Central Oscillator Research Articles

О методиках прогнозирования шума гребных винтов транспортных судов

Object and purpose of research. The object of the research is the cavitation noise of transport vessels propellers. The purpose is to analyze and generalize modern research and methods for predicting broadband noise induced by the operation of the transport vessels cavitating propellers. Materials and methods. A review of the research materials (published in the XXI century) on the cavitation noise of transport vessels propellers, in particular broadband noise, as well as the author's own research on the causes and physical aspects of the occurrence of broadband noise is carried out. Based on the Fourier analysis of the time functions of velocities and pressures in the flow near the propeller, the conditions for the occurrence of broadband noise at (4–10)-blade harmonics and the parameters that relate this noise to various types of cavitation on the propeller are found. Main results. A review of recent studies results devoted to the cavitation noise of transport vessels propellers has shown that the levels of the so-called broadband noise that occurs when the cavitating propeller operates in nonuniform flow at high (4–10)-blade harmonics are used as the basis for modern noise predicting methods. At the same time, the authors of the methods consider broadband noise only as a result of the tip vortices development. The paper considers and generalizes an alternative hypothesis of the broadband noise occurrence caused by the occurrence and collapse of cavities within the blade with the formation of a double-headed peak on the time function of pressures. The analysis of publications on the development of the vortex wake behind the propeller and the modeling of pressures at the buckling failure of the tip vortex spirals allowed to show that double pressure peaks can be formed in the flow during the development of the vortex wake behind the propeller. This made it possible to combine both hypotheses of the broadband noise formation – from the development of the tip vortex and from the occurrence and collapse of cavities on the blades – and to link the assessment of the growth possibility of high blade harmonics with the cavitation parameters. Conclusions. It is shown that modern research methods have made it possible to obtain new data on the mechanism of the occurrence and collapse of cavitation both on the blade and in the tip vortex. At the same time, the currently used methods for predicting cavitation and, in particular, broadband noise are very approximate and require refinement to assess the effect of various cavitation characteristics on broadband noise. The hypotheses of broadband noise occurrence and the proposed physical model covering both vortex cavitation and the formation and collapse of cavities can serve as a basis for such clarification.

Possibility of the total thermodynamic entropy production rate of a finite-sized isolated quantum system to be negative for the Gorini-Kossakowski-Sudarshan-Lindblad-type Markovian dynamics of its subsystem

We investigate a total thermodynamic entropy production rate of an isolated quantum system. In particular, we consider a quantum model of coupled harmonic oscillators in a star configuration, where a central harmonic oscillator (system) is coupled to a finite number of surrounding harmonic oscillators (bath). In this model, when the initial state of the total system is given by the tensor product of the Gibbs states of the system and the bath, every harmonic oscillator is always in a Gibbs state with a time-dependent temperature. This enables us to define time-dependent thermodynamic entropy for each harmonic oscillator and total nonequilibrium thermodynamic entropy as the summation of them. We analytically confirm that the total thermodynamic entropy satisfies the third law of thermodynamics. Our numerical solutions show that, even when the dynamics of the system is well approximated by the Gorini-Kossakowski-Sudarshan-Lindblad (GKSL)-type Markovian master equation, the total thermodynamic entropy production rate can be negative, while the total thermodynamic entropy satisfies the second law of thermodynamics. This result is a counterexample to the common belief that the total entropy production rate is non-negative when the system is under the GKSL-type Markovian dynamics.

Evolution of kaiA, a key circadian gene of cyanobacteria

The circadian system of cyanobacteria is built upon a central oscillator consisting of three genes, kaiA, kaiB, and kaiC. The KaiA protein plays a key role in phosphorylation/dephosphorylation cycles of KaiC, which occur over the 24-h period. We conducted a comprehensive evolutionary analysis of the kaiA genes across cyanobacteria. The results show that, in contrast to the previous reports, kaiA has an ancient origin and is as old as cyanobacteria. The kaiA homologs are present in nearly all analyzed cyanobacteria, except Gloeobacter, and have varying domain architecture. Some Prochlorococcales, which were previously reported to lack the kaiA gene, possess a drastically truncated homolog. The existence of the diverse kaiA homologs suggests significant variation of the circadian mechanism, which was described for the model cyanobacterium, Synechococcus elongatus PCC7942. The major structural modifications in the kaiA genes (duplications, acquisition and loss of domains) have apparently been induced by global environmental changes in the different geological periods.

