Clock Phase Research Articles

Vasopressin Resets the Central Circadian Clock in a Manner Influenced by Sex and Vasoactive Intestinal Polypeptide Signaling

Background/Aims: Circadian rhythms in behavior and physiology are programmed by the suprachiasmatic nucleus (SCN) of the hypothalamus. A subset of SCN neurons produce the neuropeptide arginine vasopressin (AVP), but it remains unclear whether AVP signaling influences the SCN clock directly. Methods: Here, we test that AVP signaling acting through V1A and V1B receptors influences molecular rhythms in SCN neurons. V1 receptor agonists were applied ex vivo to PERIOD2::LUCIFERASE SCN slices, allowing for real-time monitoring of changes in molecular clock function. Results: V1A/B agonists reset the phase of the SCN molecular clock in a time-dependent manner, with larger magnitude responses by the female SCN. Further, we found evidence that both G_αq and G_αs signaling pathways interact with V1A/B-induced SCN resetting, and that this response requires vasoactive intestinal polypeptide (VIP) signaling. Conclusions: Collectively, this work indicates that AVP signaling resets SCN molecular rhythms in conjunction with VIP signaling and in a manner influenced by sex. This highlights the utility of studying clock function in both sexes and suggests that signal integration in central clock circuits regulates emergent properties important for the control of daily rhythms in behavior and physiology.

A multi‐frequency method to improve the long‐term estimation of GNSS clock corrections and phase biases

<h3>Abstract</h3> The space segment of the Global Navigation Satellite System (GNSS) is equipped with highly stable atomic clocks. In order to use these clocks as references, their time offsets must be estimated from ground measurements as accurately as possible. This work presents a multi-frequency and multi-constellation method for estimating satellite and receiver clock corrections, starting from unambiguous, uncombined, and undifferenced carrier-phase measurements. A byproduct of the estimation process is phase biases (i.e., the hardware delays of the carrier-phase measurements occurring at receivers and satellites). The stability and predictability of our clock estimates for receivers and satellites (GPS and Galileo) are compared with those obtained by the International GNSS Service (IGS), whereas the phase biases are assessed against two independent determinations involving combinations of carrier-phase measurements. We conclude that the method reduces day boundary discontinuities in the clock corrections, and that the estimated phase biases reproduce variabilities already observed by other authors.

Navigator Notes

Welcome to the Winter 2021 issue of NAVIGATION . In this issue, we feature articles on GNSS interference and monitoring, autonomous orbit determination and timekeeping using X-ray pulsars, and the improvement of GNSS clock corrections and phase biases. We are also featuring articles reporting new

Design and Evaluation of Radiation-Hardened Standard Cell Flip-Flops

Use of a standard non-rad-hard digital cell library in the rad-hard design can be a cost-effective solution for space applications. In this paper we demonstrate how a standard non-rad-hard flip-flop, as one of the most vulnerable digital cells, can be converted into a rad-hard flip-flop without modifying its internal structure. We present five variants of a Triple Modular Redundancy (TMR) flip-flop: baseline TMR flip-flop, latch-based TMR flip-flop, True-Single Phase Clock (TSPC) TMR flip-flop, scannable TMR flip-flop and self-correcting TMR flip-flop. For all variants, the multi-bit upsets have been addressed by applying special placement constraints, while the Single Event Transient (SET) mitigation was achieved through the usage of customized SET filters and selection of optimal inverter sizes for the clock and reset trees. The proposed flip-flop variants feature differing performance, thus enabling to choose the optimal solution for every sensitive node in the circuit, according to the predefined design constraints. Several flip-flop designs have been validated on IHP’s 130nm BiCMOS process, by irradiation of custom-designed shift registers. It has been shown that the proposed TMR flip-flops are robust to soft errors with a threshold Linear Energy Transfer (LET) from ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$32.4\, \frac { {\mathrm { \text {M} \text {eV} }}\cdot {\mathrm { \text {c} \text {m} }}^{2}}{ {\mathrm { \text {m} \text {g} }}}$ </tex-math></inline-formula> ) to ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$62.5\, \frac { {\mathrm { \text {M} \text {eV} }}\cdot {\mathrm { \text {c} \text {m} }}^{2}}{ {\mathrm { \text {m} \text {g} }}}$ </tex-math></inline-formula> ), depending on the variant.

