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The aim of study was to investigate the effects of dark environment on production performance, intestinal barrier function and clock-related gene expression in rabbits. Forty weaned rabbits with similar body weight (35-day-old) were randomly divided into 2 treatments (20 replicates per treatment, 1 rabbit per replicate: normal light group (12 L and 12 D) or total dark group (24 D). The experimental period lasted for 10 days, with an adaptation period of 3 days and a subsequent formal experimental period of 7 days. The results showed that feed-to-weight ratio of rabbits in total dark group was significantly decreased compared with normal light group. Dark treatment significantly increased gene expression of claudin-1, mucin1 in duodenum, occludin-1, claudin-1, zona occludens 1 (ZO1), junctional adhesion molecule 2 (JAM2) and interleukin 10 (IL10) in jejunum, claudin-1, mucin1, ZO1 and IL10 in ileum and clock, melatonin 1 A, melatonin 1B, and period1 in cecum compared with normal light group. Total dark treatment increased alpha diversity via increasing chao1 index, observed species index and faith_pd index of cecal flora. Total dark treatment significantly reduced percentage of Deferobacterium at phylum level in cecum, but significantly increased percentage of Rumenococci at genus level. There is an insignificant increasing tendency of acetic acid and propionic acid content of soft feces in total dark group. In conclusion, total dark treatment improves feed conversion efficiency in rabbits and activates cecum clock system, which increased diversity of bacterial flora and production of short-chain fatty acids, then increases intestinal barrier function. Clinical trial number Not applicable.

Feed is very important for fish farming. The appropriate composition and proportion of feed ingredients can promote the growth of fish, maintain normal physiology and behavior, and even improve the resistance ability to disease and stress, etc. The core of artificial compound feed (ACF) is the composition and proportion of lipid, protein, and carbohydrate, which are also the main nutritional components required by fish. Appropriate levels and ratios can promote fish growth and save costs, and the improper would affect the biological clock systems of fish, leading to metabolic abnormalities. This study explored the preparation of ACF for H. kuda . The composition and proportion of the three main nutrients in ACF were screened based on the synchronicity between six pairs of clock genes ( Clock , Bmal1 , Per1 , Per2 , Per3 , Cry1 , and Cry2 ) in the central and peripheral clock systems, as well as the expression of eight lipid-metabolism genes ( Hmgcr , Mvk , Mvd , Lss , Fdps , Cetp , Scap , Srebp1 , Srebp2 ) in the liver and their synergy with liver clock genes. The results showed that, based on several parameters such as gene expression cycle, relative expression level, and top phase appearance time, the best synergy between the central and peripheral circadian clock systems was observed in ACF with crude fat content of 8.80%, crude protein content more than 38.4%, and carbohydrate content of 23.5%. Based on the expression relationship between lipid metabolism genes and circadian clock genes in the liver, it was further clarified that the optimal levels of fat, protein, and carbohydrate were determined with 8.80%, 38.4%, and 23.5%, respectively. After 4 weeks of breeding validation, compared with frozen Mysis , the screened ACF fed for H. kuda showed significant advantages in body length specific growth rate (SGR L ), body weight specific growth rate (SGR W ), and feed conversion rate (FCR).

The clock signal is the heartbeat of modern electronic system, and demands of increasing high‐quality signal has been raised, with the development of science and technology in the field of electronic information. The clock signal with low jitter is helpful to improve the signal‐to‐noise ratio (SNR) of sampled data and obtain high‐precision result. In this article, a programmable clock system of signal generation and distribution is designed for high‐speed acquisition system. The system can provide the clock of low jitter which frequency is as high as 3.2 GHz. The output channels for clock are 14 and each channel for clock can also be configured for synchronizing, delay adjusting or calibrating. Based on the system, a new type of configuration program is developed by using Verilog language. It can directly control the chip which has better compatibility in the application scenario of Field Programmable Gate Array (FPGA) as the master chip. It also provides a reference and guidance for the design and implementation of the dual‐Phase Locked Loop clock chips. When it provides the clocks for the high‐speed acquisition system, the SNR of the acquisition signal has been significantly improved compared with similar acquisition systems. It indicates that the clock system we designed provides an effective way for the high‐speed acquisition system to obtain the data with higher SNR. In this article, a programmable system of clock generator and distribution in microwave frequency band is designed for high‐speed acquisition system using dedicated clock chip of HMC7044. Based on the system, a new control program developed by Verilog language, the new configuration method is more concise. Without calling the underlying functions, it can directly control the clock system at the circuit system level.

