Mechanical Time Research Articles

MDM2 functions as a timer reporting the length of mitosis.

Delays in mitosis trigger p53-dependent arrest in G1 of the next cell cycle, thus preventing repeated cycles of chromosome instability and aneuploidy. Here we show that MDM2, the p53 ubiquitin ligase, is a key component of the timer mechanism triggering G1 arrest in response to prolonged mitosis. This timer function arises due to the attenuation of protein synthesis in mitosis. Because MDM2 has a short half-life and ongoing protein synthesis is therefore necessary to maintain its steady-state concentration, the amount of MDM2 gradually falls during mitosis but normally remains above a critical threshold for p53 regulation at the onset of G1. When mitosis is extended by prolonged spindle assembly checkpoint activation, the amount of MDM2 drops below this threshold, stabilizing p53. Subsequent p53-dependent p21 accumulation then channels G1 cells into a sustained cell-cycle arrest, whereas abrogation of the response in p53-deficient cells allows them to bypass this crucial defence mechanism.

LEA-RPL: lightweight energy-aware RPL protocol for internet of things based on particle swarm optimization

This paper addresses the issue of quality of service routing optimization within the Internet of Things networks. We particularly focus on the energy-aware and the lightweight aspects. By recognizing the relationship between lightweight and energy-aware routing, we set out to study their combined benefits. This study aims to enhance the Routing Protocol for Low Power and Lossy Networks by integrating energy-awareness and lightweight characteristics based on the Particle Swarm Optimization algorithm. Our approach addresses energy consumption, routing overhead and decision complexity in route establishment. The principal contributions include the introduction of an objective function that considers Expected Life Time, Delay and a new proposed metric Energy Aware-Expected Transmission Count. The improvement of the Long Short Term Memory predicting inertia weight based PSO with Online Gradient Descent that is used to optimize both the parent selection process and Trickle Timer mechanism. The controlled parent switching process to solve unnecessary and frequent changes. Our approach is validated through simulations in Contiki COOJA, with thorough comparisons with some existing protocols based on packet delivery ratio, average energy consumption, convergence time, control overhead, average end-to-end delay and average parent switching as performance metrics. The results reveal that our approach performs better. Depending on the protocol used for comparison, our approach reduced parent switching by 42.59–61.73%, convergence time by 20.31–66.06%, control overhead by 14.4–23.64%, energy consumption by 29.86–49.6%, end-to-end delay by 7.66–40.81% and increased packet delivery ratio by 2–42.92%.

ECR Spotlight – Fredrik Markussen

ECR Spotlight is a series of interviews with early-career authors from a selection of papers published in Journal of Experimental Biology and aims to promote not only the diversity of early-career researchers (ECRs) working in experimental biology but also the huge variety of animals and physiological systems that are essential for the ‘comparative’ approach. Fredrik Markussen is an author on ‘ c-fos induction in the choroid plexus, tanycytes and pars tuberalis is an early indicator of spontaneous arousal from torpor in a deep hibernator’, published in JEB. Fredrik is a PhD student in the lab of Shona Wood at UiT – Arctic University of Norway, investigating hibernation timer mechanisms in golden hamsters.

Progeny counter mechanism in malaria parasites is linked to extracellular resources.

Malaria is caused by the rapid proliferation of Plasmodium parasites in patients and disease severity correlates with the number of infected red blood cells in circulation. Parasite multiplication within red blood cells is called schizogony and occurs through an atypical multinucleated cell division mode. The mechanisms regulating the number of daughter cells produced by a single progenitor are poorly understood. We investigated underlying regulatory principles by quantifying nuclear multiplication dynamics in Plasmodium falciparum and knowlesi using super-resolution time-lapse microscopy. This confirmed that the number of daughter cells was consistent with a model in which a counter mechanism regulates multiplication yet incompatible with a timer mechanism. P. falciparum cell volume at the start of nuclear division correlated with the final number of daughter cells. As schizogony progressed, the nucleocytoplasmic volume ratio, which has been found to be constant in all eukaryotes characterized so far, increased significantly, possibly to accommodate the exponentially multiplying nuclei. Depleting nutrients by dilution of culture medium caused parasites to produce fewer merozoites and reduced proliferation but did not affect cell volume or total nuclear volume at the end of schizogony. Our findings suggest that the counter mechanism implicated in malaria parasite proliferation integrates extracellular resource status to modify progeny number during blood stage infection.

