Central Oscillator Research Articles

Entrainment within hierarchical circadian oscillator networks

Circadian rhythms are endogenous oscillations, widely found across biological species, that have the capability of entraining to the 24-h light-dark cycle. Circadian systems often consist of both central oscillators that receive direct light-dark input and peripheral oscillators that receive input from the central oscillators. In this paper, we address questions related to what governs the time to and pattern of entrainment of these hierarchical circadian systems after an abrupt switch in the light-dark phasing. For a network consisting of a single central oscillator coupled to a chain of N feed-forward peripheral oscillators, we introduce a systematic way to derive an N-dimensional entrainment map whose fixed points correspond to entrained solutions. Using the map, we explain that the direction of reentrainment can involve fairly complicated phase advancing and delaying behavior as well as reentrainment times that depend sensitively on the nature of the perturbation. We also study the dynamics of a hierarchical system in which the peripheral oscillators are mutually coupled. We study how reentrainment times vary as a function of the degree to which the oscillators are desynchronized at the time of the change in light-dark phasing. We show that desynchronizing the peripheral oscillators can, in some circumstances, speed up their ultimate reentrainment following perturbations.

Study of Brain Circadian Rhythms in Patients with Chronic Disorders of Consciousness and Healthy Individuals Using Microwave Radiometry.

The study of circadian rhythms in the human body using temperature measurements is the most informative way to assess the viability of the body’s rhythm-organizing systems. Pathological processes can affect circadian rhythm dynamics in damaged organs. Severe brain damage that caused the development of disorders of consciousness (DOC) (strokes, traumatic brain injury) disrupts the activity of central oscillators, by directly damaging or destroying the periphery links, and the level of preservation of circadian rhythms and the dynamics of their recovery can be informative diagnostic criteria for patient’s condition assessment. This study examined 23 patients with DOC by using a non-invasive method for obtaining body and cerebral cortex temperature to compare with healthy controls. Measurements were made with a 4 h interval for 52 h beginning at 08:00 on day 1 and ending at 08:00 on day 3. The profile of patients with DOC showed complete disruption compared to healthy controls with rhythmic patterns. The results indicate that the mechanisms for maintaining brain circadian rhythms are different from general homeostasis regulation of the body. Use of microwave radio thermometry for the identification of rehabilitation potential in patients with DOC is a promising area of investigation.

Real-time observation of pulsating solitons with central wavelength oscillation in an ultrafast fiber laser

We present an experimental observation of pulsating solitons with central wavelength oscillation in an ultrafast fiber laser. The spectral features of the solitons are identified by virtue of the dispersive Fourier transform technique. In this pulsating regime, the central wavelength of output solitons exhibits periodic redshift and blueshift, and the positions of their Kelly sidebands oscillate synchronously with the solitons. The corresponding field autocorrelation traces show that the pulse duration changes periodically. In addition, soliton snaking motion is observed in the temporal domain. Depending on the pump level, an intermittent pulsating state is found in the fiber laser operating in a transition regime between pulsating and stationary mode-locking states, where the quasi-stationary and energy-modulated solitons appear alternatively. Our results would stimulate further investigation of the pulsating dynamics in ultrafast fiber lasers.

Automated Training Techniques and Electronics Sensors Role in Cricket: A Review

This paper presents the study about technological involvement in game coaching. Attending multiple players with their performance and accuracy level checking is not feasible for coaches every time. Self-paced training sessions or self-learning methods are invented by different researchers & identify multiple games or the gaming apparatuses for different level automation. Methods used for analysis purpose & described the smart cricket ball & its circuit diagram. Tracking technology that are used in cricket, tennis, Gaelic football, badminton, hurling, rugby union, association football & volleyball, to visually track the trajectory of the ball, Centre of Percussion (COP) in cricket, Accelerometer & Swing angle model. Provides a systematic literature review of smart sport & various methods i.e, SVM, CART, ML, AI, CNN, SVM, ORB, SIFT & SURF. Lastly, future directions of research are proposed in the emerging field of SST.