We consider the use of quantum-limited mechanical force sensors to detect ultralight (sub-meV) dark matter (DM) candidates which are weakly coupled to the standard model. We show that mechanical sensors with masses around or below the milligram scale, operating around the standard quantum limit, would enable novel searches for DM with natural frequencies around the kHz scale. This would complement existing strategies based on torsion balances, atom interferometers, and atomic clock systems.

Currently, the most accurate and stable clocks use optical interrogation of either a single ion or an ensemble of neutral atoms confined in an optical lattice. Here, we demonstrate a new optical clock system based on an array of individually trapped neutral atoms with single-atom readout, merging many of the benefits of ion and lattice clocks as well as creating a bridge to recently developed techniques in quantum simulation and computing with neutral atoms. We evaluate single-site-resolved frequency shifts and short-term stability via self-comparison. Atom-by-atom feedback control enables direct experimental estimation of laser noise contributions. Results agree well with an ab initio Monte Carlo simulation that incorporates finite temperature, projective readout, laser noise, and feedback dynamics. Our approach, based on a tweezer array, also suppresses interaction shifts while retaining a short dead time, all in a comparatively simple experimental setup suited for transportable operation. These results establish the foundations for a third optical clock platform and provide a novel starting point for entanglement-enhanced metrology, quantum clock networks, and applications in quantum computing and communication with individual neutral atoms that require optical-clock-state control.

The high prevalence of desynchronized biological rhythms is becoming a primary public health concern. We assess complex and diverse inter-modulations among multi-frequency rhythms present in blood pressure (BP) and heart rate (HR). and Methods: We performed 7-day/24-h Ambulatory BP Monitoring in 220 (133 women) residents (23-74 years) of a rural Japanese town in Kochi Prefecture under everyday life conditions. A symphony of biological clocks contributes to the preservation of a synchronized circadian system. (1) Citizens with an average 12.02-h period had fewer vascular variability disorders than those with shorter (11.37-h) or longer (12.88-h) periods (p < 0.05), suggesting that the circasemidian rhythm is potentially important for human health. (2) An appropriate BP-HR coupling promoted healthier circadian profiles than a phase-advanced BP: lower 7-day nighttime SBP (106.8 vs. 112.9 mmHg, p = 0.0469), deeper nocturnal SBP dip (20.5% vs. 16.8%, p = 0.0101), and less frequent incidence of masked non-dipping (0.53 vs. 0.86, p = 0.0378), identifying the night as an important time window. Adaptation to irregular schedules in everyday life occurs unconsciously at night, probably initiated from the brain default mode network, in coordination with the biological clock system, including a reinforced about 12-h clock, as \"a biological clock-guided core integration system.\"

Under natural conditions, many aspects of the abiotic and biotic environment vary with time of day, season or even era, while these conditions are typically kept constant in laboratory settings. The timing information contained within the environment serves as critical timing cues for the internal biological timing system, but how this system drives daily rhythms in behaviour and physiology may also depend on the internal state of the animal. The disparity between timing of these cues in natural and laboratory conditions can result in substantial differences in the scheduling of behaviour and physiology under these conditions. In nature, temporal coordination of biological processes is critical to maximize fitness because they optimize the balance between reproduction, foraging and predation risk. Here we focus on the role of peripheral circadian clocks, and the rhythms that they drive, in enabling adaptive phenotypes. We discuss how reproduction, endocrine activity and metabolism interact with peripheral clocks, and outline the complex phenotypes arising from changes in this system. We conclude that peripheral timing is critical to adaptive plasticity of circadian organization in the field, and that we must abandon standard laboratory conditions to understand the mechanisms that underlie this plasticity which maximizes fitness under natural conditions. This article is part of the themed issue ‘Wild clocks: integrating chronobiology and ecology to understand timekeeping in free-living animals’.