Dual function of clock component OsLHY sets critical day length for photoperiodic flowering in rice.

SummaryCircadian clock, an endogenous time‐setting mechanism, allows plants to adapt to unstable photoperiod conditions and induces flowering with proper timing. In Arabidopsis, the central clock oscillator was formed by a series of interlocked transcriptional feedback loops, but little is known in rice so far. By MutMap technique, we identified the candidate gene OsLHY from a later flowering mutant lem1 and further confirmed it through genetic complementation, RNA interference knockdown, and CRISPR/Cas9‐knockout. Global transcriptome profiling and expression analyses revealed that OsLHY might be a vital circadian rhythm component. Interestingly, oslhy flowered later under ≥12 h day length but headed earlier under ≤11 h day length. qRT‐PCR results exhibited that OsLHY might function through OsGI‐Hd1 pathway. Subsequent one‐hybrid assays in yeast, DNA affinity purification qPCR, and electrophoretic mobility shift assays confirmed OsLHY could directly bind to the CBS element in OsGI promoter. Moreover, the critical day length (CDL) for function reversal of OsLHY in oslhy (11–12 h) was prolonged in the double mutant oslhy osgi (about 13.5 h), indicating that the CDL set by OsLHY was OsGI dependent. Additionally, the dual function of OsLHY entirely relied on Hd1, as the double mutant oslhy hd1 showed the same heading date with hd1 under about 11.5, 13.5, and 14 h day lengths. Together, OsLHY could fine‐tune the CDL by directly regulating OsGI, and Hd1 acts as the final effector of CDL downstream of OsLHY. Our study illustrates a new regulatory mechanism between the circadian clock and photoperiodic flowering.

Numerical simulation of vortex instabilities in the wake of a preswirl pumpjet propulsor

A numerical analysis based on detached eddy simulations is conducted to investigate vortex instabilities in the wake of a preswirl pumpjet propulsor. Three models are established to separate the roles that the rotor, stator, and duct play in the vortex structure of the pumpjet propulsor. In this paper, only the vortex structure of the rotor is considered. The results show that the vortex system of the rotor is mainly composed of the tip vortices, a hub vortex, the trailing tip vortices, and the trailing root vortices. The trailing tip vortices are generated by the premature shedding of the tip vortices in the rotor model compared with a normal single propeller. The existence of trailing root vortices increases the stability of the hub vortex. Furthermore, a unique multi-inductance instability mode of the tip vortex, called the “overlap–forward” phenomenon, is found for low values of the advance coefficient J. It is found that the instability of the tip vortex depends not only on the spiral-to-spiral distance but also on the highest-efficiency point of the propeller. The instability inception point of the tip vortex moves farther downstream with increasing J, whereas when J is greater than the highest-efficiency point of the propeller, the stable length of the tip vortices drops sharply. The energy transfer process from blade harmonics to shaft harmonics of the tip vortices depends on J and is related to the spatial evolution of the tip vortices.

Dynamic behavior of the cyanobacterial circadian clock with regulation of CikA* *Project supported by the National Natural Science Foundation of China (Grant No. 11672177).

Cyanobacteria are the simplest organisms to have circadian clocks. The central oscillator in cyanobacteria is composed by a transcriptional/translational feedback loop (TTFL) and a post-translational oscillator (PTO). The PTO is a core pacemaker which consists of three proteins KaiA, KaiB and KaiC. KaiA stimulates the phosphorylation of KaiC, while KaiB inhibits the activity of KaiA. The cyanobacterial circadian clock is an interesting topic for researchers and many mathematical models have been constructed. However, the current mathematical models of the cyanobacterial circadian clock have been made only considering the interactions between Kai proteins. CikA, as an input pathway component, plays an essential role in the circadian clock, whose mutation results in abnormal rhythms. The regulation mechanism of CikA remains unclear. In this paper, we develop a detailed mathematical model for the cyanobacterial circadian clock with incorporation CikA-regulation. Based on numerical simulations, we explore the dynamic properties of the circadian clock regulated by CikA. The results show that the regulation of CikA makes the system more sensitive. In detail, CikA strengthens the central role of PTO and improves the adaptability of the circadian clock against the change of environment. With CikA, the system is able to modulate its period more easily to face environmental perturbation. CikA also enhances slightly the fitness of cyanobacteria. The findings of this paper can supplement the biological research and may help us more clearly understand the cyanobacterial circadian clock regulated by other proteins.

