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PubMed1992

Combined effects on the circadian clock of agents with different phase response curves: phase-shifting effects of triazolam and light.

Although light provides the primary signal for the entrainment of circadian pacemakers, a number of endogenous substances and pharmacological agents are also capable of resetting circadian pacemakers. Very little is known about the combined effects of photic and nonphotic agents on clock functions. We conducted a "double-pulse" experiment, in which two discrete stimuli are presented at different times within a single circadian cycle, to determine the combined effects of a 1-hr light pulse and injections of a benzodiazepine, triazolam, on the circadian rhythm of activity in the golden hamster. Our results suggest that, first, when given together as done in these experiments, the effects of triazolam and light are partially but not completely additive. Triazolam-induced phase advances appeared to make the effects of subsequent 1-hr light pulses more negative; phase delays were increased, and phase advances were decreased. Second, it appears that triazolam and light may alter the circadian pacemaker in very different ways, beyond the obvious difference in the shape of their phase response curves. The phase-shifting mechanics of the circadian system of the golden hamster appear to involve a longer response time to triazolam than to light pulses. Alternative possibilities to account for this difference are discussed.

Animals↗
PubMed1999

Modeling circadian rhythm generation in the suprachiasmatic nucleus with locally coupled self-sustained oscillators: phase shifts and phase response curves.

Circadian rhythm generation in the suprachiasmatic nucleus was modeled by locally coupled self-sustained oscillators. The model is composed of 10,000 oscillators, arranged in a square array. Coupling between oscillators and standard deviation of (randomly determined) intrinsic oscillator periods were varied. A stable overall rhythm emerged. The model behavior was investigated for phase shifts of a 24-h zeitgeber cycle. Prolongation of either the dark or the light phase resulted in a lengthening of the period, whereas shortening of the dark or the light phase shortened the period. The model's response to shifts in the light-dark cycle was dependent only on the extent of the shift and was insensitive to changes in parameters. Phase response curves (PRC) and amplitude response curves were determined for single and triple 5-h light pulses (1000 lux). Single pulses lead to type 1 PRCs with larger phase shifts for weak coupling. Triple pulses generally evoked type 1 PRCs with the exception of weak coupling, where a type 0 PRC was observed.

Algorithms↗
PubMed1989

M phase-promoting factor: its identification as the M phase-specific H1 histone kinase and its activation by dephosphorylation.

A major protein kinase independent of Ca2+, cyclic nucleotide or diacylglycerol, the activity of which becomes maximal when cells enter M phase, decreases at ana-telophase, and is low during interphase, has been purified to near homogeneity from starfish oocytes and its catalytic subunit identified as p34cdc2. M phase-promoting factor (MPF) was found to co-purify with the M phase-specific kinase throughout its purification. p34cdc2 does not have to be associated with any specific protein for expression of H1 histone kinase or MPF activities. When p34cdc2 is phosphorylated its protein kinase activity is inhibited, preventing entry into M phase, but once p34cdc2 becomes dephosphorylated, its protein kinase activity increases and M phase is initiated. A second peak of MPF activity was separated from p34cdc2 in the ammonium sulfate fraction treated with ATP-gamma-S. It induced p34cdc2 dephosphorylation and the concomitant stimulation of its kinase activity when injected in Xenopus or starfish oocytes.

Adenosine Triphosphate↗
PubMed2002

Glycerol and NEFA kinetics in long-term fasting king penguins: phase II versus phase III.