Biological timekeeping in polar environments: lessons from terrestrial vertebrates.

The polar regions receive less solar energy than anywhere else on Earth, with the greatest year-round variation in daily light exposure; this produces highly seasonal environments, with short summers and long, cold winters. Polar environments are also characterised by a reduced daily amplitude of solar illumination. This is obvious around the solstices, when the Sun remains continuously above (polar 'day') or below (polar 'night') the horizon. Even at the solstices, however, light levels and spectral composition vary on a diel basis. These features raise interesting questions about polar biological timekeeping from the perspectives of function and causal mechanism. Functionally, to what extent are evolutionary drivers for circadian timekeeping maintained in polar environments, and how does this depend on physiology and life history? Mechanistically, how does polar solar illumination affect core daily or seasonal timekeeping and light entrainment? In birds and mammals, answers to these questions diverge widely between species, depending on physiology and bioenergetic constraints. In the high Arctic, photic cues can maintain circadian synchrony in some species, even in the polar summer. Under these conditions, timer systems may be refined to exploit polar cues. In other instances, temporal organisation may cease to be dominated by the circadian clock. Although the drive for seasonal synchronisation is strong in polar species, reliance on innate long-term (circannual) timer mechanisms varies. This variation reflects differing year-round access to photic cues. Polar chronobiology is a productive area for exploring the adaptive evolution of daily and seasonal timekeeping, with many outstanding areas for further investigation.

The Significance of Al-Jazari's Four-Bucket Water Lifting Machine in the History of Engineering and Science

The developments in the field of engineering have an eclectic structure. During ancient times, the works carried out at the School of Mechanical Engineering in Alexandria were transmitted to the Islamic world through translations at the House of Wisdom (Bayt al-Hikmah). Following this process, engineering studies became the focus of research in the Islamic world, both from theoretical and practical perspectives. Prominent researchers in this context include the Banu Musa brothers (9th century), Al-Farabi (875-950), Al-Hazini (1100s), and Al-Jazari (13th century). The renowned Turkish philosopher Al-Farabi conducted research on air and vacuum, expressing his views in the treatise "Risale li-Ebi Nasr al-Farabi fi’l-Hala" (On Vacuum). Al-Hazini's book "Mizanu’l Hikme" (The Balance of Wisdom) sheds light on the concept of balance, with Hazini turning the water balance into an extraordinary equilibrium device and creating a balance called "Mizânü'l-Câmî" (The Collector).The Banu Musa brothers presented valuable machine and mechanical system designs in their work "Kitab al-Hiyal" (The Book of Ingenious Devices). Al-Jazari, born in 1153 in Cizre, served as the chief engineer of the Artuklu palace for 32 years. During this time, he designed many mechanical and automation-based systems. Upon examining the designs in Al-Jazari's book "Kitab-ül Cami Beyn-el-İl ve'l-Amel el-Nâfi fi Sınaât el Hiyel," it becomes apparent that he elevated the designs made before him to a completely different level. Some of today's engineering designs can trace their origins to the drawings found in this book. In this study, the design features of Al-Jazari's 4-bucket water-lifting machine are examined, and its value in contemporary engineering is explored. Al-Jazari designed a mechanical timer to ensure the continuity of water flow in his design. This timer allowed each bucket to discharge water one after the other, maintaining a continuous flow of water. He achieved this through a shaft with quarter-toothed gears. This design can be considered the precursor to the eccentric and crankshafts found in modern internal combustion engines. The eccentric shaft controls the mechanical timing of valves in engines, while crankshafts ensure the continuous transmission of the force generated by four pistons in a four-stroke engine over a quarter of the cycle to the flywheel gear.

MIA-NDN: Microservice-Centric Interest Aggregation in Named Data Networking.

