Main Oscillator Research Articles

Time-modulated inerters as building blocks for nonreciprocal mechanical devices

In this work, we discuss the realization of mechanical devices with non-reciprocal attributes enabled by inertia-amplifying, time-modulated mechanisms. Our fundamental building-block features a mass, connected to a fixed ground through a spring and to a moving base through a mechanism-based inerter. Through analytical derivations and numerical simulations, we provide details on the nonlinear dynamics of such system. We demonstrate that providing a time modulation to the inerter’s base produces two additions on the dynamics of the main spring–mass oscillator: (i) an effective time-modulated mass term, and (ii) a time varying force term; both quantities are functions of the modulating frequency. With specific choices of parameters, the modulation-induced force term – that represents one of the main drawbacks in most experimental realizations of purely time-modulated systems – vanishes and we are left with an effective time-varying mass. We then illustrate that this building block can be leveraged to realize non-reciprocal wave manipulation devices, and concentrate on a non-reciprocal beam-like waveguide. The simple design and the clean performance of our system makes it an attractive candidate for the realization of fully mechanical non-reciprocal devices.

Circadian influence on neurons of the substantia nigra

Circadian rhythms, such as body temperature, hormone secretion, sleep/wake, and activity/rest, are generated by the oscillation of the clock genes in the cells of the suprachiasmatic nucleus, thus considered the main circadian oscillator. Dopamine, whose synthesis occurs in centers such as the substantia nigra pars compacta (SNc) can influence autonomic oscillation. Dopamine can modulate the expression of clock genes; meanwhile, the presence of clock genes in this area could indicate a cyclic mechanism in dopamine-producing cells. Although the involvement of SNc in motor and non-motor functions is well known, the role of the circadian system in this region is not clear. In this study, we investigated the presence of Per1, Per2, and Cry1 in dopaminergic neurons of the SNc. Per1, Per2, and Cry1 imunorreactivity were analyzed at specific times of the light-dark phase by immunohistochemistry technique in a diurnal primate. The mapping performed by immunohistochemistry showed expressive Per1-IR with predominance during daytime. The Per2-IR and Cry1-IR were similar between the light and dark times analyzed. These results reinforce the presence of proteins that regulate circadian rhythms in the SNc, an important dopaminergic source.

High-Power, Narrow-Linewidth, Continuous-Wave, Thulium-Doped Fiber Laser Based on MOPA

A high-power, narrow-linewidth, continuous-wave, thulium-doped fiber laser (TDFL) based on a master-oscillator power-amplifier (MOPA) was experimentally demonstrated. The main oscillator (seed source) yielded 0.64 W of narrow-linewidth laser output at a central wavelength of 1940.32 nm and a 3 dB spectral bandwidth of 0.05 nm. The output narrow-linewidth laser from the main oscillator was amplified by two-stage, cladding-pumped, thulium-doped, all-fiber amplifiers. The main amplifier yielded 26 W of narrow-linewidth laser at a central wavelength of 1940.33 nm. The slope efficiency of the main amplifier was approximately 55.6%. Significant residual pumping light component in the output laser was not observed. During the amplification process, no stimulated Brillouin scattering (SBS) effect, strong amplified spontaneous emission (ASE) effect, and parasitic lasers were observed at the reverse monitoring end. Moreover, the output power was only limited by the incident pump power and the output power had a good stability in a 50 min monitoring period.

Frequency Source Design of Fast Locking Laser Range Radar

Given the bad ranging precision in continuous wave laser range radar systems because of the large jitter of the main oscillator frequency source, this paper introduces the fast locking method, which is based on Field Programmable Gate Array (FPGA) and modified mixed Charge Pump Phase Locked Loop (CPPLL), effectively improving the locking time of PLL frequency source. The input frequency is generated by a temperature compensation quartz crystal oscillator with high stability frequency (TCXO). It improves the PLL performance using the two-order active filter, reduces the phase detector dead-banding, and improves the frequency stability through the buffer insertion in PFD. The traditional PLL was improved by using preset voltage mode, which improves the PLL lock time. Finally, it analyzes the influence of frequency stability on the ranging accuracy of laser radar. The test results show that PLL lock time is up to 1.6ms. It can be applied to continuous wave laser radar ranging systems.

Effect of Prenatal Glucocorticoid Exposure on Circadian Rhythm Gene Expression in the Brains of Adult Rat Offspring.