New polarization and power calculations with error elimination in ternary QCA

Quantum cellular automata (QCA) is a promising technology for replacing MOS transistors in digital and computing systems. Recently, many efforts have been made to design complex structures using Binary QCA (bQCA) cells, researchers’ attention has been drawn to multilevel structures using QCA technology, and Ternary QCA (TQCA) cells have been introduced. Many researchers have studied the structure of the TQCA cell, and several models have been proposed to design the AND and OR gates. This paper investigated the polarization in TQCA using two electron particles and eight potential wells. The distance between wells and the cell wall was also changed, and the error in the AND and OR gates was eliminated by using TQCA in one phase clock. In the following calculations, the power dissipation of TQCA cells in different polarizations and the upgrade of TQCA Sim software to implement basic gates using the performed calculations have been investigated.

Inter-satellite laser-ranging based on intradyne coherent detection

With the development of laser communication networking, laser-ranging technology is becoming more and more applicable. In this paper, high-accuracy ranging is implemented based on intradyne coherent detection at a communication rate of 1048.576 Mbps. The ranging accuracy is affected by clock phase calculation error and code loop track error. Parallel clock phase difference calculation, frame head correlation, and ranging ambiguity region handle are combined with the ranging calibration method, realizing millimeter-level corrected distance measurement. Dynamic range measurement above 1 m is proven to be continuous through the ranging ambiguity region handle. In addition, high-precision clock frequency deviation between two asynchronous terminals can be obtained through derivation of one-way distance at static ranging or by derivative of distance difference at bidirectional ranging. The methods proposed in this paper are verified by inter-satellite laser-ranging on orbit, and the results are analyzed.

Spermidine resets circadian clock phase in NIH3T3 cells.

Irregular light-dark cycles desynchronize the circadian clock via hormonal and neuronal pathways and increase the risk of various diseases. This study demonstrated that a single pulse of spermidine-a polyamine-strongly induced circadian phase advances in the presence or absence of dexamethasone (a synthetic glucocorticoid) in NIH3T3 cells transfected with the Bmal1 promotor-driven luciferase reporter gene. The spermidine-induced phase advances were 2-3 fold greater than were the dexamethasone-induced shifts. The phase resetting effect of spermidine occurred in a dose- and time-dependent manner and was not blocked by RU486, an antagonist of glucocorticoid receptors. Spermidine treatment modulated the expression of clock genes within 60 min, which was sooner than changes in the expression of autophagy-related genes. These findings suggested that spermidine is a potent modulator of the circadian phase, acting through glucocorticoid receptor-independent pathways, and may be useful for treating diseases related to circadian desynchrony.

Equalizer State Caching for Fast Data Recovery in Optically-Switched Data Center Networks

Optical switching offers the potential to significantly scale the capacity of data center networks (DCN) with a simultaneous reduction in switching time and power consumption. Previous research has shown that end-to-end switching time, which is the sum of the switch configuration time and the clock and data recovery (CDR) locking time, should be kept within a few nanoseconds for high network throughput. This challenge of low switching time has motivated research into fast optical switches, ultra-fast clock and amplitude recovery techniques. Concurrently, the data rate between server-to-server and server-to-switch interconnect is increasing drastically from the current 100 Gb/s (4 × 25 Gb/s) to 400 Gb/s and beyond, motivating the use of high order formats such as 50-GBaud four-level pulse-amplitude modulation (PAM-4) for signalling. Since PAM-4 is more sensitive to noise and distortion, digital equalizers are generally needed to compensate for impairments such as transceiver frequency roll-off, dispersion and optical filtering, adding additional time for equalizer adaptation and power consumption that are undesired for fast optical switching systems. Here we propose and investigate an equalizer state caching technique that reduces equalizer adaptation time and computation power consumption for fast optical switching systems, underpinning optically-switched DCNs using high baud rate and impairment-sensitive formats. Through a proof-of-concept experiment, we study the performance of the proposed equalizer state caching scheme in a three-node optical switching system using 56 GBaud PAM-4. Our experimental results show that the proposed scheme can tolerate up to ±0.8-nm (±100-GHz) instantaneous wavelength change with an adaptation delay of only 0.36 ns. Practical considerations such as clock phase misalignment, temperature-induced wavelength drift, and equalizer precision are also studied.