Optical atomic clocks have demonstrated revolutionary advances in precision timekeeping, but their applicability to the real world is critically dependent on whether such clocks can operate outside the laboratory. Photonic integration offers one compelling solution to address the miniaturization and ruggedization needed to enable clock portability, but brings with it a new set of challenges in recreating the functionality of an optical clock using chip-scale building blocks. The clock laser used for atom interrogation is one particular point of uncertainty, as the performance of the meticulously engineered bulk-cavity-stabilized lasers would be exceptionally difficult to transfer to chip. Here we demonstrate that an integrated ultrahigh-quality-factor spiral cavity, when interfaced with a 1,348 nm seed laser, is able to reach a fractional frequency instability of 7.5 × 10 −14 on chip. On frequency doubling the light to 674 nm, we use this laser to interrogate the narrow-linewidth transition of 88 Sr + and showcase the operation of a Sr-ion clock with short-term instability averaging down as 3.9 × 1 0 − 14 / τ ( τ , averaging time). Our demonstration of a high-performance optical atomic clock interrogated by an integrated spiral cavity laser opens the door for future advanced clock systems to be entirely constructed using lightweight, portable and mass-manufacturable integrated optics and electronics. A chip-integrated laser with 7.5 × 10 −14 fractional frequency instability is demonstrated by active stabilization to an on-chip 6.1-m-long spiral resonator. By using this laser to interrogate the narrow-linewidth transition of 88 Sr + , a clock instability averaging down as 3.9 × 1 0 − 14 / τ is achieved.

In mammals, the circadian clock consists of transcriptional and translational feedback loops through DNA cis -elements such as E-box and RRE. The E-box-mediated core feedback loop is interlocked with the RRE-mediated feedback loop, but biological significance of the RRE-mediated loop has been elusive. In this study, we established mutant cells and mice deficient for rhythmic transcription of Bmal1 gene by deleting its upstream RRE elements and hence disrupted the RRE-mediated feedback loop. We observed apparently normal circadian rhythms in the mutant cells and mice, but a combination of mathematical modeling and experiments revealed that the circadian period and amplitude of the mutants were more susceptible to disturbance of CRY1 protein rhythm. Our findings demonstrate that the RRE-mediated feedback regulation of Bmal1 underpins the E-box-mediated rhythm in cooperation with CRY1-dependent posttranslational regulation of BMAL1 protein, thereby conferring the perturbation-resistant oscillation and chronologically-organized output of the circadian clock. The mammalian circadian clock is composed of clock genes forming transcriptional feedback loops. Here, the authors identify a key role of the secondary feedback loop that is interlocked with the core loop to establish a perturbation-resilient clock system.

Light–dark cycles affect photosynthetic efficiency in autotrophic cyanobacteria; therefore, determining whether ancient cyanobacteria possessed a self-sustained circadian clock when oxygenic photosynthetic systems were established is an important issue in chronobiology. Here we examine the oscillation of the clock protein KaiC in modern cyanobacteria, as well as the function and structure of ancestral Kai proteins, to determine the evolutionary origin of the self-sustained Kai-protein oscillators. The results show that the oldest double-domain KaiC in ancestral bacteria lacks the factors functionally and structurally essential for rhythmicity. The ancestral Kai proteins have acquired these factors through molecular evolution that occurred around Global Oxidation and Snowball Earth events, and are eventually inherited as a self-sustained circadian oscillator by the most recent common ancestor of cyanobacteria capable of oxygenic photosynthesis. This autonomous Kai protein oscillator is further inherited by most freshwater and marine cyanobacteria present today as an autotrophic basis for time-optimal acquisition and consumption of energy from oxygenic photosynthesis. Autotrophic cyanobacteria use circadian clock systems to rhythmically regulate photosynthetic efficiency to adapt to the light-dark cycle on Earth. Here, the authors show that the oldest cyanobacterial clock-protein oscillator appears at approximately 2.2 Ga ago, and has been inherited by extant cyanobacteria.