waves over a range of energies below the inelastic threshold for α-12C scattering. The phase shifts were determined by Plaga et al. Potentials found by Buck and Rubio to fit the low-energy alpha cluster resonances need only an increased attraction in the surface to accurately reproduce the phase-shift behaviour. Substantial differences between the potentials for odd and even partial waves are necessary. The surface tail of the potential is postulated to be a threshold effect.

Parallel phase-shifting self-interference digital holography with faithful reconstruction using compressive sensing

NASA Astrophysics Data System (ADS)

Wan, Yuhong; Man, Tianlong; Wu, Fan; Kim, Myung K.; Wang, Dayong

2016-11-01

We present a new self-interference digital holographic approach that allows single-shot capturing three-dimensional intensity distribution of the spatially incoherent objects. The Fresnel incoherent correlation holographic microscopy is combined with parallel phase-shifting technique to instantaneously obtain spatially multiplexed phase-shifting holograms. The compressive-sensing-based reconstruction algorithm is implemented to reconstruct the original object from the under sampled demultiplexed holograms. The scheme is verified with simulations. The validity of the proposed method is experimentally demonstrated in an indirectly way by simulating the use of specific parallel phase-shifting recording device.

Phase noise optimization in temporal phase-shifting digital holography with partial coherence light sources and its application in quantitative cell imaging.

PubMed

Remmersmann, Christian; Stürwald, Stephan; Kemper, Björn; Langehanenberg, Patrik; von Bally, Gert

2009-03-10

In temporal phase-shifting-based digital holographic microscopy, high-resolution phase contrast imaging requires optimized conditions for hologram recording and phase retrieval. To optimize the phase resolution, for the example of a variable three-step algorithm, a theoretical analysis on statistical errors, digitalization errors, uncorrelated errors, and errors due to a misaligned temporal phase shift is carried out. In a second step the theoretically predicted results are compared to the measured phase noise obtained from comparative experimental investigations with several coherent and partially coherent light sources. Finally, the applicability for noise reduction is demonstrated by quantitative phase contrast imaging of pancreas tumor cells.

Phase-shifting coronagraph

NASA Astrophysics Data System (ADS)

Hénault, François; Carlotti, Alexis; Vérinaud, Christophe

2017-09-01

With the recent commissioning of ground instruments such as SPHERE or GPI and future space observatories like WFIRST-AFTA, coronagraphy should probably become the most efficient tool for identifying and characterizing extrasolar planets in the forthcoming years. Coronagraphic instruments such as Phase mask coronagraphs (PMC) are usually based on a phase mask or plate located at the telescope focal plane, spreading the starlight outside the diameter of a Lyot stop that blocks it. In this communication is investigated the capability of a PMC to act as a phase-shifting wavefront sensor for better control of the achieved star extinction ratio in presence of the coronagraphic mask. We discuss the two main implementations of the phase-shifting process, either introducing phase-shifts in a pupil plane and sensing intensity variations in an image plane, or reciprocally. Conceptual optical designs are described in both cases. Numerical simulations allow for better understanding of the performance and limitations of both options, and optimizing their fundamental parameters. In particular, they demonstrate that the phase-shifting process is a bit more efficient when implemented into an image plane, and is compatible with the most popular phase masks currently employed, i.e. fourquadrants and vortex phase masks.

Sensitivity and integration in a visual pathway for circadian entrainment in the hamster (Mesocricetus auratus).

PubMed Central

Nelson, D E; Takahashi, J S

1991-01-01

1. Light-induced phase shifts of the circadian rhythm of wheel-running activity were used to measure the photic sensitivity of a circadian pacemaker and the visual pathway that conveys light information to it in the golden hamster (Mesocricetus auratus). The sensitivity to stimulus irradiance and duration was assessed by measuring the magnitude of phase-shift responses to photic stimuli of different irradiance and duration. The visual sensitivity was also measured at three different phases of the circadian rhythm. 2. The stimulus-response curves measured at different circadian phases suggest that the maximum phase-shift is the only aspect of visual responsivity to change as a function of the circadian day. The half-saturation constants (sigma) for the stimulus-response curves are not significantly different over the three circadian phases tested. The photic sensitivity to irradiance (1/sigma) appears to remain constant over the circadian day. 3. The hamster circadian pacemaker and the photoreceptive system that subserves it are more sensitive to the irradiance of longer-duration stimuli than to irradiance of briefer stimuli. The system is maximally sensitive to the irradiance of stimuli of 300 s and longer in duration. A quantitative model is presented to explain the changes that occur in the stimulus-response curves as a function of photic stimulus duration. 4. The threshold for photic stimulation of the hamster circadian pacemaker is also quite high. The threshold irradiance (the minimum irradiance necessary to induce statistically significant responses) is approximately 10(11) photons cm-2 s-1 for optimal stimulus durations. This threshold is equivalent to a luminance at the cornea of 0.1 cd m-2. 5. We also measured the sensitivity of this visual pathway to the total number of photons in a stimulus. This system is maximally sensitive to photons in stimuli between 30 and 3600 s in duration. The maximum quantum efficiency of photic integration occurs in 300 s stimuli. 6. These results suggest that the visual pathways that convey light information to the mammalian circadian pacemaker possess several unique characteristics. These pathways are relatively insensitive to light irradiance and also integrate light inputs over relatively long durations. This visual system, therefore, possesses an optimal sensitivity of 'tuning' to total photons delivered in stimuli of several minutes in duration. Together these characteristics may make this visual system unresponsive to environmental 'noise' that would interfere with the entrainment of circadian rhythms to light-dark cycles. PMID:1895235

Nonlinear laser dynamics induced by frequency shifted optical feedback: application to vibration measurements.

PubMed

Girardeau, Vadim; Goloni, Carolina; Jacquin, Olivier; Hugon, Olivier; Inglebert, Mehdi; Lacot, Eric

2016-12-01

In this article, we study the nonlinear dynamics of a laser subjected to frequency shifted optical reinjection coming back from a vibrating target. More specifically, we study the nonlinear dynamical coupling between the carrier and the vibration signal. The present work shows how the nonlinear amplification of the vibration spectrum is related to the strength of the carrier and how it must be compensated to obtain accurate (i.e., without bias) vibration measurements. The theoretical predictions, confirmed by numerical simulations, are in good agreement with the experimental data. The main motivation of this study is the understanding of the nonlinear response of a laser optical feedback imaging sensor for quantitative phase measurements of small vibrations in the case of strong optical feedback.

The detection of brain ischaemia in rats by inductive phase shift spectroscopy.

PubMed

González, C A; Villanueva, C; Vera, C; Flores, O; Reyes, R D; Rubinsky, B

2009-08-01

Ischaemia in the brain is an important clinical problem that is often monitored and studied with expensive devices such as MRI and PET, which are not readily available in low economical resource parts of the world. We have developed a new less expensive tool for non-invasive monitoring of ischaemia in the brain. This is a first feasibility study describing the concept. The system is based on the hypothesis that electromagnetic properties of the tissue change during ischaemia and that measuring the electromagnetic properties of the bulk of the brain with non-contact means can detect these changes. The apparatus we have built and whose design we describe here consists of two electromagnetic coils placed around the head. The system measures the bulk change in time of the phase difference between the electromagnetic signal on the two coils in a range of frequencies. A mathematical model simulating the device and the measurement is also introduced. Ischaemia was induced in the brain of rats by occlusion of the right cerebral and carotid arteries. Experimental subjects were monitored for 24 h. Inductive phase shift measurements were made at five frequencies in the range of 0.1-50 MHz eight times during the observation period. An ex vivo estimation of the percentage of necrosis in the ischemic subjects at t = 24 h was done. The mathematical model was also applied to the experimental tested situation. The results of both experiments and theory show significant phase shifts increase as a function of frequency and ischaemia time. The theoretical and experimental results suggest that the tested technique has the potential to detect the processes and level of ischaemia in the brain by non-invasive, continuous, bulk volumetric monitoring with a simple and inexpensive apparatus.

Algorithms for image recovery calculation in extended single-shot phase-shifting digital holography

NASA Astrophysics Data System (ADS)

Hasegawa, Shin-ya; Hirata, Ryo

2018-04-01

The single-shot phase-shifting method of image recovery using an inclined reference wave has the advantages of reducing the effects of vibration, being capable of operating in real time, and affording low-cost sensing. In this method, relatively low reference angles compared with that in the conventional method using phase shift between three or four pixels has been required. We propose an extended single-shot phase-shifting technique which uses the multiple-step phase-shifting algorithm and the corresponding multiple pixels which are the same as that of the period of an interference fringe. We have verified the theory underlying this recovery method by means of Fourier spectral analysis and its effectiveness by evaluating the visibility of the image using a high-resolution pattern. Finally, we have demonstrated high-contrast image recovery experimentally using a resolution chart. This method can be used in a variety of applications such as color holographic interferometry.

Delineation of subsurface hydrocarbon contamination at a former hydrogenation plant using spectral induced polarization imaging

NASA Astrophysics Data System (ADS)

Flores Orozco, Adrián; Kemna, Andreas; Oberdörster, Christoph; Zschornack, Ludwig; Leven, Carsten; Dietrich, Peter; Weiss, Holger

2012-08-01

Broadband spectral induced polarization (SIP) measurements were conducted at a former hydrogenation plant in Zeitz (NE Germany) to investigate the potential of SIP imaging to delineate areas with different BTEX (benzene, toluene, ethylbenzene, and xylene) concentrations. Conductivity images reveal a poor correlation with the distribution of contaminants; whereas phase images exhibit two main anomalies: low phase shift values (< 5 mrad) for locations with high BTEX concentrations, including the occurrence of free-phase product (BTEX concentrations > 1.7 g/l), and higher phase values for lower BTEX concentrations. Moreover, the spectral response of the areas with high BTEX concentration and free-phase products reveals a flattened spectrum in the low frequencies (< 40 Hz), while areas with lower BTEX concentrations exhibit a response characterized by a frequency peak. The SIP response was modelled using a Debye decomposition to compute images of the median relaxation-time. Consistent with laboratory studies, we observed an increase in the relaxation-time associated with an increase in BTEX concentrations. Measurements were also collected in the time domain (TDIP), revealing imaging results consistent with those obtained for frequency domain (SIP) measurements. Results presented here demonstrate the potential of the SIP imaging method to discriminate source and plume of dissolved contaminants at BTEX contaminated sites.

In search of a phase response curve for lithium chloride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Readey, M.A.; Groh, K.R.; Ehret, C.F.

1987-01-01

Male rats were free-run, and one day later were exposed to a single, punctate dose of 5 mM LiCl/kg body weight by injection at one of eight equally spaced times throughout the 24-h period. For each of the six days following injection, a separate phase response curve was derived from core-temperature chronograms. Unlike the classical response induced by chronobiotics such as dexamethasone, alpha-methyl-para-tyrosine, and theophylline, statistically significant phase shifts for lithium were observed only on the first day following injection. These induced phase changes were not permanent, but instead were transient. By the sixth day of free-run, all experimental ratsmore » had drifted to the control acrophase; i.e., by the end of the experiment, most of the treated rats again had phase and confidence arcs not significantly different from their controls. The confidence arcs of the acrophases of the individual animals on the subsequent days post injection reveal that in this experiment, lithium was transiently dyschronogenic rather than definitively chronobiotic. The results suggest that punctate rather than chronic administration of lithium, followed by strict orthochronal administration of traditional zeitgebers, would be an effective way of restoring circadian synchrony in an internally desynchronized system. 122 refs.« less

A polarization-independent liquid crystal phase modulation using polymer-network liquid crystals in a 90° twisted cell

NASA Astrophysics Data System (ADS)

Lin, Yi-Hsin; Chen, Ming-Syuan; Lin, Wei-Chih; Tsou, Yu-Shih

2012-07-01

A polarization-independent liquid crystal phase modulation using polymer-network liquid crystals in a 90° twisted cell (T-PNLC) is demonstrated. T-PNLC consists of three layers. Liquid crystal (LC) directors in the two layers near glass substrates are orthogonal to each other and those two layers modulate two eigen-polarizations of an incident light. As a result, two eigen-polarizations of an incident light experience the same phase shift. In the middle layer, LC directors are perpendicular to the glass substrate and contribute no phase shift. The phase shift of T-PNLC is electrically tunable and polarization-independent. T-PNLC does not require any bias voltage for operation. The phase shift is 0.28 π rad for the voltage of 30 Vrms. By measuring and analyzing the optical phase shift of T-PNLC at the oblique incidence of transverse magnetic wave, the pretilt angle of LC directors and the effective thickness of three layers are obtained and discussed. The potential applications are spatial light modulators, laser beam steering, and micro-lens arrays.

3D motion picture of transparent gas flow by parallel phase-shifting digital holography

NASA Astrophysics Data System (ADS)

Awatsuji, Yasuhiro; Fukuda, Takahito; Wang, Yexin; Xia, Peng; Kakue, Takashi; Nishio, Kenzo; Matoba, Osamu

2018-03-01

Parallel phase-shifting digital holography is a technique capable of recording three-dimensional (3D) motion picture of dynamic object, quantitatively. This technique can record single hologram of an object with an image sensor having a phase-shift array device and reconstructs the instantaneous 3D image of the object with a computer. In this technique, a single hologram in which the multiple holograms required for phase-shifting digital holography are multiplexed by using space-division multiplexing technique pixel by pixel. We demonstrate 3D motion picture of dynamic and transparent gas flow recorded and reconstructed by the technique. A compressed air duster was used to generate the gas flow. A motion picture of the hologram of the gas flow was recorded at 180,000 frames/s by parallel phase-shifting digital holography. The phase motion picture of the gas flow was reconstructed from the motion picture of the hologram. The Abel inversion was applied to the phase motion picture and then the 3D motion picture of the gas flow was obtained.

No Escaping the Rat Race: Simulated Night Shift Work Alters the Time-of-Day Variation in BMAL1 Translational Activity in the Prefrontal Cortex.

PubMed

Marti, Andrea R; Patil, Sudarshan; Mrdalj, Jelena; Meerlo, Peter; Skrede, Silje; Pallesen, Ståle; Pedersen, Torhild T; Bramham, Clive R; Grønli, Janne

2017-01-01

Millions of people worldwide work during the night, resulting in disturbed circadian rhythms and sleep loss. This may cause deficits in cognitive functions, impaired alertness and increased risk of errors and accidents. Disturbed circadian rhythmicity resulting from night shift work could impair brain function and cognition through disrupted synthesis of proteins involved in synaptic plasticity and neuronal function. Recently, the circadian transcription factor brain-and-muscle arnt-like protein 1 (BMAL1) has been identified as a promoter of mRNA translation initiation, the most highly regulated step in protein synthesis, through binding to the mRNA "cap". In this study we investigated the effects of simulated shift work on protein synthesis markers. Male rats ( n = 40) were exposed to forced activity, either in their rest phase (simulated night shift work) or in their active phase (simulated day shift work) for 3 days. Following the third work shift, experimental animals and time-matched undisturbed controls were euthanized (rest work at ZT12; active work at ZT0). Tissue lysates from two brain regions (prefrontal cortex, PFC and hippocampus) implicated in cognition and sleep loss, were analyzed with m 7 GTP (cap) pull-down to examine time-of-day variation and effects of simulated shift work on cap-bound protein translation. The results show time-of-day variation of protein synthesis markers in PFC, with increased protein synthesis at ZT12. In the hippocampus there was little difference between ZT0 and ZT12. Active phase work did not induce statistically significant changes in protein synthesis markers at ZT0 compared to time-matched undisturbed controls. Rest work, however, resulted in distinct brain-region specific changes of protein synthesis markers compared to time-matched controls at ZT12. While no changes were observed in the hippocampus, phosphorylation of cap-bound BMAL1 and its regulator S6 kinase beta-1 (S6K1) was significantly reduced in the PFC, together with significant reduction in the synaptic plasticity associated protein activity-regulatedcytoskeleton-associated protein (Arc). Our results indicate considerable time-of-day and brain-region specific variation in cap-dependent translation initiation. We concludethat simulated night shift work in rats disrupts the pathways regulating the circadian component of the translation of mRNA in the PFC, and that this may partly explain impaired waking function during night shift work.

Ab initio-aided CALPHAD thermodynamic modeling of the Sn-Pb binary system under current stressing

PubMed Central

Lin, Shih-kang; Yeh, Chao-kuei; Xie, Wei; Liu, Yu-chen; Yoshimura, Masahiro

2013-01-01

Soldering is an ancient process, having been developed 5000 years ago. It remains a crucial process with many modern applications. In electronic devices, electric currents pass through solder joints. A new physical phenomenon – the supersaturation of solders under high electric currents – has recently been observed. It involves (1) un-expected supersaturation of the solder matrix phase, and (2) the formation of unusual “ring-shaped” grains. However, the origin of these phenomena is not yet understood. Here we provide a plausible explanation of these phenomena based on the changes in the phase stability of Pb-Sn solders. Ab initio-aided CALPHAD modeling is utilized to translate the electric current-induced effect into the excess Gibbs free energies of the phases. Hence, the phase equilibrium can be shifted by current stressing. The Pb-Sn phase diagrams with and without current stressing clearly demonstrate the change in the phase stabilities of Pb-Sn solders under current stressing. PMID:24060995

FIBER AND INTEGRATED OPTICS: Modulation of the phase and polarization of modes in a few-mode fiber waveguide subjected to axial deformation

NASA Astrophysics Data System (ADS)

Belovolov, M. I.; Vitrik, O. B.; Dianov, Evgenii M.; Kulchin, Yurii N.; Obukh, V. F.

1989-11-01

An investigation was made of modulation of the phase and polarization of modes in a few-mode fiber waveguide subjected to axial deformation. The simplest and most convenient (for analysis) controlled interference pattern was obtained on addition, at the exit from a waveguide, of the fields of two modes of different order or of components of two orthogonally polarized waves of the same mode when an additional phase shift between these waves was induced by deformation. The two investigated schemes were suitable for the construction of simple and highly sensitive sensors capable of detecting small strains with characteristics which could be varied by suitable selection of the waveguide parameters and of the signal processing method.

Using digital inline holographic microscopy and quantitative phase contrast imaging to assess viability of cultured mammalian cells

NASA Astrophysics Data System (ADS)

Missan, Sergey; Hrytsenko, Olga

2015-03-01

Digital inline holographic microscopy was used to record holograms of mammalian cells (HEK293, B16, and E0771) in culture. The holograms have been reconstructed using Octopus software (4Deep inwater imaging) and phase shift maps were unwrapped using the FFT-based phase unwrapping algorithm. The unwrapped phase shifts were used to determine the maximum phase shifts in individual cells. Addition of 0.5 mM H2O2 to cell media produced rapid rounding of cultured cells, followed by cell membrane rupture. The cell morphology changes and cell membrane ruptures were detected in real time and were apparent in the unwrapped phase shift images. The results indicate that quantitative phase contrast imaging produced by the digital inline holographic microscope can be used for the label-free real time automated determination of cell viability and confluence in mammalian cell cultures.

White-light diffraction phase microscopy at doubled space-bandwidth product.

PubMed

Shan, Mingguang; Kandel, Mikhail E; Majeed, Hassaan; Nastasa, Viorel; Popescu, Gabriel

2016-12-12

White light diffraction microscopy (wDPM) is a quantitative phase imaging method that benefits from both temporal and spatial phase sensitivity, granted, respectively, by the common-path geometry and white light illumination. However, like all off-axis quantitative phase imaging methods, wDPM is characterized by a reduced space-bandwidth product compared to phase shifting approaches. This happens essentially because the ultimate resolution of the image is governed by the period of the interferogram and not just the diffraction limit. As a result, off-axis techniques generates single-shot, i.e., high time-bandwidth, phase measurements, at the expense of either spatial resolution or field of view. Here, we show that combining phase-shifting and off-axis, the original space-bandwidth is preserved. Specifically, we developed phase-shifting diffraction phase microscopy with white light, in which we measure and combine two phase shifted interferograms. Due to the white light illumination, the phase images are characterized by low spatial noise, i.e., <1nm pathlength. We illustrate the operation of the instrument with test samples, blood cells, and unlabeled prostate tissue biopsy.

Nonlinear evolution of baryon acoustic oscillations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crocce, Martin; Institut de Ciencies de l'Espai, IEEC-CSIC, Campus UAB, Facultat de Ciencies, Torre C5 par-2, Barcelona 08193; Scoccimarro, Roman

2008-01-15

We study the nonlinear evolution of baryon acoustic oscillations in the dark matter power spectrum and the correlation function using renormalized perturbation theory. In a previous paper we showed that renormalized perturbation theory successfully predicts the damping of acoustic oscillations; here we extend our calculation to the enhancement of power due to mode coupling. We show that mode coupling generates additional oscillations that are out of phase with those in the linear spectrum, leading to shifts in the scales of oscillation nodes defined with respect to a smooth spectrum. When Fourier transformed, these out-of-phase oscillations induce percent-level shifts in themore » acoustic peak of the two-point correlation function. We present predictions for these shifts as a function of redshift; these should be considered as a robust lower limit to the more realistic case that includes, in addition, redshift distortions and galaxy bias. We show that these nonlinear effects occur at very large scales, leading to a breakdown of linear theory at scales much larger than commonly thought. We discuss why virialized halo profiles are not responsible for these effects, which can be understood from basic physics of gravitational instability. Our results are in excellent agreement with numerical simulations, and can be used as a starting point for modeling baryon acoustic oscillations in future observations. To meet this end, we suggest a simple physically motivated model to correct for the shifts caused by mode coupling.« less

Investigation of BOLD fMRI Resonance Frequency Shifts and Quantitative Susceptibility Changes at 7 T

PubMed Central

Bianciardi, Marta; van Gelderen, Peter; Duyn, Jeff H.

2013-01-01

Although blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) experiments of brain activity generally rely on the magnitude of the signal, they also provide frequency information that can be derived from the phase of the signal. However, because of confounding effects of instrumental and physiological origin, BOLD related frequency information is difficult to extract and therefore rarely used. Here, we explored the use of high field (7 T) and dedicated signal processing methods to extract frequency information and use it to quantify and interpret blood oxygenation and blood volume changes. We found that optimized preprocessing improves detection of task-evoked and spontaneous changes in phase signals and resonance frequency shifts over large areas of the cortex with sensitivity comparable to that of magnitude signals. Moreover, our results suggest the feasibility of mapping BOLD quantitative susceptibility changes in at least part of the activated area and its largest draining veins. Comparison with magnitude data suggests that the observed susceptibility changes originate from neuronal activity through induced blood volume and oxygenation changes in pial and intracortical veins. Further, from frequency shifts and susceptibility values, we estimated that, relative to baseline, the fractional oxygen saturation in large vessels increased by 0.02–0.05 during stimulation, which is consistent to previously published estimates. Together, these findings demonstrate that valuable information can be derived from fMRI imaging of BOLD frequency shifts and quantitative susceptibility changes. PMID:23897623

A 2x2 W-Band Reference Time-Shifted Phase-Locked Transmitter Array in 65nm CMOS Technology

NASA Technical Reports Server (NTRS)

Tang, Adrian; Virbila, Gabriel; Hsiao, Frank; Wu, Hao; Murphy, David; Mehdi, Imran; Siegel, P. H.; Chang, M-C. Frank

2013-01-01

This paper presents a complete 2x2 phased array transmitter system operating at W-band (90-95 GHz) which employs a PLL reference time-shifting approach instead of using traditional mm-wave phase shifters. PLL reference shifting enables a phased array to be distributed over multiple chips without the need for coherent mm-wave signal distribution between chips. The proposed phased array transmitter system consumes 248 mW per array element when implemented in a 65 nm CMOS technology.

Lateral geniculate lesions block circadian phase-shift responses to a benzodiazepine.

PubMed Central

Johnson, R F; Smale, L; Moore, R Y; Morin, L P

1988-01-01

Several pharmacological treatments, including application of an excitatory neurotoxin to the lateral geniculate nucleus (LGN) and systemic administration of triazolam, a clinically effective benzodiazepine, can elicit large phase shifts in a circadian rhythm according to the time of administration. The hypothesis that the LGN might mediate the effect of triazolam on circadian clock function was tested. Bilateral lesions of the LGN, which destroyed the connection from the intergeniculate leaflet to the suprachiasmatic nucleus, blocked phase-shift responses to triazolam. The requirement of an intact LGN for triazolam to shift circadian phase suggests that the LGN may be a site through which stimuli gain access to the circadian clock to modulate rhythm phase and entrainment. Images PMID:3293053

Superharmonic resonances in a two-dimensional non-linear photonic-crystal nano-electro-mechanical oscillator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chowdhury, A.; Yeo, I.; Tsvirkun, V.

2016-04-18

We investigate the non-linear mechanical dynamics of a nano-optomechanical mirror formed by a suspended membrane pierced by a photonic crystal. By applying to the mirror a periodic electrostatic force induced by interdigitated electrodes integrated below the membrane, we evidence superharmonic resonances of our nano-electro-mechanical system; the constant phase shift of the oscillator across the resonance tongues is observed on the onset of principal harmonic and subharmonic excitation regimes.