In spontaneously fasting birds such as penguins, below a body mass threshold corresponding to the phase II-phase III transition, a metabolic and hormonal shift occurs and feeding behaviour is stimulated ('refeeding signal'). The major aim of this study was to determine whether a decrease in non-esterified fatty acid (NEFA) release from adipose tissue could be a component of this signal. Lipolytic fluxes and primary triacylglycerol:fatty acid (TAG:FA) cycling were determined in vivo in breeding, fasting king penguins (Aptenodytes patagonicus) using continuous infusions of 2-[3H]glycerol and 1-[14C]palmitate under field conditions. In phase II (after approximately 8 days of fasting, large fat stores, body protein spared, N=8), the rate of appearance (R(a)) of glycerol and of NEFA were 5.7+/-0.8 and 10.5+/-0.4 micromol kg(-1) min(-1), respectively, and the percentage of primary TAG:FA cycling was 41+/-7%. In phase III (after approximately 25 days of fasting, fat stores reduced by fourfold, increased body protein catabolism, N=9), R(a) glycerol kg(-1) body mass remained unchanged, whereas R(a) glycerol kg(-1) fat mass and R(a) NEFA kg(-1) body mass were increased by 2.8-fold and 1.5-fold, respectively. Increased R(a) glycerol kg(-1) fat mass was possibly the result of a 3.5-fold increase in circulating glucagon, the increased R(a) NEFA kg(-1) body mass being attributable to decreased primary TAG:FA cycling. Thus, triggering of the refeeding signal that redirects the behavior of fasting, incubating penguins from incubation towards the search for food after entrance into phase III cannot be ascribed to a reduction in lipolytic fluxes and NEFA availability.

Animals↗
PubMed2006

Homogenized Fourier transform holographic data storage using phase spatial light modulators and methods for recovery of data from the phase image.

We present a method for homogenizing the Fourier spectrum for holographic digital data storage by use of a phase spatial light modulator (SLM), and methods for the recovery of data from a phase image are implemented and discussed. Binary digital data are displayed on a phase SLM operating in 0 and pi phase modes to optimally remove the intense dc peak so as to obtain a homogenized Fourier spectrum. Methods based on holographic interferometry have been developed and employed for recovery of the original amplitude data page from the phase-data page. A new edge-detection-based method also has been demonstrated and analyzed for reconstruction of the original data. Experimental results are presented to confirm the feasibility of these novel techniques.

Journal Article↗
PubMed2006

Measurement of the terahertz-induced phase shift in electro-optic sampling for an arbitrary biasing phase.

We present a simple method to correct for nonlinearities in the detection of terahertz (THz) transients by electro-optic sampling. The THz-induced phase shift of the optical probe beam is calibrated with an additional biasing phase from a variable wave plate. All the parameters that are needed for the determination of this phase shift can be directly measured, which makes the method insensitive to errors resulting from residual birefringences of the electro-optic material or imperfections of the wave plate. We show that the THz-induced phase shift is correctly revealed for a wide range of the biasing phase.

Journal Article↗
PubMed2003

Reduction of soliton phase jitter by in-line phase conjugation.

The main impairment of differential-phase-shift-keyed communication systems is phase jitter. Noise-induced phase jitter, which is mediated by self-phase modulation, can be reduced significantly by a small number of in-line phase conjugators.

Journal Article↗
PubMed2003

Phase-shifting windowed Fourier ridges for determination of phase derivatives.

Determination of the phase or phase derivative from interferometric fringe patterns is an important task in optical interferometry. The use of wavelet ridges was recently shown to be an effective method for phase retrieval from a single fringe pattern. One necessary requirement in this method is the need for carrier frequency. In cases when carrier frequency is not available, the novel phase-shifting windowed Fourier ridges method can be used. Phase derivatives with the proper sign can be directly retrieved even in the presence of noise. An application for curvature determination from speckle shearographic fringes demonstrates the effectiveness of the method.

Journal Article↗
PubMed2004

Phase modulation by polarization recording in bacteriorhodopsin: application to phase-shifting interferometry.

A novel phase-control method with application to phase-shifting interferometry is presented. The linear polarization state of an external (green) light beam is recorded on a bacteriorhodopsin film, and this polarization state is read by a circular polarized (red) laser beam. By reading the bacteriorhodopsin film, the original (red) wave reverses its circularity and becomes phase shifted by an amount that is dependent on the polarization of the external (green) beam. This method of phase control can be applied in a two-beam interferometer in which the test and reference waves are orthogonally polarized, which allows one to obtain phase modulation without moving parts inside the interferometer.