Scanning gradiometry with a single spin quantum magnetometer

Quantum sensors based on spin defects in diamond have recently enabled detailed imaging of nanoscale magnetic patterns, such as chiral spin textures, two-dimensional ferromagnets, or superconducting vortices, based on a measurement of the static magnetic stray field. Here, we demonstrate a gradiometry technique that significantly enhances the measurement sensitivity of such static fields, leading to new opportunities in the imaging of weakly magnetic systems. Our method relies on the mechanical oscillation of a single nitrogen-vacancy center at the tip of a scanning diamond probe, which up-converts the local spatial gradients into ac magnetic fields enabling the use of sensitive ac quantum protocols. We show that gradiometry provides important advantages over static field imaging: (i) an order-of-magnitude better sensitivity, (ii) a more localized and sharper image, and (iii) a strong suppression of field drifts. We demonstrate the capabilities of gradiometry by imaging the nanotesla fields appearing above topographic defects and atomic steps in an antiferromagnet, direct currents in a graphene device, and para- and diamagnetic metals.

Food, not the photoperiod, entrains the circadian rhythms in the liver of Winstar albino rats

The central oscillator is located in mammals' suprachiasmatic nucleus (SCN). The liver is the non-photic organ and the centre for metabolic activities. Food could be a potential zeitgeber for the liver as the timing of feeding is precise in animals. The present study hypothesized that the food provided at a different time of the day (consistently delay of 6 hours) could lead to the desynchronization of daily rhythms in clock genes in liver tissues. The Winstar albino rats were divided into three groups and were exposed to a daily light-dark cycle (12L:12D; 12h light and 12h dark). The Group 1 (Control group) had food ad libitum, Group 2- second group- 6h food group had daily food availability of 6h (night fed group). In contrast, Group 3- T30 group was provided food for 6 hours but delayed by 6h from the previous day's food timing. After 30 days, animals were sacrificed at six-time points and the expression of clock genes was studied in the liver. Food cycle's effect was observed on body mass, and it was significantly (P < 0.05) reduced in the T30 group. The circadian clock persisted in both food ad libitum and night fed groups but changed in phase and amplitude. However, it lost daily rhythm in clock genes in liver tissues of the T30 group. These results are significant as they suggest that the food's timing is critical for synchronizing the circadian clock in the metabolic center, i.e., the liver.

Universal Stress Protein regulates the circadian rhythm of central oscillator genes in Arabidopsis.

Environmental stresses restrict plant growth and development and decrease crop yield. The circadian clock is associated with the ability of a plant to adapt to daily environmental fluctuations and the production and consumption of energy. Here, we investigated the role of Arabidopsis Universal Stress Protein (USP; At3g53990) in the circadian regulation of nuclear clock genes. The Arabidopsis usp knockout mutant line exhibited critically diminished circadian amplitude of the central oscillator CIRCADIAN CLOCK ASSOCIATED 1 (CCA1) but enhanced the amplitude of TIMING OF CAB EXPRESSION 1 (TOC1). However, the expression of USP under the control of its own promoter restored the circadian timing of both genes, suggesting that USP regulates the circadian rhythm of Arabidopsis central clock genes, CCA1 and TOC1.

Melatonergic Receptors (Mt1/Mt2) as a Potential Additional Target of Novel Drugs for Depression.