Pressure-induced amorphization of La{sub 1/3}TaO{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noked, O., E-mail: noked@bgu.ac.il; Physics Department, Ben-Gurion University, Beer Sheva 84105; Melchior, A.

2013-06-15

La{sub 1/3}TaO{sub 3}, an A-site cation deficient perovskite, has been studied under pressure by synchrotron X-ray powder diffraction and Raman spectroscopy. It undergoes irreversible pressure induced amorphization at P=18.5 GPa. An almost linear unit cell volume decrease vs. pressure is observed from ambient pressure up to the phase transition. The Raman spectroscopy also shows amorphization at the same pressure, with positive shifts of all modes as a function of pressure. The pressure dependence of the E{sub g} and A{sub 1g} Raman modes arising from the octahedral oxygen network is discussed. - Graphical abstract: La{sub 1/3}Tao{sub 3} exhibits linear pressure–volume relationmore » until irreversible pressure induced amorphization at 18.5 Gpa. - Highlights: • La{sub 1/3}TaO{sub 3} has been studied under pressure by synchrotron XRD and Raman spectroscopy. • La{sub 1/3}TaO{sub 3} undergoes irreversible pressure induced amorphization around 18.5 GPa. • The transition is manifested in both XRD and Raman measurements. • A linear P–V relation is observed from ambient pressure up to the phase transition.« less

Improving MRI surface coil decoupling to reduce B1 distortion

NASA Astrophysics Data System (ADS)

Larson, Christian

As clinical MRI systems continue to advance, larger focus is being given to image uniformity. Good image uniformity begins with generating uniform magnetic fields, which are easily distorted by induced currents on receive-only surface coils. It has become an industry standard to combat these induced currents by placing RF blocking networks on surface coils. This paper explores the effect of blocking network impedance of phased array surface coils on B1 distortion. It has been found and verified, that traditional approaches for blocking network design in complex phased arrays can leave undesirable B1 distortions at 3 Tesla. The traditional approach of LC tank blocking is explored, but shifts from the idea that higher impedance equals better B1 distortion at 3T. The result is a new design principle for a tank with a finite inductive reactance at the Larmor Frequency. The solution is demonstrated via simulation using a simple, single, large tuning loop. The same loop, along with a smaller loop, is used to derive the new design principle, which is then applied to a complex phased array structure.

Antisite disorder induced spin glass and exchange bias effect in Nd2NiMnO6 epitaxial thin film

NASA Astrophysics Data System (ADS)

Singh, Amit Kumar; Chauhan, Samta; Chandra, Ramesh

2017-03-01

We report the observation of the exchange bias effect and spin glass behaviour at low temperature in a ferromagnetic Nd2NiMnO6 epitaxial thin film. Along with the ferromagnetic transition at ˜194 K, an additional transition is observed at lower temperature (˜55 K) as seen from M-T curves of the sample. A shift in the ac susceptibility peak with frequency has been observed at low temperature, which is a signature of a glassy phase within the sample. The detailed investigation of the memory effect and time dependent magnetic relaxation measurements reveals the presence of a spin glass phase in the Nd2NiMnO6 thin film. The exchange bias effect observed at low temperature in the sample has been associated with an antisite disorder induced spin glass phase, which results in a ferromagnetic/spin glass interface at low temperature. The exchange bias behaviour has been further confirmed by performing cooling field and temperature dependence of exchange bias along with training effect measurements.

Phase gradient algorithm based on co-axis two-step phase-shifting interferometry and its application

NASA Astrophysics Data System (ADS)

Wang, Yawei; Zhu, Qiong; Xu, Yuanyuan; Xin, Zhiduo; Liu, Jingye

2017-12-01

A phase gradient method based on co-axis two-step phase-shifting interferometry, is used to reveal the detailed information of a specimen. In this method, the phase gradient distribution can only be obtained by calculating both the first-order derivative and the radial Hilbert transformation of the intensity difference between two phase-shifted interferograms. The feasibility and accuracy of this method were fully verified by the simulation results for a polystyrene sphere and a red blood cell. The empirical results demonstrated that phase gradient is sensitive to changes in the refractive index and morphology. Because phase retrieval and tedious phase unwrapping are not required, the calculation speed is faster. In addition, co-axis interferometry has high spatial resolution.

A fast two-plus-one phase-shifting algorithm for high-speed three-dimensional shape measurement system

NASA Astrophysics Data System (ADS)

Wang, Wenyun; Guo, Yingfu

2008-12-01

Phase-shifting methods for 3-D shape measurement have long been employed in optical metrology for their speed and accuracy. For real-time, accurate, 3-D shape measurement, a four-step phase-shifting algorithm which has the advantage of its symmetry is a good choice; however, its measurement error is sensitive to any fringe image errors caused by various sources such as motion blur. To alleviate this problem, a fast two-plus-one phase-shifting algorithm is proposed in this paper. This kind of technology will benefit many applications such as medical imaging, gaming, animation, computer vision, computer graphics, etc.

Relationship of scattering phase shifts to special radiation force conditions for spheres in axisymmetric wave-fields.

PubMed

Marston, Philip L; Zhang, Likun

2017-05-01

When investigating the radiation forces on spheres in complicated wave-fields, the interpretation of analytical results can be simplified by retaining the s-function notation and associated phase shifts imported into acoustics from quantum scattering theory. For situations in which dissipation is negligible, as taken to be the case in the present investigation, there is an additional simplification in that partial-wave phase shifts become real numbers that vanish when the partial-wave index becomes large and when the wave-number-sphere-radius product vanishes. By restricting attention to monopole and dipole phase shifts, transitions in the axial radiation force for axisymmetric wave-fields are found to be related to wave-field parameters for traveling and standing Bessel wave-fields by considering the ratio of the phase shifts. For traveling waves, the special force conditions concern negative forces while for standing waves, the special force conditions concern vanishing radiation forces. An intermediate step involves considering the functional dependence on phase shifts. An appendix gives an approximation for zero-force plane standing wave conditions. Connections with early investigations of acoustic levitation are mentioned and some complications associated with viscosity are briefly noted.

Single SOA based simultaneous amplitude regeneration for WDM-PDM RZ-PSK signals.

PubMed

Wu, Wenhan; Yu, Yu; Zou, Bingrong; Yang, Weili; Zhang, Xinliang

2013-03-25

We propose and demonstrate all-optical amplitude regeneration for the wavelength division multiplexing and polarization division multiplexing (WDM-PDM) return-to-zero phase shift keying (RZ-PSK) signals using a single semiconductor optical amplifier (SOA) and subsequent filtering. The regeneration is based on the cross phase modulation (XPM) effect in the saturated SOA and the subsequent narrow filtering. The spectrum of the distorted signal can be broadened due to the phase modulation induced by the synchronous optical clock signal. A narrow band pass filter is utilized to extract part of the broadened spectrum and remove the amplitude noise, while preserving the phase information. The working principle for multi-channel and polarization orthogonality preserving is analyzed. 4-channel dual polarization signals can be simultaneously amplitude regenerated without introducing wavelength and polarization demultiplexing. An average power penalty improvement of 1.75dB can be achieved for the WDM-PDM signals.

Dielectric and Energy Storage Properties of the Heterogeneous P(VDF-HFP)/PC Composite Films

NASA Astrophysics Data System (ADS)

Zhao, Xiaojia; Peng, Guirong; Zhan, Zaiji

2017-12-01

Polymer-based materials with a high discharge energy and low energy loss have attracted considerable attention for energy storage applications. A new class of polymer-based composite films composed of amorphous polycarbonate (PC) and poly(vinylidene fluoride-hexafluoropropylene) [P(VDF-HFP)] has been fabricated by simply solution blending followed by thermal treatment under vacuum. The results show that the diameter of the spherical phase for PC and the melting temperature of P(VDF-HFP) increase, and the crystallinity and crystallization temperature of P(VDF-HFP) decrease with increasing PC content. The phase transition from the polar β phase to weak polarity γ phase is induced by PC addition. Moreover, the Curie temperature of the P(VDF-HFP)/PC composite films shifts to a lower temperature. With the addition of PC, the permittivity, polarization and discharge energy of the P(VDF-HFP)/PC composite films slightly decrease. However, the energy loss is significantly reduced.

Pressure-induced phase transition in La 1 – x Sm x O 0.5 F 0.5 BiS 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fang, Y.; Yazici, D.; White, B. D.

Electrical resistivity measurements on La 1–xSm xO 0.5F 0.5BiS 2 (x = 0.1, 0.3, 0.6, 0.8) have been performed under applied pressures up to 2.6 GPa from 2 K to room temperature. The superconducting transition temperature T c of each sample significantly increases at a Sm-concentration dependent pressure P t, indicating a pressure-induced phase transition from a low-T c to a high-T c phase. At ambient pressure, T c increases dramatically from 2.8 K at x = 0.1 to 5.4 K at x = 0.8; however, the T c values at P > P t decrease slightly with x andmore » P t shifts to higher pressures with Sm substitution. In the normal state, semiconducting-like behavior is suppressed and metallic conduction is induced with increasing pressure in all of the samples. Furthermore, these results suggest that the pressure dependence of T c for the BiS 2-based superconductors is related to the lattice parameters at ambient pressure and enable us to estimate the evolution of T c for SmO 0.5F 0.5BiS 2 under pressure.« less

Pressure-induced phase transition in La 1 – x Sm x O 0.5 F 0.5 BiS 2

DOE PAGES

Fang, Y.; Yazici, D.; White, B. D.; ...

2015-09-15

Electrical resistivity measurements on La 1–xSm xO 0.5F 0.5BiS 2 (x = 0.1, 0.3, 0.6, 0.8) have been performed under applied pressures up to 2.6 GPa from 2 K to room temperature. The superconducting transition temperature T c of each sample significantly increases at a Sm-concentration dependent pressure P t, indicating a pressure-induced phase transition from a low-T c to a high-T c phase. At ambient pressure, T c increases dramatically from 2.8 K at x = 0.1 to 5.4 K at x = 0.8; however, the T c values at P > P t decrease slightly with x andmore » P t shifts to higher pressures with Sm substitution. In the normal state, semiconducting-like behavior is suppressed and metallic conduction is induced with increasing pressure in all of the samples. Furthermore, these results suggest that the pressure dependence of T c for the BiS 2-based superconductors is related to the lattice parameters at ambient pressure and enable us to estimate the evolution of T c for SmO 0.5F 0.5BiS 2 under pressure.« less

Geometry induced sequence of nanoscale Frank–Kasper and quasicrystal mesophases in giant surfactants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yue, Kan; Huang, Mingjun; Marson, Ryan L.

Frank–Kasper (F-K) and quasicrystal phases were originally identified in metal alloys and only sporadically reported in soft materials. These unconventional sphere-packing schemes open up possibilities to design materials with different properties. The challenge in soft materials is how to correlate complex phases built from spheres with the tunable parameters of chemical composition and molecular architecture. Here, we report a complete sequence of various highly ordered mesophases by the self-assembly of specifically designed and synthesized giant surfactants, which are conjugates of hydrophilic polyhedral oligomeric silsesquioxane cages tethered with hydrophobic polystyrene tails. We show that the occurrence of these mesophases results frommore » nanophase separation between the heads and tails and thus is critically dependent on molecular geometry. Variations in molecular geometry achieved by changing the number of tails from one to four not only shift compositional phase boundaries but also stabilize F-K and quasicrystal phases in regions where simple phases of spheroidal micelles are typically observed. These complex self-assembled nanostructures have been identified by combining X-ray scattering techniques and real-space electron microscopy images. Brownian dynamics simulations based on a simplified molecular model confirm the architecture-induced sequence of phases. Our results demonstrate the critical role of molecular architecture in dictating the formation of supramolecular crystals with “soft” spheroidal motifs and provide guidelines to the design of unconventional self-assembled nanostructures.« less

Geometry induced sequence of nanoscale Frank–Kasper and quasicrystal mesophases in giant surfactants

PubMed Central

Yue, Kan; Huang, Mingjun; Marson, Ryan L.; He, Jinlin; Huang, Jiahao; Zhou, Zhe; Wang, Jing; Liu, Chang; Yan, Xuesheng; Wu, Kan; Guo, Zaihong; Liu, Hao; Ni, Peihong; Wesdemiotis, Chrys; Zhang, Wen-Bin; Glotzer, Sharon C.; Cheng, Stephen Z. D.

2016-01-01

Frank–Kasper (F-K) and quasicrystal phases were originally identified in metal alloys and only sporadically reported in soft materials. These unconventional sphere-packing schemes open up possibilities to design materials with different properties. The challenge in soft materials is how to correlate complex phases built from spheres with the tunable parameters of chemical composition and molecular architecture. Here, we report a complete sequence of various highly ordered mesophases by the self-assembly of specifically designed and synthesized giant surfactants, which are conjugates of hydrophilic polyhedral oligomeric silsesquioxane cages tethered with hydrophobic polystyrene tails. We show that the occurrence of these mesophases results from nanophase separation between the heads and tails and thus is critically dependent on molecular geometry. Variations in molecular geometry achieved by changing the number of tails from one to four not only shift compositional phase boundaries but also stabilize F-K and quasicrystal phases in regions where simple phases of spheroidal micelles are typically observed. These complex self-assembled nanostructures have been identified by combining X-ray scattering techniques and real-space electron microscopy images. Brownian dynamics simulations based on a simplified molecular model confirm the architecture-induced sequence of phases. Our results demonstrate the critical role of molecular architecture in dictating the formation of supramolecular crystals with “soft” spheroidal motifs and provide guidelines to the design of unconventional self-assembled nanostructures. PMID:27911786

Chronic Ethanol Intake Alters Circadian Phase Shifting and Free-Running Period in Mice

PubMed Central

Seggio, Joseph A.; Fixaris, Michael C.; Reed, Jeffrey D.; Logan, Ryan W.; Rosenwasser, Alan M.

2011-01-01

Chronic alcohol intake is associated with widespread disruptions in sleep and circadian rhythms in both human alcoholics and in experimental animals. Recent studies have demonstrated that chronic and acute ethanol treatments alter fundamental properties of the circadian pacemaker—including free-running period and responsiveness to photic and nonphotic phase-shifting stimuli—in rats and hamsters. In the present work, the authors extend these observations to the C57BL/6J mouse, an inbred strain characterized by very high levels of voluntary ethanol intake and by reliable and stable free-running circadian activity rhythms. Mice were housed individually in running-wheel cages under conditions of either voluntary or forced ethanol intake, whereas controls were maintained on plain water. Forced ethanol intake significantly attenuated photic phase delays (but not phase advances) and shortened free-running period in constant darkness, but voluntary ethanol intake failed to affect either of these parameters. Thus, high levels of chronic ethanol intake, beyond those normally achieved under voluntary drinking conditions, are required to alter fundamental circadian pacemaker properties in C57BL/6J mice. These observations may be related to the relative ethanol insensitivity displayed by this strain in several other phenotypic domains, including ethanol-induced sedation, ataxia, and withdrawal. Additional experiments will investigate chronobiological sensitivity to ethanol in a range of inbred strains showing diverse ethanol-related phenotypes. PMID:19625732

Chronic ethanol intake alters circadian phase shifting and free-running period in mice.

PubMed

Seggio, Joseph A; Fixaris, Michael C; Reed, Jeffrey D; Logan, Ryan W; Rosenwasser, Alan M

2009-08-01

Chronic alcohol intake is associated with widespread disruptions in sleep and circadian rhythms in both human alcoholics and in experimental animals. Recent studies have demonstrated that chronic and acute ethanol treatments alter fundamental properties of the circadian pacemaker--including free-running period and responsiveness to photic and nonphotic phase-shifting stimuli--in rats and hamsters. In the present work, the authors extend these observations to the C57BL/6J mouse, an inbred strain characterized by very high levels of voluntary ethanol intake and by reliable and stable free-running circadian activity rhythms. Mice were housed individually in running-wheel cages under conditions of either voluntary or forced ethanol intake, whereas controls were maintained on plain water. Forced ethanol intake significantly attenuated photic phase delays (but not phase advances) and shortened free-running period in constant darkness, but voluntary ethanol intake failed to affect either of these parameters. Thus, high levels of chronic ethanol intake, beyond those normally achieved under voluntary drinking conditions, are required to alter fundamental circadian pacemaker properties in C57BL/6J mice. These observations may be related to the relative ethanol insensitivity displayed by this strain in several other phenotypic domains, including ethanol-induced sedation, ataxia, and withdrawal. Additional experiments will investigate chronobiological sensitivity to ethanol in a range of inbred strains showing diverse ethanol-related phenotypes.

Fabricating fiber Bragg gratings with two phase masks based on reconstruction-equivalent-chirp technique.

PubMed

Gao, Liang; Chen, Xiangfei; Xiong, Jintian; Liu, Shengchun; Pu, Tao

2012-01-30

Based on reconstruction-equivalent-chirp (REC) technique, a novel solution for fabricating low-cost long fiber Bragg gratings (FBGs) with desired properties is proposed and initially studied. A proof-of-concept experiment is demonstrated with two conventional uniform phase masks and a submicron-precision translation stage, successfully. It is shown that the original phase shift (OPS) caused by phase mismatch of the two phase masks can be compensated by the equivalent phase shift (EPS) at the ±1st channels of sampled FBGs, separately. Furthermore, as an example, a π phase-shifted FBG of about 90 mm is fabricated by using these two 50mm-long uniform phase masks based on the presented method.

Tau-independent Phase Analysis: A Novel Method for Accurately Determining Phase Shifts.

PubMed

Tackenberg, Michael C; Jones, Jeff R; Page, Terry L; Hughey, Jacob J

2018-06-01

Estimations of period and phase are essential in circadian biology. While many techniques exist for estimating period, comparatively few methods are available for estimating phase. Current approaches to analyzing phase often vary between studies and are sensitive to coincident changes in period and the stage of the circadian cycle at which the stimulus occurs. Here we propose a new technique, tau-independent phase analysis (TIPA), for quantifying phase shifts in multiple types of circadian time-course data. Through comprehensive simulations, we show that TIPA is both more accurate and more precise than the standard actogram approach. TIPA is computationally simple and therefore will enable accurate and reproducible quantification of phase shifts across multiple subfields of chronobiology.

Optical Fibers Would Sense Local Strains

NASA Technical Reports Server (NTRS)

Egalon, Claudio O.; Rogowski, Robert S.

1994-01-01

Proposed fiber-optic transducers measure local strains. Includes lead-in and lead-out lengths producing no changes in phase shifts, plus short sensing length in which phase shift is sensitive to strain. Phase shifts in single-mode fibers vary with strains. In alternative version, multiple portions of optical fiber sensitive to strains characteristic of specific vibrational mode of object. Same principle also used with two-mode fiber.

Impurity-induced moments in underdoped cuprates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khaliullin, G.; Kilian, R.; Krivenko, S.

1997-11-01

We examine the effect of a nonmagnetic impurity in a two-dimensional spin liquid in the spin-gap phase, employing a drone-fermion representation of spin-1/2 operators. The properties of the local moment induced in the vicinity of the impurity are investigated and an expression for the nuclear-magnetic-resonance Knight shift is derived, which we compare with experimental results. Introducing a second impurity into the spin liquid an antiferromagnetic interaction between the moments is found when the two impurities are located on different sublattices. The presence of many impurities leads to a screening of this interaction as is shown by means of a coherent-potentialmore » approximation. Further, the Kondo screening of an impurity-induced local spin by charge carriers is discussed. {copyright} {ital 1997} {ital The American Physical Society}« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shaw, K.C.; Bitzer, R.J.; Galliart, L.

We investigated the effect of a strong, DC-induced electromagnetic field (EMF) on the circadian singing activity of the house cricket, Acheta domesticus (L.). Groups of 10 crickets were exposed to strong, DC-induced EMFs under two light regimes, 12:12 (L:D) h and 0:24 (L:D) h. Exposure to the strong EMF resulted in an increase in mean time per hour during which one or more crickets were singing and in number of crickets singing per hour. Correcting for phase shift during O:24 (L:D) h, the daily pattern of singing was apparently unaffected by any treatment. The greatest percentage of singing and numbermore » of crickets singing per hour occurred during actual or expected scotophase. This is the first report of an increase in insect activity during exposure to a strong DC-induced EMF.« less

Probiotic Bacteria Induce a ‘Glow of Health’

PubMed Central

Smillie, Christopher; Varian, Bernard J.; Ibrahim, Yassin M.; Lakritz, Jessica R.; Alm, Eric J.; Erdman, Susan E.

2013-01-01

Radiant skin and hair are universally recognized as indications of good health. However, this ‘glow of health’ display remains poorly understood. We found that feeding of probiotic bacteria to aged mice induced integumentary changes mimicking peak health and reproductive fitness characteristic of much younger animals. Eating probiotic yogurt triggered epithelial follicular anagen-phase shift with sebocytogenesis resulting in thick lustrous fur due to a bacteria-triggered interleukin-10-dependent mechanism. Aged male animals eating probiotics exhibited increased subcuticular folliculogenesis, when compared with matched controls, yielding luxuriant fur only in probiotic-fed subjects. Female animals displayed probiotic-induced hyperacidity coinciding with shinier hair, a feature that also aligns with fertility in human females. Together these data provide insights into mammalian evolution and novel strategies for integumentary health. PMID:23342023

General anesthesia alters time perception by phase shifting the circadian clock.

PubMed

Cheeseman, James F; Winnebeck, Eva C; Millar, Craig D; Kirkland, Lisa S; Sleigh, James; Goodwin, Mark; Pawley, Matt D M; Bloch, Guy; Lehmann, Konstantin; Menzel, Randolf; Warman, Guy R

2012-05-01

Following general anesthesia, people are often confused about the time of day and experience sleep disruption and fatigue. It has been hypothesized that these symptoms may be caused by general anesthesia affecting the circadian clock. The circadian clock is fundamental to our well-being because it regulates almost all aspects of our daily biochemistry, physiology, and behavior. Here, we investigated the effects of the most common general anesthetic, isoflurane, on time perception and the circadian clock using the honeybee (Apis mellifera) as a model. A 6-h daytime anesthetic systematically altered the time-compensated sun compass orientation of the bees, with a mean anticlockwise shift in vanishing bearing of 87° in the Southern Hemisphere and a clockwise shift in flight direction of 58° in the Northern Hemisphere. Using the same 6-h anesthetic treatment, time-trained bees showed a delay in the start of foraging of 3.3 h, and whole-hive locomotor-activity rhythms were delayed by an average of 4.3 h. We show that these effects are all attributable to a phase delay in the core molecular clockwork. mRNA oscillations of the central clock genes cryptochrome-m and period were delayed by 4.9 and 4.3 h, respectively. However, this effect is dependent on the time of day of administration, as is common for clock effects, and nighttime anesthesia did not shift the clock. Taken together, our results suggest that general anesthesia during the day causes a persistent and marked shift of the clock effectively inducing "jet lag" and causing impaired time perception. Managing this effect in humans is likely to help expedite postoperative recovery.

Crosstalk Cancellation for a Simultaneous Phase Shifting Interferometer

NASA Technical Reports Server (NTRS)

Olczak, Eugene (Inventor)

2014-01-01

A method of minimizing fringe print-through in a phase-shifting interferometer, includes the steps of: (a) determining multiple transfer functions of pixels in the phase-shifting interferometer; (b) computing a crosstalk term for each transfer function; and (c) displaying, to a user, a phase-difference map using the crosstalk terms computed in step (b). Determining a transfer function in step (a) includes measuring intensities of a reference beam and a test beam at the pixels, and measuring an optical path difference between the reference beam and the test beam at the pixels. Computing crosstalk terms in step (b) includes computing an N-dimensional vector, where N corresponds to the number of transfer functions, and the N-dimensional vector is obtained by minimizing a variance of a modulation function in phase shifted images.

Canceling the momentum in a phase-shifting algorithm to eliminate spatially uniform errors.

PubMed

Hibino, Kenichi; Kim, Yangjin

2016-08-10

In phase-shifting interferometry, phase modulation nonlinearity causes both spatially uniform and nonuniform errors in the measured phase. Conventional linear-detuning error-compensating algorithms only eliminate the spatially variable error component. The uniform error is proportional to the inertial momentum of the data-sampling weight of a phase-shifting algorithm. This paper proposes a design approach to cancel the momentum by using characteristic polynomials in the Z-transform space and shows that an arbitrary M-frame algorithm can be modified to a new (M+2)-frame algorithm that acquires new symmetry to eliminate the uniform error.

[INVITED] Nanofabrication of phase-shifted Bragg gratings on the end facet of multimode fiber towards development of optical filters and sensors

NASA Astrophysics Data System (ADS)

Gallego, E. E.; Ascorbe, J.; Del Villar, I.; Corres, J. M.; Matias, I. R.