Design and Testing of the Front-End Electronics of WCDA in LHAASO

Water Cherenkov detector array (WCDA) is one of the key parts of the Large High Altitude Air Shower Observatory (LHAASO), the construction of which was completed by the end of 2020. The WCDA covers a 78 000-m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> area and there exist 3120 large size photomultiplier tubes (PMTs) in three ponds: 8-in PMTs are used in WCDA pond No. 1 and 20-in PMTs are used in ponds No. 2 and No. 3. The front-end electronics (FEE) system based on multigain measurement technique is designed to achieve both high-precision time and charge measurements over a large dynamic range from single photon electron (S.P.E.) to 4000 P.E. (for water pond No. 1)/1800 P.E. (for water ponds No. 2 and No. 3). To achieve a high-quality clock distribution and phase alignment as well as mixed transmission of data, clock, and commands in one fiber over a long distance, an enhanced white rabbit (WR) technique is used. Testing of all the 350 FEE modules for the WCDA is presented in this article. Test results indicate that the charge resolution is better than 20% at S.P.E. and 1% at 1800/4000 P.E. and the time resolution is better than 300 ps root mean square (rms), which successfully meets the application requirement. All the FEE modules have been fabricated and installed for the LHAASO WCDA from 2018 to 2020, and the initial commissioning operation indicates that the FEEs function well.

Prototype of Clock and Timing Distribution and Synchronization Electronics for SHINE

Shanghai high repetition rate X-ray-free electron laser (XFEL) and extreme light facility (SHINE) has been under construction. It aims at producing X-ray pulses in a photon energy range from 0.4 to 25 keV. To achieve the design goal, SHINE requires precise distribution and synchronization of the clock and timing signals over a long distance of approximately 3.1 km. Based on the standard White Rabbit (WR) protocol, a prototype of a high-precision clock and timing electronics is designed based on a customized clock frequency. Great attention is paid to the design of hardware and field programmable gate array (FPGA) logic to achieve high-precision clock synchronization, fine phase adjustment, and frequency tuning, as well as flexible shaping of timing signals. Test results indicate that the skew jitter of the clock signal is better than 20 ps within the frequency range from around 1 Hz to 1 MHz, and the clock phase delay can be adjusted with a step size of about 500 ps. As for the timing signals, the skew jitter is better than 40 ps rms. Moreover, the temperature drifts of the clock and timing signals are better than 3 ps/°C.

The Sun’s Magnetic (Hale) Cycle and 27 Day Recurrences in the aa Geomagnetic Index

Abstract We construct a new solar cycle phase clock which maps each of the last 18 solar cycles onto a single normalized epoch for the approximately 22 yr Hale (magnetic polarity) cycle, using the Hilbert transform of daily sunspot numbers (SSNs) since 1818. The occurrences of solar maxima show almost no discernible Hale cycle dependence, consistent with the clock being synchronized to polarity reversals. We reengineer the Sargent R27 index and combine it with our epoch analysis to obtain a high time resolution parameter for 27 day recurrence in aa, 〈acv(27)〉. This reveals that the transition to recurrence, that is, to an ordered solar wind dominated by high-speed streams, is fast, with an upper bound of a few solar rotations. It resolves an extended late declining phase which is approximately twice as long on even Schwabe cycles as odd. Galactic cosmic ray flux rises in step with 〈acv(27)〉 but then stays high. Our analysis also identifies a slow-timescale trend in SSN that simply tracks the Gleissberg cycle. We find that this trend is in phase with the slow-timescale trend in the modulus of sunspot latitudes, and in antiphase with that of the R27 index.