Analytical Investigation of Propellant Slosh Stability Boundary on a Space Vehicle

The effect of propellant sloshing upon the stability of a liquid-propelled space vehicle in a high-g environment has been studied extensively. For a typical space vehicle with thrust vector control and a single slosh tank, the Bauer slosh danger zone is located between the vehicle center of mass and the center of percussion while ignoring effects, like aerodynamics and axial acceleration. If the slosh mass is located between these two locations, baffles may be required to provide additional damping for stability. Although this criterion is widely used in the launch-vehicle flight control community, its application is limited to the aforementioned configuration and assumptions. In this work, the methodology behind the classic single-tank criteria is extended to other tank configurations and includes previously ignored effects. First, a vehicle with a single centerline tank and a pair of outboard reaction jets, rather than thrust vectoring, for attitude control is studied. Second, the impacts of aerodynamics and vehicle axial acceleration on the classic single-tank criteria are analyzed. Finally, the variation of the classic danger zone for a tandem tank configuration, where the tanks are located along the vehicle centerline or symmetrically offset from the centerline, is investigated.

A central circadian oscillator confers defense heterosis in hybrids without growth vigor costs

Plant immunity frequently incurs growth penalties, which known as the trade-off between immunity and growth. Heterosis, the phenotypic superiority of a hybrid over its parents, has been demonstrated for many traits but rarely for disease resistance. Here, we report that the central circadian oscillator, CCA1, confers heterosis for bacterial defense in hybrids without growth vigor costs, and it even significantly enhances the growth heterosis of hybrids under pathogen infection. The genetic perturbation of CCA1 abrogated heterosis for both defense and growth in hybrids. Upon pathogen attack, the expression of CCA1 in F1 hybrids is precisely modulated at different time points during the day by its rhythmic histone modifications. Before dawn of the first infection day, epigenetic activation of CCA1 promotes an elevation of salicylic acid accumulation in hybrids, enabling heterosis for defense. During the middle of every infection day, diurnal epigenetic repression of CCA1 leads to rhythmically increased chlorophyll synthesis and starch metabolism in hybrids, effectively eliminating the immunity-growth heterosis trade-offs in hybrids.

Intensification of functional neural control on heartbeat dynamics in subclinical depression

Subclinical depression (dysphoria) is a common condition that may increase the risk of major depression and leads to impaired quality of life and severe comorbid somatic diseases. Despite its prevalence, specific biological markers are unknown; consequently, the identification of dysphoria currently relies exclusively on subjective clinical scores and structured interviews. Based on recent neurocardiology studies that link brain and cardiovascular disorders, it was hypothesized that multi-system biomarkers of brain–body interplay may effectively characterize dysphoria. Thus, an ad hoc computational technique was developed to quantify the functional bidirectional brain–heart interplay. Accordingly, 32-channel electroencephalographic and heart rate variability series were obtained from 24 young dysphoric adults and 36 healthy controls. All participants were females of a similar age, and results were obtained during a 5-min resting state. The experimental results suggest that a specific feature of dysphoria is linked to an augmented functional central-autonomic control to the heart, which originates from central, frontopolar, and occipital oscillations and acts through cardiovascular sympathovagal activity. These results enable further development of a large set of novel biomarkers for mood disorders based on comprehensive brain–body measurements.

Identification and expression profiling of genes involved in circadian clock regulation in red dragon fruit (Hylocereus polyrhizus) by full-length transcriptome sequencing