Circadian clocks control many vital aspects of physiology from the sleep-wake cycle to metabolism. The circadian clock operates through transcriptional-translational feedback loops. The normal circadian signaling relies on a ‘master clock’, located in the suprachiasmatic nucleus (SCN), which synchronizes peripheral oscillators. Glucocorticoid receptor (GR) signaling has the ability to reset the phase of peripheral clocks. It has been shown that maternal exposure to glucocorticoids (GCs) can lead to modification of hypothalamic-pituitary-adrenal (HPA) function, impact stress-related behaviors, and result in a hypertensive state via GR activation. We previously demonstrated altered circadian rhythm signaling in the adrenal glands of offspring exposed to the synthetic GC, dexamethasone (Dex). Results from the current study show that prenatal exposure to Dex affects circadian rhythm gene expression in a brain region-specific and a sex-specific manner within molecular oscillators of the amygdala, hippocampus, paraventricular nucleus, and prefrontal cortex, as well as the main oscillator in the SCN. Results also show that spontaneously hypertensive rats (SHR) exhibited dysregulated circadian rhythm gene expression in these same brain regions compared with normotensive Wistar-Kyoto rats (WKY), although the pattern of dysregulation was markedly different from that seen in adult offspring prenatally exposed to GCs.

5 kW oscillating-amplifying integrated fiber laser with high reliability

We demonstrated a novel fiber laser system with oscillating-amplifying integrated configuration and a 5 kW output power was achieved experimentally for the first time with optical-to-optical efficiency of 80%. The reliability and the boot order of the laser system were studied intensively at high power level. When the laser system is deliberately turn on in a wrong order, such as the pump of the amplifying section is switched on before the oscillating section, or the pump of the oscillating section is switched off before the amplifying section, which is normally a disaster in a classic main oscillator power amplifier (MOPA) system, the laser system can trouble-free operate at full power level. For the first time, it is verified that there is no priority between the amplifier and the seed in the oscillating-amplifying integrated fiber laser system.

5 kW monolithic fiber amplifier employing homemade spindle-shaped ytterbium-doped fiber.

We have demonstrated a 5 kW high-power monolithic fiber amplifier employing a homemade spindle-shaped ytterbium-doped fiber (YDF) based on the main oscillator power amplifier configuration. The YDF consists of a spindle-shaped core and cladding along the fiber length, with a core/cladding diameter of 27/410 µm at both ends and 39.5/600 µm in the middle. An output power of over 5 kW and beam quality of about 1.9 and an optical-to-optical conversion efficiency of 66.6% were achieved in the amplifier under a bidirectional pump scheme. While operating at the maximum power, the laser performance was evaluated, and the transverse mode instability and stimulated Raman scattering effects were well mitigated. To the best of our knowledge, this is the highest power demonstration in a continuous-wave fiber laser employing a tapered fiber. Further power scaling is promising by optimizing the structure of the YDF.

5 kW all-fiber amplifier based on homemade spindle-shaped Yb-doped fiber

To enhance the thresholds of both stimulated Raman scattering and transverse mode instability, we proposed a novel active Yb-doped fiber with a spindle-shaped core and inner-cladding. An all-fiber main oscillator power amplifier (MOPA) was experimentally established based on this homemade fiber. A maximum power of 5 kW was achieved with the optical-to-optical efficiency of 66.6%, Raman-suppression ratio of ＞45 dB and M2 factor of about 2.0. We believe that the brightness and the efficiency of the laser can be improved by optimizing the structure of the Yb-doped fiber.

An effective heterogeneous whole-heart mathematical model of cardiac induction system with heart rate variability.

The main objective of this research work is to develop an effective mathematical model of cardiac conduction system using a heterogeneous whole-heart model. The model is in the form of a system of modified Van der Pol and FitzHugh-Nagumo differential equations capable of describing the heart dynamics. The proposed model extends the range of normal and pathological electrocardiogram (ECG) waveforms that can be generated by the model. The effects of the respiratory sinus arrhythmia (RSA) and the Mayer waves (MW) are both incorporated to modulate the intrinsic frequency of the main oscillator that represents the sinoatrial node. Also, three pathological conditions are incorporated into the model. The heart rate variability (HRV) phenomenon is incorporated into the synthetic ECGs produced which yields valuable information about the cardiovascular health and the performance of the autonomic nervous system. The spectral analysis of the generated RR tachogram delivers power spectrums that resemble those obtained from real recordings. Also, the proposed model generates synthetic ECGs that characteristic the three considered pathological conditions, namely, the tall T wave, the ECG with U wave, and the Wolff-Parkinson-White syndrome. In general, the significance of this research work is in developing a mathematical model that represents the interactions between different pacemakers and allows analysis of cardiac rhythms. To show the effectiveness and the accuracy of the presented model, the results are compared to published results. The proposed model can be a useful tool to study the influences of different physiological conditions on the profile of the ECG. The synthetic ECG signals produced can be used as signal sources for the assessment of diagnostic ECG signal processing devices.

