Phase Reference Point Research Articles

Diurnal and circadian rhythmicity of the human blood transcriptome overlaps with organ- and tissue-specific expression of a non-human primate

BackgroundTwenty-four-hour rhythmicity in mammalian tissues and organs is driven by local circadian oscillators, systemic factors, the central circadian pacemaker and light-dark cycles. At the physiological level, the neural and endocrine systems synchronise gene expression in peripheral tissues and organs to the 24-h-day cycle, and disruption of such regulation has been shown to lead to pathological conditions. Thus, monitoring rhythmicity in tissues/organs holds promise for circadian medicine; however, most tissues and organs are not easily accessible in humans and alternative approaches to quantify circadian rhythmicity are needed. We investigated the overlap between rhythmic transcripts in human blood and transcripts shown to be rhythmic in 64 tissues/organs of the baboon, how these rhythms are aligned with light-dark cycles and each other, and whether timing of tissue-specific rhythmicity can be predicted from a blood sample.ResultsWe compared rhythmicity in transcriptomic time series collected from humans and baboons using set logic, circular cross-correlation, circular clustering, functional enrichment analyses, and least squares regression. Of the 759 orthologous genes that were rhythmic in human blood, 652 (86%) were also rhythmic in at least one baboon tissue and most of these genes were associated with basic processes such as transcription and protein homeostasis. In total, 109 (17%) of the 652 overlapping rhythmic genes were reported as rhythmic in only one baboon tissue or organ and several of these genes have tissue/organ-specific functions. The timing of human and baboon rhythmic transcripts displayed prominent ‘night’ and ‘day’ clusters, with genes in the dark cluster associated with translation. Alignment between baboon rhythmic transcriptomes and the overlapping human blood transcriptome was significantly closer when light onset, rather than midpoint of light, or end of light period, was used as phase reference point. The timing of overlapping human and baboon rhythmic transcriptomes was significantly correlated in 25 tissue/organs with an average earlier timing of 3.21 h (SD 2.47 h) in human blood.ConclusionsThe human blood transcriptome contains sets of rhythmic genes that overlap with rhythmic genes of tissues/organs in baboon. The rhythmic sets vary across tissues/organs, but the timing of most rhythmic genes is similar in human blood and baboon tissues/organs. These results have implications for development of blood transcriptome-based biomarkers for circadian rhythmicity in tissues and organs.

A new phase efficiency calculation model for optimization of ahat‐fedreflector antenna with arbitrary radius of ring‐shaped phase center

A hat-fed reflector antenna with large radius of ring-shaped phase center (RSPC) is reported in this article. First, a new phase efficiency calculation model (PECM) based on new phase reference point is presented, which can accurately calculate the phase efficiency of a hat-fed with arbitrary radius of RSPC. Second, based on the invented PECM, the hat-fed can be optimized by using cosimulation method of HFSS and MATLAB, high aperture efficiencies are achieved in the whole band. To prove the validity of the new PECM, a hat-fed reflector antenna with large radius of RSPC is designed, manufactured, and measured. The measured results are in good agreement with the simulations. The results show that the developed hat-fed reflector antenna has achieved a VSWR of less than 1.18, the peak realized gain of 43.5 dBi and an aperture efficiency of higher than 67.4% in the entire band from 12.25 to 14.5 GHz.

Mixed Far-Field and Near-Field Source Localization Using a Linear Electromagnetic-Vector-Sensor Array With Gain/Phase Uncertainties

This paper investigates the problem of mixed far-field (FF) and near-field (NF) source localization using a linear electromagnetic-vector-sensor array with gain/phase uncertainties. Firstly, several special fourth-order cumulant matrices are constructed, such that the shift invariance structure in the cumulant domain can be derived to estimate the DOA and polarization angles of each source at two electromagnetic vector sensors (EMVSs). Then, by computing the determinant of the coefficient matrix, the sources types can be classified with the prior knowledge of the number of both the FF and NF sources. On this basis, the range of NF sources and the DOAs of mixed sources at the phase reference point are captured subsequently. Finally, these estimates can be employed to generate the unknown gain/phase errors. Compared to the existing methods, the proposed one exploits both the spatial and polarization information of sources and provides a satisfactory parameters estimation performance under unknown phase/gain responses. Moreover, it does not need to perform any spectral search and not impose restriction on EMVSs placement, as well as realizes a more reasonable classification of the signal types. Simulations are carried out to verify the effectiveness of the proposed method.