2018-05-01

This work describes the process of nanofabrication of phase-shifted Bragg gratings on the end facet of a multimode optical fiber with a pulsed DC sputtering system based on a single target. Several structures have been explored as a function of parameters such as the number of layers or the phase-shift. The experimental results, corroborated with simulations based on plane-wave propagation in a stack of homogeneous layers, indicate that the phase-shift can be controlled with a high degree of accuracy. The device could be used both in communications, as a filter, or in the sensors domain. As an example of application, a humidity sensor with wavelength shifts of 12 nm in the range of 30 to 90% relative humidity (200 pm/% relative humidity) is presented.

Improved phase shift approach to the energy correction of the infinite order sudden approximation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, B.; Eno, L.; Rabitz, H.

1980-07-15

A new method is presented for obtaining energy corrections to the infinite order sudden (IOS) approximation by incorporating the effect of the internal molecular Hamiltonian into the IOS wave function. This is done by utilizing the JWKB approximation to transform the Schroedinger equation into a differential equation for the phase. It is found that the internal Hamiltonian generates an effective potential from which a new improved phase shift is obtained. This phase shift is then used in place of the IOS phase shift to generate new transition probabilities. As an illustration the resulting improved phase shift (IPS) method is appliedmore » to the Secrest--Johnson model for the collinear collision of an atom and diatom. In the vicinity of the sudden limit, the IPS method gives results for transition probabilities, P/sub n/..-->..n+..delta..n, in significantly better agreement with the 'exact' close coupling calculations than the IOS method, particularly for large ..delta..n. However, when the IOS results are not even qualitatively correct, the IPS method is unable to satisfactorily provide improvements.« less

Method, memory media and apparatus for detection of grid disconnect

DOEpatents

Ye, Zhihong [Clifton Park, NY; Du, Pengwei [Troy, NY

2008-09-23

A phase shift procedure for detecting a disconnect of a power grid from a feeder that is connected to a load and a distributed generator. The phase shift procedure compares a current phase shift of the output voltage of the distributed generator with a predetermined threshold and if greater, a command is issued for a disconnect of the distributed generator from the feeder. To extend the range of detection, the phase shift procedure is used when a power mismatch between the distributed generator and the load exceeds a threshold and either or both of an under/over frequency procedure and an under/over voltage procedure is used when any power mismatch does not exceed the threshold.

Experimental evaluation of a new form of M-ary (M = 8) phase shift keying including design of the transmitter and receiver

NASA Astrophysics Data System (ADS)

Thompson, G. E.

1984-12-01

For transmitting digital information over bandpass channels, M-ary Phase Shift Keying 8(PSK) schemes are used to conserve bandwidth at the expense of signal power. A block of k bits is used to change the phase of the carrier. These k bits represent M possible phase shifts since M = 2. Common forms of M-ary PSK use equally spaced phase angles. For example, if M = 8 and k=3, 8-ary PSK uses eight phase angles spaced 45 degrees apart. This thesis considers a hybrid form of PSK when M = 8 and k = 3. Each of eight blocks of data with three bits per block are represented by different phase shifts of the carrier. The phase angles are chosen to give an equal distance between states (symbols) when projected onto the sine axis and the cosine axis of a phasor diagram. Thus, when the three bits are recovered, using two coherent phase detectors, the separation of the decision regions (voltage levels) are equal.

Rules for Phase Shifts of Quantum Oscillations in Topological Nodal-Line Semimetals

NASA Astrophysics Data System (ADS)

Li, Cequn; Wang, C. M.; Wan, Bo; Wan, Xiangang; Lu, Hai-Zhou; Xie, X. C.

2018-04-01

Nodal-line semimetals are topological semimetals in which band touchings form nodal lines or rings. Around a loop that encloses a nodal line, an electron can accumulate a nontrivial π Berry phase, so the phase shift in the Shubnikov-de Haas (SdH) oscillation may give a transport signature for the nodal-line semimetals. However, different experiments have reported contradictory phase shifts, in particular, in the WHM nodal-line semimetals (W =Zr /Hf , H =Si /Ge , M =S /Se /Te ). For a generic model of nodal-line semimetals, we present a systematic calculation for the SdH oscillation of resistivity under a magnetic field normal to the nodal-line plane. From the analytical result of the resistivity, we extract general rules to determine the phase shifts for arbitrary cases and apply them to ZrSiS and Cu3 PdN systems. Depending on the magnetic field directions, carrier types, and cross sections of the Fermi surface, the phase shift shows rich results, quite different from those for normal electrons and Weyl fermions. Our results may help explore transport signatures of topological nodal-line semimetals and can be generalized to other topological phases of matter.

Ultra-wideband microwave photonic phase shifter with a 360° tunable phase shift based on an erbium-ytterbium co-doped linearly chirped FBG.

PubMed

Liu, Weilin; Yao, Jianping

2014-02-15

A simple photonic approach to implementing an ultra-wideband microwave phase shifter based on an erbium-ytterbium (Er/Yb) co-doped linearly chirped fiber Bragg grating (LCFBG) is proposed and experimentally demonstrated. The LCFBG is designed to have a constant magnitude response over a reflection band, and a phase response that is linear and nonlinear in two sections in the reflection band. When an optical single-sideband with carrier (OSSB+C) signal is sent to the LCFBG, by locating the optical carrier at the section corresponding to the nonlinear phase response and the sideband at the section corresponding to the linear phase response, a phase shift is introduced to the optical carrier, which is then translated to the microwave signal by beating the optical carrier and the sideband at a photodetector. The tuning of the phase shift is realized by optically pumping the Er/Yb co-doped LCFBG by a 980-nm laser diode. The proposed ultra-wideband microwave photonic phase shifter is experimentally demonstrated. A phase shifter with a full 360° phase shift with a bandwidth from 10 to 40 GHz is experimentally demonstrated.

Highly noise-tolerant hybrid algorithm for phase retrieval from a single-shot spatial carrier fringe pattern

NASA Astrophysics Data System (ADS)

Dong, Zhichao; Cheng, Haobo

2018-01-01

A highly noise-tolerant hybrid algorithm (NTHA) is proposed in this study for phase retrieval from a single-shot spatial carrier fringe pattern (SCFP), which effectively combines the merits of spatial carrier phase shift method and two dimensional continuous wavelet transform (2D-CWT). NTHA firstly extracts three phase-shifted fringe patterns from the SCFP with one pixel malposition; then calculates phase gradients by subtracting the reference phase from the other two target phases, which are retrieved respectively from three phase-shifted fringe patterns by 2D-CWT; finally, reconstructs the phase map by a least square gradient integration method. Its typical characters include but not limited to: (1) doesn't require the spatial carrier to be constant; (2) the subtraction mitigates edge errors of 2D-CWT; (3) highly noise-tolerant, because not only 2D-CWT is noise-insensitive, but also the noise in the fringe pattern doesn't directly take part in the phase reconstruction as in previous hybrid algorithm. Its feasibility and performances are validated extensively by simulations and contrastive experiments to temporal phase shift method, Fourier transform and 2D-CWT methods.

Simultaneous phase-shifting interferometry study based on the common-path Fizeau interferometer

NASA Astrophysics Data System (ADS)

Liu, Feng-wei; Wu, Yong-qian

2014-09-01

A simultaneous phase-shifting interferometry(SPSI) based on the common-path Fizeau interferometer has been discussed.In this system,two orthogonal polarized beams, using as the reference beam and test beam ,are detached by a particular Wollaston prism at a very small angle,then four equal sub-beams are achieved by a combination of three non-polarizing beam splitters(NPBS),and the phase shifts are introduced by four polarizers whose polarization azimuths are 0°, 45°, 90°, 135° with the horizontal direction respectively,the four phase shift interferograms are collected simultaneously by controlling the CCDs working at the same time .The SPSI principle is studied at first,then is the error analysis, finally we emulate the process of surface recovery by four steps phase shifts algorithm,the results indicate that, to ensure the feasibility of the SPSI system, we have to control the polarization azimuth error of the polarizer in +/- 0.5°.

Mechanism of endothelium-dependent relaxation induced by substance P in the coronary artery of the pig.

PubMed Central

Kuroiwa, M.; Aoki, H.; Kobayashi, S.; Nishimura, J.; Kanaide, H.

1995-01-01

1. Using front-surface fluorometry of fura-2-loaded porcine coronary arterial strips with the endothelium intact, we investigated the mechanisms of vasorelaxation induced by substance P (SP). Fura-2 fluorescence signals which indicated the cytosolic Ca2+-concentration ([Ca2+]i), were observed to arise exclusively from teh smooth muscle cells in these strips. 2. During the contractions induced by U46619 (100 nM), a thromboxane A2 analogue, an SP-induced endothelium-dependent, biphasic vasorelaxation was observed, which consisted of an initial rapid relaxation phase followed by a sustained phase, with a transient decrease in [Ca2+]i. Pretreatment with indomethacin (Ind) had no effect on the SP-induced relaxation; however, pretreatment with NG-nitro-L-arginine (L-NOARG) partially, but significantly inhibited the decrease in both the [Ca2+]i and tension abolished. Thus, part of the relaxation was considered to be mediated by L-NOARG-sensitive relaxing factor (endothelium-derived relaxing factor: EDRF). 3. During the 40 mM K+-depolarization-induced contraction which may eliminate the effects of endothelium-derived hyperpolarizing factor (EDRF), the vasorelaxation reduced by SP was completely inhibited by L-NOARG. 4. During the vasorelaxation induced SP, the [Ca2+]i-tension relationships shifted to the right of the contractions induced by either U46619 or high K+-depolarization. 5. Using front-surface fluorometry of fura-2 loaded porcine aortic valvular strips, we examined the effects of SP on [Ca2+]i in endothelial cells in situ. SP induced a rapid increase in [Ca2+]i of endothelial cells in situ followed by a small sustained phase in normal PSS (5.9 mM K+). The increase in extracellular K+ had no apparent effect on the SP-induced [Ca2+]i elevation of endothelial cells. Images Figure 1 PMID:8640343

Increasing Optimism Protects Against Pain-Induced Impairment in Task-Shifting Performance.

PubMed

Boselie, Jantine J L M; Vancleef, Linda M G; Peters, Madelon L

2017-04-01

Persistent pain can lead to difficulties in executive task performance. Three core executive functions that are often postulated are inhibition, updating, and shifting. Optimism, the tendency to expect that good things happen in the future, has been shown to protect against pain-induced performance deterioration in executive function updating. This study tested whether this protective effect of a temporary optimistic state by means of a writing and visualization exercise extended to executive function shifting. A 2 (optimism: optimism vs no optimism) × 2 (pain: pain vs no pain) mixed factorial design was conducted. Participants (N = 61) completed a shifting task once with and once without concurrent painful heat stimulation after an optimism or neutral manipulation. Results showed that shifting performance was impaired when experimental heat pain was applied during task execution, and that optimism counteracted pain-induced deterioration in task-shifting performance. Experimentally-induced heat pain impairs shifting task performance and manipulated optimism or induced optimism counteracted this pain-induced performance deterioration. Identifying psychological factors that may diminish the negative effect of persistent pain on the ability to function in daily life is imperative. Copyright © 2016 American Pain Society. Published by Elsevier Inc. All rights reserved.

Chronic phase advance alters circadian physiological rhythms and peripheral molecular clocks

PubMed Central

Wolff, Gretchen; Duncan, Marilyn J.

2013-01-01

Shifting the onset of light, acutely or chronically, can profoundly affect responses to infection, tumor progression, development of metabolic disease, and mortality in mammals. To date, the majority of phase-shifting studies have focused on acute exposure to a shift in the timing of the light cycle, whereas the consequences of chronic phase shifts alone on molecular rhythms in peripheral tissues such as skeletal muscle have not been studied. In this study, we tested the effect of chronic phase advance on the molecular clock mechanism in two phenotypically different skeletal muscles. The phase advance protocol (CPA) involved 6-h phase advances (earlier light onset) every 4 days for 8 wk. Analysis of the molecular clock, via bioluminescence recording, in the soleus and flexor digitorum brevis (FDB) muscles and lung demonstrated that CPA advanced the phase of the rhythm when studied immediately after CPA. However, if the mice were placed into free-running conditions (DD) for 2 wk after CPA, the molecular clock was not phase shifted in the two muscles but was still shifted in the lung. Wheel running behavior remained rhythmic in CPA mice; however, the endogenous period length of the free-running rhythm was significantly shorter than that of control mice. Core body temperature, cage activity, and heart rate remained rhythmic throughout the experiment, although the onset of the rhythms was significantly delayed with CPA. These results provide clues that lifestyles associated with chronic environmental desynchrony, such as shift work, can have disruptive effects on the molecular clock mechanism in peripheral tissues, including both types of skeletal muscle. Whether this can contribute, long term, to increased incidence of insulin resistance/metabolic disease requires further study. PMID:23703115

Development of Michelson interferometer based spatial phase-shift digital shearography

NASA Astrophysics Data System (ADS)

Xie, Xin

Digital shearography is a non-contact, full field, optical measurement method, which has the capability of directly measuring the gradient of deformation. For high measurement sensitivity, phase evaluation method has to be introduced into digital shearography by phase-shift technique. Catalog by phase-shift method, digital phase-shift shearography can be divided into Temporal Phase-Shift Digital Shearography (TPS-DS) and Spatial Phase-Shift Digital Shearography (SPS-DS). TPS-DS is the most widely used phase-shift shearography system, due to its simple algorithm, easy operation and good phase-map quality. However, the application of TPS-DS is only limited in static/step-by-step loading measurement situation, due to its multi-step shifting process. In order to measure the strain under dynamic/continuous loading situation, a SPS-DS system has to be developed. This dissertation aims to develop a series of Michelson Interferometer based SPS-DS measurement methods to achieve the strain measurement by using only a single pair of speckle pattern images. The Michelson Interferometer based SPS-DS systems utilize special designed optical setup to introduce extra carrier frequency into the laser wavefront. The phase information corresponds to the strain field can be separated on the Fourier domain using a Fourier Transform and can further be evaluated with a Windowed Inverse Fourier Transform. With different optical setups and carrier frequency arrangements, the Michelson Interferometer based SPS-DS method is capable to achieve a variety of measurement tasks using only single pair of speckle pattern images. Catalog by the aimed measurand, these capable measurement tasks can be divided into five categories: 1) measurement of out-of-plane strain field with small shearing amount; 2) measurement of relative out-of-plane deformation field with big shearing amount; 3) simultaneous measurement of relative out-of-plane deformation field and deformation gradient field by using multiple carrier frequencies; 4) simultaneous measurement of two directional strain field using dual measurement channels 5) measurement of pure in-plane strain and pure out-of-plane strain with multiple carrier frequencies. The basic theory, optical path analysis, preliminary studies, results analysis and research plan are shown in detail in this dissertation.

Vacancy-driven magnetocaloric effect in Prussian blue analogues

NASA Astrophysics Data System (ADS)

Evangelisti, Marco; Manuel, Espérança; Affronte, Marco; Okubo, Masashi; Train, Cyrille; Verdaguer, Michel

2007-09-01

We experimentally show that the magnetocaloric properties of molecule-based Prussian blue analogues can be adjusted by controlling during the synthesis the amount of intrinsic vacancies. For CsxNi4II[CrIII(CN)6], we find indeed that the ferromagnetic phase transition induces significantly large magnetic entropy changes, whose maxima shift from ˜68 to ˜95 K by varying the number of [CrIII(CN)6] vacancies, offering a unique tunability of the magnetocaloric effect in this complex.

OPTICAL FIBRES AND FIBREOPTIC SENSORS: Spun microstructured optical fibresfor Faraday effect current sensors

NASA Astrophysics Data System (ADS)

Chamorovsky, Yury K.; Starostin, Nikolay I.; Morshnev, Sergey K.; Gubin, Vladimir P.; Ryabko, Maksim V.; Sazonov, Aleksandr I.; Vorob'ev, Igor'L.

2009-11-01

We report a simple design of spun holey fibres and the first experimental study of the magneto-optical response of spun microstructured fibres with high built-in birefringence. Such fibres enable the Faraday-effect-induced phase shift to effectively accumulate in a magnetic field even at very small coiling diameters. For example, the magneto-optical sensitivity of a 5-mm-diameter fibre coil consisting of 100 turns is ~70% that of an ideal fibre, in good agreement with theoretical predictions.

Macrolactone Nuiapolide, Isolated from a Hawaiian Marine Cyanobacterium, Exhibits Anti-Chemotactic Activity.

PubMed

Mori, Shogo; Williams, Howard; Cagle, Davey; Karanovich, Kristopher; Horgen, F David; Smith, Roger; Watanabe, Coran M H

2015-10-09

A new bioactive macrolactone, nuiapolide (1) was identified from a marine cyanobacterium collected off the coast of Niihau, near Lehua Rock. The natural product exhibits anti-chemotactic activity at concentrations as low as 1.3 μM against Jurkat cells, cancerous T lymphocytes, and induces a G2/M phase cell cycle shift. Structural characterization of the natural product revealed the compound to be a 40-membered macrolactone with nine hydroxyl functional groups and a rare tert-butyl carbinol residue.

Macrolactone Nuiapolide, Isolated from a Hawaiian Marine Cyanobacterium, Exhibits Anti-Chemotactic Activity

PubMed Central

Mori, Shogo; Williams, Howard; Cagle, Davey; Karanovich, Kristopher; Horgen, F. David; Smith, Roger; Watanabe, Coran M. H.

2015-01-01

A new bioactive macrolactone, nuiapolide (1) was identified from a marine cyanobacterium collected off the coast of Niihau, near Lehua Rock. The natural product exhibits anti-chemotactic activity at concentrations as low as 1.3 μM against Jurkat cells, cancerous T lymphocytes, and induces a G2/M phase cell cycle shift. Structural characterization of the natural product revealed the compound to be a 40-membered macrolactone with nine hydroxyl functional groups and a rare tert-butyl carbinol residue. PMID:26473885

Optical bistability in a single-sided cavity coupled to a quantum channel

NASA Astrophysics Data System (ADS)

Payravi, M.; Solookinejad, Gh; Jabbari, M.; Nafar, M.; Ahmadi Sangachin, E.

2018-06-01

In this paper, we discuss the long wavelength optical reflection and bistable behavior of an InGaN/GaN quantum dot nanostructure coupled to a single-sided cavity. It is found that due to the presence of a strong coupling field, the reflection coefficient can be controlled at long wavelength, which is essential for adjusting the threshold of reflected optical bistability. Moreover, the phase shift features of the reflection pulse inside an electromagnetically induced transparency window are also discussed.

Promoting a culture of disaster preparedness.

PubMed

Medina, Angeli

2016-01-01

Disasters from all hazards, ranging from natural disasters, human-induced disasters, effects of climate change to social conflicts can significantly affect the healthcare system and community. This requires a paradigm shift from a reactive approach to a disaster risk management 'all-hazards' approach. Disaster management is a joint effort of the city, state, regional, national, multi-agencies and international organisations that requires effective communication, collaboration and coordination. This paper offers lessons learned and best practices, which, when taken into consideration, can strengthen the phases of disaster risk management.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xi, P. W.; Lawrence Livermore National Laboratory, Livermore, California 94550; Xu, X. Q.

We demonstrate that the occurrence of Edge-Localized-Modes (ELM) crashes does not depend only on the linear peeling-ballooning threshold, but also relies on nonlinear processes. Wave-wave interaction constrains the growth time of a mode, thus inducing a shift in the criterion for triggering an ELM crash. An ELM crash requires the P-B growth rate to exceed a critical value γ>γ{sub c}, where γ{sub c} is set by 1/τ{sup ¯}{sub c}, and τ{sup ¯}{sub c} is the averaged mode phase coherence time. For 0

Knowledge-based support for the participatory design and implementation of shift systems.

PubMed

Gissel, A; Knauth, P

1998-01-01

This study developed a knowledge-based software system to support the participatory design and implementation of shift systems as a joint planning process including shift workers, the workers' committee, and management. The system was developed using a model-based approach. During the 1st phase, group discussions were repeatedly conducted with 2 experts. Thereafter a structure model of the process was generated and subsequently refined by the experts in additional semistructured interviews. Next, a factual knowledge base of 1713 relevant studies was collected on the effects of shift work. Finally, a prototype of the knowledge-based system was tested on 12 case studies. During the first 2 phases of the system, important basic information about the tasks to be carried out is provided for the user. During the 3rd phase this approach uses the problem-solving method of case-based reasoning to determine a shift rota which has already proved successful in other applications. It can then be modified in the 4th phase according to the shift workers' preferences. The last 2 phases support the final testing and evaluation of the system. The application of this system has shown that it is possible to obtain shift rotas suitable to actual problems and representative of good ergonomic solutions. A knowledge-based approach seems to provide valuable support for the complex task of designing and implementing a new shift system. The separation of the task into several phases, the provision of information at all stages, and the integration of all parties concerned seem to be essential factors for the success of the application.

Broadband and high efficiency all-dielectric metasurfaces for wavefront steering with easily obtained phase shift

NASA Astrophysics Data System (ADS)

Yang, Hui; Deng, Yan

2017-12-01

All-dielectric metasurfaces for wavefront deflecting and optical vortex generating with broadband and high efficiency are demonstrated. The unit cell of the metasurfaces is optimized to function as a half wave-plate with high polarization conversion efficiency (94%) and transmittance (94.5%) at the telecommunication wavelength. Under such a condition, we can get rid of the complicated parameter sweep process for phase shift selecting. Hence, a phase coverage ranges from 0 to 2 π can be easily obtained by introducing the Pancharatnam-Berry phase. Metasurfaces composed of the two pre-designed super cells are demonstrated for optical beam deflecting and vortex beam generating. It is found that the metasurfaces with more phase shift sampling points (small phase shift increment) exhibit better performance. Moreover, optical vortex beams can be generated by the designed metasurfaces within a wavelength range of 200 nm. These results will provide a viable route for designing broadband and high efficiency devices related to phase modulation.

Coral-macroalgal phase shifts or reef resilience: links with diversity and functional roles of herbivorous fishes on the Great Barrier Reef

NASA Astrophysics Data System (ADS)

Cheal, A. J.; MacNeil, M. Aaron; Cripps, E.; Emslie, M. J.; Jonker, M.; Schaffelke, B.; Sweatman, H.

2010-12-01

Changes from coral to macroalgal dominance following disturbances to corals symbolize the global degradation of coral reefs. The development of effective conservation measures depends on understanding the causes of such phase shifts. The prevailing view that coral-macroalgal phase shifts commonly occur due to insufficient grazing by fishes is based on correlation with overfishing and inferences from models and small-scale experiments rather than on long-term quantitative field studies of fish communities at affected and resilient sites. Consequently, the specific characteristics of herbivorous fish communities that most promote reef resilience under natural conditions are not known, though this information is critical for identifying vulnerable ecosystems. In this study, 11 years of field surveys recorded the development of the most persistent coral-macroalgal phase shift (>7 years) yet observed on Australia’s Great Barrier Reef (GBR). This shift followed extensive coral mortality caused by thermal stress (coral bleaching) and damaging storms. Comparisons with two similar reefs that suffered similar disturbances but recovered relatively rapidly demonstrated that the phase shift occurred despite high abundances of one herbivore functional group (scraping/excavating parrotfishes: Labridae). However, the shift was strongly associated with low fish herbivore diversity and low abundances of algal browsers (predominantly Siganidae) and grazers/detritivores (Acanthuridae), suggesting that one or more of these factors underpin reef resilience and so deserve particular protection. Herbivorous fishes are not harvested on the GBR, and the phase shift was not enhanced by unusually high nutrient levels. This shows that unexploited populations of herbivorous fishes cannot ensure reef resilience even under benign conditions and suggests that reefs could lose resilience under relatively low fishing pressure. Predictions of more severe and widespread coral mortality due to global climate change emphasize the need for more effective identification and protection of ecosystem components that are critical for the prevention of coral reef phase shifts.

External noise-induced transitions in a current-biased Josephson junction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Qiongwei; Xue, Changfeng, E-mail: cfxue@163.com; Tang, Jiashi

We investigate noise-induced transitions in a current-biased and weakly damped Josephson junction in the presence of multiplicative noise. By using the stochastic averaging procedure, the averaged amplitude equation describing dynamic evolution near a constant phase difference is derived. Numerical results show that a stochastic Hopf bifurcation between an absorbing and an oscillatory state occurs. This means the external controllable noise triggers a transition into the non-zero junction voltage state. With the increase of noise intensity, the stationary probability distribution peak shifts and is characterised by increased width and reduced height. And the different transition rates are shown for large andmore » small bias currents.« less

Beyond the single-atom response in absorption line shapes: probing a dense, laser-dressed helium gas with attosecond pulse trains.