A complex pathogenesis involving several physiological systems is theorized to underline the development of depressive disorders. Depression is accompanied by circadian regulation disruption and interaction with the functioning of both central and peripheral oscillators. Many aspects of melatonin function unite these systems. The use of drugs for circadian rhythm disorders could inspire a potential treatment strategy for depression. Melatonin plays an essential role in the regulation of circadian rhythms. It exerts effect by activating two types of melatonin receptors, type 1A (MT1) and 1B (MT2). These are G-protein-coupled receptors, predominantly located in the central nervous system. MT1/MT2 agonists could be a useful treatment approach according to all three prevalent theories of the pathogenesis of depression involving either monoamines, synaptic remodeling, or immune/inflammatory events. MT1/MT2 receptors can be a potential target for novel antidepressants with impact on concentrations of neurotrophins or neurotransmitters, and reducing levels of pro-inflammatory cytokines. There is an interesting cross-talk mediated via the physical association of melatonin and serotonin receptors into functional heteromers. The antidepressive and neurogenetic effects of MT1/MT2 agonists can also be caused by the inhibition of the acid sphingomyelinase, leading to reduced ceramide, or increasing monoamine oxidase A levels in the hippocampus. Compounds targeting MT1 and MT2 receptors could have potential for new anti-depressants that may improve the quality of therapeutic interventions in treating depression and relieving symptoms. In particular, a combined effect on MT1 and/or MT2 receptors and neurotransmitter systems may be useful, since the normalization of the circadian rhythm through the melatonergic system will probably contribute to improved treatment. In this review, we discuss melatonergic receptors as a potential additional target for novel drugs for depression.

Studies of the Origin and Nature of the Energetic Forces Exerted on a Torsion Pendulum by Human Subjects

These results extend what is known about the effects of a human subject sitting under a torsion pendulum. Previous results showed that subjects affected the pendulum in significant ways. Substantial shifts of the center of oscillation of the pendulum, shifts as large as 2.2 cm (7 deg) requiring a force that is equivalent to 45 mg were observed. Many new frequencies of oscillation of the pendulum were introduced when a subject was present. Dramatic changes in the amplitudes of oscillation of the pendulum were observed throughout the experiments; increasing, decreasing, and increasing again, in quasi-consistent patterns. These shifts of the center of oscillation, the new frequencies of oscillation, and the changes in amplitudes all persisted for 30-60 min after the subject has left the pendulum. These effects have been variously attributed to ‘human bioenergy,’ or to simple cranial heat convection currents. The physical nature of the forces causing these effects remains uncertain. Until now all the experiments we have performed have used ‘control subjects,’ which refers to subjects with no known abilities that would affect the pendulum in unusual ways. In this work, a subject who had 45 years of daily experience with a particular type of meditation ‘sound current meditation’ was recruited. The purpose was to see if different mental states such as a meditative state versus a non-meditative sate, would affect the pendulum differently. These results establish that they are different, both qualitatively and quantitatively, and that the effects by the experienced meditator were significantly different than those routinely seen with ‘control subjects.’ A new kind of experiment was performed by having subjects sit beside the pendulum instead of directly under it. Subjects were the ‘experienced meditator,’ and a ‘control subject.’ Effects on the pendulum with subjects sitting beside the pendulum were diminished in amplitude but were otherwise similar to subjects sitting directly under the pendulum. Although the possibility of cranial heat convection currents being able to exert these effects from a significant distance is not eliminated, the argument that cranial heat convection currents are solely responsible for subject effects on the pendulum is weakened.

Cryo-EM Data Statistics and Theoretical Analysis of KaiC Hexamer

Cryo-electron microscopy (cryo-EM) provides a powerful tool to resolve the structure of biological macromolecules in natural state. One advantage of cryo-EM technology is that different conformation states of a protein complex structure can be simultaneously built, and the distribution of different states can be measured. This provides a tool to push cryo-EM technology beyond just to resolve protein structures, but to obtain the thermodynamic properties of protein machines. Here, we used a deep manifold learning framework to get the conformational landscape of KaiC proteins, and further obtained the thermodynamic properties of this central oscillator component in the circadian clock by means of statistical physics.