Melatonin Adjusts the Phase of Mouse Circadian Clocks in the Cornea Both Ex Vivo and In Vivo.

The presence of an endogenous circadian clock within most mammalian cells is associated with the amazing observation that within a given tissue, these clocks are largely in synchrony with each other. Different tissues use a variety of systemic or environmental cues to precisely coordinate the phase of these clocks. The cornea is a unique tissue in that it is largely isolated from the direct blood supply that most tissues experience, it is transparent to visible light, and it is exposed directly to environmental light and temperature. Melatonin is a hormone that has been implicated in regulation of the cornea's circadian clocks. Here, we analyze the ability of rhythmic melatonin to entrain corneas ex vivo, and analyze the phase of corneal circadian clocks in vivo both in light: dark cycles and in constant darkness. We find that the presence of a retina from a melatonin-proficient mouse strain, C3Sn, can photoentrain the circadian clocks of a co-cultured mouse cornea, but a retina from a melatonin-deficient strain, C57Bl/6, cannot. Furthermore, pharmacologic blockade of melatonin or use of a retina with advanced retinal degeneration, Pde6brd1, blocks the photoentraining effect. Corneal circadian clocks in vivo adopt an advanced phase in C3Sn mice compared with C57Bl/6, but the circadian clocks in the liver are unaffected. This observation is not attributable to a shorter endogenous period of the cornea or behavior between the strains. Some transcripts of circadian genes in the corneas of C3Sn mice also show an advanced phase of expression in a light: dark cycle, while the transcript of Per2 exhibits a light-dependent transient induction at the onset of darkness. We conclude that melatonin acts as a phase modifying factor in a rhythmic manner for the circadian clocks of the cornea.

Effects of Daytime Dry Fasting on Hydration, Glucose Metabolism and Circadian Phase: A Prospective Exploratory Cohort Study in Bahá'í Volunteers

Background: Religiously motivated Bahá'í fasting (BF) is a form of intermittent dry fasting celebrated by abstaining from food and drinks during daylight hours every year in March for 19 consecutive days.Aim: To test the safety and effects of BF on hydration, metabolism, and the circadian clock.Methods: Thirty-four healthy Bahá'í volunteers (15 women) participated in this prospective, exploratory cohort study. Laboratory examinations were carried out in four study visits: before fasting (V0), in the third week of fasting (V1) as well as 3 weeks (V3) and 3 months (V4) after fasting. Data collection included blood and urine samples, anthropometric measurements and bioelectrical impedance analysis. At V0 and V1, 24- and 12-hour urine and serum osmolality were measured. At V0–V2, alterations in the circadian clock phase were monitored in 16 participants. Our study was augmented by an additional survey with 144 healthy Bahá'í volunteers filling out questionnaires and with subgroups attending metabolic measurements (n = 11) and qualitative interviews (n = 13), the results of which will be published separately.Results: Exploratory data analysis revealed that serum osmolality (n = 34, p < 0.001) and 24-hour urine osmolality (n = 34, p = 0.003) decreased during daytime fasting but remained largely within the physiological range and returned to pre-fasting levels during night hours. BMI (body mass index), total body fat mass, and resting metabolic rate decreased during fasting (n = 34, p < 0.001), while body cell mass and body water appeared unchanged. The circadian phase estimated by transcript biomarkers of blood monocytes advanced by 1.1 h (n = 16, p < 0.005) during fasting and returned to pre-fasting values 3 weeks after fasting. Most observed changes were not detectable anymore 3 months after fasting.Conclusions: Results indicate that BF (Bahá'í fasting) is safe, has no negative effects on hydration, can improve fat metabolism and can cause transient phase shifts of circadian rhythms.Trial Registration:https://www.clinicaltrials.gov/, identifier: NCT03443739.