Effect of Prenatal Glucocorticoid Exposure on Circadian Rhythm Gene Expression in the Brains of Adult Rat Offspring

Circadian clocks developed in organisms as a way of estimating the time of day. In mammals, the circadian clock is based on molecular oscillators that operate through transcriptional‐translational feedback loops. While normal circadian signaling relies on a ‘master clock’, in the suprachiasmatic nucleus (SCN), to synchronize peripheral oscillators to environmental light, glucocorticoid receptor (GR) signaling has the ability to reset the phase of peripheral clocks. GR is responsive to cortisol and is central to the regulation of genes involved in stress response, immune regulation and metabolism. Phase shifts allow peripheral clocks to become uncoupled from the master clock. The SCN does not express GR and this ensures it stays tied to the light‐dark cycle. It has been shown that maternal exposure to glucocorticoids (GCs) can lead to modification of hypothalamic‐pituitary‐adrenal (HPA) function and impact stress‐related behaviours via GR activation. While exploring the effects of prenatal GC exposure on rat offspring, our lab previously demonstrated altered circadian rhythm signaling in the adrenal glands using whole transcriptomic profiling. Pregnant WKY rats were given daily subcutaneous injections of 0.1 mg/kg/day DEX (Dexamethasone, a synthetic GC), or a saline vehicle throughout the third semester, and offspring sacrificed at 18 weeks of age for tissue collection. Brain regions were isolated through a micropunch technique and RNA extracted. Results from the current study show that prenatal GC exposure affects circadian rhythm gene expression in the molecular oscillators of the amygdala, hippocampus, prefrontal cortex, paraventricular nucleus as well as the main oscillator in the SCN. Transcripts of circadian rhythm genes in these tissues were measured through RT‐qPCR and demonstrated both sex and tissue specific alteration in expression of circadian genes including Bmal1, Clock, Npas2, as well as the Per and Cry genes. This widespread dysregulation of the circadian rhythm system points to a mechanism whereby the dysfunction seen previously in the adrenal gland arises from a programmed dysregulation of the entire circadian system beginning at the master clock in the SCN.Support or Funding InformationSupported by grants from CIHR and NOSMFA Research Development Fund.

3 kW narrow-linewidth all-fiber amplifier with near diffraction limited beam quality

A theoretical model is established to simulate the stimulated Brillouin scattering (SBS) effect in fiber amplifiers using white noise signal (WNS) phase-modulated seed. Based on the theoretical model, the influences of amplifier structure and cut-off frequency of WNS on SBS threshold are discussed in detail. Through theoretical analysis, optimized amplifier structure and phase modulation signal are achieved to suppress SBS, and a fiber laser based on a main oscillator power amplifier with counter-pumped scheme is established. The oscillator, with 3 dB spectral linewidth of 48 GHz, is produced by a WNS phase-modulated single-frequency seed. The amplifier uses a 915 nm diode laser pump and 25/400 Yb-doped optical fiber. The output power reaches 3.02 kW at 1064 nm, with 3 dB root-mean-square linewidth of 48 GHz. Amplified quality is obtained with M, M at maximum power.

Exact density matrix of an oscillator-bath system: Alternative derivation

Starting from a total Lagrangian describing an oscillator-bath system, an alternative derivation of exact quantum propagator is presented. Having the quantum propagator, the exact density matrix, reduced density matrix of the main oscillator and thermal equilibrium fixed point are obtained. The modified quantum propagator is obtained in the generalised case where the main oscillator is under the influence of a classical external force. By introducing auxiliary classical external fields, the generalised quantum propagator or generating functional of position correlation functions is obtained.

V-band Doppler backscattering diagnostic in the TCV tokamak.

A variable configuration V-band heterodyne Doppler back-scattering diagnostic has been recently made operational in the tokamak configuration variable. This article describes the hardware setup options, flexible quasi-optical launcher antenna, data-analysis techniques, and first data. The diagnostic uses a fast arbitrary waveform generator as the main oscillator and commercial vector network analyzer extension modules as the main mm-wave hardware. It allows sweepable single or multi-frequency operation. A flexible quasi-optical launcher antenna allows 3D poloidal (10°-58°) and toroidal (-180° to 180°) steering of the beam with 0.2° accuracy. A pair of fast HE11 miter-bend polarizers allow flexible coupling to either O or X mode and programmable polarization changes during the shot. These have been used to measure the magnetic-field pitch angle in the edge of the plasma by monitoring the backscattered signal power. Ray-tracing simulations reveal an available k⊥ range between 3 and 16 cm-1 with a resolution of 2-4 cm-1. Perpendicular rotation velocity estimates compare well against ExB plasma poloidal rotation estimates from charge exchange recombination spectroscopy.