PubMed

Liao, Chen-Ting; Sandhu, Arvinder; Camp, Seth; Schafer, Kenneth J; Gaarde, Mette B

2015-04-10

We investigate the absorption line shapes of laser-dressed atoms beyond the single-atom response, by using extreme ultraviolet (XUV) attosecond pulse trains to probe an optically thick helium target under the influence of a strong infrared (IR) field. We study the interplay between the IR-induced phase shift of the microscopic time-dependent dipole moment and the resonant-propagation-induced reshaping of the macroscopic XUV pulse. Our experimental and theoretical results show that as the optical depth increases, this interplay leads initially to a broadening of the IR-modified line shape, and subsequently, to the appearance of new, narrow features in the absorption line.

Phase-shift parametrization and extraction of asymptotic normalization constants from elastic-scattering data

NASA Astrophysics Data System (ADS)

Ramírez Suárez, O. L.; Sparenberg, J.-M.

2017-09-01

We introduce a simplified effective-range function for charged nuclei, related to the modified K matrix but differing from it in several respects. Negative-energy zeros of this function correspond to bound states. Positive-energy zeros correspond to resonances and "echo poles" appearing in elastic-scattering phase-shifts, while its poles correspond to multiple-of-π phase shifts. Padé expansions of this function allow one to parametrize phase shifts on large energy ranges and to calculate resonance and bound-state properties in a very simple way, independently of any potential model. The method is first tested on a d -wave 12C+α potential model. It is shown to lead to a correct estimate of the subthreshold-bound-state asymptotic normalization constant (ANC) starting from the elastic-scattering phase shifts only. Next, the 12C+α experimental p -wave and d -wave phase shifts are analyzed. For the d wave, the relatively large error bars on the phase shifts do not allow one to improve the ANC estimate with respect to existing methods. For the p wave, a value agreeing with the 12C(6Li,d )16O transfer-reaction measurement and with the recent remeasurement of the 16Nβ -delayed α decay is obtained, with improved accuracy. However, the method displays two difficulties: the results are sensitive to the Padé-expansion order and the simplest fits correspond to an imaginary ANC, i.e., to a negative-energy "echo pole," the physical meaning of which is still debatable.

Formation of graded vanadium oxide (V-O compound) under strong gravitational field

NASA Astrophysics Data System (ADS)

Khandaker, Jahirul Islam; Tokuda, Makoto; Ogata, Yudai; Januszko, Kamila; Nishiyama, Tadao; Yoshiasa, Akira; Mashimo, Tsutomu

2015-05-01

Sedimentation of atoms induced under strong gravitational field gives a tool for controlling elemental compositions in condensed matter. We performed a strong-gravity experiment (0.397 × 106 G at 400 °C for 24 h) on a V2O5 polycrystal using the high-temperature ultracentrifuge to examine the composition change and further the structure change. The graded composition structure of V and O was formed along gravity direction, where V increases and O decreases with gravity. It was found by the x-ray diffraction and Raman scattering method that VO2 and V2O3 phases appeared and the amounts increased, while one of the V2O5 phase decreased gradually along gravity direction. The X-ray absorption near edge structure spectra analysis identified the chemical valency decrease (+5 to +3). The UV-Vis absorption spectroscopy addressed the shifting in center of major absorption peak to longer wavelength (red shift) with the increase in gravitational field. The tail absorption peak (band gap 2.09 eV) at strong gravity region in the graded structure showed transparent conductive oxide.

A tone-aided dual vestigial sideband system for digital communications on fading channels

NASA Technical Reports Server (NTRS)

Hladik, Stephen M.; Saulnier, Gary J.; Rafferty, William

1989-01-01

A spectrally efficient tone-aided dual vestigial sideband (TA/DVSB) system for digital data communications on fading channels is presented and described analytically. This PSK (phase-shift-keying) system incorporates a feed-forward, tone-aided demodulation technique to compensate for Doppler frequency shift and channel- induced, multipath fading. In contrast to other tone-in-band-type systems, receiver synchronization is derived from the complete data VSBs. Simulation results for the Rician fading channel are presented. These results demonstrate the receiver's ability to mitigate performance degradation due to fading and to obtain proper data carrier synchronization, suggesting that the proposed TA/DVSB system has promise for this application. Simulated BER (bit-error rate) data indicate that the TA/DVSB system effectively alleviates the channel distortions of the land mobile satellite application.

Self-Organization in 2D Traffic Flow Model with Jam-Avoiding Drive

NASA Astrophysics Data System (ADS)

Nagatani, Takashi

1995-04-01

A stochastic cellular automaton (CA) model is presented to investigate the traffic jam by self-organization in the two-dimensional (2D) traffic flow. The CA model is the extended version of the 2D asymmetric exclusion model to take into account jam-avoiding drive. Each site contains either a car moving to the up, a car moving to the right, or is empty. A up car can shift right with probability p ja if it is blocked ahead by other cars. It is shown that the three phases (the low-density phase, the intermediate-density phase and the high-density phase) appear in the traffic flow. The intermediate-density phase is characterized by the right moving of up cars. The jamming transition to the high-density jamming phase occurs with higher density of cars than that without jam-avoiding drive. The jamming transition point p 2c increases with the shifting probability p ja. In the deterministic limit of p ja=1, it is found that a new jamming transition occurs from the low-density synchronized-shifting phase to the high-density moving phase with increasing density of cars. In the synchronized-shifting phase, all up cars do not move to the up but shift to the right by synchronizing with the move of right cars. We show that the jam-avoiding drive has an important effect on the dynamical jamming transition.

Development of new two-dimensional spectral/spatial code based on dynamic cyclic shift code for OCDMA system

NASA Astrophysics Data System (ADS)

Jellali, Nabiha; Najjar, Monia; Ferchichi, Moez; Rezig, Houria

2017-07-01

In this paper, a new two-dimensional spectral/spatial codes family, named two dimensional dynamic cyclic shift codes (2D-DCS) is introduced. The 2D-DCS codes are derived from the dynamic cyclic shift code for the spectral and spatial coding. The proposed system can fully eliminate the multiple access interference (MAI) by using the MAI cancellation property. The effect of shot noise, phase-induced intensity noise and thermal noise are used to analyze the code performance. In comparison with existing two dimensional (2D) codes, such as 2D perfect difference (2D-PD), 2D Extended Enhanced Double Weight (2D-Extended-EDW) and 2D hybrid (2D-FCC/MDW) codes, the numerical results show that our proposed codes have the best performance. By keeping the same code length and increasing the spatial code, the performance of our 2D-DCS system is enhanced: it provides higher data rates while using lower transmitted power and a smaller spectral width.

A first principles approach to the electronic properties of liquid and supercritical CO2.

PubMed

Cabral, Benedito J Costa; Rivelino, Roberto; Coutinho, Kaline; Canuto, Sylvio

2015-01-14

The electronic absorption spectra of liquid and supercritical CO2 (scCO2) are investigated by coupling a many-body energy decomposition scheme to configurations generated by Born-Oppenheimer molecular dynamics. A Frenkel exciton Hamiltonian formalism was adopted and the excitation energies were calculated with time dependent density functional theory. A red-shift of ∼ 0.2 eV relative to the gas-phase monomer is observed for the first electronic absorption maximum in liquid and scCO2. The origin of this shift, which is not very dependent on deviations from the linearity of the CO2 molecule, is mainly related to polarization effects. However, the geometry changes of the CO2 monomer induced by thermal effects and intermolecular interactions in condensed phase lead to the appearance of an average monomeric electric dipole moment〈μ〉= 0.26 ± 0.04 D that is practically the same at liquid and supercritical conditions. The predicted average quadrupole moment for both liquid and scCO2 is〈Θ〉= - 5.5 D Å, which is increased by ∼ -0.9 D Å relative to its gas-phase value. The importance of investigating the electronic properties for a better understanding of the role played by CO2 in supercritical solvation is stressed.

Synchronized metronome training induces changes in the kinematic properties of the golf swing.

PubMed

Sommer, Marius; Häger, Charlotte; Rönnqvist, Louise

2014-03-01

The purpose of this study was to evaluate possible effects of synchronized metronome training (SMT) on movement dynamics during golf-swing performance, as captured by kinematic analysis. A one-group, between-test design was applied on 13 male golfers (27.5 +/- 4.6 years old, 12.7 +/- 4.9 handicap) who completed 12 sessions of SMT over a four-week period. Pre- and post-assessments of golf swings with three different clubs (4-iron, 7-iron, and pitching wedge) were performed using a three-dimensional motion capture system. Club velocity at three different swing phases (backswing, downswing, and follow-through) was measured and cross-correlation analysis of time-series signals were made on joint couplings (wrist-elbow-shoulder) of both arms, and between joints and the club, during the full golf swing. There were significantly higher cross-correlations between joint-couplings and concomitant changes of the associated phase-shift differences, as well as reduced phase-shift variability at post-test. No significant effect of SMT was found for the club velocities. We suggest that domain-general influences of SMT on the underlying brain-based motor control strategies lead to a more coordinated movement pattern of the golf-swing performance, which may explain previous observations of significantly improved golf-shot accuracy and decreased variability after SMT.

Attosecond control of electronic processes by intense light fields.

PubMed

Baltuska, A; Udem, Th; Uiberacker, M; Hentschel, M; Goulielmakis, E; Gohle, Ch; Holzwarth, R; Yakovlev, V S; Scrinzi, A; Hänsch, T W; Krausz, F

2003-02-06

The amplitude and frequency of laser light can be routinely measured and controlled on a femtosecond (10(-15) s) timescale. However, in pulses comprising just a few wave cycles, the amplitude envelope and carrier frequency are not sufficient to characterize and control laser radiation, because evolution of the light field is also influenced by a shift of the carrier wave with respect to the pulse peak. This so-called carrier-envelope phase has been predicted and observed to affect strong-field phenomena, but random shot-to-shot shifts have prevented the reproducible guiding of atomic processes using the electric field of light. Here we report the generation of intense, few-cycle laser pulses with a stable carrier envelope phase that permit the triggering and steering of microscopic motion with an ultimate precision limited only by quantum mechanical uncertainty. Using these reproducible light waveforms, we create light-induced atomic currents in ionized matter; the motion of the electronic wave packets can be controlled on timescales shorter than 250 attoseconds (250 x 10(-18) s). This enables us to control the attosecond temporal structure of coherent soft X-ray emission produced by the atomic currents--these X-ray photons provide a sensitive and intuitive tool for determining the carrier-envelope phase.

The Study of Phase-shift Super-Frequency Induction Heating Power Supply

NASA Astrophysics Data System (ADS)

Qi, Hairun; Peng, Yonglong; Li, Yabin

This paper combines pulse-width phase-shift power modulation with fixed-angle phase-locked-control to adjust the inverter's output power, this method not only meets the work conditions of voltage inverter, but also realizes the large-scale of power modulation, and the main circuit is simple, the switching devices realize soft switching. This paper analyzes the relationship between the output power and phase-shift angle, the control strategy is simulated by Matlab/Simulink, and the results show that the method is feasible and meets the theoretical analysis

Resetting of circadian melatonin and cortisol rhythms in humans by ordinary room light

NASA Technical Reports Server (NTRS)

Boivin, D. B.; Czeisler, C. A.

1998-01-01

The present study was designed to investigate whether a weak photic stimulus can reset the endogenous circadian rhythms of plasma melatonin and plasma cortisol in human subjects. A stimulus consisting of three cycles of 5 h exposures to ordinary room light (approximately 180 lux), centered 1.5 h after the endogenous temperature nadir, significantly phase-advanced the plasma melatonin rhythm in eight healthy young men compared with the phase delays observed in eight control subjects who underwent the same protocol but were exposed to darkness (p < or = 0.003). After light-induced phase advances, the circadian rhythms of plasma melatonin and plasma cortisol maintained stable temporal relationships with the endogenous core body temperature cycle, consistent with the conclusion that exposure to ordinary indoor room light had shifted a master circadian pacemaker.

Spin-injection optical pumping of molten cesium salt and its NMR diagnosis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ishikawa, Kiyoshi

2015-07-15

Nuclear spin polarization of cesium ions in the salt was enhanced during optical pumping of cesium vapor at high magnetic field. Significant motional narrowing and frequency shift of NMR signals were observed by intense laser heating of the salt. When the hyperpolarized salt was cooled by blocking the heating laser, the signal width and frequency changed during cooling and presented the phase transition from liquid to solid. Hence, we find that the signal enhancement is mostly due to the molten salt and nuclear spin polarization is injected into the salt efficiently in the liquid phase. We also show that opticalmore » pumping similarly induces line narrowing in the solid phase. The use of powdered salt provided an increase in effective surface area and signal amplitude without glass wool in the glass cells.« less

Generalized Autobalanced Ramsey Spectroscopy of Clock Transitions

NASA Astrophysics Data System (ADS)

Yudin, V. I.; Taichenachev, A. V.; Basalaev, M. Yu.; Zanon-Willette, T.; Pollock, J. W.; Shuker, M.; Donley, E. A.; Kitching, J.

2018-05-01

When performing precision measurements, the quantity being measured is often perturbed by the measurement process itself. Such measurements include precision frequency measurements for atomic clock applications carried out with Ramsey spectroscopy. With the aim of eliminating probe-induced perturbations, a method of generalized autobalanced Ramsey spectroscopy (GABRS) is presented and rigorously substantiated. The usual local-oscillator frequency control loop is augmented with a second control loop derived from secondary Ramsey sequences interspersed with the primary sequences and with a different Ramsey period. This second loop feeds back to a secondary clock variable and ultimately compensates for the perturbation of the clock frequency caused by the measurements in the first loop. We show that such a two-loop scheme can lead to perfect compensation for measurement-induced light shifts and does not suffer from the effects of relaxation, time-dependent pulse fluctuations and phase-jump modulation errors that are typical of other hyper-Ramsey schemes. Several variants of GABRS are explored based on different secondary variables including added relative phase shifts between Ramsey pulses, external frequency-step compensation, and variable second-pulse duration. We demonstrate that a universal antisymmetric error signal, and hence perfect compensation at a finite modulation amplitude, is generated only if an additional frequency step applied during both Ramsey pulses is used as the concomitant variable parameter. This universal technique can be applied to the fields of atomic clocks, high-resolution molecular spectroscopy, magnetically induced and two-photon probing schemes, Ramsey-type mass spectrometry, and the field of precision measurements. Some variants of GABRS can also be applied for rf atomic clocks using coherent-population-trapping-based Ramsey spectroscopy of the two-photon dark resonance.

Mitomycin C and decarbamoyl mitomycin C induce p53-independent p21WAF1/CIP1 activation

PubMed Central

Cheng, Shu-Yuan; Seo, Jiwon; Huang, Bik Tzu; Napolitano, Tanya; Champeil, Elise

2016-01-01

Mitomycin C (MC), a commonly used anticancer drug, induces DNA damage via DNA alkylation. Decarbamoyl mitomycin C (DMC), another mitomycin lacking the carbamate at C10, generates similar lesions as MC. Interstrand cross-links (ICLs) are believed to be the lesions primarily responsible for the cytotoxicity of MC and DMC. The major ICL generated by MC (α-ICL) has a trans stereochemistry at the guanine-drug linkage whereas the major ICL from DMC (β-ICL) has the opposite, cis, stereochemistry. In addition, DMC can provoke strong p53-independent cell death. Our hypothesis is that the stereochemistry of the major unique β-ICL generated by DMC is responsible for this p53-independent cell death signaling. p53 gene is inactively mutated in more than half of human cancers. p21WAF1/CIP1 known as a major effector of p53 is involved in p53-dependent and -independent control of cell proliferation and death. This study revealed the role of p21WAF1/CIP1 on MC and DMC triggered cell damage. MCF-7 (p53-proficient) and K562 (p53-deficient) cells were used. Cell cycle distributions were shifted to the G1/S phase in MCF-7 treated with MC and DMC, but were shifted to the S phase in K562. p21WAF1/CIP1 activation was observed in both cells treated with MC and DMC, and DMC triggered more significant activation. Knocking down p53 in MCF-7 did not attenuate MC and DMC induced p21WAF1/CIP1 activation. The α-ICL itself was enough to cause p21WAF1/CIP1 activation. PMID:27666201

Application of ANFIS to Phase Estimation for Multiple Phase Shift Keying

NASA Technical Reports Server (NTRS)

Drake, Jeffrey T.; Prasad, Nadipuram R.

2000-01-01

The paper discusses a novel use of Adaptive Neuro-Fuzzy Inference Systems (ANFIS) for estimating phase in Multiple Phase Shift Keying (M-PSK) modulation. A brief overview of communications phase estimation is provided. The modeling of both general open-loop, and closed-loop phase estimation schemes for M-PSK symbols with unknown structure are discussed. Preliminary performance results from simulation of the above schemes are presented.

Q-band 4-state phase shifter in planar technology: Circuit design and performance analysis.

PubMed

Villa, E; Cagigas, J; Aja, B; de la Fuente, L; Artal, E

2016-09-01

A 30% bandwidth phase shifter with four phase states is designed to be integrated in a radio astronomy receiver. The circuit has two 90° out-of-phase microwave phase-shifting branches which are combined by Wilkinson power dividers. Each branch is composed of a 180° phase shifter and a band-pass filter. The 180° phase shifter is made of cascaded hybrid rings with microwave PIN diodes as switching devices. The 90° phase shift is achieved with the two band-pass filters. Experimental characterization has shown significant results, with average phase shift values of -90.7°, -181.7°, and 88.5° within the operation band, 35-47 GHz, and mean insertion loss of 7.4 dB. The performance of its integration in a polarimetric receiver for radio astronomy is analyzed, which validates the use of the presented phase shifter in such type of receiver.

Method for the manufacture of phase shifting masks for EUV lithography

DOEpatents

Stearns, Daniel G.; Sweeney, Donald W.; Mirkarimi, Paul B.; Barty, Anton

2006-04-04

A method for fabricating an EUV phase shift mask is provided that includes a substrate upon which is deposited a thin film multilayer coating that has a complex-valued reflectance. An absorber layer or a buffer layer is attached onto the thin film multilayer, and the thickness of the thin film multilayer coating is altered to introduce a direct modulation in the complex-valued reflectance to produce phase shifting features.

Broadband one-dimensional photonic crystal wave plate containing single-negative materials.

PubMed

Chen, Yihang

2010-09-13

The properties of the phase shift of wave reflected from one-dimensional photonic crystals consisting of periodic layers of single-negative (permittivity- or permeability-negative) materials are demonstrated. As the incident angle increases, the reflection phase shift of TE wave decreases, while that of TM wave increases. The phase shifts of both polarized waves vary smoothly as the frequency changes across the photonic crystal stop band. Consequently, the difference between the phase shift of TE and that of TM wave could remain constant in a rather wide frequency range inside the stop band. These properties are useful to design wave plate or retarder which can be used in wide spectral band. In addition, a broadband photonic crystal quarter-wave plate is proposed.

Flexible digital modulation and coding synthesis for satellite communications

NASA Technical Reports Server (NTRS)

Vanderaar, Mark; Budinger, James; Hoerig, Craig; Tague, John

1991-01-01

An architecture and a hardware prototype of a flexible trellis modem/codec (FTMC) transmitter are presented. The theory of operation is built upon a pragmatic approach to trellis-coded modulation that emphasizes power and spectral efficiency. The system incorporates programmable modulation formats, variations of trellis-coding, digital baseband pulse-shaping, and digital channel precompensation. The modulation formats examined include (uncoded and coded) binary phase shift keying (BPSK), quatenary phase shift keying (QPSK), octal phase shift keying (8PSK), 16-ary quadrature amplitude modulation (16-QAM), and quadrature quadrature phase shift keying (Q squared PSK) at programmable rates up to 20 megabits per second (Mbps). The FTMC is part of the developing test bed to quantify modulation and coding concepts.

Anticipating regime shifts in gene expression: The case of an autoactivating positive feedback loop

NASA Astrophysics Data System (ADS)

Sharma, Yogita; Dutta, Partha Sharathi; Gupta, A. K.

2016-03-01

Considerable evidence suggests that anticipating sudden shifts from one state to another in bistable dynamical systems is a challenging task; examples include ecosystems, financial markets, and complex diseases. In this paper, we investigate the effects of additive, multiplicative, and cross-correlated stochastic perturbations on determining the regime shifts in a bistable gene regulatory system, which gives rise to two distinct states of low and high concentrations of protein. We obtain the stationary probability density and mean first-passage time of the system. We show that increasing the additive (multiplicative) noise intensity induces a regime shift from a low (high) to a high (low) protein concentration state. However, an increase in the cross-correlation intensity always induces regime shifts from a high to a low protein concentration state. For both bifurcation-induced (often called the tipping point) and noise-induced (called stochastic switching) regime shifts, we further explore the robustness of recently developed critical-down-based early warning signal (EWS) indicators (e.g., rising variance and lag-1 autocorrelation) on our simulated time-series data. We identify that using EWS indicators, prediction of an impending bifurcation-induced regime shift is relatively easier than that of a noise-induced regime shift in the considered system. Moreover, the success of EWS indicators also strongly depends upon the nature of the noise.

Potential Influence of Climate-Induced Vegetation Shifts on Future Land Use and Associated Land Carbon Fluxes in Northern Eurasia

NASA Astrophysics Data System (ADS)

Kicklighter, D. W.; Cai, Y.; Zhuang, Q.; Parfenova, E. I.; Paltsev, S.; Sokolov, A. P.; Melillo, J. M.; Reilly, J. M.; Tchebakova, N. M.; Lu, X.

2014-12-01

Climate change will alter ecosystem metabolism and may lead to a redistribution of vegetation and changes in fire regimes in Northern Eurasia over the 21st century. Land management decisions will interact with these climate-driven changes to reshape the region's landscape. Here we present an assessment of the potential consequences of climate change on land use and associated land carbon sink activity for Northern Eurasia in the context of climate-induced vegetation shifts. Under a 'business-as-usual' scenario, climate-induced vegetation shifts allow expansion of areas devoted to food crop production (15%) and pastures (39%) over the 21st century. Under a climate stabilization scenario, climate-induced vegetation shifts permit expansion of areas devoted to cellulosic biofuel production (25%) and pastures (21%), but reduce the expansion of areas devoted to food crop production by 10%. In both climate scenarios, vegetation shifts further reduce the areas devoted to timber production by 6-8% over this same time period. Fire associated with climate-induced vegetation shifts causes the region to become more of a carbon source than if no vegetation shifts occur. Consideration of the interactions between climate-induced vegetation shifts and human activities through a modeling framework has provided clues to how humans may be able to adapt to a changing world and identified the tradeoffs, including unintended consequences, associated with proposed climate/energy policies.

Pressure-induced transformations of nitrogen implanted into silicon

NASA Astrophysics Data System (ADS)

Akhmetov, V. D.; Misiuk, A.; Barcz, A.; Richter, H.

2006-03-01

Czochralski (CZ) Si samples implanted with nitrogen, with doses 1017 ion/cm2 and 1018 ion/cm2, at 140 keV, were studied by means of Fourier transform infrared spectroscopy after annealing at 1130 °C/5 h under different hydrostatic pressures, from 1 bar to 10.7 kbar. It has been found for each pressure applied, that the increased nitrogen dose leads to transformation of the broadband spectra to the fine structure ones, corresponding to crystalline silicon nitride. The spectral position of observed sharp peaks in the investigated pressure region is red shifted in comparison to that for the peaks of crystalline silicon oxynitride found recently by other investigators in nitrogen-containing poly-Si as well as in a residual melt of nitrogen-doped CZ-Si. The application of the pressure during annealing results in further red shift of the nitrogen-related bands. The observed decrease of frequency of vibrational bands is explained in terms of the pressure induced lowered incorporation of oxygen into growing oxynitride phase. Secondary ion mass spectrometry data reveal the decrease of oxygen content in implanted layer with increasing pressure during annealing.

The CRTC1-SIK1 Pathway Regulates Entrainment of the Circadian Clock

PubMed Central

Jagannath, Aarti; Butler, Rachel; Godinho, Sofia I.H.; Couch, Yvonne; Brown, Laurence A.; Vasudevan, Sridhar R.; Flanagan, Kevin C.; Anthony, Daniel; Churchill, Grant C.; Wood, Matthew J.A.; Steiner, Guido; Ebeling, Martin; Hossbach, Markus; Wettstein, Joseph G.; Duffield, Giles E.; Gatti, Silvia; Hankins, Mark W.; Foster, Russell G.; Peirson, Stuart N.

2013-01-01

Summary Retinal photoreceptors entrain the circadian system to the solar day. This photic resetting involves cAMP response element binding protein (CREB)-mediated upregulation of Per genes within individual cells of the suprachiasmatic nuclei (SCN). Our detailed understanding of this pathway is poor, and it remains unclear why entrainment to a new time zone takes several days. By analyzing the light-regulated transcriptome of the SCN, we have identified a key role for salt inducible kinase 1 (SIK1) and CREB-regulated transcription coactivator 1 (CRTC1) in clock re-setting. An entrainment stimulus causes CRTC1 to coactivate CREB, inducing the expression of Per1 and Sik1. SIK1 then inhibits further shifts of the clock by phosphorylation and deactivation of CRTC1. Knockdown of Sik1 within the SCN results in increased behavioral phase shifts and rapid re-entrainment following experimental jet lag. Thus SIK1 provides negative feedback, acting to suppress the effects of light on the clock. This pathway provides a potential target for the regulation of circadian rhythms. PMID:23993098

A geometrical shift results in erroneous appearance of low frequency tissue eddy current induced phase maps.