Journal Article↗
PubMed2004

Advanced iterative algorithm for phase extraction of randomly phase-shifted interferograms.

An advanced random phase-shifting algorithm to extract phase distributions from randomly phase-shifted interferograms is proposed. The algorithm is based on a least-squares iterative procedure, but it copes with the limitation of the existing iterative algorithms by separating a frame-to-frame iteration from a pixel-to-pixel iteration. The algorithm provides stable convergence and accurate phase extraction with as few as three interferograms, even when the phase shifts are completely random. The algorithm is simple, fast, and fully automatic. A computer simulation is conducted to prove the concept.

Journal Article↗
PubMed1988

Changes in the secretion of LH pulses, FSH and prolactin during the preovulatory phase of the oestrous cycle of the ewe and the influence of treatment with bovine follicular fluid during the luteal phase.

It has previously been shown that treatment of ewes with bovine follicular fluid (bFF) throughout the luteal phase of the oestrous cycle lowers plasma levels of FSH but increases the frequency and amplitude of the pulses of LH. Under these conditions, ovarian follicles grow to a maximum diameter of 2.7 mm and have a reduced capacity to release oestradiol. We have examined the nature of the gonadotrophin signals controlling follicular development in the normally cycling ewe and have investigated the effects of previous exposure to bFF on these signals and the follicular responses to them. Control ewes (n = 7) were injected i.v. with 9 ml bovine serum and treated ewes were injected with 9 ml bFF, twice daily from days 1 to 10 of the luteal phase (day 0 = oestrus). The ewes were injected with prostaglandin analogue on day 11 of the cycle to induce luteolysis and the gonadotrophin patterns were studied in blood sampled from these animals every 10 min for up to 72 h during the subsequent follicular phase. Following luteolysis (and the end of bFF treatment), LH pulse frequency increased rapidly in both groups and reached 1 pulse/h within 6 h. Thereafter, pulse frequency increased marginally and reached 1 pulse/50 min by the onset of the LH surge. This pattern was not affected by previous treatment with bFF. In the control ewes, the amplitude of the LH pulses did not change significantly following luteolysis or at any time during the follicular phase, while the levels of FSH declined slowly until the onset of the surge. In the treated ewes, on the other hand, there was an immediate increase in both LH pulse amplitude and the concentration of FSH immediately after the end of bFF treatment at luteolysis, and they remained above control levels for 24 and 16 h respectively. Plasma prolactin levels did not appear to change around the time of luteolysis but showed a marked and significant diurnal rhythm (nadir around noon and peak around midnight) in both groups. The concentrations of prolactin were significantly (P less than 0.001) lower and the preovulatory peak was delayed and reduced in the bFF-treated ewes relative to controls. The onset of oestrus was also significantly (P less than 0.01) delayed by bFF treatment, but the ovulation rates did not differ between the groups. Furthermore, comparisons within or between groups revealed no significant relationships between any of the variables of plasma LH secretion during the follicular phase and the subsequent ovulation rate.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2004

Micro-organic ion-associate phase extraction via in situ fresh phase formation for the preconcentration and determination of di(2-ethylhexyl)phthalate in river water by HPLC.

A high-enrichment method was proposed for the HPLC determination of trace di(2-ethylhexyl)phthalate (DEHP) in environmental water. A micro-organic ion-associate phase (IAP) was formed in situ from an aqueous sample by adding 4-trifluoromethylanilinium ion and dodecylbenzenesulfonate ions. Centrifugation of the solution led to the isolation of a liquid organic phase containing DEHP at the bottom of the centrifuge tube. The volume of the phase formed was less than 30 microL. DEHP was extracted into the IAP quantitatively during phase formation. After discarding the aqueous phase, the ion associate was dissolved with 50 microL of 2-methoxyethanol, and DEHP in the concentrate was determined by HPLC with an ultra-violet (UV) diode-array detector. DEHP in the concentrations range from 0.8 to 78 microg L(-1) was determined with good precision. The recovery tests for DEHP added to some river water were satisfactory. The detection limit of DEHP, defined as 3-times the standard deviation of the blank signals, was 0.07 microg L(-1) (n = 3). The present method is very simple, and was applied to the determination of DEHP in the river water samples collected around Toyama City, Japan.