ABSTRACT Crassulacean acid metabolism (CAM) plants fix CO2 at night, exhibiting a reversed regulatory pattern of metabolomic pathways compared with most model plants, which have C3 and C4 pathways. In this study, we used a valuable tropic fruit, red dragon fruit (Hylocereus polyrhizus), as model plant to identify and analyze the circadian regulation genes. Due to the absence of red dragon fruit’s whole-genome dataset, we established a full-length transcriptome dataset using single-molecule real-time (SMRT) sequencing method. A 7.66-Gb dataset with 4,552,474 subreads was generated, with an average length of 1,683 bp and an N50 of 2,446 bp. Using this dataset, we identified center oscillator genes: CCA1 (CIRCADIAN CLOCK ASSOCIATED1), ELF3 (EARLY FLOWERING 3), GI (GIGANTEA), LHY (LATE ELONGATED HYPOCOTYL), LNK1 (NIGHT LIGHT-INDUCIBLE AND CLOCK-REGULATED 1), and TOC1 (TIMING OF CAB EXPRESSION 1); a gene for the input pathway: CRY1 (CRYPTOCHROME); a gene for the output pathway: CO (CONSTANS); and genes related to the CAM pathway: MDH (MALATE DEHYDROGENASE), ME (MALIC ENZYMES), and PPDK (PYRUVATE PHOSPHATE DIKINASE). We further established the 24-h rhythmic expression pattern of these genes and classified these into three groups: HpCCA1, HpELF3, HpLHY, HpLNK1, and HpGI have expression peaks during the day; HpTOC1, HpCO, and HpCRY1 have highest expression levels at night; The genes involved in the CAM pathways, namely, HpMDH, HpME1, and HpPPDK, have double expression peaks in the day and night. Comparison of these expression patterns between red dragon fruit and model plants could provide clues in understanding the circadian clock regulation and the activity of the CAM pathways in cactus plants.

Posttranslational regulation of multiple clock-related transcription factors triggers cold-inducible gene expression in Arabidopsis

Cold stress is an adverse environmental condition that affects plant growth, development, and crop productivity. Under cold stress conditions, the expression of numerous genes that function in the stress response and tolerance is induced in various plant species, and the dehydration-responsive element (DRE) binding protein 1/C-repeat binding factor (DREB1/CBF) transcription factors function as master switches for cold-inducible gene expression. Cold stress strongly induces these DREB1 genes. Therefore, it is important to elucidate the mechanisms of DREB1 expression in response to cold stress to clarify the perception and response of cold stress in plants. Previous studies indicated that the central oscillator components of the circadian clock, CIRCADIAN CLOCK-ASSOCIATED 1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY), are involved in cold-inducible DREB1 expression, but the underlying mechanisms are not clear. We revealed that the clock-related MYB proteins REVEILLE4/LHY-CCA1-Like1 (RVE4/LCL1) and RVE8/LCL5 are quickly and reversibly transferred from the cytoplasm to the nucleus under cold stress conditions and function as direct transcriptional activators of DREB1 expression. We found that CCA1 and LHY suppressed the expression of DREB1s under unstressed conditions and were rapidly degraded specifically in response to cold stress, which suggests that they act as transcriptional repressors and indirectly regulate the cold-inducible expression of DREB1s We concluded that posttranslational regulation of multiple clock-related transcription factors triggers cold-inducible gene expression. Our findings clarify the complex relationship between the plant circadian clock and the regulatory mechanisms of cold-inducible gene expression.

Improving Robustness of Legged Robots Against Mechanical Shock Using Impulsive Dynamics

This manuscript presents a method to calculate and analyze mechanical shock of a multi-rigid body system, based on the revised concept of the center of percussion and a newly derived variable called the radius of percussion. The objective is to improve the mechanism’s robustness against mechanical shocks that are caused by certain impacts, such as those experienced by legged robots from landing a jump or making a step. In practice, it can be used for placement of shock-sensitive components in robots, such as inertial measurement units and cameras, and for mechanical and controller design improvements and optimizations that aim to reduce shock in certain body parts. Several case studies are presented to support the usefulness of the theory.

Analysis of static stiffness fluctuation in radially loaded ball and roller bearings

The radial stiffness of rolling bearings is the basis for analyzing the dynamic performance of bearing-rotor systems. The changes of rolling element position may cause continuous change of radial stiffness and relative displacement of inner and outer ring during the operation of the bearing-rotor systems. As a result, the vibration of bearing-rotor systems would be aggravated. In order to accurately study the influence of the changes of rolling element position on radial stiffness, two boundary positions of the inner ring supported by even or odd number of rolling elements are considered in this paper. A mathematical method for rolling bearings modeling and stiffness calculation is proposed based on Hertz elastic contact theory. Then, the differences of radial stiffness under two boundary positions and that of rotor center displacements are studied. The results show that there exist obvious fluctuation of radial stiffness and oscillation of rotor center during the operation of bearing-rotor systems. Moreover, the effect of bearing structure parameters including internal clearance, number of rolling elements on the fluctuation of radial stiffness and oscillation of rotor center has been systematically investigated for ball and roller bearings. Consequently, this paper not only proposes an effective method for the radial stiffness, load distribution and the displacement of rotor center calculation of radially loaded rolling bearings, but also provides a direction for the design of bearing-rotor systems to eliminate vibration.