PubMed

Mandija, Stefano; van Lier, Astrid L H M W; Katscher, Ulrich; Petrov, Petar I; Neggers, Sebastian F W; Luijten, Peter R; van den Berg, Cornelis A T

2016-09-01

Knowledge on low frequency (LF) tissue conductivity is relevant for various biomedical purposes. To obtain this information, LF phase maps arising from time-varying imaging gradients have been demonstrated to create a LF conductivity contrast. Essential in this methodology is the subtraction of phase images acquired with opposite gradient polarities to separate LF and RF phase effects. Here we demonstrate how sensitive these subtractions are with respect to geometrical distortions. The effect of geometrical distortions on LF phase maps is mathematically defined. After quantifying typical geometrical distortions, their effects on LF phase maps are evaluated using conductive phantoms. For validation, electromagnetic simulations of LF phase maps were performed. Even sub-voxel distortions of 10% of the voxel size, measured for a typical LF MR sequence, cause leakage of RF phase into LF phase of several milli-radians, leading to a misleading pattern of LF phase maps. This leakage is mathematically confirmed, while simulations indicate that the expected LF phase should be in order of micro-radians. The conductivity scaling of LF phase maps is attributable to the RF phase leakage, thus dependent on the RF conductivity. In fact, simulations show that the LF phase is not measurable. Magn Reson Med 76:905-912, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Electric-field induced phase transitions of dielectric colloids: Impact of multiparticle effects

NASA Astrophysics Data System (ADS)

Wood, Jeffery A.; Docoslis, Aristides

2012-05-01

The thermodynamic framework for predicting the electric-field induced fluid like-solid like phase transition of dielectric colloids developed by Khusid and Acrivos [Phys. Rev. E. 54, 5428 (1996)] is extended to examine the impact of multiscattering/multiparticle effects on the resulting phase diagrams. This was accomplished using effective permittivity models suitable both over the entire composition region for hard spheres (0≤c

Inverse effects of flowing phase-shift nanodroplets and lipid-shelled microbubbles on subsequent cavitation during focused ultrasound exposures.

PubMed

Zhang, Siyuan; Cui, Zhiwei; Xu, Tianqi; Liu, Pan; Li, Dapeng; Shang, Shaoqiang; Xu, Ranxiang; Zong, Yujin; Niu, Gang; Wang, Supin; He, Xijing; Wan, Mingxi

2017-01-01

This paper compared the effects of flowing phase-shift nanodroplets (NDs) and lipid-shelled microbubbles (MBs) on subsequent cavitation during focused ultrasound (FUS) exposures. The cavitation activity was monitored using a passive cavitation detection method as solutions of either phase-shift NDs or lipid-shelled MBs flowed at varying velocities through a 5-mm diameter wall-less vessel in a transparent tissue-mimicking phantom when exposed to FUS. The intensity of cavitation for the phase-shift NDs showed an upward trend with time and cavitation for the lipid-shelled MBs grew to a maximum at the outset of the FUS exposure followed by a trend of decreases when they were static in the vessel. Meanwhile, the increase of cavitation for the phase-shift NDs and decrease of cavitation for the lipid-shelled MBs had slowed down when they flowed through the vessel. During two discrete identical FUS exposures, while the normalized inertial cavitation dose (ICD) value for the lipid-shelled MB solution was higher than that for the saline in the first exposure (p-value <0.05), it decreased to almost the same level in the second exposure. For the phase-shift NDs, the normalized ICD was 0.71 in the first exposure and increased to 0.97 in the second exposure. At a low acoustic power, the normalized ICD values for the lipid-shelled MBs tended to increase with increasing velocities from 5 to 30cm/s (r>0.95). Meanwhile, the normalized ICD value for the phase-shift NDs was 0.182 at a flow velocity of 5cm/s and increased to 0.188 at a flow velocity of 15cm/s. As the flow velocity increased to 20cm/s, the normalized ICD was 0.185 and decreased to 0.178 at a flow velocity of 30cm/s. At high acoustic power, the normalized ICD values for both the lipid-shelled MBs and the phase-shift NDs increased with increasing flow velocities from 5 to 30cm/s (r>0.95). The effects of the flowing phase-shift NDs vaporized into gas bubbles as cavitation nuclei on the subsequent cavitation were inverse to those of the flowing lipid-shelled MBs destroyed after focused ultrasound exposures. Copyright © 2016 Elsevier B.V. All rights reserved.

Blind phase error suppression for color-encoded digital fringe projection profilometry

NASA Astrophysics Data System (ADS)

Ma, S.; Zhu, R.; Quan, C.; Li, B.; Tay, C. J.; Chen, L.

2012-04-01

Color-encoded digital fringe projection profilometry (CDFPP) has the advantage of fast speed, non-contact and full-field testing. It is one of the most important dynamic three-dimensional (3D) profile measurement techniques. However, due to factors such as color cross-talk and gamma distortion of electro-optical devices, phase errors arise when conventional phase-shifting algorithms with fixed phase shift values are utilized to retrieve phases. In this paper, a simple and effective blind phase error suppression approach based on isotropic n-dimensional fringe pattern normalization (INFPN) and carrier squeezing interferometry (CSI) is proposed. It does not require pre-calibration for the gamma and color-coupling coefficients or the phase shift values. Simulation and experimental works show that our proposed approach is able to effectively suppress phase errors and achieve accurate measurement results in CDFPP.

Spatial phase-shift dual-beam speckle interferometry.

PubMed

Gao, Xinya; Yang, Lianxiang; Wang, Yonghong; Zhang, Boyang; Dan, Xizuo; Li, Junrui; Wu, Sijin

2018-01-20

The spatial phase-shift technique has been successfully applied to an out-of-plane speckle interferometry system. Its application to a pure in-plane sensitive system has not been reported yet. This paper presents a novel optical configuration that enables the application of the spatial phase-shift technique to pure in-plane sensitive dual-beam speckle interferometry. The new spatial phase-shift dual-beam speckle interferometry (SPS-DBSP) uses a dual-beam in-plane electronic speckle pattern interferometry configuration with individual aperture shears, avoiding the interference in the object plane by the use of a low-coherence source, and different optical paths. The measured object is illuminated by two incoherent beams that are generated by a delay line, which is larger than the coherence length of the laser. The two beams reflected from the object surface interfere with each other at the CCD plane because of different optical paths. A spatial phase shift is introduced by the angle between the two apertures when they are mapped to the same optical axis. The phase of the in-plane deformation can directly be extracted from the speckle patterns by the Fourier transform method. The capability of SPS-DBSI is demonstrated by theoretical discussion as well as experiments.

Effects of modulation phase on profile analysis in normal-hearing and hearing-impaired listeners

NASA Astrophysics Data System (ADS)

Rogers, Deanna; Lentz, Jennifer

2003-04-01

The ability to discriminate between sounds with different spectral shapes in the presence of amplitude modulation was measured in normal-hearing and hearing-impaired listeners. The standard stimulus was the sum of equal-amplitude modulated tones, and the signal stimulus was generated by increasing the level of half the tones (up components) and decreasing the level of half the tones (down components). The down components had the same modulation phase, and a phase shift was applied to the up components to encourage segregation from the down tones. The same phase shift was used in both standard and signal stimuli. Profile-analysis thresholds were measured as a function of the phase shift between up and down components. The phase shifts were 0, 30, 45, 60, 90, and 180 deg. As expected, thresholds were lowest when all tones had the same modulation phase and increased somewhat with increasing phase disparity. This small increase in thresholds was similar for both groups. These results suggest that hearing-impaired listeners are able to use modulation phase to group sounds in a manner similar to that of normal listeners. [Work supported by NIH (DC 05835).

Accounting for phase drifts in SSVEP-based BCIs by means of biphasic stimulation.

PubMed

Wu, Hung-Yi; Lee, Po-Lei; Chang, Hsiang-Chih; Hsieh, Jen-Chuen

2011-05-01

This study proposes a novel biphasic stimulation technique to solve the issue of phase drifts in steady-state visual evoked potential (SSVEPs) in phase-tagged systems. Phase calibration was embedded in stimulus sequences using a biphasic flicker, which is driven by a sequence with alternating reference and phase-shift states. Nine subjects were recruited to participate in off-line and online tests. Signals were bandpass filtered and segmented by trigger signals into reference and phase-shift epochs. Frequency components of SSVEP in the reference and phase-shift epochs were extracted using the Fourier method with a 50% overlapped sliding window. The real and imaginary parts of the SSVEP frequency components were organized into complex vectors in each epoch. Hotelling's t-square test was used to determine the significances of nonzero mean vectors. The rejection of noisy data segments and the validation of gaze detections were made based on p values. The phase difference between the valid mean vectors of reference and phase-shift epochs was used to identify user's gazed targets in this system. Data showed an average information transfer rate of 44.55 and 38.21 bits/min in off-line and online tests, respectively. © 2011 IEEE

A High Resolution Phase Shifting Interferometer.

NASA Astrophysics Data System (ADS)

Bayda, Michael; Bartscher, Christoph; Wilkinson, Allen

1997-03-01

Configuration, operation, and performance details of a high resolution phase shifting Twyman-Green interferometer are presented. The instrument was used for density relaxation experiments of very compressible liquid-vapor critical fluids.(A companion talk in the Nonequilibrium Phenomena session under Complex Fluids presents density equilibration work.) A sample assembly contained the cell, beam splitter, phase shifter, and mirrors inside a 6 cm diameter by 6 cm long aluminum cylinder. This sample assembly was contained inside a thermostat stable to 50 μK RMS deviation. A thin phase retarding Liquid Crystal Cell (LCC) was placed in the reference arm of the interferometer. The LCC provided four cumulative 90 degree phase shifts to produce four images used in computing each phase map. The Carré technique was used to calculate a phase value for each pixel from the four intensities of each pixel. Four images for one phase map could be acquired in less than two seconds. The spatial resolution was 25 μm. The phase resolution of the interferometer in a six second period was better than λ/400. The phase stability of the interferometer during 25 hours was better than λ/70. Factors affecting timing, resolution, and other phase shifting devices will be discussed. WWW Presentation

A novel design measuring method based on linearly polarized laser interference

NASA Astrophysics Data System (ADS)

Cao, Yanbo; Ai, Hua; Zhao, Nan

2013-09-01

The interferometric method is widely used in the precision measurement, including the surface quality of the large-aperture mirror. The laser interference technology has been developing rapidly as the laser sources become more and more mature and reliable. We adopted the laser diode as the source for the sake of the short coherent wavelength of it for the optical path difference of the system is quite shorter as several wavelengths, and the power of laser diode is sufficient for measurement and safe to human eye. The 673nm linearly laser was selected and we construct a novel form of interferometric system as we called `Closed Loop', comprised of polarizing optical components, such as polarizing prism and quartz wave plate, the light from the source split by which into measuring beam and referencing beam, they've both reflected by the measuring mirror, after the two beams transforming into circular polarization and spinning in the opposite directions we induced the polarized light synchronous phase shift interference technology to get the detecting fringes, which transfers the phase shifting in time domain to space, so that we did not need to consider the precise-controlled shift of optical path difference, which will introduce the disturbance of the air current and vibration. We got the interference fringes from four different CCD cameras well-alignment, and the fringes are shifted into four different phases of 0, π/2, π, and 3π/2 in time. After obtaining the images from the CCD cameras, we need to align the interference fringes pixel to pixel from different CCD cameras, and synthesis the rough morphology, after getting rid of systematic error, we could calculate the surface accuracy of the measuring mirror. This novel design detecting method could be applied into measuring the optical system aberration, and it would develop into the setup of the portable structural interferometer and widely used in different measuring circumstances.

Dynamic and magneto-optic properties of bent-core liquid crystals

NASA Astrophysics Data System (ADS)

Salili, Seyyed Muhammad

In this work, we describe dynamic behavior of free-standing bent-core liquid crystal filaments under dilative and axial compressive stresses in the B7 phase. We found that such filaments demonstrate very complex structures depending on the filament's temperature relative to the isotropic phase, initial filament thickness, and velocity at which the filament is pulled or compressed. We also present our experimental methods, results and analysis of the rupture and recoil properties of several bent-core liquid crystal filaments, anticipating that they may serve as a model system for complex biological fibers. After that, we systematically describe rheological measurements for dimeric liquid crystal compounds. We studied the shear-induced alignment properties, measured the viscoelastic properties as a function of temperature, shear rate, stress and frequency, and compared the results with the rheological properties of conventional chiral nematic and smectic phases. Then we present results of chiral nematic liquid crystals composed of flexible dimer molecules subject to large DC magnetic fields between 0 and 31T. We observe that these fields lead to selective reflection of light depending on temperature and magnetic field. The band of reflected wavelengths can be tuned from ultraviolet to beyond the IR-C band. A similar effect induced by electric fields has been presented previously, and was explained by a field-induced oblique-heliconical director deformation in accordance with early theoretical predictions. Finally, we report an unprecedented magnetic field-induced shifts of the isotropic-nematic phase transition temperature observed in liquid crystal dimers where two rigid linear mesogens are linked by flexible chains of either even- or odd-numbered hydrocarbon groups. This effect is explained in terms of quenching of the thermal fluctuations and decrease of the average bend angle of molecules in the odd-numbered dimers.

Frequency shift of the Bragg and Non-Bragg backscattering from periodic water wave

NASA Astrophysics Data System (ADS)

Wen, Biyang; Li, Ke

2016-08-01

Doppler effect is used to measure the relative speed of a moving target with respect to the radar, and is also used to interpret the frequency shift of the backscattering from the ocean wave according to the water-wave phase velocity. The widely known relationship between the Doppler shift and the water-wave phase velocity was deduced from the scattering measurements data collected from actual sea surface, and has not been verified under man-made conditions. Here we show that this ob- served frequency shift of the scattering data from the Bragg and Non-Bragg water wave is not the Doppler shift corresponding to the water-wave phase velocity as commonly believed, but is the water-wave frequency and its integral multiple frequency. The power spectrum of the backscatter from the periodic water wave consists of serials discrete peaks, which is equally spaced by water wave frequency. Only when the water-wave length is the integer multiples of the Bragg wave, and the radar range resolution is infinite, does the frequency shift of the backscattering mathematically equal the Doppler shift according to the water-wave phase velocity.

Simulations of absorption spectra of conjugated oligomers: role of planar conformation and aggregation in condensed phase

NASA Astrophysics Data System (ADS)

Yuan, Xiang-Ai; Wen, Jin; Zheng, Dong; Ma, Jing

2018-04-01

This Review highlights the structure/property relationship underlying the morphology modulation through various factors towards the exploration of light-absorbing materials for efficient utilisation of solar power. Theoretical study using a combination of molecular dynamics imulations and the time-dependent density functional theory demonstrated that the planarity plays an important role in tuning spectral properties of oligomer aggregates. The aggregation-induced blue-shift in absorption spectra of oligothiophenes and the red-shift for oligofluorenols were rationalised in a unified way from the reduced (and increased) content of planar conformations in molecular aggregates. The planarity versus non-planarity of oligomers can be modulated by introduction of alkyl side chain or steric bulky substituents. The substitution with various groups in the ortho-position of azobenzene leads to the distorted backbone, breaking symmetry, and hence the red-shift in spectra, expanding the application in biological systems with visible light absorption. The donor-acceptor substituent groups in conjugated oligomers can increase the degree of planarity, electron delocalisation and polarisation, and charge separation, giving rise to the red-shift in spectra and enhancement in polarisability and charge mobility for device applications. The solvent dependent and pH-sensitive properties and intramolecular hydrogen bonds also caused the shift of absorption spectra with the appearance of planar conformers.

An Extrinsic Fabry-Perot Interferometric Sensor using Intermodal Phase Shifting and Demultiplexing of the Propagating Modes in a Few-Mode Fiber

NASA Astrophysics Data System (ADS)

Chatterjee, Julius

This dissertation demonstrates a fiber-optic phase shifted Fabry-Perot interferometer (PS-FPI) as a sensor using modal demultiplexing. Single wavelength Fabry-Perot interferometers suffer from fringe ambiguity and loss of sensitivity at fringe extremes. These hindrances cause it to be a secondary choice when being selected for a measurement task at hand, and more often than not, white light based sensors are selected in favor of the single wavelength Fabry-Perot sensors. This work aims to introduce a technique involving the demultiplexing of the propagating linearly polarized (LP) modes in few mode fibers to obtain two fringe systems from the same sensing cavity. This results in a few-mode interferometer that effectively has two to three orders of magnitude higher perturbation sensitivity than a conventional few mode interferometer for the same sensing region. In this work, two different modal demultiplexing techniques (MD) are used to demodulate the propagating modes and to obtain two fringe sets. These output fringe sets are shifted in phase with respect to each other by a phase shift due to the propagation of the modes in the fiber-optic layout. A method of controlling this phase shift by straining a length of a two mode fiber located separate from the PS-FPI cavity is demonstrated and corresponding changes in phase shifts are shown. The results show a controllable phase shift for both the MD techniques, which is useful in sensing by permitting quadrature demodulation of interferometric fringes and also results in a novel few-mode sensing system having more than two orders of magnitude sensitivity than conventional few-mode devices.

Dual-phase-shift spherical Fizeau interferometer for reduction of noise due to internally scattered light

NASA Astrophysics Data System (ADS)

Kumagai, Toshiki; Hibino, Kenichi; Nagaike, Yasunari

2017-03-01

Internally scattered light in a Fizeau interferometer is generated from dust, defects, imperfect coating of the optical components, and multiple reflections inside the collimator lens. It produces additional noise fringes in the observed interference image and degrades the repeatability of the phase measurement. A method to reduce the phase measurement error is proposed, in which the test surface is mechanically translated between each phase measurement in addition to an ordinary phase shift of the reference surface. It is shown that a linear combination of several measured phases at different test surface positions can reduce the phase errors caused by the scattered light. The combination can also compensate for the nonuniformity of the phase shift that occurs in spherical tests. A symmetric sampling of the phase measurements can cancel the additional primary spherical aberrations that occur when the test surface is out of the null position of the confocal configuration.

Phase Shift Interferometer and Growth Set Up to Step Pattern Formation During Growth From Solutions. Influence of the Oscillatory solution Flow on Stability

NASA Technical Reports Server (NTRS)

Chernov, Alex A.; Booth, N. A.; Vekilov, P. G.; Murray, B. T.; McFadden, G. B.

2000-01-01

We have assembled an experimental setup based on Michelson interferometry with the growing crystal surface as one of the reflective surfaces. The crystallization part of the device allows optical monitoring of a face of a crystal growing at temperature stable within 0.05 C in a flow of solution of controlled direction and speed. The reference arm of the interferometer contains a liquid crystal element that allows controlled shifts of the phase of the interferograms. We employ an image-processing algorithm, which combines five images with a pi/2 phase difference between each pair of images. The images are transferred to a computer by a camera capable of capturing 60 frames per second. The device allows data collection on surface morphology and kinetics during the face layers growth over a relatively large area (approximately 4 sq. mm) in situ and in real time during growth. The estimated depth resolution of the phase shifting interferometry is approximately 50 Angstroms. The data will be analyzed in order to reveal and monitor step bunching during the growth process. The crystal chosen as a model for study in this work is KH2PO4 (KDP). This optically non-linear material is widely used in frequency doubling applications. There have been a number of studies of the kinetics of KDP crystallization that can serve as a benchmark for our investigations. However, so far, systematic quantitative characteristics of step interaction and bunching are missing. We intend to present our first quantitative results on the onset, initial stages and development of instabilities in moving step trains on vicinal crystal surfaces at varying supersaturation, flow rate, and flow direction. Behavior of a vicinal face growing from solution flowing normal to the steps and periodically changing its direction in time was considered theoretically. It was found that this oscillating flow reduces both stabilization and destabilization effects resulted from the unidirectional solution flow directed up the step stream and down the step stream. This reduction of stabilization and destabilization comes from effective mixing which entangles the phase shifts between the spatially periodic interface perturbation and the concentration wave induced by this perturbation. Numerical results and simplified mixing criterion will be discussed.

Real-Time and High-Resolution 3D Face Measurement via a Smart Active Optical Sensor.

PubMed

You, Yong; Shen, Yang; Zhang, Guocai; Xing, Xiuwen

2017-03-31

The 3D measuring range and accuracy in traditional active optical sensing, such as Fourier transform profilometry, are influenced by the zero frequency of the captured patterns. The phase-shifting technique is commonly applied to remove the zero component. However, this phase-shifting method must capture several fringe patterns with phase difference, thereby influencing the real-time performance. This study introduces a smart active optical sensor, in which a composite pattern is utilized. The composite pattern efficiently combines several phase-shifting fringes and carrier frequencies. The method can remove zero frequency by using only one pattern. Model face reconstruction and human face measurement were employed to study the validity and feasibility of this method. Results show no distinct decrease in the precision of the novel method unlike the traditional phase-shifting method. The texture mapping technique was utilized to reconstruct a nature-appearance 3D digital face.

Real-Time and High-Resolution 3D Face Measurement via a Smart Active Optical Sensor

PubMed Central

You, Yong; Shen, Yang; Zhang, Guocai; Xing, Xiuwen

2017-01-01

The 3D measuring range and accuracy in traditional active optical sensing, such as Fourier transform profilometry, are influenced by the zero frequency of the captured patterns. The phase-shifting technique is commonly applied to remove the zero component. However, this phase-shifting method must capture several fringe patterns with phase difference, thereby influencing the real-time performance. This study introduces a smart active optical sensor, in which a composite pattern is utilized. The composite pattern efficiently combines several phase-shifting fringes and carrier frequencies. The method can remove zero frequency by using only one pattern. Model face reconstruction and human face measurement were employed to study the validity and feasibility of this method. Results show no distinct decrease in the precision of the novel method unlike the traditional phase-shifting method. The texture mapping technique was utilized to reconstruct a nature-appearance 3D digital face. PMID:28362349

Visual measurement of the evaporation process of a sessile droplet by dual-channel simultaneous phase-shifting interferometry.

PubMed

Sun, Peng; Zhong, Liyun; Luo, Chunshu; Niu, Wenhu; Lu, Xiaoxu

2015-07-16

To perform the visual measurement of the evaporation process of a sessile droplet, a dual-channel simultaneous phase-shifting interferometry (DCSPSI) method is proposed. Based on polarization components to simultaneously generate a pair of orthogonal interferograms with the phase shifts of π/2, the real-time phase of a dynamic process can be retrieved with two-step phase-shifting algorithm. Using this proposed DCSPSI system, the transient mass (TM) of the evaporation process of a sessile droplet with different initial mass were presented through measuring the real-time 3D shape of a droplet. Moreover, the mass flux density (MFD) of the evaporating droplet and its regional distribution were also calculated and analyzed. The experimental results show that the proposed DCSPSI will supply a visual, accurate, noncontact, nondestructive, global tool for the real-time multi-parameter measurement of the droplet evaporation.

Three-step interferometric method with blind phase shifts by use of interframe correlation between interferograms

NASA Astrophysics Data System (ADS)

Muravsky, Leonid I.; Kmet', Arkady B.; Stasyshyn, Ihor V.; Voronyak, Taras I.; Bobitski, Yaroslav V.

2018-06-01

A new three-step interferometric method with blind phase shifts to retrieve phase maps (PMs) of smooth and low-roughness engineering surfaces is proposed. Evaluating of two unknown phase shifts is fulfilled by using the interframe correlation between interferograms. The method consists of two stages. The first stage provides recording of three interferograms of a test object and their processing including calculation of unknown phase shifts, and retrieval of a coarse PM. The second stage implements firstly separation of high-frequency and low-frequency PMs and secondly producing of a fine PM consisting of areal surface roughness and waviness PMs. Extraction of the areal surface roughness and waviness PMs is fulfilled by using a linear low-pass filter. The computer simulation and experiments fulfilled to retrieve a gauge block surface area and its areal surface roughness and waviness have confirmed the reliability of the proposed three-step method.

Manipulation of wavefront using helical metamaterials.

PubMed

Yang, Zhenyu; Wang, Zhaokun; Tao, Huan; Zhao, Ming

2016-08-08

Helical metamaterials, a kind of 3-dimensional structure, has relatively strong coupling effect among the helical nano-wires. Therefore, it is expected to be a good candidate for generating phase shift and controlling wavefront with high efficiency. In this paper, using the finite-difference time-domain (FDTD) method, we studied the phase shift properties in the helical metamaterials. It is found that the phase shift occurs for both transmitted and reflected light waves. And the maximum of reflection coefficients can reach over 60%. In addition, the phase shift (φ) is dispersionless in the range of 600 nm to 860 nm, that is, it is only dominated by the initial angle (θ) of the helix. The relationship between them is φ = ± 2θ. Using Jones calculus we give a further explanation for these properties. Finally, by arranging the helixes in an array with a constant phase gradient, the phenomenon of anomalous refraction was also observed in a broad wavelength range.