Principal process analysis of biological models

BackgroundUnderstanding the dynamical behaviour of biological systems is challenged by their large number of components and interactions. While efforts have been made in this direction to reduce model complexity, they often prove insufficient to grasp which and when model processes play a crucial role. Answering these questions is fundamental to unravel the functioning of living organisms.ResultsWe design a method for dealing with model complexity, based on the analysis of dynamical models by means of Principal Process Analysis. We apply the method to a well-known model of circadian rhythms in mammals. The knowledge of the system trajectories allows us to decompose the system dynamics into processes that are active or inactive with respect to a certain threshold value. Process activities are graphically represented by Boolean and Dynamical Process Maps. We detect model processes that are always inactive, or inactive on some time interval. Eliminating these processes reduces the complex dynamics of the original model to the much simpler dynamics of the core processes, in a succession of sub-models that are easier to analyse. We quantify by means of global relative errors the extent to which the simplified models reproduce the main features of the original system dynamics and apply global sensitivity analysis to test the influence of model parameters on the errors.ConclusionThe results obtained prove the robustness of the method. The analysis of the sub-model dynamics allows us to identify the source of circadian oscillations. We find that the negative feedback loop involving proteins PER, CRY, CLOCK-BMAL1 is the main oscillator, in agreement with previous modelling and experimental studies. In conclusion, Principal Process Analysis is a simple-to-use method, which constitutes an additional and useful tool for analysing the complex dynamical behaviour of biological systems.

Neuroanatomical details of the lateral neurons of Drosophila melanogaster support their functional role in the circadian system.

Drosophila melanogaster is a long‐standing model organism in the circadian clock research. A major advantage is the relative small number of about 150 neurons, which built the circadian clock in Drosophila. In our recent work, we focused on the neuroanatomical properties of the lateral neurons of the clock network. By applying the multicolor‐labeling technique Flybow we were able to identify the anatomical similarity of the previously described E2 subunit of the evening oscillator of the clock, which is built by the 5th small ventrolateral neuron (5th s‐LNv) and one ITP positive dorsolateral neuron (LNd). These two clock neurons share the same spatial and functional properties. We found both neurons innervating the same brain areas with similar pre‐ and postsynaptic sites in the brain. Here the anatomical findings support their shared function as a main evening oscillator in the clock network like also found in previous studies. A second quite surprising finding addresses the large lateral ventral PDF‐neurons (l‐LNvs). We could show that the four hardly distinguishable l‐LNvs consist of two subgroups with different innervation patterns. While three of the neurons reflect the well‐known branching pattern reproduced by PDF immunohistochemistry, one neuron per brain hemisphere has a distinguished innervation profile and is restricted only to the proximal part of the medulla‐surface. We named this neuron “extra” l‐LNv (l‐LNvx). We suggest the anatomical findings reflect different functional properties of the two l‐LNv subgroups.

Chrono-nutrition and n-3 polyunsaturated fatty acid

Circadian clock system has been widely maintained in many spices from prokaryote to mammals. "Circadian" means "approximately day" in Latin, thus circadian rhythm means about 24 hour rhythms. The earth revolves once every 24 hours, and our circadian system has been developed for adjusting to this 24 hour cycles, to get sun light information for getting their foods or for alive in birds or mammals. We have two different circadian systems so-called main oscillator located in the suprachiasmatic nucleus (SCN) of the hypothalamus, and local oscillator located in the various peripheral organ tissues such as liver, kidney and skeletal muscle. The SCN is directly entrained by light-dark information through retinal-hypothalamic tract, and then organizes local clock in peripheral tissues via many pathways including neural and hormonal functions. On the other hand, peripheral local clocks are entrained by feeding, exercise and stress stimuli through several cell signaling. Foods (protein, carbohydrate, and lipid) are important regulator of circadian clocks in peripheral tissues. Thus, controlling the timing of food consumption and food composition, a concept known as chrononutrition, is one area of active research to aid recovery from many physiological dysfunctions. In this review, we focus on molecular mechanisms of entrainment and the relationships between circadian clock systems and n-3 polyunsaturated fatty acid. We concentrate on experimental data obtained from cells or animals and humans and discuss how these findings translate into clinical research, and we highlight the latest developments in chrononutritional studies.