Нелинейное возбуждение гиперзвуковых колебаний в ферритовой пластине в условиях комбинированного воздействия на двух частотах. Часть 3. Вариация толщины пластины

The task about nonlinear excitation of hypersound vibrations in ferrite plate in conditions of combine influence in two frequencies is investigated. As a most important parameter which is varied it is proposed the relative thickness of plate which is determined as relation of real thickness to the thickness which correspond to elastic resonance on the difference of excitation frequencies. It is established the necessity of choosing of character value of constant field which is determined by enough effective excitation of elastic vibrations. The system of nonlinear equations of motion of magnetization and elastic displacement is described. For solving of this system, the numerical Rounge-Cutta method is applied. The results of this calculation are the time-evolvent of vibrations, dependencies magnetic end elastic vibrations amplitudes and the spectra of vibrations in permanent conditions after end of relaxation processes. It is found the multi-regime character of elastic vibrations which takes place by variation of plate thickness. In the character of development of elastic vibrations in time by the increasing of plate thickness it is found four regimes: regime №1 – regular beatings, regime №2 – established resonance, regime №3 – displacement of center of established vibrations, regime №4 – gigantic oscillations. The intervals of thickness values which are necessary, or realization of these regimes are determined. The properties of each regimes taken separately are investigated. It is found that the regime №1 is realized when the thickness of plate is more less then the thickness of resonance on differential frequency. In this case the elastic vibrations in generally repeats the vibrations of magnetization which are realized as beating between two frequencies of excitation. The regime №2 takes place when the plate thickness is near to resonance on differential frequency. When thickness is corresponds to resonance on differential frequency it is found large raising of resonance character. In the vibrations of elastic displacement, the constant component is discovered. The regime №3 takes place when the plate thickness is exceeded of resonance on several (from two to seven) times. The vibrations of magnetization in this regime are the same as in regimes №1 and №2. The elastic displacement has two components: oscillatory on differential frequency and constant which value by increasing of thickness smoothly is increased. The displacement of center of oscillatory component by thickness is increased has quadratic character. The regime №4 takes place by plate thickness exceeds resonance thickness on the order and more. The vibrations of magnetization maintain the character of beating which are the same as in regimes №1, №2 and №3. The vibrations of elastic displacement are characterized by extremely large amplitude which is more then the amplitude in regime №3 on order and more and has extremely large period which is more then period of differential frequency vibrations on two-three order and more. The amplitude of vibrations and its period by the thickness is increases also increase by linear meaning. The some quality opinions about the nature of observed phenomena are proposed. It is established the specific character of two-frequency excitation in comparison to single-frequency excitation. As the possible task it is proposed the plan of singing the part of solution as dependence of vibration amplitude from plate thickness has quadratic character with necessary appreciation of two-frequency excitation. The mechanical analogy for vibrations of hard rod which is compressed on both ends by approaching forces is proposed. This analogy allows to interpret the displacement of vibrations center and gigantic oscillations regime.

THE ROLE OF CIRCADIAN REGULATION OF GHRELIN LEVELS IN PARKINSON’S DISEASE (LITERATURE REVIEW)

The paper is aimed at the analysis of the role of the circadian regulation of ghrelin levels in patients with Parkinson’s disease. Based on the literature data, patients with Parkinson’s disease have clinical fluctuations in the symptoms of the disease, manifested by the diurnal changes in motor activity, autonomic functions, sleep-wake cycle, visual function, and the efficacy of dopaminergic therapy. Biological rhythms are controlled by central and peripheral oscillators which links with dopaminergic neurotransmission – core of the pathogenesis of Parkinson`s disease. Circadian system is altered in Parkinson`s disease due to that ghrelin fluctuations may be changed. Ghrelin is potential food-entrainable oscillator because it is linked with clock genes expression. In Parkinson`s disease this hormone may induce eating behavior changing and as a result metabolic disorder. The “hunger hormone” ghrelin can be a biomarker of the Parkinson’s disease, and the study of its role in the pathogenesis, as well as its dependence on the period of the day, intake of levodopa medications to improve the effectiveness of treatment is promising.