Isochronic carrier-envelope phase-shift compensator.

PubMed

Görbe, Mihaly; Osvay, Karoly; Grebing, Christian; Steinmeyer, Günter

2008-11-15

A concept for orthogonal control of phase and group delay inside a laser cavity by a specially designed compensator assembly is discussed. Similar to the construction of variable polarization retarder, this assembly consists of two thin wedge prisms made from appropriately chosen optical materials. Being shifted as a whole, the assembly allows changing the phase delay with no influence on the cavity round-trip time, whereas relative shifting of the prisms enables adjustment of the latter. This scheme is discussed theoretically and verified experimentally, indicating a factor 30 reduction of the influence on the repetition rate compared to the commonly used silica wedge pair. For a 2pi adjustment of the carrier-envelope phase shift, single-pass timing differences are reduced to the single-femtosecond regime. With negligible distortions of timing and dispersion, the described compensator device greatly simplifies carrier-envelope phase control and experiments in extreme nonlinear optics. Copyright (c) 2008 Optical Society of America.

PHASE-SHIFT, STIMULI-RESPONSIVE PERFLUOROCARBON NANODROPLETS FOR DRUG DELIVERY TO CANCER

PubMed Central

2012-01-01

This review focuses on phase-shift perfluorocarbon nanoemulsions whose action depends on an ultrasound-triggered phase shift from a liquid to gas state. For drug-loaded perfluorocarbon nanoemulsions, microbubbles are formed under the action of tumor-directed ultrasound and drug is released locally into tumor volume in this process. This review covers in detail mechanisms involved in the droplet-to-bubble transition as well as mechanisms of ultrasound-mediated drug delivery. PMID:22730185

Aspects of Clock Resetting in Flowering of Xanthium 1

PubMed Central

Papenfuss, Herbert D.; Salisbury, Frank B.

1967-01-01

Flowering is induced in Xanthium strumarium by a single dark period exceeding about 8.3 hours in length (the critical night). To study the mechanism which measures this dark period, plants were placed in growth chambers for about 2 days under constant light and temperature, given a phasing dark period terminated by an intervening light period (1 min to several hrs in duration), and finally a test dark period long enough normally to induce flowering. In some experiments, light interruptions during the test dark period were given to establish the time of maximum sensitivity. If the phasing dark period was less than 5 hours long, its termination by a light flash only broadened the subsequent time of maximum sensitivity to a light flash, but the critical night was delayed. In causing the delay, the end of the intervening light period was acting like the dusk signal which initiated time measurement at the beginning of the phasing dark period. If the phasing dark period was 6 hours or longer, time of maximum sensitivity during the subsequent test dark period was shifted by as much as 10 to 14 hours. In this case the light terminating the phasing dark period acted as a rephaser or a dawn signal. Following a 7.5-hour phasing dark period, intervening light periods of 1 minute to 5 hours did not shift the subsequent time of maximum sensitivity, but with intervening light periods longer than 5 hours, termination of the light acts clearly like a dusk signal. The clock appears to be suspended during intervening light periods longer than 5 to 15 hours. It is restarted by a dusk signal. There is an anomaly with intervening light periods of 10 to 13 hours, following which time of maximum sensitivity is actually less than the usual 8 hours after dusk. Ability of the clock in Xanthium to be rephased, suspended, restarted, or delayed, depending always upon conditions of the experiment, is characteristic of an oscillating timer and may confer upon this plant its ability to respond to a single inductive cycle. It is suggested that phytochrome may influence only the phase of the clock and not other aspects of flowering such as synthesis of flowering hormone. PMID:16656693

Conception and test of Echoes, a spectro-imager dedicated to the seismology of Jupiter

NASA Astrophysics Data System (ADS)

Soulat, L.; Schmider, F.-X.; Robbe-Dubois, S.; Appourchaux, T.; Gaulme, P.; Bresson, Y.; Gay, J.; Daban, J.-B.; Gouvret, C.

2017-11-01

Echoes is a project of a spaceborne Doppler Spectro-Imager (DSI) which has been proposed as payload to the JUICE mission project selected in the Cosmic Vision program of the European Space Agency (ESA). It is a Fourier transform spectrometer which measures phase shifts in the interference patterns induced by Doppler shifts of spectral lines reflected at the surface of the planet. Dedicated to the seismology of Jupiter, the instrument is designed to analyze the periodic movements induced by internal acoustic modes of the planet. It will allow the knowledge of the internal structure of Jupiter, in particular of the central region, which is essential for the comprehension of the scenario of the giant planets' formation. The optical design is based on a modified Mach-Zehnder interferometer operating in the visible domain and takes carefully into account the sensitivity of the optical path difference to the temperature. The instrument produces simultaneously four images in quadrature which allows the measurement of the phase without being contaminated by the continuum component of the incident light. We expect a noise level less than 1 cm2s-2µHz-1 in the frequency range [0.5 -10] mHz. In this paper, we present the prototype implemented at the Observatoire de la Côte d'Azur (OCA) in collaboration with Institut d'Astrophysique Spatiale (IAS) to study the real performances in laboratory and to demonstrate the capability to reach the required Technology Readiness Level 5.

A high accuracy ultrasonic distance measurement system using binary frequency shift-keyed signal and phase detection

NASA Astrophysics Data System (ADS)

Huang, S. S.; Huang, C. F.; Huang, K. N.; Young, M. S.

2002-10-01

A highly accurate binary frequency shift-keyed (BFSK) ultrasonic distance measurement system (UDMS) for use in isothermal air is described. This article presents an efficient algorithm which combines both the time-of-flight (TOF) method and the phase-shift method. The proposed method can obtain larger range measurement than the phase-shift method and also get higher accuracy compared with the TOF method. A single-chip microcomputer-based BFSK signal generator and phase detector was designed to record and compute the TOF, two phase shifts, and the resulting distance, which were then sent to either an LCD to display or a PC to calibrate. Experiments were done in air using BFSK with the frequencies of 40 and 41 kHz. Distance resolution of 0.05% of the wavelength corresponding to the frequency of 40 kHz was obtained. The range accuracy was found to be within ±0.05 mm at a range of over 6000 mm. The main advantages of this UDMS system are high resolution, low cost, narrow bandwidth requirement, and ease of implementation.

Two solitons oblique collision in anisotropic non-extensive dusty plasma

NASA Astrophysics Data System (ADS)

El-Labany, S. K.; El-Taibany, W. F.; Behery, E. E.; Fouda, S. M.

2017-03-01

Using an extended Poincaré-Lighthill-Kue method, the oblique collision of two dust acoustic solitons (DASs) in a magnetized non-extensive plasma with the effect of dust pressure anisotropy is studied. The dust fluid is supposed to have an arbitrary charge. A couple of Korteweg-de Vries (KdV) equations are derived for the colliding DASs. The phase shift of each soliton is obtained. It is found that the dust pressure anisotropy, the non-extensive parameter for electrons and ions, plays an important role in determining the collision phase shifts. The present results show that, for the negative dust case, the phase shift of the first soliton decreases, while that of the second soliton increases as either the dust pressure ratio increases or the ion non-extensive parameter decreases. On the other hand, for the positive dust case, the phase shift of the first soliton decreases, while the phase shift of the second soliton increases as either the dust pressure ratio or the ion non-extensive parameter increases. The application of the present findings to some dusty plasma phenomena occurring in space and laboratory plasmas is briefly discussed.

Phase-shifting interference microscope with extendable field of measurement

NASA Astrophysics Data System (ADS)

Lin, Shyh-Tsong; Hsu, Wei-Feng; Wang, Ming-Shiang

2018-04-01

An innovative phase-shifting interference microscope aimed at extending the field of measurement is proposed in this paper. The microscope comprises a light source module, a phase modulation module, and an interferometric module, which reconstructs the micro-structure contours of samples using the five-step phase-shifting algorithm. This paper discusses the measurement theory and outlines the configuration, experimental setup, and experimental results obtained using the proposed interference microscope. The results confirm the efficacy of the microscope, achieving a standard deviation of 2.4 nm from a step height of 86.2 nm in multiple examinations.

Optimal control of the gear shifting process for shift smoothness in dual-clutch transmissions

NASA Astrophysics Data System (ADS)

Li, Guoqiang; Görges, Daniel

2018-03-01

The control of the transmission system in vehicles is significant for the driving comfort. In order to design a controller for smooth shifting and comfortable driving, a dynamic model of a dual-clutch transmission is presented in this paper. A finite-time linear quadratic regulator is proposed for the optimal control of the two friction clutches in the torque phase for the upshift process. An integral linear quadratic regulator is introduced to regulate the relative speed difference between the engine and the slipping clutch under the optimization of the input torque during the inertia phase. The control objective focuses on smoothing the upshift process so as to improve the driving comfort. Considering the available sensors in vehicles for feedback control, an observer design is presented to track the immeasurable variables. Simulation results show that the jerk can be reduced both in the torque phase and inertia phase, indicating good shift performance. Furthermore, compared with conventional controllers for the upshift process, the proposed control method can reduce shift jerk and improve shift quality.

Magnetism-Structure Correlations during the epsilon ->tau Transformation in Rapidly-Solidified MnAl Nanostructured Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jimenez-Villacorta, F; Marion, JL; Oldham, JT

2014-01-21

Magnetic and structural aspects of the annealing-induced transformation of rapidly-solidified Mn55Al45 ribbons from the as-quenched metastable antiferromagnetic (AF) epsilon-phase to the target ferromagnetic (FM) L1(0) tau-phase are investigated. The as-solidified material exhibits a majority hexagonal epsilon-MnAl phase revealing a large exchange bias shift below a magnetic blocking temperature T-B similar to 95 K (H-ex similar to 13 kOe at 10 K), ascribed to the presence of compositional fluctuations in this antiferromagnetic phase. Heat treatment at a relatively low annealing temperature T-anneal approximate to 568 K (295 degrees C) promotes the nucleation of the metastable L1(0) tau-MnAl phase at the expensemore » of the parent epsilon-phase, donating an increasingly hard ferromagnetic character. The onset of the epsilon ->tau transformation occurs at a temperature that is similar to 100 K lower than that reported in the literature, highlighting the benefits of applying rapid solidification for synthesis of the rapidly-solidified parent alloy.« less

Electron microscope phase enhancement

DOEpatents

Jin, Jian; Glaeser, Robert M.

2010-06-15

A microfabricated electron phase shift element is used for modifying the phase characteristics of an electron beam passing though its center aperture, while not affecting the more divergent portion of an incident beam to selectively provide a ninety-degree phase shift to the unscattered beam in the back focal plan of the objective lens, in order to realize Zernike-type, in-focus phase contrast in an electron microscope. One application of the element is to increase the contrast of an electron microscope for viewing weakly scattering samples while in focus. Typical weakly scattering samples include biological samples such as macromolecules, or perhaps cells. Preliminary experimental images demonstrate that these devices do apply a ninety degree phase shift as expected. Electrostatic calculations have been used to determine that fringing fields in the region of the scattered electron beams will cause a negligible phase shift as long as the ratio of electrode length to the transverse feature-size aperture is about 5:1. Calculations are underway to determine the feasibility of aspect smaller aspect ratios of about 3:1 and about 2:1.

Carrier recovery techniques on satellite mobile channels

NASA Technical Reports Server (NTRS)

Vucetic, B.; Du, J.

1990-01-01

An analytical method and a stored channel model were used to evaluate error performance of uncoded quadrature phase shift keying (QPSK) and M-ary phase shift keying (MPSK) trellis coded modulation (TCM) over shadowed satellite mobile channels in the presence of phase jitter for various carrier recovery techniques.

A Refinement of the McMillen (1988) Recursive Digital Filter for the Analysis of Atmospheric Turbulence

NASA Astrophysics Data System (ADS)

Falocchi, Marco; Giovannini, Lorenzo; Franceschi, Massimiliano de; Zardi, Dino

2018-05-01

We present a refinement of the recursive digital filter proposed by McMillen (Boundary-Layer Meteorol 43:231-245, 1988), for separating surface-layer turbulence from low-frequency fluctuations affecting the mean flow, especially over complex terrain. In fact, a straightforward application of the filter causes both an amplitude attenuation and a forward phase shift in the filtered signal. As a consequence turbulence fluctuations, evaluated as the difference between the original series and the filtered one, as well as higher-order moments calculated from them, may be affected by serious inaccuracies. The new algorithm (i) produces a rigorous zero-phase filter, (ii) restores the amplitude of the low-frequency signal, and (iii) corrects all filter-induced signal distortions.

Pixel-by-pixel absolute phase retrieval using three phase-shifted fringe patterns without markers

NASA Astrophysics Data System (ADS)

Jiang, Chufan; Li, Beiwen; Zhang, Song

2017-04-01

This paper presents a method that can recover absolute phase pixel by pixel without embedding markers on three phase-shifted fringe patterns, acquiring additional images, or introducing additional hardware component(s). The proposed three-dimensional (3D) absolute shape measurement technique includes the following major steps: (1) segment the measured object into different regions using rough priori knowledge of surface geometry; (2) artificially create phase maps at different z planes using geometric constraints of structured light system; (3) unwrap the phase pixel by pixel for each region by properly referring to the artificially created phase map; and (4) merge unwrapped phases from all regions into a complete absolute phase map for 3D reconstruction. We demonstrate that conventional three-step phase-shifted fringe patterns can be used to create absolute phase map pixel by pixel even for large depth range objects. We have successfully implemented our proposed computational framework to achieve absolute 3D shape measurement at 40 Hz.

Motion compensation and noise tolerance in phase-shifting digital in-line holography.

PubMed

Stenner, Michael D; Neifeld, Mark A

2006-05-15

We present a technique for phase-shifting digital in-line holography which compensates for lateral object motion. By collecting two frames of interference between object and reference fields with identical reference phase, one can estimate the lateral motion that occurred between frames using the cross-correlation. We also describe a very general linear framework for phase-shifting holographic reconstruction which minimizes additive white Gaussian noise (AWGN) for an arbitrary set of reference field amplitudes and phases. We analyze the technique's sensitivity to noise (AWGN, quantization, and shot), errors in the reference fields, errors in motion estimation, resolution, and depth of field. We also present experimental motion-compensated images achieving the expected resolution.

Concatenated shift registers generating maximally spaced phase shifts of PN-sequences

NASA Technical Reports Server (NTRS)

Hurd, W. J.; Welch, L. R.

1977-01-01

A large class of linearly concatenated shift registers is shown to generate approximately maximally spaced phase shifts of pn-sequences, for use in pseudorandom number generation. A constructive method is presented for finding members of this class, for almost all degrees for which primitive trinomials exist. The sequences which result are not normally characterized by trinomial recursions, which is desirable since trinomial sequences can have some undesirable randomness properties.

Contribution of cerebellar intracortical inhibition to Purkinje cell response during vestibulo-ocular reflex of alert rabbits.

PubMed Central

Miyashita, Y; Nagao, S

1984-01-01

Ionophoretic application of bicuculline, an antagonist of gamma-aminobutyric acid (GABA), was used to examine the contribution of intracortical inhibition to vestibular responses of Purkinje cells in the cerebellar flocculus of alert rabbits. Purkinje cells were sampled extracellularly (with triple-barrelled micropipettes) from the floccular area where electrical stimulation through the micro-electrode evoked abduction of the ipsilateral eye, indicating its close functional relationship to the horizontal vestibulo-ocular reflex. These cells exhibited frequency modulation of simple spike discharges in-phase or out-phase with sinusoidal head rotation (0.5 cycles/s, 5 degrees peak-to-peak) in the horizontal plane. Bicuculline was ejected ionophoretically through one barrel with a 20-60 nA current. The pharmacological effectiveness of the ejected bicuculline was confirmed for each Purkinje cell by its blocking action upon the depressant action of GABA applied ionophoretically through another barrel. Bicuculline usually shifted the simple spike modulation in the in-phase direction: it reduced the amplitude of out-phase modulation in three cells, converted out-phase modulation to the in-phase type in four cells, and increased in-phase modulation in five cells. In three other cells, however, bicuculline shifted the modulation in the out-phase direction. Because bicuculline application usually increased the resting discharge level of a Purkinje cell, ionophoretic application of DL-homocysteate was used in ten Purkinje cells to control for the effect of a generalized increase in excitability. In contrast to bicuculline, DL-homocysteate generally induced a slight increase of the simple spike modulation regardless of the phase relationship. Since frequency modulation of the simple spike discharges of flocculus Purkinje cells is presumed to contribute to the control of vestibulo-ocular reflexes, these results point to an important functional role of intracortical post-synaptic inhibition in the cerebellar cortex. PMID:6611408

System Construction for the Measurement of Bragg Grating Characteristics in Optical Fibers

NASA Technical Reports Server (NTRS)

West, Douglas P.

1995-01-01

Bragg gratings are used to measure strain in optical fibers. To measure strain they are sometimes used as a smart structure. They must be characterized after they are written to determine their spectral response. This paper deals with the test setup to characterize Bragg grating spectral responses.Bragg gratings are a photo-induced phenomena in optical fibers. The gratings can be used to measure strain by measuring the shift in wavelength. They placed the fibers into a smart structure to measure the stress and strain produced on support columns placed in bridges. As the cable is subjected to strain the grating causes a shift to a longer wavelength if the fiber is stretched and a shift to a shorter wavelength shift if the fiber is compacted. Our applications involve using the fibers to measure stress and strain on airborne systems. There are many ways to write Bragg gratings into optical fibers. Our focus is on side writing the grating. Our capabilities are limited in the production rate of the gratings. The Bragg grating is written into a fiber and becomes a permanent fixture. We are writing the grating to be centered at 1300 nm because that is the standard phase mask wavelength.

Relative phase shifts for metaplectic isotopies acting on mixed Gaussian states

NASA Astrophysics Data System (ADS)

de Gosson, Maurice A.; Nicacio, Fernando

2018-05-01

We address in this paper the notion of relative phase shift for mixed quantum systems. We study the Pancharatnam-Sjöqvist phase shift φ (t ) =ArgTr(U^ tρ ^ ) for metaplectic isotopies acting on Gaussian mixed states. We complete and generalize the previous results obtained by one of us, while giving rigorous proofs. The key actor in this study is the theory of the Conley-Zehnder index which is an intersection index related to the Maslov index.

Application of virtual phase-shifting speckle-interferometry for detection of polymorphism in the Chlamydia trachomatis omp1 gene

NASA Astrophysics Data System (ADS)

Feodorova, Valentina A.; Saltykov, Yury V.; Zaytsev, Sergey S.; Ulyanov, Sergey S.; Ulianova, Onega V.

2018-04-01

Method of phase-shifting speckle-interferometry has been used as a new tool with high potency for modern bioinformatics. Virtual phase-shifting speckle-interferometry has been applied for detection of polymorphism in the of Chlamydia trachomatis omp1 gene. It has been shown, that suggested method is very sensitive to natural genetic mutations as single nucleotide polymorphism (SNP). Effectiveness of proposed method has been compared with effectiveness of the newest bioinformatic tools, based on nucleotide sequence alignment.

Simulated night shift work induces circadian misalignment of the human peripheral blood mononuclear cell transcriptome.

PubMed

Kervezee, Laura; Cuesta, Marc; Cermakian, Nicolas; Boivin, Diane B

2018-05-22

Misalignment of the endogenous circadian timing system leads to disruption of physiological rhythms and may contribute to the development of the deleterious health effects associated with night shift work. However, the molecular underpinnings remain to be elucidated. Here, we investigated the effect of a 4-day simulated night shift work protocol on the circadian regulation of the human transcriptome. Repeated blood samples were collected over two 24-hour measurement periods from eight healthy subjects under highly controlled laboratory conditions before and 4 days after a 10-hour delay of their habitual sleep period. RNA was extracted from peripheral blood mononuclear cells to obtain transcriptomic data. Cosinor analysis revealed a marked reduction of significantly rhythmic transcripts in the night shift condition compared with baseline at group and individual levels. Subsequent analysis using a mixed-effects model selection approach indicated that this decrease is mainly due to dampened rhythms rather than to a complete loss of rhythmicity: 73% of transcripts rhythmically expressed at baseline remained rhythmic during the night shift condition with a similar phase relative to habitual bedtimes, but with lower amplitudes. Functional analysis revealed that key biological processes are affected by the night shift protocol, most notably the natural killer cell-mediated immune response and Jun/AP1 and STAT pathways. These results show that 4 days of simulated night shifts leads to a loss in temporal coordination between the human circadian transcriptome and the external environment and impacts biological processes related to the adverse health effects associated to night shift work.

Digital second-order phase-locked loop

NASA Technical Reports Server (NTRS)

Holmes, J. K.; Carl, C. C.; Tagnelia, C. R.

1975-01-01

Actual tests with second-order digital phase-locked loop at simulated relative Doppler shift of 1x0.0001 produced phase lock with timing error of 6.5 deg and no appreciable Doppler bias. Loop thus appears to achieve subcarrier synchronization and to remove bias due to Doppler shift in range of interest.

Cocaine Shifts the Estrus Cycle Out of Phase and Caffeine Restores It

PubMed Central

Malave, Lauren B.

2014-01-01

Background: Sex differences in cocaine abuse are well established. Females have a higher sensitivity and thus higher vulnerability to cocaine abuse compared to males. There are many studies showing that sensitivity to cocaine reward varies during the estrus cycle. Methods: Vaginal smears were examined through a DIFF staining kit and viewed through a microscope to determine the estrus cycle stage. Smears were taken immediately before and after cocaine and/or caffeine injections. Furthermore, we suggest a new tool to analyze the estrus cycle by using electrical resistance of the vaginal mucosa. Results: In the present study, we discovered that cocaine directly induced changes in the estrus cycle. Interestingly, caffeine did not affect the estrus cycle and nor did the combination of cocaine and caffeine. We observed that caffeine blocked the cocaine-induced estrus cycle changes using conventional exfoliate cytology. Therefore, caffeine may have neuroprotective properties on the changes induced by cocaine. Conclusion: These phase changes in the estrus cycle may be the underlying cause of sex differences in cocaine addiction that can be blocked by caffeine. Thus, we propose a valuable insight into sex differences in cocaine abuse and reveal a possible treatment with antagonizing the adenosine system. PMID:25538863

Effects of caffeine on circadian phase, amplitude and period evaluated in cells in vitro and peripheral organs in vivo in PER2::LUCIFERASE mice

PubMed Central

Narishige, Seira; Kuwahara, Mari; Shinozaki, Ayako; Okada, Satoshi; Ikeda, Yuko; Kamagata, Mayo; Tahara, Yu; Shibata, Shigenobu

2014-01-01

Background and Purpose Caffeine is one of the most commonly used psychoactive substances. Circadian rhythms consist of the main suprachiasmatic nucleus (SCN) clocks and peripheral clocks. Although caffeine lengthens circadian rhythms and modifies phase changes in SCN-operated rhythms, the effects on caffeine on the phase, period and amplitude of peripheral organ clocks are not known. In addition, the role of cAMP/Ca2+ signalling in effects of caffeine on rhythm has not been fully elucidated. Experimental Approach We examined whether chronic or transient application of caffeine affects circadian period/amplitude and phase by evaluating bioluminescence rhythm in PER2::LUCIFERASE knock-in mice. Circadian rhythms were monitored in vitro using fibroblasts and ex vivo and in vivo for monitoring of peripheral clocks. Key Results Chronic application of caffeine (0.1–10 mM) increased period and amplitude in vitro. Transient application of caffeine (10 mM) near the bottom of the decreasing phase of bioluminescence rhythm caused phase advance in vitro. Caffeine (0.1%) intake caused a phase delay under light–dark or constant dark conditions, suggesting a period-lengthening effect in vivo. Caffeine (20 mg·kg−1) at daytime or at late night-time caused phase advance or delay in bioluminescence rhythm in the liver and kidney respectively. The complicated roles of cAMP/Ca2+ signalling may be involved in the caffeine-induced increase of period and amplitude in vitro. Conclusions and Implications Caffeine affects circadian rhythm in mice by lengthening the period and causing a phase shift of peripheral clocks. These results suggest that caffeine intake with food/drink may help with food-induced resetting of peripheral circadian clocks. PMID:25160990

Interaction of acute-phase-inducible and liver-enriched nuclear factors with the promoter region of the mouse alpha sub 1 -acid glycoprotein gene-1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alam, T.; Papaconstantinou, J.