The named data networking (NDN)-based microservice-centric in-network computation poses various challenges in terms of interest aggregation and pending interest table (PIT) lifetime management. A same-named microservice-centric interest packet may have a different number of input parameters with nonidentical input values. In addition, the same-named interest packet with the same number of parameters may have different corresponding parameter values. The vanilla NDN request aggregation (based on the interest name, while ignoring the input parameters count and/or their corresponding values) may result in false aggregation. Moreover, the microservice-centric requested computations may fail to accomplish in the default 4s PIT timer due to the input size. To address these challenges, this paper presents MIA-NDN: microservice-centric interest aggregation in named data networking. We designed microservice-centric interest-naming to enable name-based communication. MIA-NDN develops a robust interest aggregation mechanism that not only performs the interest aggregation based on the interest name but also considers the input parameter counts and their corresponding values in the interest aggregation process to avoid false packet aggregations. A dynamic PIT timer mechanism based on input size was devised that avoids the PIT entry losses if the execution time exceeds the default PIT timer value to avoid computation losses and uphold the application quality of service (QoS). Extensive software-based simulations confirm that the MIA-NDN outperforms the benchmark scheme in terms of microservice-centric interest aggregation, microservice satisfaction rate, and communication overhead.

Multi crop high efficiency seed drill with solar hybrid seed metering: A step toward precision and sustainability

High crop production with limited energy resources is always the priority area of developing countries. Conventional agricultural experimenting and crop production methods are time-consuming, challenging, laborious, and energy intensive. Various developments and experimental studies have been carried out for advancement in agriculture technologies. This study is mainly focused on the design and development of a unique high-efficiency seed drill machine to increase the energy efficiency of agricultural experiments, and crop production and conserve the tillage, seed, fertilizer, and power requirement. This machine has a special seed dividing head and seed distributor triggered with a mechanical timer. The mechanical timer is responsible to deliver seed to the seed distributor as per fixed plotting intervals. The seed distribution unit distributes the seeds uniformly in all furrows as per the pre-decided seed rate aided with a centrifugal glider aided with a DC motor powered by a 30 W solar PV plate and backup battery. Moreover, the machine has 9 × 9 s-type spring tines for seed and fertilizer, which are mainly designed for better soil pulverization and aeration with significant in-field resource conservation as per conventional alternatives. The effective width is seven feet and adjustable rows with versatile seed rate options. Overall, the results from different field tests verified the uniform seed dispersal with improved germination rate. The analysis of power requirements compared to conventional machines results in the 40% less power requirement. Overall, the machine has customized unique features for experiments and energy-efficient precision agriculture to conserve input resources.

Real-Time Collection of Conidia Released from Living Single Colonies of Podosphaera aphanis on Strawberry Leaves under Natural Conditions with Electrostatic Techniques.

Powdery mildew fungi produce progeny conidia on conidiophores, and promote the spread of powdery mildew diseases by dispersal of the conidia from conidiophores in the natural environment. To gain insights and devise strategies for preventing the spread of powdery mildew infection, it is important to clarify the ecological mechanism of conidial dispersal from conidiophores. In this study, all of the progeny conidia released from single colonies of strawberry powdery mildew fungus (Podosphaera aphanis (Wallroth) U. Braun and S. Takamatsu var. aphanis KSP-7N) on true leaves of living strawberry plants (Fragaria × ananassa Duchesne ex Rozier cv. Sagahonoka) were consecutively collected over the lifetime of the colony with an electrostatic rotational spore collector (insulator drum) under greenhouse conditions, and counted under a high-fidelity digital microscope. The insulator drum consisted of a round plastic container, copper film, thin and transparent collector film, electrostatic voltage generator, and timer mechanism. When negative charge was supplied from the voltage generator to the copper film, the collector film created an attractive force to trap conidia. The electrostatically activated collector film successfully attracted progeny conidia released from the colony. Experiment was carried out at just one colony on one leaf for each month (in February, May, July, October, November, and December in 2021), respectively. Each collector film was exchanged for a new collector film at 24 h intervals until KSP-7N ceased to release progeny conidia from single colonies. Collection experiments were carried out to estimate the total number of conidia released from a single KSP-7N colony over a 35-45-day period after inoculation. During the fungal lifetime, KSP-7N released an average of 6.7 × 104 conidia from each of the single colonies at approximately 816 h. In addition, conidial release from KSP-7N colonies was largely affected by the light intensity and day length throughout a year; the number of conidia released from single KSP-7N colonies in night-time was clearly smaller than that in daytime, and the time of conidial release from single KSP-7N colonies was shorter by approximately 2 to 4 h in autumn and winter than in spring and summer. The ecological characteristics related to conidial releases from KSP-7N colonies will be helpful information for us to successfully suppress the spread of strawberry powdery mildews onto host plants under greenhouse conditions.

