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Melatonin is a neurohormone synthesized from dietary tryptophan in various organs, including the pineal gland and the retina. In the pineal gland, melatonin is produced at night under the control of the master clock located in the suprachiasmatic nuclei of the hypothalamus. Under physiological conditions, the pineal gland seems to constitute the unique source of circulating melatonin. Melatonin is involved in cellular metabolism in different ways. First, the circadian rhythm of melatonin helps the maintenance of proper internal timing, the disruption of which has deleterious effects on metabolic health. Second, melatonin modulates lipid metabolism, notably through diminished lipogenesis, and it has an antidiabetic effect, at least in several animal models. Third, pharmacological doses of melatonin have antioxidative, free radical‐scavenging, and anti‐inflammatory properties in various in vitro cellular models. As a result, melatonin can be considered both a circadian time‐giver and a homeostatic monitor of cellular metabolism, via multiple mechanisms of action that are not all fully characterized. Aging, circadian disruption, and artificial light at night are conditions combining increased metabolic risks with diminished circulating levels of melatonin. Accordingly, melatonin supplementation could be of potential therapeutic value in the treatment or prevention of metabolic disorders. More clinical trials in controlled conditions are needed, notably taking greater account of circadian rhythmicity. [ABSTRACT FROM AUTHOR]

Predation pressure and herbivory exert cascading effects on coral reef health and stability. However, the extent of these cascading effects can vary considerably across space and time. This variability is likely a result of the complex interactions between coral reefs' biotic and abiotic dimensions. A major biological component that has been poorly integrated into the reefs' trophic studies is the microbial community, despite its role in coral death and bleaching susceptibility. Viruses that infect bacteria can control microbial densities and may positively affect coral health by controlling microbialization. We hypothesize that viral predation of bacteria has analogous effects to the top-down pressure of macroorganisms on the trophic structure and reef health. Here, we investigated the relationships between live coral cover and viruses, bacteria, benthic algae, fish biomass, and water chemistry in 110 reefs spanning inhabited and uninhabited islands and atolls across the Pacific Ocean. Statistical learning showed that the abundance of turf algae, viruses, and bacteria, in that order, were the variables best predicting the variance in coral cover. While fish biomass was not a strong predictor of coral cover, the relationship between fish and corals became apparent when analyzed in the context of viral predation: high coral cover (> 50%) occurred on reefs with a combination of high predator fish biomass (sum of sharks and piscivores > 200 g m-2) and high virus-to-bacteria ratios (> 10), an indicator of viral predation pressure. However, these relationships were non-linear, with reefs at the higher and lower ends of the coral cover continuum displaying a narrow combination of abiotic and biotic variables, while reefs at intermediate coral cover showed a wider range of parameter combinations. The results presented here support the hypothesis that viral predation of bacteria is associated with high coral cover and, thus, coral health and stability. We propose that combined predation pressures from fishes and viruses control energy fluxes, inhibiting the detrimental accumulation of ecosystem energy in the microbial food web.

Copyright of Japanese Journal of JSCE / Doboku Gakkai Ronbunshu is the property of Japan Society of Civil Engineers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Este artigo apresenta a análise e operação de um conversor CA-CC trifásico, bidirecional e isolado em alta frequência, de único estágio com correção do fator de potência, destinado para aplicação como carregador embarcado de baterias de veículos elétricos. Este conversor pode operar nos modos Grid-to-Vehicle (G2V) e Vehicle-to-Grid (V2G). No lado primário tem-se um conversor boost trifásico intercalado (interleaving) com modulação PWM senoidal para conexão com a rede elétrica, e na saída um barramento CC com ponto médio. O lado secundário é composto por uma topologia em ponte completa com modulação PWM convencional de razão cíclica de 50%. A transferência de potência do lado primário ao secundário é realizada por meio da técnica de defasamento angular (phase-shift), a mesma utilizada em conversores Dual-Active Bridge (DAB). Devido a defasagem natural do sistema trifásico, é possível obter transferência de potência constante, de reduzida ondulação, por meio do controle do defasamento angular também constante. Os princípios de operação do conversor são apresentados e demonstrados por análises qualitativas e quantitativas. Resultados experimentais de um protótipo de potência de 3 kW, tensão de entrada da rede elétrica de 127 V/60 Hz, tensão de saída de 300 V e frequência de comutação de 50 kHz são apresentados. Em conformidade com as análises, o protótipo doconversor apresentou fator de potência de 0,997, potência transferida entre primário e secundário constante e de baixa ondulação e dinâmica satisfatória e rápida durante ensaios de inversão do fluxo de potência.