1992-02-25

The synthesis and secretion of several acute-phase proteins increases markedly following physiological stress. {alpha}{sub 1}-Acid glycoprotein (AGP), a major acute-phase reactant made by the liver, is strongly induced by inflammatory agents such as lipopolysaccharide (LPS). Nuclear run-on assay showed a 17-fold increase in the rate of AGP transcription 4 h following LPS injection. DNase I footprinting assays revealed multiple protein binding domains in the mouse AGP-1 promoter region. Region B ({minus}104 to {minus}91) is protected by a liver-enriched transcription factor that is heat labile and in limiting quantity. An adjacent region, C ({minus}125 to {minus}104), is well-protected by nuclear extractsmore » from hepatocytes. Electrophoretic mobility shift assays indicated that only one DNA-protein complex can form with an oligonucleotide corresponding to region B. However, nuclear proteins from untreated mouse liver can form three strong complexes (C1, C2, and C3) and a weak one (C4) with oligonucleotide C. An acute-phase-inducible DNA-binding protein (AP-DBP) forms complex 4. A dramatic increase (over 11-fold) in AP-DBP binding activity is seen with nuclear proteins from LPS-stimulated animals. Interestingly, AP-DBP, a heat-stable factor, can form heterodimers with the transcription factor CCAAT/enhancer binding protein (C/EBP). Furthermore, purified C/EBP also binds avidly to region C. The studies indicate that several liver-enriched nuclear factors can interact with AGP-1 promoter and that AP-DBP binds to the AGP-1 promoter with high affinity only during the acute-phase induction.« less

Accuracy concerns in digital speckle photography combined with Fresnel digital holographic interferometry

NASA Astrophysics Data System (ADS)

Zhao, Yuchen; Zemmamouche, Redouane; Vandenrijt, Jean-François; Georges, Marc P.

2018-05-01

A combination of digital holographic interferometry (DHI) and digital speckle photography (DSP) allows in-plane and out-of-plane displacement measurement between two states of an object. The former can be determined by correlating the two speckle patterns whereas the latter is given by the phase difference obtained from DHI. We show that the amplitude of numerically reconstructed object wavefront obtained from Fresnel in-line digital holography (DH), in combination with phase shifting techniques, can be used as speckle patterns in DSP. The accuracy of in-plane measurement is improved after correcting the phase errors induced by reference wave during reconstruction process. Furthermore, unlike conventional imaging system, Fresnel DH offers the possibility to resize the pixel size of speckle patterns situated on the reconstruction plane under the same optical configuration simply by zero-padding the hologram. The flexibility of speckle size adjustment in Fresnel DH ensures the accuracy of estimation result using DSP.

In situ Mössbauer investigation of iron oxide catalyst in water gas shift reaction - Impact of oxyreduction potential and temperature

NASA Astrophysics Data System (ADS)

Cherkezova-Zheleva, Z.; Mitov, I.

2010-03-01

The aim of the study is to obtain the exact state of iron oxide catalyst active phase in reaction conditions, as well as the correlation between the active phase and catalytic properties of iron-containing catalysts. In situ Mössbauer spectroscopy is the major investigation technique. It is established that the change of reaction conditions (temperature and gas reaction mixture) lead to redistribution of the relative weight of spectra components and influence mainly tetrahedrally and octahedrally coordinated cations in Fe3O4 phase. It was concluded, that the active sites of the catalyst in studied reaction are probably pairs of Fe3++Fe2+-(Fe2.5+) ions, i.e. the mixed valance iron ions. The obtained catalytic activity can be explained with combination of the natural thermo-activated and catalytically induced electron exchange and better synchronizing of oxidation and reduction steps of the catalytic reaction.

Influence of the UV-induced fiber loss on the distributed feedback fiber lasers

NASA Astrophysics Data System (ADS)

Fan, Wei; Chen, Bai; Qiao, Qiquan; Chen, Jialing; Lin, Zunqi

2003-06-01

It was found that the output power of the distributed feedback fiber lasers would be improved after annealing or left unused for several days after the laser had been fabricated, and the output of the fundamental mode would not increase but be clamped while the ±1 order modes would be predominant with the enhancement of the coupling coefficient during the fabrication. The paper discussed the influence of UV-induced fiber loss on the fiber phase-shifted DFB lasers. Due to the gain saturation and fiber internal loss, which included the temperament loss and permanent loss, there was an optimum coupling coefficient for the DFB fiber lasers that the higher internal fiber loss corresponded to the lower optimum values of coupling coefficient.

Corrections to hyperfine splitting and Lamb shift induced by diagrams with second order radiative insertions in the electron line

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eides, M.I.; Karshenboim, S.G.; Shelyuto, V.A.

1994-12-31

Contributions to HFS and to the Lamb shift intervals of order a{sup 2}(Za){sup 5} induced by gauge invariant set of nineteen topologically different graphs with two radiative photons inserted in the electron line are considered. Corrections both to HFS and Lamb shift induced by nine diagrams are calculated in the Fried-Yennie gauge.

Phase estimation for magnetic resonance imaging near metal prostheses

NASA Astrophysics Data System (ADS)

Bones, Philip J.; King, Laura J.; Millane, Rick P.

2015-09-01

Magnetic resonance imaging (MRI) has the potential to be the best technique for assessing complications in patients with metal orthopedic implants. The presence of fat can obscure definition of the other soft tissues in MRI images, so fat suppression is often required. However, the performance of existing fat suppression techniques is inadequate near implants, due to very significant magnetic field perturbations induced by the metal. The three-point Dixon technique is potentially a method of choice as it is able to suppress fat in the presence of inhomogeneities, but the success of this technique depends on being able to accurately calculate the phase shift. This is generally done using phase unwrapping and/or iterative reconstruction algorithms. Most current phase unwrapping techniques assume that the phase function is slowly varying and phase differences between adjacent points are limited to less than π radians in magnitude. Much greater phase differences can be present near metal implants. We present our experience with two phase unwrapping techniques which have been adapted to use prior knowledge of the implant. The first method identifies phase discontinuities before recovering the phase along paths through the image. The second method employs a transform to find the least squares solution to the unwrapped phase. Simulation results indicate that the methods show promise.

Molecular genetic analysis of circadian timekeeping in Drosophila

PubMed Central

Hardin, Paul E.

2014-01-01

A genetic screen for mutants that alter circadian rhythms in Drosophila identified the first clock gene - the period (per) gene. The per gene is a central player within a transcriptional feedback loop that represents the core mechanism for keeping circadian time in Drosophila and other animals. The per feedback loop, or core loop, is interlocked with the Clock (Clk) feedback loop, but whether the Clk feedback loop contributes to circadian timekeeping is not known. A series of distinct molecular events are thought to control transcriptional feedback in the core loop. The time it takes to complete these events should take much less than 24h, thus delays must be imposed at different steps within the core loop. As new clock genes are identified, the molecular mechanisms responsible for these delays have been revealed in ever-increasing detail, and provide an in depth accounting of how transcriptional feedback loops keep circadian time. The phase of these feedback loops shift to maintain synchrony with environmental cycles, the most reliable of which is light. Although a great deal is known about cell-autonomous mechanisms of light-induced phase shifting by CRYPTOCHROME (CRY), much less is known about non-cell autonomous mechanisms. CRY mediates phase shifts through an uncharacterized mechanism in certain brain oscillator neurons, and carries out a dual role as a photoreceptor and transcription factor in other tissues. Here I will review how transcriptional feedback loops function to keep time in Drosophila, how they impose delays to maintain a 24h cycle, and how they maintain synchrony with environmental light:dark cycles. The transcriptional feedback loops that keep time in Drosophila are well conserved in other animals, thus what we learn about these loops in Drosophila should continue to provide insight into the operation of analogous transcriptional feedback loops in other animals. PMID:21924977

Spacecraft-to-Earth Communications for Juno and Mars Science Laboratory Critical Events

NASA Technical Reports Server (NTRS)

Soriano, Melissa; Finley, Susan; Jongeling, Andre; Fort, David; Goodhart, Charles; Rogstad, David; Navarro, Robert

2012-01-01

Deep Space communications typically utilize closed loop receivers and Binary Phase Shift Keying (BPSK) or Quadrature Phase Shift Keying (QPSK). Critical spacecraft events include orbit insertion and entry, descent, and landing.---Low gain antennas--> low signal -to-noise-ratio.---High dynamics such as parachute deployment or spin --> Doppler shift. During critical events, open loop receivers and Multiple Frequency Shift Keying (MFSK) used. Entry, Descent, Landing (EDL) Data Analysis (EDA) system detects tones in real-time.

Nonadiabatic Josephson current pumping by chiral microwave irradiation

NASA Astrophysics Data System (ADS)

Venitucci, B.; Feinberg, D.; Mélin, R.; Douçot, B.

2018-05-01

Irradiating a Josephson junction with microwaves can operate not only on the amplitude but also on the phase of the Josephson current. This requires breaking time-inversion symmetry, which is achieved by introducing a phase lapse between the microwave components acting on the two sides of the junction. General symmetry arguments and the solution of a specific single-level quantum dot model show that this induces chirality in the Cooper pair dynamics due to the topology of the Andreev bound-state wave function. Another essential condition is to break electron-hole symmetry within the junction. A shift of the current-phase relation is obtained, which is controllable in sign and amplitude with the microwave phase and an electrostatic gate, thus producing a "chiral" Josephson transistor. The dot model is solved in the infinite-gap limit by Floquet theory and in the general case with Keldysh nonequilibrium Green's functions. The chiral current is nonadiabatic: it is extremal and changes sign close to resonant chiral transitions between the Andreev bound states.

Energy-resolved attosecond interferometric photoemission from Ag(111) and Au(111) surfaces

NASA Astrophysics Data System (ADS)

Ambrosio, M. J.; Thumm, U.

2018-04-01

Photoelectron emission from solid surfaces induced by attosecond pulse trains into the electric field of delayed phase-coherent infrared (IR) pulses allows the surface-specific observation of energy-resolved electronic phase accumulations and photoemission delays. We quantum-mechanically modeled interferometric photoemission spectra from the (111) surfaces of Au and Ag, including background contributions from secondary electrons and direct emission by the IR pulse, and adjusted parameters of our model to energy-resolved photoelectron spectra recently measured at a synchrotron light source by Roth et al. [J. Electron Spectrosc. 224, 84 (2018), 10.1016/j.elspec.2017.05.008]. Our calculated spectra and photoelectron phase shifts are in fair agreement with the experimental data of Locher et al. [Optica 2, 405 (2015), 10.1364/OPTICA.2.000405]. Our model's not reproducing the measured energy-dependent oscillations of the Ag(111) photoemission phases may be interpreted as evidence for subtle band-structure effects on the final-state photoelectron-surface interaction not accounted for in our simulation.

Quantum simulation of thermally-driven phase transition and oxygen K-edge x-ray absorption of high-pressure ice

PubMed Central

Kang, Dongdong; Dai, Jiayu; Sun, Huayang; Hou, Yong; Yuan, Jianmin

2013-01-01

The structure and phase transition of high-pressure ice are of long-standing interest and challenge, and there is still a huge gap between theoretical and experimental understanding. The quantum nature of protons such as delocalization, quantum tunneling and zero-point motion is crucial to the comprehension of the properties of high-pressure ice. Here we investigated the temperature-induced phase transition and oxygen K-edge x-ray absorption spectra of ice VII, VIII and X using ab initio path-integral molecular dynamics simulations. The tremendous difference between experiments and the previous theoretical predictions is closed for the phase diagram of ice below 300 K at pressures up to 110 GPa. Proton tunneling assists the proton-ordered ice VIII to transform into proton-disordered ice VII where only thermal activated proton-transfer cannot occur. The oxygen K edge with its shift is sensitive to the order-disorder transition, and therefore can be applied to diagnose the dynamics of ice structures. PMID:24253589

Rapid Measurement and Correction of Phase Errors from B0 Eddy Currents: Impact on Image Quality for Non-Cartesian Imaging

PubMed Central

Brodsky, Ethan K.; Klaers, Jessica L.; Samsonov, Alexey A.; Kijowski, Richard; Block, Walter F.

2014-01-01

Non-Cartesian imaging sequences and navigational methods can be more sensitive to scanner imperfections that have little impact on conventional clinical sequences, an issue which has repeatedly complicated the commercialization of these techniques by frustrating transitions to multi-center evaluations. One such imperfection is phase errors caused by resonant frequency shifts from eddy currents induced in the cryostat by time-varying gradients, a phenomemon known as B0 eddy currents. These phase errors can have a substantial impact on sequences that use ramp sampling, bipolar gradients, and readouts at varying azimuthal angles. We present a method for measuring and correcting phase errors from B0 eddy currents and examine the results on two different scanner models. This technique yields significant improvements in image quality for high-resolution joint imaging on certain scanners. The results suggest that correction of short time B0 eddy currents in manufacturer provided service routines would simplify adoption of non-Cartesian sampling methods. PMID:22488532

White light phase shifting interferometry and color fringe analysis for the detection of contaminants in water

NASA Astrophysics Data System (ADS)

Dubey, Vishesh; Singh, Veena; Ahmad, Azeem; Singh, Gyanendra; Mehta, Dalip Singh

2016-03-01

We report white light phase shifting interferometry in conjunction with color fringe analysis for the detection of contaminants in water such as Escherichia coli (E.coli), Campylobacter coli and Bacillus cereus. The experimental setup is based on a common path interferometer using Mirau interferometric objective lens. White light interferograms are recorded using a 3-chip color CCD camera based on prism technology. The 3-chip color camera have lesser color cross talk and better spatial resolution in comparison to single chip CCD camera. A piezo-electric transducer (PZT) phase shifter is fixed with the Mirau objective and they are attached with a conventional microscope. Five phase shifted white light interferograms are recorded by the 3-chip color CCD camera and each phase shifted interferogram is decomposed into the red, green and blue constituent colors, thus making three sets of five phase shifted intererograms for three different colors from a single set of white light interferogram. This makes the system less time consuming and have lesser effect due to surrounding environment. Initially 3D phase maps of the bacteria are reconstructed for red, green and blue wavelengths from these interferograms using MATLAB, from these phase maps we determines the refractive index (RI) of the bacteria. Experimental results of 3D shape measurement and RI at multiple wavelengths will be presented. These results might find applications for detection of contaminants in water without using any chemical processing and fluorescent dyes.

Correction of phase-shifting error in wavelength scanning digital holographic microscopy

NASA Astrophysics Data System (ADS)

Zhang, Xiaolei; Wang, Jie; Zhang, Xiangchao; Xu, Min; Zhang, Hao; Jiang, Xiangqian

2018-05-01

Digital holographic microscopy is a promising method for measuring complex micro-structures with high slopes. A quasi-common path interferometric apparatus is adopted to overcome environmental disturbances, and an acousto-optic tunable filter is used to obtain multi-wavelength holograms. However, the phase shifting error caused by the acousto-optic tunable filter reduces the measurement accuracy and, in turn, the reconstructed topographies are erroneous. In this paper, an accurate reconstruction approach is proposed. It corrects the phase-shifting errors by minimizing the difference between the ideal interferograms and the recorded ones. The restriction on the step number and uniformity of the phase shifting is relaxed in the interferometry, and the measurement accuracy for complex surfaces can also be improved. The universality and superiority of the proposed method are demonstrated by practical experiments and comparison to other measurement methods.

Precise determination of lattice phase shifts and mixing angles

DOE PAGES

Lu, Bing -Nan; Lähde, Timo A.; Lee, Dean; ...

2016-07-09

Here, we introduce a general and accurate method for determining lattice phase shifts and mixing angles, which is applicable to arbitrary, non-cubic lattices. Our method combines angular momentum projection, spherical wall boundaries and an adjustable auxiliary potential. This allows us to construct radial lattice wave functions and to determine phase shifts at arbitrary energies. For coupled partial waves, we use a complex-valued auxiliary potential that breaks time-reversal invariance. We benchmark our method using a system of two spin-1/2 particles interacting through a finite-range potential with a strong tensor component. We are able to extract phase shifts and mixing angles formore » all angular momenta and energies, with precision greater than that of extant methods. We discuss a wide range of applications from nuclear lattice simulations to optical lattice experiments.« less

Comprehensive time average digital holographic vibrometry

NASA Astrophysics Data System (ADS)

Psota, Pavel; Lédl, Vít; Doleček, Roman; Mokrý, Pavel; Vojtíšek, Petr; Václavík, Jan

2016-12-01

This paper presents a method that simultaneously deals with drawbacks of time-average digital holography: limited measurement range, limited spatial resolution, and quantitative analysis of the measured Bessel fringe patterns. When the frequency of the reference wave is shifted by an integer multiple of frequency at which the object oscillates, the measurement range of the method can be shifted either to smaller or to larger vibration amplitudes. In addition, phase modulation of the reference wave is used to obtain a sequence of phase-modulated fringe patterns. Such fringe patterns can be combined by means of phase-shifting algorithms, and amplitudes of vibrations can be straightforwardly computed. This approach independently calculates the amplitude values in every single pixel. The frequency shift and phase modulation are realized by proper control of Bragg cells and therefore no additional hardware is required.

Solitary waves of surface plasmon polariton via phase shifts under Doppler broadening and Kerr nonlinearity

NASA Astrophysics Data System (ADS)

Ahmad, S.; Ahmad, A.; Bacha, B. A.; Khan, A. A.; Abdul Jabar, M. S.

2017-12-01

Surface Plasmon Polaritons (SPPs) are theoretically investigated at the interface of a dielectric metal and gold. The output pulse from the dielectric is used as the input pulse for the generation of SPPs. The SPPs show soliton-like behavior at the interface. The solitary form of a SPP is maintained under the effects of Kerr nonlinearity, Doppler broadening and Fresnel dragging whereas its phase shift is significantly modified. A 0.3radian phase shift is calculated in the presence of both Kerr nonlinearity and Fresnel dragging in the absence of plasma motion. The phase shift is enhanced to 60radian due to the combined effect of Doppler broadening, Kerr nonlinearity and Fresnel dragging. The results may have significant applications in nano-photonics, optical tweezers, photovoltaic devices, plasmonster and sensing technology.

Determination of baryon-baryon elastic scattering phase shift from finite volume spectra in elongated boxes

NASA Astrophysics Data System (ADS)

Li, Ning; Wu, Ya-Jie; Liu, Zhan-Wei

2018-01-01

The relations between the baryon-baryon elastic scattering phase shifts and the two-particle energy spectrum in the elongated box are established. We studied the cases with both the periodic boundary condition and twisted boundary condition in the center of mass frame. The framework is also extended to the system of nonzero total momentum with periodic boundary condition in the moving frame. Moreover, we discussed the sensitivity functions σ (q ) that represent the sensitivity of higher scattering phases. Our analytical results will be helpful to extract the baryon-baryon elastic scattering phase shifts in the continuum from lattice QCD data by using elongated boxes.

Composition and structure of whey protein/gum arabic coacervates.

PubMed

Weinbreck, F; Tromp, R H; de Kruif, C G

2004-01-01

Complex coacervation in whey protein/gum arabic (WP/GA) mixtures was studied as a function of three main key parameters: pH, initial protein to polysaccharide mixing ratio (Pr:Ps)(ini), and ionic strength. Previous studies had already revealed under which conditions a coacervate phase was obtained. This study is aimed at understanding how these parameters influence the phase separation kinetics, the coacervate composition, and the internal coacervate structure. At a defined (Pr:Ps)(ini), an optimum pH of complex coacervation was found (pH(opt)), at which the strength of electrostatic interaction was maximum. For (Pr:Ps)(ini) = 2:1, the phase separation occurred the fastest and the final coacervate volume was the largest at pH(opt) = 4.0. The composition of the coacervate phase was determined after 48 h of phase separation and revealed that, at pH(opt), the coacervate phase was the most concentrated. Varying the (Pr:Ps)(ini) shifted the pH(opt) to higher values when (Pr:Ps)(ini) was increased and to lower values when (Pr:Ps)(ini) was decreased. This phenomenon was due to the level of charge compensation of the WP/GA complexes. Finally, the structure of the coacervate phase was studied with small-angle X-ray scattering (SAXS). SAXS data confirmed that at pH(opt) the coacervate phase was dense and structured. Model calculations revealed that the structure factor of WP induced a peak at Q = 0.7 nm(-1), illustrating that the coacervate phase was more structured, inducing the stronger correlation length of WP molecules. When the pH was changed to more acidic values, the correlation peak faded away, due to a more open structure of the coacervate. A shoulder in the scattering pattern of the coacervates was visible at small Q. This peak was attributed to the presence of residual charges on the GA. The peak intensity was reduced when the strength of interaction was increased, highlighting a greater charge compensation of the polyelectrolyte. Finally, increasing the ionic strength led to a less concentrated, a more heterogeneous, and a less structured coacervate phase, induced by the screening of the electrostatic interactions.

Homodyne Phase-Shift-Keying Systems: Past Challenges and Future Opportunities

NASA Astrophysics Data System (ADS)

Kazovsky, Leonid G.; Kalogerakis, Georgios; Shaw, Wei-Tao

2006-12-01

Homodyne phase-shift-keying systems can achieve the best receiver sensitivity and the longest transmission distance among all optical communication systems. This paper reviews recent research efforts in the field and examines future possibilities that might lead toward potential practical use of these systems. Additionally, phase estimation techniques based on feed-forward phase recovery and digital delay-lock loop approaches are examined, simulated, and compared.

Giant enhancement in Goos-Hänchen shift at the singular phase of a nanophotonic cavity

NASA Astrophysics Data System (ADS)

Sreekanth, Kandammathe Valiyaveedu; Ouyang, Qingling; Han, Song; Yong, Ken-Tye; Singh, Ranjan

2018-04-01

In this letter, we experimentally demonstrate thirtyfold enhancement in Goos-Hänchen shift at the Brewster angle of a nanophotonic cavity that operates at the wavelength of 632.8 nm. In particular, the point-of-darkness and the singular phase are achieved using a four-layered metal-dielectric-dielectric-metal asymmetric Fabry-Perot cavity. A highly absorbing ultra-thin layer of germanium in the stack gives rise to the singular phase and the enhanced Goos-Hänchen shift at the point-of-darkness. The obtained giant Goos-Hänchen shift in the lithography-free nanophotonic cavity could enable many intriguing applications including cost-effective label-free biosensors.

Superconductivity-induced features in the electronic Raman spectrum of monolayer graphene

NASA Astrophysics Data System (ADS)

García-Ruiz, A.; Mucha-Kruczyński, M.; Fal'ko, V. I.

2018-04-01

Using the continuum model, we investigate theoretically the contribution of the low-energy electronic excitations to the Raman spectrum of superconducting monolayer graphene. We consider superconducting phases characterised by an isotropic order parameter in a single valley and find a Raman peak at a shift set by the size of the superconducting gap. The height of this peak is proportional to the square root of the gap and the third power of the Fermi level, and we estimate its quantum efficiency as I ˜10-14 .

Permeability determination through NMR detection of acoustically induced fluid oscillation.

PubMed

Looyestijn, Wim J; Smits, Robert M M; Abu-Shiekah, Issa; Kuvshinov, Boris; Hofman, Jan P; Schwing, Alex

2006-11-01

We present a novel approach for directly measuring the permeability of reservoir rocks by an instrument lowered in a well bore. The measurement is made by creating an oscillatory motion of fluids in the pores by acoustic stimulation and by detecting the amplitude response as a phase shift on a nuclear magnetic resonance relaxation signal. A full theoretical description is given. The feasibility of the method has been verified in the laboratory on a set of sandstone and carbonate samples spanning the entire range of practical interest.

Orbital resonances around black holes.

PubMed

Brink, Jeandrew; Geyer, Marisa; Hinderer, Tanja

2015-02-27

We compute the length and time scales associated with resonant orbits around Kerr black holes for all orbital and spin parameters. Resonance-induced effects are potentially observable when the Event Horizon Telescope resolves the inner structure of Sgr A*, when space-based gravitational wave detectors record phase shifts in the waveform during the resonant passage of a compact object spiraling into the black hole, or in the frequencies of quasiperiodic oscillations for accreting black holes. The onset of geodesic chaos for non-Kerr spacetimes should occur at the resonance locations quantified here.

Quantum computers based on electron spins controlled by ultrafast off-resonant single optical pulses.

PubMed

Clark, Susan M; Fu, Kai-Mei C; Ladd, Thaddeus D; Yamamoto, Yoshihisa

2007-07-27

We describe a fast quantum computer based on optically controlled electron spins in charged quantum dots that are coupled to microcavities. This scheme uses broadband optical pulses to rotate electron spins and provide the clock signal to the system. Nonlocal two-qubit gates are performed by phase shifts induced by electron spins on laser pulses propagating along a shared waveguide. Numerical simulations of this scheme demonstrate high-fidelity single-qubit and two-qubit gates with operation times comparable to the inverse Zeeman frequency.

Ramsey's method of separated oscillating fields and its application to gravitationally induced quantum phase shifts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abele, H.; Jenke, T.; Leeb, H.