Traffic signal control in mixed traffic environment based on advance decision and reinforcement learning

Abstract Reinforcement learning-based traffic signal control systems (RLTSC) can enhance dynamic adaptability, save vehicle travelling time and promote intersection capacity. However, the existing RLTSC methods do not consider the driver's response time requirement, so the systems often face efficiency limitations and implementation difficulties. We propose the advance decision-making reinforcement learning traffic signal control (AD-RLTSC) algorithm to improve traffic efficiency while ensuring safety in mixed traffic environment. First, the relationship between the intersection perception range and the signal control period is established and the trust region state (TRS) is proposed. Then, the scalable state matrix is dynamically adjusted to decide the future signal light status. The decision will be displayed to the human-driven vehicles (HDVs) through the bi-countdown timer mechanism and sent to the nearby connected automated vehicles (CAVs) using the wireless network rather than be executed immediately. HDVs and CAVs optimize the driving speed based on the remaining green (or red) time. Besides, the Double Dueling Deep Q-learning Network algorithm is used for reinforcement learning training; a standardized reward is proposed to enhance the performance of intersection control and prioritized experience replay is adopted to improve sample utilization. The experimental results on vehicle micro-behaviour and traffic macro-efficiency showed that the proposed AD-RLTSC algorithm can simultaneously improve both traffic efficiency and traffic flow stability.

Mechanical Timer-Actuated Fluidic Dispensing System: Applications to an Automated Multistep Lateral Flow Immunoassay with High Sensitivity.

In this study, we present a fluidic dispensing system that can automate the sequential fluidic delivery of multiple reagents for lateral flow assays. Highly sensitive assays typically require multiple solution-based sequences, including washing steps and signal amplification. However, implementation of these types of sequences on an automated and highly sensitive point-of-care testing (POCT) platform remains challenging. Our platform consists of two disposable cartridges with reagent chambers and a test strip and an instrument that has a mechanical timer to actuate the cam-follower-gear components. The timer rotation sequentially shifts the position of the chambers and loads the reagents to the test paper strip. The dispensing intervals are controlled at a variation of <1% within a total actuation time of 60 min. Unlike other POCT devices, the timing of fluid delivery in our timer-actuated platform is not dependent on the selection of substrates and reagents, and the unique approach to fluidic delivery results in no reagent overlap or carryover, minimal reagent loss, and highly accurate fluidic timing control for highly sensitive solution-based assays. As a model application, the proposed platform applies a gold enhancement solution to amplify the detection signal and detect prostate-specific antigen with a limit of detection of 86 pg/mL within 27 min. This platform provides an opportunity for solution-based POCT applications with high sensitivity, thereby satisfying the requirement for user-friendly operations in resource-limited settings.

The people behind the papers - Adélaïde Allais and Greg FitzHarris.

Aneuploidy is relatively common in mammalian preimplantation embryos, due to chromosome segregation errors in mitosis. A new paper in Development investigates whether the mitotic timer mechanism, a checkpoint that detects prolonged M phase, which may indicate an unhealthy cell division, is active in preimplantation mouse embryos. We caught up with first author Adélaïde Allais and corresponding author Greg FitzHarris (Professor at the Université de Montréal) to find out more about their research.

Absence of a robust mitotic timer mechanism in early preimplantation mouse embryos leads to chromosome instability

Preimplantation embryos often consist of a combination of euploid and aneuploid cells, suggesting that safeguards preventing the generation and propagation of aneuploid cells in somatic cells might be deficient in embryos. In somatic cells, a mitotic timer mechanism has been described, in which even a small increase in the duration of M phase can cause a cell cycle arrest in the subsequent interphase, preventing further propagation of cells that have undergone a potentially hazardously long M phase. Here, we report that cell divisions in the mouse embryo and embryonic development continue even after a mitotic prolongation of several hours. However, similar M-phase extensions caused cohesion fatigue, resulting in prematurely separated sister chromatids and the production of micronuclei. Only extreme prolongation of M phase caused a subsequent interphase arrest, through a mechanism involving DNA damage. Our data suggest that the simultaneous absence of a robust mitotic timer and susceptibility of the embryo to cohesion fatigue could contribute to chromosome instability in mammalian embryos. This article has an associated 'The people behind the papers' interview.