The central circadian regulator CCA1 functions in Glycine max during defense to a root pathogen, regulating the expression of genes acting in effector triggered immunity (ETI) and cell wall metabolism

Expression of the central circadian oscillator components CIRCADIAN CLOCK ASSOCIATED 1 (CCA1), TIMING OF CAB1 (TOC1), GIGANTEA (GI), and CONSTANS (CO) occurs in Glycine max root cells (syncytia) parasitized by the nematode Heterodera glycines while undergoing resistance, indicating a defense role. GmCCA1-1 relative transcript abundance (RTA) in roots experiencing overexpression (OE) or RNA interference (RNAi) is characterized by rhythmic oscillations, compared to a ribosomal protein gene (GmRPS21) control. A GmCCA1-1 RTA change, advancing by 12 h, exists in H. glycines-infected as compared to uninfected controls in wild-type, H. glycines-resistant, G. max[Peking/PI 548402]. The G. max[Peking/PI 548402] transgenic controls exhibit the RTA change by 4 h post infection (hpi), not consistently occurring in the H. glycines-susceptible G. max[Williams 82/PI 518671] until 56 hpi. GmCCA1-1 expression is observed to be reduced in H. glycines-infected GmCCA1-1-OE roots as compared to non-infected transgenic roots with no significant change observed among RNAi roots. The GmCCA1-1 expression in transgenic GmCCA1-1-OE roots remains higher than control and RNAi roots. Decreased GmCCA1-1 mRNA among infected roots shows the altered expression is targeted by H. glycines. Gene expression of proven defense genes including 9 different mitogen activated protein kinases (GmMAPKs), NON-RACE SPECIFIC DISEASE RESISTANCE 1 (GmNDR1-1), RPM1-INTERACTING PROTEIN 4 (GmRIN4-4), and the secreted xyloglucan endotransglycosylase/hydrolase 43 (GmXTH43) in GmCCA1-1-OE and GmCCA1-1-RNAi roots, compared to controls, reveal a significant role of GmCCA1-1 expression in roots undergoing defense to H. glycines parasitism. The observation that GmCCA1-1 regulates GmXTH43 expression links the central circadian oscillator to the functionality of the secretion system.

Arabidopsis cryptochrome 2 forms photobodies with TCP22 under blue light and regulates the circadian clock

Cryptochromes are blue light receptors that regulate plant growth and development. They also act as the core components of the central clock oscillator in animals. Although plant cryptochromes have been reported to regulate the circadian clock in blue light, how they do so is unclear. Here we show that Arabidopsis cryptochrome 2 (CRY2) forms photobodies with the TCP22 transcription factor in response to blue light in plant cells. We provide evidence that PPK kinases influence the characteristics of these photobodies and that together these components, along with LWD transcriptional regulators, can positively regulate the expression of CCA1 encoding a central component of the circadian oscillator.

Investigation of injection‐locked ring oscillators for process, voltage, and temperature‐aware low phase‐noise reference clock generation

In this paper, injection-locked coupled ring oscillators (ROs) are studied regarding their capabilities for process, voltage, and temperature (PVT) compensated reference clock generation. A PVT resilient RO is implemented by means of injection-locked coupled ROs where the injection locking mechanism is realized by employing adjustable coupling factors. It is shown that the oscillation frequency can be highly compensated for temperature-related variations through the coupling factors. In addition, it is possible to compensate the center oscillation frequency for process-induced variations and supply voltage fluctuations. The proposed technique is fully open loop without any frequency tracking loop and can be easily adopted by other architectures of oscillators such as RC and LC counterparts. A 2.4 GHz reference clock generator is implemented in a 0.18 μm standard CMOS process. While the temperature coefficient (TC) of the free-running ROs is about 640 ppm/°C, the coupled structure offers a TC of 80 ppm/°C. Furthermore, the phase-noise of the coupled structure is about 4 dB lower compared with the free-running ROs. The proposed RO consumes about 2.8 mW and occupies a silicon area of 0.09 mm2.

Data‐model driven rescheduling considering both rotor angle stability and transient voltage stability constraints

Facing the problem of workforce and time costs caused by the rescheduling of large-scale power grids with renewable energy penetration, and the lack of parallel control research on rotor angle instability and transient voltage instability, a rescheduling method based on trajectory sensitivity and deep reinforcement learning (DRL) is proposed to meet the requirements of rotor angle stability and transient voltage stability at the same time. By introducing the process of rescheduling to meet the transient stability constraint, the Markov decision-making process of rescheduling is first constructed. Then, a simple dominant instability type identification method is proposed according to the occurrence time, location, voltage pattern, and position of the oscillation centre. Moreover, a rescheduling strategy is formulated based on the dominant instability mode identification, trajectory sensitivity calculation, actionable device selection, action amount computation, and action of the device. Next, according to the improved distributed distributive deep deterministic policy gradients (D4PG), a DRL model is established to map the action to actionable generator pairs and capacitors/reactors, so as to realize parallel rescheduling of rotor angle instability and transient voltage instability. Finally, the improved New England 39-bus system and an actual power grid are used to verify the effectiveness and advantages of the method.