Circadian clock-dependent increase in salivary IgA secretion modulated by sympathetic receptor activation in mice

The salivary gland is rhythmically controlled by sympathetic nerve activation from the suprachiasmatic nucleus (SCN), which functions as the main oscillator of circadian rhythms. In humans, salivary IgA concentrations reflect circadian rhythmicity, which peak during sleep. However, the mechanisms controlling this rhythmicity are not well understood. Therefore, we examined whether the timing of parasympathetic (pilocarpine) or sympathetic (norepinephrine; NE) activation affects IgA secretion in the saliva. The concentrations of saliva IgA modulated by pilocarpine activation or by a combination of pilocarpine and NE activation were the highest in the middle of the light period, independent of saliva flow rate. The circadian rhythm of IgA secretion was weakened by an SCN lesion and Clock gene mutation, suggesting the importance of the SCN and Clock gene on this rhythm. Adrenoceptor antagonists blocked both NE- and pilocarpine-induced basal secretion of IgA. Dimeric IgA binds to the polymeric immunoglobulin receptor (pIgR) on the basolateral surface of epithelial cells and forms the IgA-pIgR complex. The circadian rhythm of Pigr abundance peaked during the light period, suggesting pIgR expression upon rhythmic secretion of IgA. We speculate that activation of sympathetic nerves during sleep may protect from bacterial access to the epithelial surface through enhanced secretion of IgA.

Experimental study of the novel tuned mass damper with inerter which enables changes of inertance

In this paper we present the experimental verification of the novel tuned mass damper which enables changes of inertance. Characteristic feature of the proposed device is the presence of special type of inerter. This inerter incorporates a continuously variable transmission that enables stepless changes of inertance. Thus, it enables to adjust the parameters of the damping device to the current forcing characteristic. In the paper we present and describe the experimental rig that consists of the massive main oscillator forced kinematically and the prototype of the investigated damper. We perform a series of dedicated experiments to characterize the device and asses its damping efficiency. Moreover, we perform numerical simulations using the simple mathematical model of investigated system. Comparing the numerical results and the experimental data we legitimize the model and demonstrate the capabilities of the investigated tuned mass damper. Presented results prove that the concept of the novel type of tuned mass damper can be realized and enable to confirm its main advantages. Investigated prototype device offers excellent damping efficiency in a wide range of forcing frequencies.

2.36 J, 50 Hz nanosecond pulses from a diode side-pumped Nd:YAG MOPA system

We report on a high-energy high-repetition-rate nanosecond Nd:YAG main oscillator power amplifier (MOPA) system. Maximum output pulse energy of 2.36J with duration of 9.4ns at 50Hz has been achieved. The master oscillator was a LD side-pumped electro-optical Q-switched Nd:YAG rod laser adopting unstable cavity with variable reflectivity mirror (VRM). It delivered a pulse train with energy up to 180mJ and pulse duration of 10.7ns. The near-field pattern demonstrated a nearly super Gaussian flat top profile. In the amplification stage, the pulse was boosted via double-pass two Nd:YAG rod amplifiers. Maximum pulse energy was obtained at the peak pump power of 37.5kW, corresponding to an optical-optical conversion efficiency of 25.2%. The correlative peak power was deduced to be 251MW. We also presented the result of 100Hz nanosecond laser with average output power of >100W.

A 250- $\mu\text{W}$ 2.4-GHz Fast-Lock Fractional-N Frequency Generation for Ultralow-Power Applications

This brief presents a fast-lock 2.4-GHz fractional-N phase-locked loop (PLL) for ultralow-power applications. To minimize the power consumed by all the other circuits except for the main oscillator, we propose a master-slave PLL structure in which a low-frequency master PLL is followed by a slave injection-locked oscillator operating at high frequency. A frequency-error compensation circuit is also implemented in the slave oscillator to eliminate possible drift in the free-running frequency. With a fractional-N coarse-lock unit in the master PLL and a fine frequency initialization unit in the slave oscillator, the PLL supports two fast-lock modes: 1) start-up locking from deep-power-down mode and 2) instantaneous relocking from standby mode. The implemented PLL in 65-nm complementary metal-oxide-semiconductor (CMOS) consumes 250 μW from a 0.8-V supply, demonstrating a power efficiency of 0.102 mW/GHz. The PLL performs the two fast-lock operations with lock times of less than 22 μs from deep power down and 1 μs from standby, respectively.