Shock reduction technique and its application by applying center of percussion

Shock reduction technique and its application by applying center of percussion

Перестраиваемый источник многочастотного излучения Ka-диапазона на основе импульсной гирорезонансной лампы обратной волны

The multifrequency radiation in a pulsed gyro-resonance backward-wave oscillator (gyro-BWO) of the Ka-band based on a waveguide with helical corrugation are obtained. The radiation power achieved 30-35 kW with a pulse duration of about 120 μs and a repetition rate of up to 10 Hz. Due to the change in the magnetostatic field in the interaction region and the pitch factor of the particles, the center oscillation frequency and the distance between the main spectral lines are tuned in the 32–35.5 GHz and in the 360–550 MHz ranges, correspondingly.

Relative frequency and conditional probability based associated dynamic features in extended haptic accuracy

Purpose This study measured the haptic extroperception accuracy, that is, judging one hit position in a hand-held object. Especially, what factors associated the estimation of contact position when the impact is made at the grasped implement by hitting the ball. Methods Relative frequency and conditional probability based analysis verified that perceivers influenced not only the amount of pressure distinguished impressions by the coefficient of restitution but also the pressure distributions encoded impressions by the distance from the hand to the impact. Results Results conformed to previous invariant characteristic on dynamic touch in showing that perceiving the location of the impact of grasped objects, including dominant perceiving selectively modality, is constrained by inertial properties with such success requires appreciating the location of the implement’s center of percussion. Conclusion Investigated in this planes captured as a mechanical factor, we would suggest a broader hypothesis for further research into the effects of the rotational inertia related to haptic position accuracy in the hand-held object, and leading to different estimates of system function providing an account of generalization that accommodates of its varied aspects.

Age-associated increase in postural variability relate to greater low-frequency center of pressure oscillations

BackgroundPostural control is impaired in older adults, as evidenced from greater variability of the center of pressure (COP) during postural tasks. Although COP variability associates with low-frequency COP oscillations (<1 Hz) in young adults, it remains unknown if the age-associated increase in COP variability relates to greater low-frequency COP oscillations. Research questionDo low-frequency oscillations contribute to greater postural sway (center of pressure (COP) variability) in older adults when attempting to voluntarily maintain posture in a forward leaning position compared to young adults? MethodsSeven young (25.7 ± 4.8) and seven older (71.0 ± 7.0) adults performed a postural lean forward task and attempted to match a COP target in the anterior-posterior direction as steady as possible. We quantified the COP variability as the standard deviation (SD) of COP displacements in the anterior-posterior and medial-lateral directions and quantified the frequency modulation of COP as the power in COP displacement spectra from 0-1 Hz. ResultsWe found that older adults had significantly greater anterior-posterior SD of COP (p = 0.027) and power below 0.5 Hz (p = 0.048) than young adults, but power from 0.5-1 Hz was similar (p = 0.083). In contrast, the medial-lateral SD of COP (p = 0.5) and power from 0-1 Hz (p = 0.228) was similar for the two age groups. For both the anterior-posterior and medial-lateral direction, the SD of COP was related to low frequency oscillations below 0.5 Hz. SignificanceFor the first time, we show that the age-associated increase in postural variability relates to greater COP oscillations below 0.5 Hz.

The Circadian Clock-A Molecular Tool for Survival in Cyanobacteria.

Cyanobacteria are photosynthetic organisms that are known to be responsible for oxygenating Earth’s early atmosphere. Having evolved to ensure optimal survival in the periodic light/dark cycle on this planet, their genetic codes are packed with various tools, including a sophisticated biological timekeeping system. Among the cyanobacteria is Synechococcus elongatus PCC 7942, the simplest clock-harboring organism with a powerful genetic tool that enabled the identification of its intricate timekeeping mechanism. The three central oscillator proteins—KaiA, KaiB, and KaiC—drive the 24 h cyclic gene expression rhythm of cyanobacteria, and the “ticking” of the oscillator can be reconstituted inside a test tube just by mixing the three recombinant proteins with ATP and Mg2+. Along with its biochemical resilience, the post-translational rhythm of the oscillation can be reset through sensing oxidized quinone, a metabolite that becomes abundant at the onset of darkness. In addition, the output components pick up the information from the central oscillator, tuning the physiological and behavioral patterns and enabling the organism to better cope with the cyclic environmental conditions. In this review, we highlight our understanding of the cyanobacterial circadian clock and discuss how it functions as a molecular chronometer that readies the host for predictable changes in its surroundings.