Role of Circadian Rhythms in Major Plant Metabolic and Signaling Pathways.

Plants require an endogenous regulatory network and mechanism to cope with diurnal environmental changes and compensate for their sessile nature. Plants use the circadian clock to anticipate diurnal changes. Circadian rhythm predicts a 24-h cycle with 16 h of light and 8 h of darkness in response to abiotic and biotic factors as well as the appropriate temperature. For a plant’s fitness, proper growth, and development, these rhythms synchronize the diurnal photoperiodic changes. Input pathway, central oscillator, and output pathway are the three components that make up the endogenous clock. There are also transcriptional and translational feedback loops (TTFLs) in the clock, which are dependent on the results of gene expression. Several physiological processes, such as stress acclimatization, hormone signaling, morphogenesis, carbon metabolism, and defense response, are currently being investigated for their interactions with the circadian clock using phenotypic, genomic, and metabolic studies. This review examines the role of circadian rhythms in the regulation of plant metabolic pathways, such as photosynthesis and carbon metabolism, as well as developmental and degenerative processes, such as flowering and senescence. Furthermore, we summarized signaling pathways related to circadian rhythms, such as defense response and gene regulatory pathways.

Mean field versus random-phase approximation calculation of the energy of an impurity immersed in a spin-1/2 superfluid

In this article we calculate the energy of an impurity weakly coupled to a spin 1/2 fermionic superfluid. We show that the divergences resulting from three-body physics can only be cured using a proper description of the excitations of the many-body background. We highlight the crucial role played by interactions between quasiparticles which are overlooked within BCS (Bardeen-Cooper-Schrieffer) mean-field theory of fermionic superfluidity. By contrast, we prove that their addition using the Random Phase Approximation (RPA) allows us to regularize the energy of the impurity. Finally, we show that these beyond mean-field corrections should be observable by the analysis of the frequency shift of the impurity center of mass oscillations in an external confining potential.

Acute Effects of Self-Correction on Spine Deviation and Balance in Adolescent Girls with Idiopathic Scoliosis.

Background: Adolescent idiopathic scoliosis (AIS) is a three-dimensional deformity of spine and trunk with a higher incidence in girls. AIS alters and reduces postural control and balance. Self-correction movement (SCM) is a well-known non-invasive approach to ameliorate spine curve in AIS subjects. We aimed to evaluate the effects of SCM on the spine and on the balance of adolescents with AIS with a new non-invasive instrumentation. Methods: A total of 38 girls with AIS were recruited. To evaluate the acute effects of SCM and the oscillations of center of pressure (COP), we used LiDAR technology combined with a stabilometric platform to evaluate both changes in spinal curves and balance at the same time. Two tests were carried out simultaneously using the two instruments: before the execution of SCM, in the spontaneously assumed position of each subject (SP) and after the execution of SCM, during the achieved position (SC). Sway area, COP medio-lateral and antero-posterior directions, eccentricity of the ellipse and vertebral lateral deviation were recorded. The two conditions were compared with a Wilcoxon signed-rank test. Results: In general, all measures showed lower values in SC condition (p < 0.05), except the variation along the Y axis. Conclusions: Thanks to objective measured data, the therapists observed real-time changes during the performance of SCM, appreciating its efficacy on curve correction.