Mixed Far-Field and Near-Field Source Localization Using a Linear Tripole Array

This letter presents a novel algorithm for mixed far-field (FF) and near-field (NF) source localization using a linear tripole array. Firstly, several special fourth-order cumulants are constructed, then the shift invariant properties in the cumulant domain are utilized to estimate the parameters of each source at two tripoles with spacing exceeds a half wavelength. On this basis, a matrix equation is derived to classify the sources types and estimate the parameters of mixed sources at the phase reference point. Finally, the obtained locate estimates can be used to disambiguate the cyclically ambiguous estimates to produce the high-accuracy parameters estimation. Compared to the existing methods, the proposed one doesn’t need to know each sensor’s position and not restrict the array configuration to be uniform linear array (ULA). Moreover, it estimates both the spatial and polarization information of mixed sources and provides improved accuracy without any spectral search, as well as realizes a more reasonable classification of the signal types. Numerical simulation results show the effectiveness of the proposed method.

A simple humidity sensor utilizing air-gap as sensing part of the Mach–Zehnder interferometer

A simple high-resolution refractive index (RI) and phase sensor has been demonstrated and the results numerically verified. A free space gap is employed in one arm of a Mach–Zehnder interferometer (MZI) to serve as the sensing mechanism with a physical spacing of 1.4 mm. The propagation constant of transmitted light in the MZI’s gap changes due to the small variation in the ambient RI that will further shift the optical phase of the signal. A free space optical delay line is embedded within the MZI’s other arm to set the phase reference point and compensate for variations in the optical phase difference. The ambient RI is computed by measuring the phase shift in the transmission spectrum A high-resolution sensing of 0.8 pm/%RH corresponds to phase change of 0.012°/%RH has been achieved in 1520 nm.

Mixed Near-Field and Far-Field Sources Localization Based on Uniform Linear Array Partition

Based on the polynomial decomposing method and high-order cumulant technique, a novel localization algorithm for the mixed near-field (NF) and far-field (FF) sources is proposed by using a uniform linear array (ULA). First, the ULA is divided into two sub-arrays, with different phase reference points. Three special fourth-order cumulant matrices are designed to eliminate the range parameters of the NF sources in the steering vectors, which only contain the direction of arrival (DOA) information. Second, based on the ESPRIT algorithm, the DOA of each source at the phase reference point is estimated. Third, with the DOA estimation, the type of the sources is classified by computing its coefficient matrix. Finally, the range parameters of NF sources and the DOAs of FF sources are captured. The proposed algorithm does not require any spectral search, which leads to low computational complexity. Moreover, this algorithm avoids the parameter matching procedure. Numerical experiments are conducted to verify the effectiveness of the proposed algorithm.

Interrelation between the amplitude and length of the 11-year sunspot cycle

Alternative procedures for determining the length (duration) of the 11�year sunspot cycle are con� sidered. For cycles 12-23 it is shown that the cycle and the cycle growth branch latitudinal lengths are much more closely related to the cycle amplitude than similar traditional lengths, if the time when the exponent, describing the average sunspot latitude drift, reaches the "reference" latitude value (the latitude phase refer� ence time) is selected as a cycle starting time. Two relationships are obtained. The first relationship makes it possible to rather accurately determine the cycle amplitude based on information about two cycle time intervals: the shift in the latitude phase reference point and the cycle latitudinal length. The second relationship relates the value of the interval between the above exponents of adjacent cycles to the cycle amplitudes. The found relationships between the important amplitude, latitude, and time parameters of the 11�year solar magnetic cycle should be taken into account in the construction of adequate physical models.

Calculation of Antenna Radiation Center Using Angular Momentum

An algorithm to compute the radiation center of an antenna, using the Spherical wave expansion (SWE) of the far field or the far field directly, is introduced. The method is based on the angular momentum that is uniquely defined for any antenna far field pattern. The radiation center is defined as the phase reference point where the angular momentum is minimized and corresponds to minimizing the phase variations in the antenna far field pattern. In addition, this approach also allows for determination of the current distribution axis.