A tunable population timer in multicellular consortia

SummaryProcessing time-dependent information requires cells to quantify the duration of past regulatory events and program the time span of future signals. At the single-cell level, timer mechanisms can be implemented with genetic circuits. However, such systems are difficult to implement in single cells due to saturation in molecular components and stochasticity in the limited intracellular space. In contrast, multicellular implementations outsource some of the components of information-processing circuits to the extracellular space, potentially escaping these constraints. Here, we develop a theoretical framework, based on trilinear coordinate representation, to study the collective behavior of populations composed of three cell types under stationary conditions. This framework reveals that distributing different processes (in our case the production, detection and degradation of a time-encoding signal) across distinct strains enables the implementation of a multicellular timer. Our analysis also shows that the circuit can be easily tunable by varying the cellular composition of the consortium.

Chaperones for dancing on chromatin: Role of post-translational modifications in dynamic damage detection hand-offs during nucleotide excision repair.

We highlight a recent study exploring the hand-off of UV damage to several key nucleotide excision repair (NER) proteins in the cascade: UV-DDB, XPC and TFIIH. The delicate dance of DNA repair proteins is choreographed by the dynamic hand-off of DNA damage from one recognition complex to another damage verification protein or set of proteins. These DNA transactions on chromatin are strictly chaperoned by post-translational modifications (PTM). This new study examines the role that ubiquitylation and subsequent DDB2 degradation has during this process. In total, this study suggests an intricate cellular timer mechanism that under normal conditions DDB2 helps recruit and ubiquitylate XPC, stabilizing XPC at damaged sites. If DDB2 persists at damaged sites too long, it is turned over by auto-ubiquitylation and removed from DNA by the action of VCP/p97 for degradation in the 26S proteosome.

ТЕМПЕРАТУРНИЙ КОНТРОЛЕР НА СУЧАСНИХ НАПІВПРОВІДНИКОВИХ ДАТЧИКАХ

The ultra-fast development of electronics in the last decade, as well as the constant reduction in the price of electronic components, lead to the fact that many manufacturers of household and industrial equipment replace electromechanical components with microcontroller-controlled electronic circuits in the manufactured equipment. The regulator, on the bimetallic plate and the mechanical timer are inferior in many respects to the electronic regulator and the digital timer. In this work, there was a study of an intelligent temperature module, since in industrial automation there is a tendency for widespread use of such intelligent sensor devices and microcontrollers that collect information, preprocess it, and then forward or store it. Such modules can work autonomously, collecting information about the measurement object and accumulating it until the moment of transfer to the operator (usually implemented on the basis of battery power), or they can be combined into a sensor network while standing but interacting with the main measurement unit. The sensor is powered via an interface cable, and in some cases using signal lines. The criteria for choosing a microcontroller for these purposes are: 1. Kernel performance, the required size of program and data memory, a sufficient number of I / O port lines. 2. The cost of the microcontroller. 3. Technical parameters of the microcontroller (supply voltage range, operating temperature range, resistance to electromagnetic interference). 4. The life cycle of the selected family. 5. FLASH-memory of programs possessing a sufficient resource for programming (minimum resource 1000 times, desirable 100 000). 6. Reduction to the actually necessary value of the frequency of the processor (the use of clock quartz in order to reduce current consumption). 7. Power supply to peripheral microcircuits (external ADCs, FLASH-memory) directly from the processor outputs or through key elements only for the duration of their operation. In the article, a circuit diagram based on the PIC16F84A microcontroller is designed, in which a general circuit model based on Brock’s cell and an operational amplifier-comparator was used as a heat-sensitive sensor. A feature of this microcontroller system is that it is equipped with an optocoupler and triac assembly, which allows you to connect a powerful load of up to 20 A and control it remotely. In addition, volt-temperature characteristics for the presence of non-linearity were considered in the work and the choice of sensor was justified. Keywords: microcontroller, data acquisition system, temperature, measurement error.