Chromatography, High Pressure Liquid↗
PubMed2004

Synthesis, characterization of silica gel phases-chemically immobilized-4-aminoantipyrene and applications in the solid phase extraction, preconcentration and potentiometric studies.

Two new 4-aminoantipyrene chemically-immobilized silica gel phases: ii (N,N-donor) and iii (N,O-donor), were synthesized and characterized by IR and surface coverage determination. The latter was accomplished by thermal desorption and metal probe methods, giving 0.300 and 0.312 mmol g(-1) for ii and 0.220 and 0.250 mmol g(-1) for iii. Moreover, potentiometric titration provided a surface coverage of 0.323 mmol g(-1) for ii. The metal capacity values in mmol g(-1) of ii, iii and the active silica gel phase i for a series of di- and trivalent metal ions were determined at pH 1.0 - 6.7. Phase i showed the lowest values, while ii and iii reflected higher affinity toward most of the metal ions. The highest values were 0.300 for Hg(II)-ii and 0.220 mmol g(-1) for Cd(II)-iii. Distribution coefficients (log Kd) were in the range of 3.57 - 4.76 for ii and 2.32 - 3.46 for iii, thus confirming certain selectivity characters of the solid extractors. The application of the phases as solid extractors and preconcentrators for some heavy metal ions is presented. Good percentage extraction and removal of 94 - 98 +/- 4 - 6% of the spiked 1.000 microg ml(-1) of Hg(II), Cd(II), Pb(II), Cu(II) and Zn(II) and good percentage recovery of 94 - 99 +/- 3 - 6% of 50 ng ml(-1) of these ions from tap water samples were obtained. Stability constants of H(I) and Cu(II) with ii for the two-phase mixture at 25 degrees C and I = 0.1 (KCI) were determined potentiometrically. The pKa of ii are 5.6 and 8.4, while the log K values for CuHL and CuL (L = ii) are 6.3 and 5.8, respectively, leading to the determination of several analytical data for Cu(II)-ii.

Journal Article↗
PubMedDate not supplied

Detection of hepatic VX2 tumors in rabbits: comparison of conventional US and phase-inversion harmonic US during the liver-specific late phase of contrast enhancement.

OBJECTIVE: To compare phase-inversion sonography during the liver-specific phase of contrast enhancement using a microbubble contrast agent with conventional B-mode sonography for the detection of VX2 liver tumors. MATERIALS AND METHODS: Twenty-three rabbits, 18 of which had VX2 liver tumor implants, received a bolus injection of 0.6 g of Levovist (200 mg/ml). During the liver-specific phase of this agent, they were evaluated using both conventional sonography and contrast-enhanced phase-inversion harmonic imaging (CEPIHI). Following sacrifice of the animals, pathologic analysis was performed and the reference standard thus obtained. The conspicuity, size and number of the tumors before and after contrast administration, as determined by a sonographer, were compared between the two modes and with the pathologic findings. RESULTS: CE-PIHI demonstrated marked hepatic parenchymal enhancement in all rabbits. For VX2 tumors detected at both conventional US and CE- PIHI, conspicuity was improved by contrast-enhanced PIHI. On examination of gross specimens, 52 VX2 tumors were identified. Conventional US correctly detected 18 of the 52 (34.6%), while PIHI detected 35 (67.3%) (p < 0.05). In particular, conventional US detected only three (8.3%) of the 36 tumors less than 10 mm in diameter, but CE-PIHI detected 19 such tumors (52.8%) (p < 0.05). CONCLUSION: Compared to conventional sonography, PIHI performed during the liver-specific phase after intravenous injection of Levovist is markedly better at detecting VX2 liver tumors.