Phase Shift Analysis and Phase Identification for Distribution System with 3-Phase Unbalanced Constant Current Loads

Power grids are large complicated networks in use around. An absolute phase value for a particular unknown-phase line at a local site should be identified for the operation and management of a 3-phase distribution network. The phase shift for a specific point in the line, as compared with a phase reference point at a substation, must be within a range of ± 60 o for correct identification. However, the phase shift at a particular point can fluctuate depending on the line constants, transformer wiring method, line length, and line amperage, etc. Conducted in this study is a theoretical formulation for the determination of phase at a specific point in the line, Simulink modeling, and analysis for a distribution network. In particular, through evaluating the effects of unbalanced current loads, the limitations of the present phase identification methods are described.

3상 불평형 정전류 부하 조건에서의 동 위상 판별에 대한 분석 및 한계에 관한 연구

In this paper, the necessity for the identification of the absolute phase value is introduced and analyzed for a particular conductor line of a 3-phase type distribution network and the recent methods are also introduced. For the determination of the exact phase value for a specific point in the line, as compared with the phase reference point, the measured phase value must be within a range of ±60[°]. However, the phase of a particular point can fluctuate depending on the line constant, transformer wiring method, line length, line amperage, etc. A theoretical formulation such as Simulink modeling and analysis for a distribution network are conducted for the identification of phase at a specific point in the line. In particular, through evaluating the effects of unbalanced current loads at the time of determination of the phase value, the limitations of the present method for the determination of phases is described.

Twelve‐hour days in the brain and behavior of split hamsters

Hamsters will spontaneously 'split' and exhibit two rest-activity cycles each day when housed in constant light (LL). The suprachiasmatic nucleus (SCN) is the locus of a brain clock organizing circadian rhythmicity. In split hamsters, the right and left SCN oscillate 12 h out of phase with each other, and the twice-daily locomotor bouts alternately correspond to one or the other. This unique configuration of the circadian system is useful for investigation of SCN communication to efferent targets. To track phase and period in the SCN and its targets, we measured wheel-running and FOS expression in the brains of split and unsplit hamsters housed in LL or light-dark cycles. The amount and duration of activity before splitting were correlated with latency to split, suggesting behavioral feedback to circadian organization. LL induced a robust rhythm in the SCN core, regardless of splitting. The split hamsters' SCN exhibited 24-h rhythms of FOS that cycled in antiphase between left and right sides and between core and shell subregions. In contrast, the medial preoptic area, paraventricular nucleus of the hypothalamus, dorsomedial hypothalamus and orexin-A neurons all exhibited 12-h rhythms of FOS expression, in-phase between hemispheres, with some detectable right-left differences in amplitude. Importantly, in all conditions studied, the onset of FOS expression in targets occurred at a common phase reference point of the SCN oscillation, suggesting that each SCN may signal these targets once daily. Finally, the transduction of 24-h SCN rhythms to 12-h extra-SCN rhythms indicates that each SCN signals both ipsilateral and contralateral targets.

Dichotomy in human population based on variability in peak spread of rest – activity rhythm in respect of internal phase reference point

The present study was aimed at ascertaining the best reference point for the peak in rest – activity rhythm in a group of apparently healthy randomly chosen young university students consisting of nine males and seven females. The rest – activity was monitored by using an actiwatch (AW64, Mini Mitter Co. Inc., USA) at one-minute epoch length. Data were analyzed with the help of Actiware sleep software, Cosinor rhythmometry, SPSS software and Excel Analysis Toolpak. A statistically significant circadian rhythm in rest – activity was documented in all subjects, irrespective of gender. Further, the subjects were divided into two groups depending upon the variability in their computed peaks determined with reference to the conventional mid-night, start-sleep, mid-sleep and end-sleep timings. The peak spread in each case and in each subject was computed. Results indicate that mid-sleep and end-sleep timings produce peak spreads that are considerably shorter than the conventional phase reference timing, i.e., local mid-night. Thereafter, two distinct groups, namely “mid-sleep group” (MSG) with the least peak spread when the mid-sleep timing was taken as phase reference and “non-mid-sleep group” (NMSG) with the least peak spread when either start-sleep or end-sleep timing was taken as phase reference, were identified. Further a statistically highly significant difference between amplitudes in MSG and NMSG (p < 0.01) was obtained. A negative relationship was obtained between fragmentation index and amplitude in NMSG (r = −0.756). We have a hunch that there could be a phenotypical variation among the human population with respect to the mechanism of phase resetting. Furthermore, the amplitude could be a significant predictor of fragmentation index in the model that we fitted to elucidate an inverse relationship between them.