Heart rate variability indices in children with syncope due to orthostatic hypotension

Summary. Orthostatic hypotension (OH) in children may be accompanied by symptoms such as dizziness and syncope and is often a manifestation of baroreflex failure due to autonomic imbalance. Heart rate variability (HRV) is one of the most effective methods of assessing the modulation of the autonomic nervous system and its balance. The aim of the study – to learn the features of autonomic nervous system modulation in children with syncope due to OH using HRV parameters. Materials and Methods. Twenty-five children aged 8–17 with a diagnosis of syncope due to OH and 41 practically healthy children were examined. The diagnostic criteria of the European Society of Cardiology (ESC 2018) were used to diagnose syncope due to OH. All patients were provided with accurate history taking, physical examination, active standing test, electrocardiography in 12 leads, echocardiography, electroencephalography and 24-hour Holter monitoring for HRV assessment. Results. There were no differences in values ​​of HRV parameters SDANN, RMSSD and pNN50 in children with syncope due to OH compared to healthy ones (p 0.05). These results generally indicate the normal activity of humoral influences and central oscillators against the background of balanced parasympathetic effects on the cardiovascular system in children with syncope. However, there were increased TP (10502.59±1526.62 ms2; 5482.44±396.87 ms2; p=0.0016), VLF (5768.27±774.29 ms2; 3906.29±269.09 ms2; p=0.046) and LF/HF ratio (1.75±0.18; 1.29 ± 0.09; p=0.044) in the group of syncope due to OH. Correlations were found between the number of syncope events and SDANN (r=-0.62; p=0.002), and RMSSD (r=-0.46; p=0.03), duration of the last presyncope event and VLF (r=0.44; p =0.04), duration of the last syncope event and LF/HF ratio (r=0.57; p=0.006), 24-hour average interval PQ duration and SDANN (r=0.64; p=0.001), and RMSSD (r=0.63; p=0.002), 24-hour average interval QT duration and SDANN (r=0.43; p=0.04), and RMSSD (r=0.43; p=0.05) in patients with syncope due to OH. Conclusions. In children with syncope due to OH markers of pathological autonomic regulation are HRV parameters TP, VLF, and LF/HF ratio, and their increase values is evidence of predominance of the sympathetic circuit of heart rate regulation against the background of increased baroreflex activity of the heart and impaired adaptive-compensatory capabilities of the cardiovascular system including the activity of the central circuits of heart rate regulation

Adventures in Life and Science, from Light to Rhythms.

The author describes her life's pathway from her beginnings at a time when women were not well represented in the sciences. Her grandparents were immigrants to the United States. Although her parents were not able to go to college because of the Great Depression, they supported her education and other adventures. In addition to her interest in science, she describes her interest and involvement in politics. Her education at Oberlin, Stanford, and Harvard prepared her for her independent career at the University of California, Los Angeles, where she was an affirmative action appointment. Her research initially centered on the plant photoreceptor phytochrome, but later in her career she investigated circadian rhythms in plants, discovering and characterizing one of the members of the central oscillator.

Role of Sleep Restriction in Daily Rhythms of Expression of Hypothalamic Core Clock Genes in Mice.

Lack of sleep time is a menace to modern people, and it leads to chronic diseases and mental illnesses. Circadian processes control sleep, but little is known about how sleep affects the circadian system. Therefore, we performed a 28-day sleep restriction (SR) treatment in mice. Sleep restriction disrupted the clock genes’ circadian rhythm. The circadian rhythms of the Cry1 and Per1/2/3 genes disappeared. The acrophase of the clock genes (Bmal1, Clock, Rev-erbα, and Rorβ) that still had a circadian rhythm was advanced, while the acrophase of negative clock gene Cry2 was delayed. Clock genes’ upstream signals ERK and EIFs also had circadian rhythm disorders. Accompanied by changes in the central oscillator, the plasma output signal (melatonin, corticosterone, IL-6, and TNF-α) had an advanced acrophase. While the melatonin mesor was decreased, the corticosterone, IL-6, and TNF-α mesor was increased. Our results indicated that chronic sleep loss could disrupt the circadian rhythm of the central clock through ERK and EIFs and affect the output signal downstream of the core biological clock.