Tree/link method for transfer function and stability analysis of switched‐capacitor circuits

SummaryThe wide spread application of switched‐capacitor circuits has resulted in complex structures wherein the derivation of transfer function in discrete form is not quite straight forward. A computer‐aided tool for direct transfer function analysis of switched‐capacitor circuits using state formulation method is proposed in this paper. The state equation matrices are directly constructed from the circuit topology using tree/link analysis. The entire topology is formulated only using cutset equations to obtain the state matrices without any modifications. The discretized topological state matrices are used to generate the transfer function in z form by forward substitution of state equation in successive clock phase. Lyapunov criteria‐based matrix equation constructed using the same state matrix is used to investigate the circuit stability. The formulation is also suitable in addressing the effect of non‐idealities like switch resistance and finite gain of operational amplifiers, on the location of poles and zeros. Various numerical examples have been presented to demonstrate the performance of the simulator.

A new approach to bypass wire crossing problem in QCA nano technology

PurposeThis study aims to replace current multi-layer and coplanar wire crossing methods in QCA technology to avoid fabrication difficulties caused by them.Design/methodology/approachQuantum-dot cellular automata (QCA) is one of the newly emerging nanoelectronics technology tools that is proposed as a good replacement for complementary metal oxide semiconductor (CMOS) technology. This technology has many challenges, among them being component interconnection and signal routing. This paper will propose a new wire crossing method to enhance layout use in a single layer. The presented method depends on the central cell clock phase to enable two signals to cross over without interference. QCADesigner software is used to simulate a full adder circuit designed with the proposed wire crossing method to be used as a benchmark for further analysis of the presented wire crossing approach. QCAPro software is used for power dissipation analysis of the proposed adder.FindingsA new cost function is presented in this paper to draw attention to the fabrication difficulties of the technology when designing QCA circuits. This function is applied to the selected benchmark circuit, and the results show good performance of the proposed method compared to others. The improvement is around 59, 33 and 75% compared to the best reported multi-layer wire crossing, coplanar wire crossing and logical crossing, respectively. The power dissipation analysis shows that the proposed method does not cause any extra power consumption in the circuit.Originality/valueIn this paper, a new approach is developed to bypass the wire crossing problem in the QCA technique.

Evaluation of multi-level Bang–Bang phase detector with metastability effect using Markov chain

Bang–Bang phase detector (BBPD) as a bistable system has the metastability problem. In addition, BBPD is a non-linear block in the phase locked-loop (PLL) and clock and data recovery (CDR) that makes their analysis complicate. To simplify the analysis of the non-linear BBPD, the linear expression for the gain of multi-level BBPD (ML-BBPD) is derived in this paper by considering the metastability failure. The ML-BBPD gain is developed based on Markov chain to provide more realistic model. Simulation results show that the metastability failure not only attenuates the gain of ML-BBPD for the small input jitter, but also increases the output jitter and consequently the BER of the CDR. It is shown that by increasing the number of sampling clocks the output jitter and BER is reduced. Also, the gain of ML-BBPD is decreased for small values of the input jitter, but for the large values of input jitter ML-BBPD gain is the same for every over sampling ratio.

Wicsync: A wireless multi-node clock synchronization solution based on optimized UWB two-way clock synchronization protocol

The clock synchronization accuracy directly determines the performance of wireless distributed cooperative systems. However, the mature high accuracy wireless clock synchronization schemes are generally based on GNSS or other auxiliary sources to complete the synchronization process, which cannot be applied to GNSS degraded and denied environments. In this paper, a wireless high-accuracy clock synchronization solution for multi-node distributed cooperative systems – Wicsync – is proposed, which contains an optimized wireless two-way clock synchronization and mutual calibration protocol to support wireless multi-node clock synchronization. Based on the UWB synchronization hardware architecture with local clock phase adjustment we designed, Wicsync implements a non GNSS-aided, high-accuracy, multi-node, low cost wireless clock synchronization performance through the protocol. Experiments shows that the Wicsync can support the instantaneous clock synchronization accuracy of less than 3 ns (@75 m at least) for 10 nodes (more than 100 nodes theoretically).

