Many processes in mammalian body exhibit circadian rhythms. These rhythms are driven by an intricate system composed of the central pacemaker, suprachiasmatic nuclei (SCN) in the brain, which entrains the peripheral oscillators in various organs, such as pancreas, liver, colon and lungs. Circadian clocks are autonomously driven in each cell based on molecular circuits involving so called clock genes, such as BMAL, CLOCK, PER and CRY. Age- dependent impairment of physiological functions of mammalian body, such as behaviour and metabolic functions, has been well documented. However, it has not been fully elucidated whether the impairment is linked with worsening of the circadian clock function. The aim of our study was to find out whether i) aging affects basic properties of the circadian clock in SCN and peripheral organs, such as pancreas, colon, liver and lungs, ii) aging- induced changes in glucose homeostasis affect the properties of the circadian clock in the pancreas, and iii) the sensitivity of circadian clock in SCN and peripheral organs to disturbances in environmental lightning conditions is altered during aging. We used groups of adult (9 months) and aged (25 months) animals which were subjected to 3 different light regimes, namely to light/dark regime (LD 12:12), constant light (LL) and...

Despite recent interest, there still is relatively little known about the ecology and physiology of diel and circadian rhythms in spiders. However, previous work on spiders suggests that there is a striking amount of variation in circadian period both among, and within, species, when compared to model organisms. Whereas previous studies of behavioral rhythms in spiders focused on females, here we describe the diel and circadian patterns of locomotor activity in male Parasteatoda tepidariorum (C. L. Koch, 1841) (Theridiidae). We found that the males showed mostly nocturnal activity under a light:dark cycle, with activity peaking very early after lights off and steadily declining to near zero just prior to lights on. Under constant darkness most individuals showed significant circadian rhythmicity with a mean free-running period of about 21.2 h. Though not the shortest average free-running period described for spiders, being so out of resonance with the 24 h solar day strains conventional circadian rhythm theory. Our data also suggest that the phase angle of entrainment for locomotor activity is in the mid-to-late photophase, but that activity may be masked by light. Of particular note is that both the diel and circadian activity patterns reported here for male P. tepidariorum are similar to those reported elsewhere for females of the species. This study deepens our understanding of the nature and variation in circadian rhythm in spiders and builds a case for further developing spiders as a model system for research integrating the fields of chronobiology and ecology.

Circadian rhythms are endogenous cycles that control physiological and behavioral changes that can be affected by environmental factors which allow most eukaryotic organisms to synchronize their daily activities with the 24-hour day. Parasteatoda tepidariorum,the common house spider, demonstrates a short-period circadian clock averaging 21.6 hours when left in constant darkness, yet they are able to entrain to a 24-hour light cycle. We tested whether these spiders were able to use non-photic Zeitgebers to entrain to the 24-hour day. Periodic presentation of food and disturbance were not found to be effective cues for the spiders’ entrainment. A few individuals were clearly able to entrain to an 8 oC amplitude temperature cycle, while most did not.

Methods of timekeeping have changed drastically throughout history and especially in the last century, as has humanity’s relationship to nature. Building upon existing research into the history of clocks and clock-time this study sketches a long-term chronology with a novel environmental, sensory, and aesthetic analysis. The connection between everyday time(keeping) and the environment, as well as the significant role of objects in how we tell the time. The interactions with our surroundings is explored in order to understand the material role of technology, techno-aesthetics, and eco-social cues. The thesis investigates the aesthetic and sensory dimensions of historical timekeeping, particularly with regards to sound and vision. The thesis follows a chronological narrative so that the significant shifts in European timekeeping can be identified at particular moments in history, as well as demonstrating the overall arc of change. It begins with the lead up to the invention of mechanical clocks followed by a case study – conducted using imaginative phenomenology – of an Uppsala student in 1482 interacting with the clock-bell in his local timescape. After sketching the significant inventions and shifts in the proceeding centuries, there is a comparative case study that conducts a phenomenological autoethnography of the author’s timekeeping practices in Uppsala in 2022 and aesthetic analysis of personal clock devices. This seeks to identify what characterises timekeeping in the Anthropocene. Throughout, the thesis compares the experiences of ‘time foraging’ as opposed to ‘self-referential timekeeping’ to explore how different timekeeping affects our relations on an ecological and social scale.

No description available.

The immaculate control of atoms and molecules with light is the defining trait of modern experiments in ultracold physics. The rich internal degrees of freedom afforded by molecules enrich the toolbox of precision spectroscopy for fundamental physics, and hold great promise for applications in quantum simulation and quantum information science. A vibrational molecular lattice clock with systematic fractional uncertainty at the 14th decimal place is demonstrated for the first time, matching the performance of the earliest optical atomic clocks. Van der Waals dimers of strontium are created at ultracold temperatures and levitated by an optical standing wave, whose wavelength is finely tuned to preserve the delicate molecular vibrational coherence. Guided by quantum chemistry theory refined by highly accurate frequency-comb-assisted laser spectroscopy, record-long Rabi oscillations were demonstrated between vibrational molecular states that span the entire depth of the ground molecular potential. Enabled by the narrow molecular clock linewidth, hertz-level frequency shifts were resolved, facilitating the first characterization of molecular hyperpolarizability in this context. In a parallel effort, deeply bound strontium dimers are coherently created using the technique of stimulated Raman adiabatic passage. Ultracold collisions of alkaline-earth metal molecules in the absolute ground state are studied for the first time, revealing inelastic losses at the universal rate. This thesis reports one of the most accurate measurement of a molecule's vibrational transition frequency to date, which may potentially serve as a secondary representation of the SI unit of time in the terahertz (THz) band where standards are scarce. The prototypical molecular clock lays the important groundwork for future explorations into THz metrology, quantum chemistry, and fundamental interactions at atomic length scales.