2010-03-15

We propose to apply Ramsey's method of separated oscillating fields to the spectroscopy of the quantum states in the gravity potential above a horizontal mirror. This method allows a precise measurement of quantum mechanical phaseshifts of a Schroedinger wave packet bouncing off a hard surface in the gravitational field of the Earth. Measurements with ultracold neutrons will offer a sensitivity to Newton's law or hypothetical short-ranged interactions, which is about 21 orders of magnitude below the energy scale of electromagnetism.

KW-4679-induced inhibition of tachykininergic contraction in the guinea-pig bronchi by prejunctional inhibition of peripheral sensory nerves.

PubMed

Ikemura, T; Okarmura, K; Sasaki, Y; Ishi, H; Ohmori, K

1996-03-01

1. Sensory mechanisms play an important role in the vagal regulation of tracheobronchial smooth muscle tone. We examined the effect of KW-4679, an anti-allergic drug, on guinea-pig tachykinin-mediated contractile responses induced by electrical field stimulation (EFS) in guinea-pig bronchial muscles. 2. EFS (8 Hz, 0.5 ms, 15 V, for 15 s) evoked biphasic contractile responses in the guinea-pig isolated main bronchus in the presence of 5 microM indomethacin. The contractions consisted of a fast phase of an atropine-sensitive transient contraction and a slow phase of a sustained contraction which was inhibited by a combination of the tachykinin NK1 receptor antagonist, (+/-)-CP-96,345 (1 microM) and the NK2 receptor antagonist, SR 48969 (0.1 microM). 3. KW-4679 preferentially inhibited the slow phase in a concentration-dependent manner by 43.2 +/- 7.7% at 10 microM, whereas the drug had no effect on the fast phase at concentrations up to 10 microM. KW-4679, at a concentration of 100 microM, inhibited not only the slow phase by 49.2 +/- 11.4%, but also the fast phase by 36.8 +/- 9.3% [corrected]. 4. KW-4679 (10 microM and 100 microM) did not affect the substance P-induced or neurokinin A-induced contraction. Against the acetylcholine-induced contractile responses, 100 microM KW-4679 had a marked effect producing a 10.2 fold shift to the right in the curve. 5. The inhibitory effect of KW-4679 (10 microM) on the slow phase contraction was not influenced by treatment with naloxone (100 nM), propranolol (1 microM), thioperamide (1 microM), saclofen (50 microM), yohimbine (1 microM), methiothepin (1 microM) or methysergide (1 microM). 6. The inhibitory effect of KW-4679 (10 microM) on the slow phase contraction was not influenced by treatment with intermediate or large conductance Ca(2+)-activated K+ channel blockers (charybdotoxin (10 nM) or iberiotoxin (10 nM)), but suppressed by treatment with small conductance Ca(2+)-activated K+ channel blockers, apamin (500 nM) or scyllatoxin (300 nM). Apamin or scyllatoxin per se did not influence the slow phase contractions. 7. The results suggest that KW-4679 preferentially inhibits the release of tachykinins from the bronchial sensory nerves through activation of small conductance Ca(2+)-activated K+ channels.

Robust phase-shifting interferometry resistant to multiple disturbances

NASA Astrophysics Data System (ADS)

Liu, Qian; Yue, Xiaobin; Li, Lulu; Zhang, Hui; He, Jianguo

2018-04-01

Phase-shifting interferometry (PSI) is sensitive to many disturbances, including the environmental vibration, laser instability, phase-shifting error and camera nonlinearity. A robust PSI (RPSI) based on the temporal spectrum analysis is proposed to suppress the effects of these common disturbances. RPSI retrieves wavefront phase from the temporal Fourier spectrum peak, which is identified by detecting the modulus of spectrum, and a referencing method is presented to improve the phase extracting accuracy. Simulations demonstrate the feasibility and effectiveness of RPSI. Experimental results indicate that RPSI is resistant to common disturbances in implementing PSI and achieves accuracy better than 0.03 rad in the disturbed environment. RPSI relaxes requirements on the hardware, environment and operator, and provides an easy-to-use design of an interferometer.

Edge effects in phase-shifting masks for 0.25-µm lithography

NASA Astrophysics Data System (ADS)

Wong, Alfred K. K.; Neureuther, Andrew R.

1993-03-01

The impact on image quality of scattering from phase-shifter edges and of interactions between phase-shifter and chrome edges is assessed using rigorous electromagnetic simulation. Effects of edge taper in phase-shift masks, spacing between phase-shifter and chrome edges, small outrigger features with a trench phase-shifter, and of the repair of phase defects by etching to 360 degree(s) are considered. Near field distributions and diffraction efficiencies are examined and images are compared with more approximate results from the commonly used Hopkins' theory of imaging.

Intrawave sand suspension in the shoaling and surf zone of a field-scale laboratory beach

NASA Astrophysics Data System (ADS)

Brinkkemper, J. A.; de Bakker, A. T. M.; Ruessink, B. G.

2017-01-01

Short-wave sand transport in morphodynamic models is often based solely on the near-bed wave-orbital motion, thereby neglecting the effect of ripple-induced and surface-induced turbulence on sand transport processes. Here sand stirring was studied using measurements of the wave-orbital motion, turbulence, ripple characteristics, and sand concentration collected on a field-scale laboratory beach under conditions ranging from irregular nonbreaking waves above vortex ripples to plunging waves and bores above subdued bed forms. Turbulence and sand concentration were analyzed as individual events and in a wave phase-averaged sense. The fraction of turbulence events related to suspension events is relatively high (˜50%), especially beneath plunging waves. Beneath nonbreaking waves with vortex ripples, the sand concentration close to the bed peaks right after the maximum positive wave-orbital motion and shows a marked phase lag in the vertical, although the peak in concentration at higher elevations does not shift to beyond the positive to negative flow reversal. Under plunging waves, concentration peaks beneath the wavefront without any notable phase lags in the vertical. In the inner-surf zone (bores), the sand concentration remains phase coupled to positive wave-orbital motion, but the concentration decreases with distance toward the shoreline. On the whole, our observations demonstrate that the wave-driven suspended load transport is onshore and largest beneath plunging waves, while it is small and can also be offshore beneath shoaling waves. To accurately predict wave-driven sand transport in morphodynamic models, the effect of surface-induced turbulence beneath plunging waves should thus be included.

Shift Work and Cognitive Flexibility: Decomposing Task Performance.

PubMed

Cheng, Philip; Tallent, Gabriel; Bender, Thomas John; Tran, Kieulinh Michelle; Drake, Christopher L

2017-04-01

Deficits in cognitive functioning associated with shift work are particularly relevant to occupational performance; however, few studies have examined how cognitive functioning is associated with specific components of shift work. This observational study examined how circadian phase, nocturnal sleepiness, and daytime insomnia in a sample of shift workers ( N = 30) were associated with cognitive flexibility during the night shift. Cognitive flexibility was measured using a computerized task-switching paradigm, which produces 2 indexes of flexibility: switch cost and set inhibition. Switch cost represents the additional cognitive effort required in switching to a different task and can impact performance when multitasking is involved. Set inhibition is the efficiency in returning to previously completed tasks and represents the degree of cognitive perseveration, which can lead to reduced accuracy. Circadian phase was measured via melatonin assays, nocturnal sleepiness was assessed using the Multiple Sleep Latency Test, and daytime insomnia was assessed using the Insomnia Severity Index. Results indicated that those with an earlier circadian phase, insomnia, and sleepiness exhibited reduced cognitive flexibility; however, specific components of cognitive flexibility were differentially associated with circadian phase, insomnia, and sleepiness. Individuals with an earlier circadian phase (thus more misaligned to the night shift) exhibited larger switch costs, which was also associated with reduced task efficiency. Shift workers with more daytime insomnia demonstrated difficulties with cognitive inhibition, whereas nocturnal sleepiness was associated with difficulties in reactivating previous tasks. Deficits in set inhibition were also related to reduced accuracy and increased perseverative errors. Together, this study indicates that task performance deficits in shift work are complex and are variably impacted by different mechanisms. Future research may examine phenotypic differences in shift work and the associated consequences. Results also suggest that fatigue risk management strategies may benefit from increased scope and specificity in assessment of sleep, sleepiness, and circadian rhythms in shift workers.

Control of the spin geometric phase in semiconductor quantum rings.

PubMed

Nagasawa, Fumiya; Frustaglia, Diego; Saarikoski, Henri; Richter, Klaus; Nitta, Junsaku

2013-01-01

Since the formulation of the geometric phase by Berry, its relevance has been demonstrated in a large variety of physical systems. However, a geometric phase of the most fundamental spin-1/2 system, the electron spin, has not been observed directly and controlled independently from dynamical phases. Here we report experimental evidence on the manipulation of an electron spin through a purely geometric effect in an InGaAs-based quantum ring with Rashba spin-orbit coupling. By applying an in-plane magnetic field, a phase shift of the Aharonov-Casher interference pattern towards the small spin-orbit-coupling regions is observed. A perturbation theory for a one-dimensional Rashba ring under small in-plane fields reveals that the phase shift originates exclusively from the modulation of a pure geometric-phase component of the electron spin beyond the adiabatic limit, independently from dynamical phases. The phase shift is well reproduced by implementing two independent approaches, that is, perturbation theory and non-perturbative transport simulations.

Simultaneously frequency down-conversion, independent multichannel phase shifting and zero-IF receiving using a phase modulator in a sagnac loop and balanced detection

NASA Astrophysics Data System (ADS)

Zhu, Zihang; Zhao, Shanghong; Li, Xuan; Lin, Tao; Hu, Dapeng

2018-03-01

Photonic microwave frequency down-conversion with independent multichannel phase shifting and zero-intermediate frequency (IF) receiving is proposed and demonstrated by simulation. By combined use of a phase modulator (PM) in a sagnac loop and an optical bandpass filter (OBPF), orthogonal polarized carrier suppression single sideband (CS-SSB) signals are obtained. By adjusting the polarization controllers (PCs) to introduce the phase difference in the optical domain and using balanced detection to eliminate the direct current components, the phase of the generated IF signal can be arbitrarily tuned. Besides, the radio frequency (RF) vector signal can be also frequency down-converted to baseband directly by choosing two quadrature channels. In the simulation, high gain and continuously tunable phase shifts over the 360 degree range are verified. Furthermore, 2.5 Gbit/s RF vector signals centered at 10 GHz with different modulation formats are successfully demodulated.

Channel Acquisition for Massive MIMO-OFDM With Adjustable Phase Shift Pilots

NASA Astrophysics Data System (ADS)

You, Li; Gao, Xiqi; Swindlehurst, A. Lee; Zhong, Wen

2016-03-01

We propose adjustable phase shift pilots (APSPs) for channel acquisition in wideband massive multiple-input multiple-output (MIMO) systems employing orthogonal frequency division multiplexing (OFDM) to reduce the pilot overhead. Based on a physically motivated channel model, we first establish a relationship between channel space-frequency correlations and the channel power angle-delay spectrum in the massive antenna array regime, which reveals the channel sparsity in massive MIMO-OFDM. With this channel model, we then investigate channel acquisition, including channel estimation and channel prediction, for massive MIMO-OFDM with APSPs. We show that channel acquisition performance in terms of sum mean square error can be minimized if the user terminals' channel power distributions in the angle-delay domain can be made non-overlapping with proper phase shift scheduling. A simplified pilot phase shift scheduling algorithm is developed based on this optimal channel acquisition condition. The performance of APSPs is investigated for both one symbol and multiple symbol data models. Simulations demonstrate that the proposed APSP approach can provide substantial performance gains in terms of achievable spectral efficiency over the conventional phase shift orthogonal pilot approach in typical mobility scenarios.

Phase shifts in I = 2 ππ-scattering from two lattice approaches

NASA Astrophysics Data System (ADS)

Kurth, T.; Ishii, N.; Doi, T.; Aoki, S.; Hatsuda, T.

2013-12-01

We present a lattice QCD study of the phase shift of I = 2 ππ scattering on the basis of two different approaches: the standard finite volume approach by Lüscher and the recently introduced HAL QCD potential method. Quenched QCD simulations are performed on lattices with extents N s = 16 , 24 , 32 , 48 and N t = 128 as well as lattice spacing a ~ 0 .115 fm and a pion mass of m π ~ 940 MeV. The phase shift and the scattering length are calculated in these two methods. In the potential method, the error is dominated by the systematic uncertainty associated with the violation of rotational symmetry due to finite lattice spacing. In Lüscher's approach, such systematic uncertainty is difficult to be evaluated and thus is not included in this work. A systematic uncertainty attributed to the quenched approximation, however, is not evaluated in both methods. In case of the potential method, the phase shift can be calculated for arbitrary energies below the inelastic threshold. The energy dependence of the phase shift is also obtained from Lüscher's method using different volumes and/or nonrest-frame extension of it. The results are found to agree well with the potential method.

Estimation of vibration frequency of loudspeaker diaphragm by parallel phase-shifting digital holography

NASA Astrophysics Data System (ADS)

Kakue, T.; Endo, Y.; Shimobaba, T.; Ito, T.

2014-11-01

We report frequency estimation of loudspeaker diaphragm vibrating at high speed by parallel phase-shifting digital holography which is a technique of single-shot phase-shifting interferometry. This technique records multiple phaseshifted holograms required for phase-shifting interferometry by using space-division multiplexing. We constructed a parallel phase-shifting digital holography system consisting of a high-speed polarization-imaging camera. This camera has a micro-polarizer array which selects four linear polarization axes for 2 × 2 pixels. We set a loudspeaker as an object, and recorded vibration of diaphragm of the loudspeaker by the constructed system. By the constructed system, we demonstrated observation of vibration displacement of loudspeaker diaphragm. In this paper, we aim to estimate vibration frequency of the loudspeaker diaphragm by applying the experimental results to frequency analysis. Holograms consisting of 128 × 128 pixels were recorded at a frame rate of 262,500 frames per second by the camera. A sinusoidal wave was input to the loudspeaker via a phone connector. We observed displacement of the loudspeaker diaphragm vibrating by the system. We also succeeded in estimating vibration frequency of the loudspeaker diaphragm by applying frequency analysis to the experimental results.

Understanding strain-induced phase transformations in BiFeO 3 thin films

DOE PAGES

Dixit, Hemant; Beekman, Christianne; Schlepütz, Christian M.; ...

2015-05-01

Bismuth ferrite (BiFeO 3) is a promising lead free multiferroic with large polarization, ferroelectricity and robust antiferomagnetism. Experiments demonstrate that epitaxial strain substantially enhance the piezoelectric response of BiFeO 3 thin films. Here, through a synergestic combination of theory and experiments, we characterize the co-existing polymorphs (specifically an intermediate S' phase between the bulk rhombohedral-R and the pseudotetragonal T' phases) observed in strained BiFeO 3 thin films. We show that the S' phase, although energetically very close to the T' phase, exhibits structural similarities with the bulk R phase. G-type antiferromagnetic ordering is predicted for the S' and R phases,more » whereas, the G/C-type antiferromagnetic order types are energetically indistinguishable for the T' phase. Furthermore, we predict a blue-shift in the band gap Eg when moving from R to S' to T', which we confirm by Electron Energy Loss Spectroscopy measurements. The flat energy landscape and the absence of an energy barrier between the T and S' phases indicate that a reversible phase transformation between the two is possible under the application of an external electric field. This may make it possible to strain engineer the electromechanical response or, utilizing the corresponding changes in Eg, create unique photonic structures.« less

Protonated Alcohols Are Examples of Complete Charge-Shift Bonds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, Peter; Petit, Alban; Ho, Junming

2014-10-15

Accurate gas-phase and solution-phase valence bond calculations reveal that protonation of the hydroxyl group of aliphatic alcohols transforms the C–O bond from a principally covalent bond to a complete charge-shift bond with principally “no-bond” character. All bonding in this charge-shift bond is due to resonance between covalent and ionic structures, which is a different bonding mechanism from that of traditional covalent bonds. Until now, charge-shift bonds have been previously identified in inorganic compounds or in exotic organic compounds. This work showcases that charge-shift bonds can occur in common organic species.

Reaching quantum limits for phase-shift detection with semiclassical states

NASA Astrophysics Data System (ADS)

Luis, Alfredo

2004-01-01

We present two measuring strategies reaching the Heisenberg limit for phase-shift measurements using semiclassical coherent states exclusively. We examine their performance by assuming practical experimental conditions such as losses and nonideal detectors.

Behavioral and Genetic Dissection of a Mouse Model for Advanced Sleep Phase Syndrome

PubMed Central

Jiang, Peng; Striz, Martin; Wisor, Jonathan P.; O'Hara, Bruce F.

2011-01-01

Study Objective: The adaptive value of the endogenous circadian clock arises from its ability to synchronize (i.e., entrain) to external light-dark (LD) cycles at an appropriate phase. Studies have suggested that advanced circadian phase alignment might result from shortening of the period length of the clock. Here we explore mechanisms that contribute to an early activity phase in CAST/EiJ (CAST) mice. Methods: We investigated circadian rhythms of wheel-running activity in C57BL/6J (B6), CAST and 2 strains of B6.CAST congenic mice, which carry CAST segments introgressed in a B6 genome. Results: When entrained, all CAST mice initiate daily activity several hours earlier than normal mice. This difference could not be explained by alterations in the endogenous period, as activity onset did not correlate with period length. However, the photic phase-shifting responses in these mice were phase-lagged by 3 hours relative to their activity. Attenuated light masking responses were also found in CAST mice, which allow for activity normally inhibited by light. A previously identified quantitative trait locus (QTL), Era1, which contributes to the early activity trait, was confirmed and refined here using two B6.CAST congenic strains. Surprisingly, these B6.CAST mice exhibited longer rather than shorter endogenous periods, further demonstrating that the advanced phase in these mice is not due to alterations in period. Conclusions: CAST mice have an advanced activity phase similar to human advanced sleep phase syndrome. This advanced phase is not due to its shorter period length or smaller light-induced phase shifts, but appears to be related to both light masking and altered coupling of the circadian pacemaker with various outputs. Lastly, a QTL influencing this trait was confirmed and narrowed using congenic mice as a first step toward gene identification. Citation: Jiang P; Striz M; Wisor JP; O'Hara BF. Behavioral and genetic dissection of a mouse model for advanced sleep phase syndrome. SLEEP 2011;34(1):39-48. PMID:21203370

Effects of Nonhydrostatic Stress on Structural and Optoelectronic Properties of Methylammonium Lead Bromide Perovskite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Rong; Cai, Weizhao; Bi, Tiange

We report synchrotron X-ray diffraction, photoconductivity, and photoluminescence investigations of methylammonium-lead-bromide (MAPbBr3) under various stress conditions, supported by density-functional-theory (DFT) calculations. The properties of MAPbBr3 show substantial dependence on the hydrostatic conditions. While nonhydrostatic compression of MAPbBr3 leads to amorphization above 2.4 GPa, under quasi-hydrostatic (Ar) and hydrostatic (He) pressure, the sample remains in crystalline phases. A sequence of phase transitions between two cubic phases and orthorhombic Pnma phase is observed when using Ar, or no pressure-transmitting-medium (PTM). In helium-PTM only transitions between the two cubic structures and a new isostructural phase transition with a large volume collapse to amore » third cubic-phase at 2.7 GPa was observed. The photoluminescence measurements indicate a pressure-induced band gap-narrowing in the cubic phase I, and a blue-shift in the orthorhombic structure. DFT calculations illustrate that the dynamics of the organic molecules and the inorganic lattice, coupled via the N–H···Br hydrogen-bonding interactions, affect the Pb–Br distance and the bandgap evolution under pressure.« less

A Phase-Shifting Zernike Wavefront Sensor for the Palomar P3K Adaptive Optics System

NASA Technical Reports Server (NTRS)

Wallace, J. Kent; Crawford, Sam; Loya, Frank; Moore, James

2012-01-01

A phase-shifting Zernike wavefront sensor has distinct advantages over other types of wavefront sensors. Chief among them are: 1) improved sensitivity to low-order aberrations and 2) efficient use of photons (hence reduced sensitivity to photon noise). We are in the process of deploying a phase-shifting Zernike wavefront sensor to be used with the realtime adaptive optics system for Palomar. Here we present the current state of the Zernike wavefront sensor to be integrated into the high-order adaptive optics system at Mount Palomar's Hale Telescope.

PT-symmetry of coupled fiber lasers

NASA Astrophysics Data System (ADS)

Smirnov, Sergey V.; Churkin, Dmitry V.; Makarenko, Maxim; Vatnik, Ilya; Suchkov, Sergey V.; Sukhorukov, Andrey A.

2017-10-01

In this work, we propose a concept of a coupled fiber laser exhibiting PT-symmetry properties. We consider a system operated via Raman gain. The scheme comprises two identical fiber loops (ring cavities) connected by means of two fiber couplers with variable phase shift between them. We show that by changing the phase shift one can switch between generation regimes, realizing either PT-symmetric or PT-broken solution. Furthermore, the paper investigates some peculiarities of the system such as power oscillations and the role of nonlinear phase shift in fiber rings.

Correction of I/Q channel errors without calibration

DOEpatents

Doerry, Armin W.; Tise, Bertice L.

2002-01-01

A method of providing a balanced demodular output for a signal such as a Doppler radar having an analog pulsed input; includes adding a variable phase shift as a function of time to the input signal, applying the phase shifted input signal to a demodulator; and generating a baseband signal from the input signal. The baseband signal is low-pass filtered and converted to a digital output signal. By removing the variable phase shift from the digital output signal, a complex data output is formed that is representative of the output of a balanced demodulator.

Single- and two-phase flow characterization using optical fiber bragg gratings.

PubMed

Baroncini, Virgínia H V; Martelli, Cicero; da Silva, Marco José; Morales, Rigoberto E M

2015-03-17

Single- and two-phase flow characterization using optical fiber Bragg gratings (FBGs) is presented. The sensor unit consists of the optical fiber Bragg grating positioned transversely to the flow and fixed in the pipe walls. The hydrodynamic pressure applied by the liquid or air/liquid flow to the optical fiber induces deformation that can be detected by the FBG. Given that the applied pressure is directly related to the mass flow, it is possible to establish a relationship using the grating resonance wavelength shift to determine the mass flow when the flow velocity is well known. For two phase flows of air and liquid, there is a significant change in the force applied to the fiber that accounts for the very distinct densities of these substances. As a consequence, the optical fiber deformation and the correspondent grating wavelength shift as a function of the flow will be very different for an air bubble or a liquid slug, allowing their detection as they flow through the pipe. A quasi-distributed sensing tool with 18 sensors evenly spread along the pipe is developed and characterized, making possible the characterization of the flow, as well as the tracking of the bubbles over a large section of the test bed. Results show good agreement with standard measurement methods and open up plenty of opportunities to both laboratory measurement tools and field applications.

Evaluating the use of Spectral Induced Conductivity to Detect Biofilm Development within Porous Media

NASA Astrophysics Data System (ADS)

Rosier, C. L.; Atekwana, E. A.; Price, A.; Sharma, S.; Patrauchan, M.

2015-12-01

Microbial biomass accumulation in subsurface sediments dynamically alters porosity/permeability; factors critical to contaminant transport and management of bioremediation efforts. Current methodologies (i.e. plate counts, tracer/slug tests) offer some understanding of biofilm effect on subsurface hydrology, yet do not provide real-time information regarding biofilm development. Due to these limitations there is interest in assessing the near surface geophysical technique Spectral Induced Polarization (SIP), to measure biofilm formation. Our study assesses the influence of cell density and biofilm production on SIP response. Laboratory experiments monitored changes in SIP, measured colony forming units (CFU), and cellular protein levels on sand packed columns inoculated with either Pseudomonas aeruginosa PAO1 (non-mucoid strain) or Pseudomonas aeruginosa FRD1 (biofilm-overproducing mucoid strain) cells over one month. Confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) were used to confirm the presence of biofilm. Our results indicate that phase and imaginary conductivity remained stable in PAO1 treatments as cell densities and cellular protein levels remained low (1.7x105 CFUml-1; 111 μg ml-1). However, we observed a significant decrease in both phase (0.5 to -0.20 mrad) and imaginary conductivity (0.0 to -3.0x10-5 S m-1) when both cell densities and cellular protein levels increased. In FRD1 treatments we observed an immediate decrease in phase (0.1 mrad) and imaginary conductivity (-2.0x10-6 S m-1) as cell densities were an order of magnitude greater then PAO1 treatments and cellular protein levels surpassed 500 μg ml-1. CLSM and SEM analysis confirmed the presence of biofilm and cells within both PAO1 and FRD1 treatments. Our findings suggest that the ratio of cells to cellular protein production is an important factor influencing both phase and imaginary conductivity response. However, our results are not in agreement with previous studies suggesting large phase shift (~50 mrads) and imaginary conductivity (5.5 S m-1) values due to biofilm development. We hypothesize that large phase shift and imaginary conductivity response are due to trapping of conductive materials within the biofilm matrix, studies are currently underway to address this hypothesis.