Sea urchin overgrazing is a leading cause of kelp forest loss and in such cases their removal is increasingly advocated for kelp forest restoration. However, refining removal approaches is needed to improve the efficiency and success of restoration, as most previous removal studies have been small scale and require ongoing removals to maintain low densities and allow kelp recovery. We investigated the effectiveness of one‐off urchin removal from large, semi‐discrete areas of urchin barrens as a tool to promote kelp recovery. We removed sea urchins (Evechinus chloroticus) from four areas (1.6–2 ha) of urchin barrens in northeastern New Zealand. Exposed urchins were reduced to approximately 7% of initial densities and remained low, yet cryptic urchin densities increased after 2 years. Kelp (Ecklonia radiata) and fucoid (Sargassum sinclairii, Carpophyllum spp.) densities increased rapidly in removal areas, but remained constant or declined in adjacent control urchin barren areas. Macroalgal canopy recovery varied among and within removal areas, but increased on average from approximately 5 to 43% in 2 years. Densities of large sea urchin predators did not increase with kelp recovery, likely due to ongoing fishing within removal areas. Our results demonstrate that a single urchin removal from large, semi‐discrete areas of urchin barrens can effectively and efficiently promote rapid multi‐species macroalgal recovery without additional actions (e.g. repeated urchin removals or macroalgae enhancement) for at least 2 years. However, this approach does not restore whole ecosystems and consequently restoration benefits through kelp recovery will be temporary without longer‐term urchin management and/or rebuilding of predator populations. [ABSTRACT FROM AUTHOR]

AbstractIn this work, we report experimental results of a proposed gear system for optimization of phase shifts used for extraction of phase between a reference and a test object in a Double Aperture Common Path Interferometer. The electromechanical approach is designed to increase the precision and control of automated transverse translation of a diffraction grating to obtain equidistant displacements, typically carried out manually. Calculations and analytics for the design and operation of the mechanical gear system are presented. The experimental results demonstrate significant error minimizing for equally spaced phase shifts compared to a previously reported implementation of our research group. The proposed system represents a reliable and low-cost implementation to improve the obtaining of suitable interferogram captures for equally spaced phase-shifting interferometry techniques.

Abstract Background Predation pressure and herbivory exert cascading effects on coral reef health and stability. However, the extent of these cascading effects can vary considerably across space and time. This variability is likely a result of the complex interactions between coral reefs’ biotic and abiotic dimensions. A major biological component that has been poorly integrated into the reefs' trophic studies is the microbial community, despite its role in coral death and bleaching susceptibility. Viruses that infect bacteria can control microbial densities and may positively affect coral health by controlling microbialization. We hypothesize that viral predation of bacteria has analogous effects to the top-down pressure of macroorganisms on the trophic structure and reef health. Results Here, we investigated the relationships between live coral cover and viruses, bacteria, benthic algae, fish biomass, and water chemistry in 110 reefs spanning inhabited and uninhabited islands and atolls across the Pacific Ocean. Statistical learning showed that the abundance of turf algae, viruses, and bacteria, in that order, were the variables best predicting the variance in coral cover. While fish biomass was not a strong predictor of coral cover, the relationship between fish and corals became apparent when analyzed in the context of viral predation: high coral cover (> 50%) occurred on reefs with a combination of high predator fish biomass (sum of sharks and piscivores > 200 g m−2) and high virus-to-bacteria ratios (> 10), an indicator of viral predation pressure. However, these relationships were non-linear, with reefs at the higher and lower ends of the coral cover continuum displaying a narrow combination of abiotic and biotic variables, while reefs at intermediate coral cover showed a wider range of parameter combinations. Conclusions The results presented here support the hypothesis that viral predation of bacteria is associated with high coral cover and, thus, coral health and stability. We propose that combined predation pressures from fishes and viruses control energy fluxes, inhibiting the detrimental accumulation of ecosystem energy in the microbial food web.

This paper proposes a new isolated high step-down DC–DC converter based on the phase-shift full-bridge converter. The proposed converter has some properties very suitable for high step-down applications including a high step-down ratio, low transformer turns ratio, low voltage stress on power switches, wide soft-switching range, and no saturation problem. These attractive features are achieved by a simple pulse-width modulation control method and a unique split-capacitor structure on the input side. By split-capacitor structure, both switching voltage and stress voltage of the power switches are decreased significantly. As a result, the required ZVS energy is reduced greatly, which means that an extended ZVS range can be obtained. This structure also leads to an inherent high step-down ratio, low transformer turns ratio, and de-saturation feature because the primary transformer voltage is decreased to a quarter of the input voltage and there are capacitors in series with the primary winding in power modes. In this paper, the operation principle is presented; the ZVS range and de-saturation feature are discussed in detail. In addition, a comprehensive comparison with some new isolated high step-down converters in the literature is also completed. Finally, a simulation verification using the LTspice simulation program and an 800 W, 400 V input, and 48 V output prototype are developed and tested to verify the salient features of the proposed converter.