Assignment of an essential role for the Neurospora frequency gene in circadian entrainment to temperature cycles

Circadian systems include slave oscillators and central pacemakers, and the cores of eukaryotic circadian clocks described to date are composed of transcription and translation feedback loops (TTFLs). In the model system Neurospora, normal circadian rhythmicity requires a TTFL in which a White Collar complex (WCC) activates expression of the frequency (frq) gene, and the FRQ protein feeds back to attenuate that activation. To further test the centrality of this TTFL to the circadian mechanism in Neurospora, we used low-amplitude temperature cycles to compare WT and frq-null strains under conditions in which a banding rhythm was elicited. WT cultures were entrained to these temperature cycles. Unlike those normal strains, however, frq-null mutants did not truly entrain to the same cycles. Their peaks and troughs always occurred in the cold and warm periods, respectively, strongly suggesting that the rhythm in Neurospora lacking frq function simply is driven by the temperature cycles. Previous reports suggested that a FRQ-less oscillator (FLO) could be entrained to temperature cycles, rather than being driven, and speculated that the FLO was the underlying circadian-rhythm generator. These inferences appear to derive from the use of a phase reference point affected by both the changing waveform and the phase of the oscillation. Examination of several other phase markers as well as results of additional experimental tests indicate that the FLO is, at best, a slave oscillator to the TTFL, which underlies circadian rhythm generation in Neurospora.

A Simple Approach for the Computation of Multiple Periodicities in Biological Time Series

We have described a simple approach for the analysis and isolation of multiple periodicities from a biological time series. For the estimation of the periodicities, we used simulated data and data from ongoing experiments in our laboratory. Two time series were simulated, one which consisted of only white noise and the other consisted white noise along with periodicities of 6, 11, 17 and 23 h, to demonstrate that our method can successfully isolate multiple patterns in a time series. Our method of analysis is objective, simple, flexible and adaptive since it distinctly delineates the individual contribution from an overlap of multiple periodicities. The key features of our method are: (i) identification of a reliable phase reference point, (ii) scanning the time series using a moving window in increments, (iii) use of Siegel's modification of Fisher's method to detect significant periodicit(y)ies in the time series. The use of window sizes of increasing length to examine the time series elegantly reduces noise while identifying periodicities that are otherwise not apparent. Finally, the periodogram can be smoothed in order to normalize the contribution by attendant frequency components within the waveform. A minimum critical value for relative contribution of various frequencies was calculated to delineate the periodicities that contributed significantly to the time series. We executed this method of time series analysis using MS Excel and C.

VLBI observation of OH masers in G 45.07+0.13

Both the left-and right-handed circularly polarized radiations of the masers in the ultra-compact hydrogen II region G45.07+0.13, due to the transition from the OH ground state 2II 3 2 , J = 3 2 , F = 1 → 1, have been observed with the US VLBI array. using the multiplepoint fringe rate method, we have constructed the map of the maser structure with a relative position accuracy of 20 mas. With the fringe rate of the calibration source and that of the maser component with a velocity of 56.7 km s −1, taken to be the phase reference point, the absolute position of the phase reference point has been calculated as given by α (1950.0) = 19 h11 m00.46 s, δ(1950.0) = 10°45′ 43.2″. We have found that most maser components are located in the front of the comet-shaped HII region and that their distance to the center of hydrogen II region is approximately 0.4″. This agrees well with the distance from the vertex of the parabolic ionization wavefront to the young celestial body, as estimated with the bow shock model. By use of the tube-shaped model and under the assumption of fully saturated radiation, the number density of the hydrogen molecules in maser regions has been derived to be 4.5×10 8cm −3. Such high density regions are very possibly the thick clouds of neutral molecules swept up by shock waves and are located in the front side of ionization wavefront. In this maser active region a pair of Zeemansplit lines have been found and from the difference of their radial velocities a magnetic field of 3 mG has been inferred. Its direction is away from the Earth. Similar to the observation of G34.3±0.2, the diameter of the maser cluster near the compact hydrogen II region has the order of magnitude of 10 16 cm. This is 50 times larger than the thickness of a neutral gas layer possibly swept up by shock waves. It is still not clear how this can be explained.