EPF—An Efficient Forwarding Mechanism in SDN Controller Enabled Named Data IoTs

The vision of the Internet of Things (IoT) is that it connects all kinds of things by leveraging the creation of increasingly affordable and small devices that can be embedded for sensing, processing, wireless communication, and actuation. Named data networking (NDN) is a newly emerging Internet paradigm that may replace the current Internet architecture and that fulfills most of the expectations of the IoT. Software-defined networking (SDN) is an emerging paradigm of technology that is highly capable of managing overall networks efficiently and transforming complex network architectures into manageable, simple ones. The combination of the SDN controller, NDN, and IoT can be lethal in the overall performance of the network. Broadcast storms, due to the flooding nature of NDN’s wireless channel, are a serious issue when it comes to forwarding interest and data packets. Energy consumption of sensor nodes in dense IoT scenarios causes problems in forwarding as well as unnecessary delays, decreases network performance, and increases the cost and packet delay for important packets. We took these problems as our baseline and proposed an energy-efficient, priority-based forwarding (EPF) in SDN-enabled NDN–IoT. Our scheme EPF used the efficient flow management of the SDN controller to control the broadcast storm and efficiently forward the priority-based packets. A defer timer mechanism was used to prioritized the packet upon its arrival to the node. An energy threshold mechanism was used to control energy consumption and improve overall energy efficiency. We compared our scheme with the traditional flooding mechanism and geographic interest forwarding; EPF outclassed the other schemes and produced the best results in terms of total number of interests and retransmissions, content retrieval time, total number of priority interests, energy consumption, and network lifetime.

Current timer switch in a GaAs-based nanowire coupled with polyoxometalate nanoparticle and conductive AFM tip

We demonstrate a current timer switch function in a GaAs-based nanowire electrostatically coupled with a polyoxometalate nanoparticle (POM NP) and a conductive atomic force microscopy (AFM) tip. The nanowire current associated with the charge state of the POM NP on the nanowire surface abruptly changed after several ten seconds from biasing the conductive tip. The current switch timing changed depending on the tip voltage. The timer switch function appeared when the tip approached the POM NP where the AFM phase image showed phase lag at high atmospheric humidity condition. We discuss the timer mechanism in terms of the configuration of the electromechanical potential of the cantilever and dynamic potential modulation by mobile ions and polarized molecules in the water-absorbed POM NP surface.

Circadian clock mechanism driving mammalian photoperiodism

The annual photoperiod cycle provides the critical environmental cue synchronizing rhythms of life in seasonal habitats. In 1936, Bünning proposed a circadian-based coincidence timer for photoperiodic synchronization in plants. Formal studies support the universality of this so-called coincidence timer, but we lack understanding of the mechanisms involved. Here we show in mammals that long photoperiods induce the circadian transcription factor BMAL2, in the pars tuberalis of the pituitary, and triggers summer biology through the eyes absent/thyrotrophin (EYA3/TSH) pathway. Conversely, long-duration melatonin signals on short photoperiods induce circadian repressors including DEC1, suppressing BMAL2 and the EYA3/TSH pathway, triggering winter biology. These actions are associated with progressive genome-wide changes in chromatin state, elaborating the effect of the circadian coincidence timer. Hence, circadian clock-pituitary epigenetic pathway interactions form the basis of the mammalian coincidence timer mechanism. Our results constitute a blueprint for circadian-based seasonal timekeeping in vertebrates.

Photoperiodic induction without light-mediated circadian entrainment in a High Arctic resident bird.

Organisms use changes in photoperiod to anticipate and exploit favourable conditions in a seasonal environment. While species living at temperate latitudes receive day length information as a year-round input, species living in the Arctic may spend as much as two-thirds of the year without experiencing dawn or dusk. This suggests that specialised mechanisms may be required to maintain seasonal synchrony in polar regions. Svalbard ptarmigan (Lagopus muta hyperborea) are resident at 74-81°N latitude. They spend winter in constant darkness (DD) and summer in constant light (LL); extreme photoperiodic conditions under which they do not display overt circadian rhythms. Here, we explored how Arctic adaptation in circadian biology affects photoperiodic time measurement in captive Svalbard ptarmigan. For this purpose, DD-adapted birds, showing no circadian behaviour, either remained in prolonged DD, were transferred into a simulated natural photoperiod (SNP) or were transferred directly into LL. Birds transferred from DD to LL exhibited a strong photoperiodic response in terms of activation of the hypothalamic thyrotropin-mediated photoperiodic response pathway. This was assayed through expression of the Eya3, Tshβ and deiodinase genes, as well as gonadal development. While transfer to SNP established synchronous diurnal activity patterns, activity in birds transferred from DD to LL showed no evidence of circadian rhythmicity. These data show that the Svalbard ptarmigan does not require circadian entrainment to develop a photoperiodic response involving conserved molecular elements found in temperate species. Further studies are required to define how exactly Arctic adaptation modifies seasonal timer mechanisms.