An efficient 70 GHz divide‐by‐4 CMOS frequency divider employing low threshold devices

The idea to use a lower threshold, but slightly slower transistor over the fastest transistor type for large-signal circuits is presented with experimental verification for a compact divide-by-4 true single phase clock (TSPC) frequency divider. The use of the lowest threshold PMOS devices resulted in self-resonance frequencies of 41.7, 56, and 60 GHz at supply voltages of 0.5, 0.8 and 0.9 V, respectively. Compared to a divider of the same architecture in the same technology, but with higher threshold voltage devices, this corresponds to improvements of 67%, 33% and 27%, respectively. Power consumptions of 26 and 355 μW were measured for a 20 GHz and a 70 GHz input signal for supply voltages of 0.5 and 0.9 V, respectively. The best knowledge of the authors, these results are the best reported to date for TSPC divider architecture, and they compete with state of the art for inductorless current-mode logic dividers.

076 Bright light during wakefulness improves objective and subjective sleep quality: a forced desynchrony study

Abstract Introduction Under real life conditions, increased light exposure during wakefulness seems associated with improved sleep quality, quantified as reduced time awake during bed time, increased time spent in non-REM (NREM) sleep or increased power in the EEG delta band (0.5–4 Hz). The causality of these important relationships and their dependency on circadian clock phase and/or time awake has not been studied in depth. To establish causality of light effects during wake time on subsequent sleep, and to disentangle possible circadian and homeostatic interactions, we employed a forced desynchrony (FD) protocol under dim light (6.5 lux) and bright light (1307 lux) during wakefulness. Methods The protocol consisted of a fast cycling sleep-wake schedule (13h wakefulness – 5h sleep; 4 cycles), followed by 3h recovery sleep in a within subject cross-over design. Individuals (7 men) were equipped with 10 polysomnography electrodes. Subjective sleep quality was measured immediately after wakening. Results Results indicated that circadian variation in delta power was only detected under dim light. Circadian variation in time in rapid eye movement (REM) sleep and wakefulness were uninfluenced by light. Prior light exposure increased accumulation of delta power and time in NREM sleep, while decreasing wakefulness, especially during the circadian wake phase. Subjective sleep quality scores showed that participants were only able to assess light induced improvement of sleep quality correctly when the circadian system promoted wakefulness. Conclusion This study presents significant effects of bright light exposure on sleep architecture, leading to sleep pressure related changes in objective sleep quality. At the end of the scheduled sleep phase after increased light exposure, more delta power and NREM sleep were detected, especially when sleep occurred outside the normal sleep phase. Subjective sleep quality scores showed light-induced improvements coinciding with increased delta power and time spend in NREM sleep, suggesting that light during wakefulness may improve subsequent sleep quality. These findings may have important implications for insomnia treatment and clinical applications of light therapy. Support (if any) This research was funded by the University of Groningen Campus Fryslân (Grant No. 01110939; co-financed by Philips Drachten and Provincie Fryslân). Additional financial support was obtained from a NWO-STW Program Grant “OnTime” (project 12185).

Challenges to adopting adiabatic circuits for systems‐on‐a‐chip

Adiabatic complementary metal–oxide–semiconductor (CMOS) circuits have been proposed as a low-power option for CMOS systems-on-a-chip (SoCs) but have not gained popularity due to practical difficulties in scaling to millions of gates. The architecture of a pipeline of stages with slow-transitioning clock phases demands the generation and distribution of clock phases precisely and efficiently. This power must be more than offset by the power saved by using adiabatic circuits. The problems in adiabatic logic circuits are described, and solutions are proposed to address them. Three published topologies are considered, namely positive-feedback adiabatic logic (PFAL), two-level adiabatic logic (2-LAL) and clocked adiabatic logic in 40 nm CMOS technology at 100 MHz. New circuit ideas for complete level restore in PFAL and avoidance of floating nodes in 2-LAL are presented. The problem with 2-LAL multi-input gates is published and solved for the first time here using a modified PFAL. The conclusion is that a 3X power savings in PFAL is about the best that can be achieved in an SoC context—a low return given the required investments in area and complexity. This should motivate the future discovery of more efficient solutions.