Per mRNA cycling is locked to lights-off under photoperiodic conditions that support circadian feedback loop function.

Circadian fluctuations in per mRNA and protein are central to the operation of a negative feedback loop that is necessary for setting the free-running period and for entraining the circadian oscillator to light-dark cycles. In this study, per mRNA cycling and locomotor activity rhythms were measured under different light and dark cycling regimes to determine how photoperiods affect the molecular feedback loop and circadian behavior, respectively. These experiments reveal that per mRNA peaks in abundance 4 h after lights-off in photoperiods of < or = 16 h, that, phase shifts in per mRNA cycling and behavioral rhythmicity occur rapidly after flies are transferred from one photoperiod to another, and that photoperiods longer than 20 h abolish locomotor activity rhythms and leave per mRNA at a median constitutive level. These results indicate that the per feedback loop uses lights-off as a phase reference point and suggest (along with previous findings for per01 and tim01) that per mRNA cycling is not regulated via simple negative feedback from the per protein.

画像磁気記録再生系におけるＦＭ信号の伝達特性の測定

A new measurement scheme for transfer characteristics using FM signals is proposed for the magnetic recording system of a VCR. The modulating signal of the FM signal is sinusoidal. The transfer characteristics are calculated from the complex frequency spectra of the FM signals before recording and after playback. A few cycles of an unmodulated FM carrier signal are added before the modulated FM signal as a phase reference signal. Several methods are introduced to reduce the influences of the phase reference point, jitter, and skew, and the transfer characteristics of an S-VHS VCR are measured. The experimental results show that the phase characteristic is approximately linear, and varies very little with the recording level. The amplitude characteristic is very nearly an odd function of the frequency centered at the carrier frequency, and it varies with the recording level, especially in the uppersideband.

Temperature‐compensated ultradian rhythms in lower eukaryotes: Periodic turnover coupled to a timer for cell division

Abstract During the cell cycles of synchronous cultures of several different yeasts and protozoa, oscillations in the rate of respiration and of total cellular protein content have been demonstrated. Energy supply (from mitochondrial oxidative phosphorlation) and energy demand (biosynthetic reactions, especially protein accumulation) are closely coupled oscillating systems. Phase correspondence between O2 consumption rates, intracellular ADP pool size, and total cellular protein indicates that it is energetic demand that determines mitochondrial activity (respiratory control in vivo). The dynamics of the coupled oscillators indicate that the rate‐determining control circuit operates on a time scale expected of epigenetic reactions (transcription and translation). Thus the energy‐yielding reactions are enslaved to the slower time constants of biosynthesis. Temperature compensation indicates a timing function, and a common phase reference point makes subcycles commensurate with the cell cycle. It is suggest...

Response of the Rhythmic Leaf Movements of Soybean (Glycine max L. Merr) to the Light Intensity of Light/Dark Cycles

The rhythmic (circadian) leaf movements of soybean were entrained to various light/dark cycles. The phase relation of the rhythm to light/dark cycles varied depending on the light/dark schedules. The light intensity in the light periods, however, had no effect on the phase relation although the light intensity in continuous light schedules had a strong effect on the free-running period. Leaf movements also were controlled by a non-circadian factor which occasionally affect the lowest leaf position that is usually taken as a phase reference point of rhythmic leaf movement.

Phase theory of radiation pattern

The conventional requirements on the antenna are reviewed. The importance of the phase pattern of the antenna in modern science and technology is pointed out. Under such a background, the problems concerning the phase characteristic of the radiation pattern and the current distribution of the antenna aperture are attempted to be systematized on the basis of previous works, namely, the phase reference point, the transformation of the radiation patterns corresponding to different phase reference points of an antenna, the null level and the phase difference between the adjacent lobes, and the resolution of current distribution of a linear source, are summarized and discussed. The general condition of the equiphase lobe and the condition of the symmetric lobe of a linear source are proposed and proved theoretically. Some theorems are proposed by induction from the above and the overall discussion is termed the phase theory of radiation pattern.