[pt] Neste trabalho nós procuramos uma solução para o problema: como construir uma escala de tempo atômico baseada em um pequeno grupo de relógios atômicos? Nós geramos uma escala de tempo atômico independente a partir de um conjunto de relógios atômicos, chamada ETAB1(onrj). Nós propomos que a ETAB1(ONRJ) seja usada como referência para a geração de um o novo Tempo Universal Coordenado Brasileiro, chamado de TUC(ONRJ) proposto. Nós mostramos que o TUC(ONRJ) proposto será mantido coordenado com o TUC(BIPM) dentro dos limites recomendados pelo Comité Consultatif pour la Définition de la Seconde, isto é, a diferença entre TUC e TUC(ONRJ) proposto, menor que mais ou menos 100ns. Para menter a Hora Legal Brasileira (TUC(ONRJ)) coordenada com a Hora Mundial (TUC(BIPM) é necessário realizar a rastreabilidade internacional da grandeza tempo. Um método é proposto para obtenção de uma estimativa diária da posição do TUC(ONRJ) utilizando o filtro de Kalman e um receptor GPS, com uma incerteza de mais ou menos 35ns. Uma comparação do desempenho entre as escalas de tempo TUC (ONRJ) proposto, TUC(NIST) e TUC(USNO) é apresentada / [en] In the present work we look we look for a solution of the problem: how to construction na atomic time scale based in a smallgroup of atomic clocks. We generate an independent atomic time scale from an ensemble of atomic clocks, named ETAB 1 (ONRJ). We propose that ETAB 1(ONRJ) be used as a reference for the generation of a new Brazilian Coordinated Universal Time, named UTC (ONRJ)proposed. We show that the UTC (ONRJ)proposed will be maintained coordinated with UTC (BIPM) within the limitis recommended by the Comité consultatif pour la Définition de la Seconde, that is, the difference between UTC (BIMP) and UTC (ONRJ)proposed less than +/-100ns. To maintain the UTC (onrj) coordinated with UTC(BIPM) it is necessary to realize the international traceability of time quantity. A method is proposed for obtain ddaily estimates of UTC (ONRJ) - UTC(BIPM) using Kalman filter and GPS receiver with uncertainty of +/-35ns. A comparison of performance between the time scales UTC(ONRJ)proposed, UTC(NIST) and UTC(USNO) is presented.

For years, frequency standards have been the cornerstone of precision measurement. Among these frequency standards, atomic clocks have set records in both precision and accuracy, and have redefined the second. There is growing interest in more complex molecular systems to complement precision measurements with atoms. The rich internal structure of even the simplest diatomic molecules could provide new avenues for fundamental physics research, including searches for extensions to the Standard Model, dark matter candidates, novel forces or corrections to gravity at short distances, and tests of the variation of fundamental constants. In this thesis, we discuss the fundamental architecture for a precise molecular system based on a strongly forbidden weakly-bound to deeply-bound vibrational transition in 88Sr dimers. We discuss early studies to characterise our system and gain technical and quantum control over the experiment in anticipation of a precise metrological measurement. We, then, demonstrate a record-breaking precision for our 88Sr2 molecular clock ushering in a new era for precision measurement with clocks. Borrowing techniques from previous atomic clock architecture, we measure a ∼32 THz clock transition between two vibrational levels in the electronic ground state, achieving a fractional uncertainty of 4.6 × 10−14 in a new frequency regime. In this current iteration, our molecular clock is fundamentally limited by two-body loss lifetimes of 200 ms and light scattering induced by our high-intensity lattice. Given these limitations, we suggest improvements to combat the effects from both the lattice and two-body collisions in our 1D trap. These include technical improvements to our experiment and strategic choices of particular clock states in our ground electronic potential. We describe in-depth studies of the chemistry and polarizability behaviour of our molecule, which elucidates preferential future directions for a second generation clock system. These empirical results are substantiated by an improved theoretical picture. Ultimately, our molecular system is built in order to probe new physics and as a tool for precision measurement. Leveraging our record-precision clock and our new-found understanding of our molecule, we predict the capacity for our system to place meaningful, competitive constraints on new physics, in particular on Yukawa-type extensions to gravity. These predictions motivate improvements to our current generation clock and set the stage for future measurements with this system.

No description available.

Yes / The essay revisits the puzzle of the ‘passage’ of time in relation to EPR-type measurements and asks what philosophical consequences can be drawn from them. Some argue that the lack of invariance of temporal order in the measurement of a space-like related EPR pair, under relativistic motion, casts serious doubts on the ‘reality’ of the lapse of time. Others argue that certain features of quantum mechanics establish a tensed theory of time – understood here as Possibilism or the growing block universe. The paper analyzes the employment of frame-invariant entropic clocks in a relativistic setting and argues that tenselessness does not imply timelessness. But this conclusion does not support a tensed theory of time, which requires a preferred foliation. It is argued that the only reliable inference from the EPR example and the use of entropic clocks is an inference not just to a Leibnizian order of the succession of events but a frame-invariant order according to some selected clocks.