Animals↗
PubMed1998

The diastolic debate: is it time to discard Korotkoff phase IV in favour of phase V for blood pressure measurements in pregnancy?

Current guidelines recommend using Korotkoff phase IV for measuring diastolic blood pressure in pregnant women. However, phase IV does not approximate "true" blood pressure as closely as phase V, is more difficult to detect, and has limited reproducibility. Many practitioners use phase V despite the guidelines. Universal adoption of phase V would improve the reliability of blood pressure measurements.

Blood Pressure↗
PubMed2000

Neuropeptide Y phase advances the in vitro hamster circadian clock during the subjective day with no effect on phase during the subjective night.

The mammalian daily (circadian) clock is located in the suprachiasmatic nuclei of the hypothalamus. Clock function can be detected by the measurement of the circadian change in spontaneous firing rate of suprachiasmatic nuclei cells in a brain slice preparation in vitro. We investigated the effects of neuropeptide Y on this rhythm of firing rate in hamster suprachiasmatic nuclei neurons. Slices were prepared using standard techniques. On the 1st day in vitro, neuropeptide Y (200 ng/200 nL; 47 pmol) was applied as a microdrop to the suprachiasmatic nuclei region at various times. Spontaneous single-unit firing was measured for 6-12 h on the 2nd day in vitro. Peak firing rate in treated slices was compared with that of untreated control slices to measure phase shifts induced by the peptide. Neuropeptide Y induced phase advances of circa-3h when applied during the subjective day (ZT 2-10) but did not significantly alter phase when applied during the subjective night. The phase shifts to neuropeptide Y in the hamster tissue in vitro are similar in phase dependency and magnitude to shifts measured in vivo.

Animals↗
PubMed1999

Effect of alpha/gamma phase ratio on corrosion behavior of dual-phase stainless steels.

Dual-phase stainless steels have been developed in order to reduce the nickel content, which is potentially responsible to an allergic reaction when these steels are used as medical or dental applications. In this study, two different dual-phase stainless steels (2205 and Z100) were electrochemically tested to evaluate their corrosion resistance in three corrosive solutions (i.e., synthetic saliva, 0.9% NaCl solution, and Ringer solution). Particularly, an attempt was made to correlate the corrosion resistance to a metallographic parameter, which is, in this study, the alpha/gamma phase ratio. It was concluded that (1) type 2205 stainless steel exhibited excellent corrosion resistance in all three corrosion media; however 2205 stainless steel decreases its corrosion resistance by increasing chloride concentration in tested electrolytes from synthetic saliva through 0.9% NaCl solution to Ringer solution. (2) X-ray diffraction analysis indicated that the alpha/gamma phase ratio of 2205 (1.735) was higher than that of Z100 (0.905). As a result, it is suggested that by increasing the alpha/gamma phase ratio the material shows more corrosion-prone behavior when being subjected to a hostile environment containing higher chloride ion concentration.

Chemical Phenomena↗
PubMed2002

Analysis of phospholipids from Coxiella burnetii by fast atom bombardment mass spectrometry. A rapid method for differentiation of virulent phase I and low virulent phase II cells.

Phospholipids extracted from the Coxiella burnetii strain Nine Mile virulent phase I and low-virulent phase II cells were directly analyzed by fast atom bombardment mass spectrometry (FAB-MS). Constant neutral loss (CNL) scanning mass spectra (MS) were acquired to identify various phospholipids within phospholipid classes. Phospholipids from the phase I C. burnetii cells were much more complex than those from the phase II cells. Moreover, in the latter, the absence of phospholipids of the phosphatidylinositol class could be noticed. The results indicate that CNL scanning of phospholipid samples provides a rapid and simple method for identification of the phase state of the bacterium.

Coxiella burnetii↗