Exposed to the constant light, the master clock located in the bilaterally paired suprachiasmatic nucleus (SCN) above the optic chiasma exhibits three rhythmic behaviors in hamsters. Some hamsters remain or lose circadian rhythms due to synchronization or desynchronization between the SCN neurons, respectively. Interestingly, the other hamsters show a phenomenon called "split", in which the left SCN and right SCN oscillate with a stable anti-phase. In this paper, a modified Kuramoto model is built to explain these three rhythmic behaviors, where the phase-shift of cellular coupling is taken into account. Three cases of phase-shifts are considered, including that first case exists in all the SCN neurons, second case exists between the left and right SCN, and the last case exists within each group. We found that the phase-shift is able to induce the anti-phase synchronization between the left SCN and right SCN in the former two cases, but eliminate this anti-phase synchronization in the latter case. Our findings provide an alternative explanation for the emergency of the split and shed light on the collective behaviors of the SCN neurons. [ABSTRACT FROM AUTHOR]

In this work, we report experimental results of a proposed gear system for optimization of phase shifts used for extraction of phase between a reference and a test object in a Double Aperture Common Path Interferometer. The electromechanical approach is designed to increase the precision and control of automated transverse translation of a diffraction grating to obtain equidistant displacements, typically carried out manually. Calculations and analytics for the design and operation of the mechanical gear system are presented. The experimental results demonstrate significant error minimizing for equally spaced phase shifts compared to a previously reported implementation of our research group. The proposed system represents a reliable and low-cost implementation to improve the obtaining of suitable interferogram captures for equally spaced phase-shifting interferometry techniques. [ABSTRACT FROM AUTHOR]

Symmetries play an essential role in the field of physics. In this paper, we examine the relationship between the eigen-amplitudes of four (2 × 2) symmetrical antennas and the symmetry of the amplitudes of their sources (excitations) using mirroring effects. In our case, we find that changing mirrors using symmetry is identical to the point group theory. By exploiting the symmetry problem, we can show the advantage of reducing the size of the analysis domain, at least by a factor of two or more (2, 4, and 8...etc.) (depending on the problem). Several simulation examples have been developed by the MoM-GEC and HFSS to validate this approach. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

da Silva, I.M.; Lobo, M.; Muipela, A.; Rocha, R.J.M., and Quintino, V., 2024. Coral reefs community structure in Pemba, Northern Mozambique: 2012 vs 2016. In: Phillips, M.R.; Al-Naemi, S., and Duarte, C.M. (eds.), Coastlines under Global Change: Proceedings from the International Coastal Symposium (ICS) 2024 (Doha, Qatar). Journal of Coastal Research, Special Issue No. 113, pp. 931-935. Charlotte (North Carolina), ISSN 0749-0208. The composition of the coral community in Pemba, Northern Mozambique, was assessed in 2012 and 2016. The composition and coral coverage were evaluated in two sites, Kaori and Wimbe, by analyzing 20-meter transects of 40 underwater photographs, each arranged along the reef crest. The coral community changed during the study period, with decreasing coverage of the reef-building coral and increasing macroalgae and soft coral. These findings suggest a potential long-term change to soft coral- or macroalgae-dominated reefs, combining climate change with anthropogenic forcing, mainly due to fishing and urban pressure. In 2019, cyclone Kenneth destroyed most of the reef, especially the ones under study. The monitoring places still didn't recover after the cyclone, which is mainly rubble, probably due to the area's extensive use of fishing nets. [ABSTRACT FROM AUTHOR]

Across many temperate coastlines worldwide, kelp habitat has degraded to be replaced by alternative reef‐states with consequences to ecosystem functioning. Identifying both causes of decline and mechanisms of resilience of remnant kelp habitat is critical for managing and restoring these ecosystems.We use a combination of aerial imagery and field experiments to reveal dynamics of kelp habitat fragmentation during phase‐shift from kelp Ecklonia radiata to overgrazed sea urchin barrens Heliocidaris erythrogramma in Port Phillip bay (Australia).Analysis of aerial images spanning 6 years (2009–2014) revealed fragmentation of kelp patches to result in increase in perimeter‐to‐area ratio during phase‐shift.Sea urchin foraging behaviour also changed from the edge to interior of kelp patches, with destructive grazing at the patch edge. Multiple modes of grazing were observed, with greatest rates of kelp bed decline occurring when urchins simultaneously grazed from the 'outside‐in' and 'inside‐out' of kelp patches. Overgrazing also triggered establishment of invasive kelp Undaria pinnatifida and proliferation of turf algae. Overgrazing reinforced native kelp decline, with overgrazing exacerbated by reduced provision of drift‐kelp.Synthesis and applications. Perimeter–area ratio of kelp patches can predict phase‐shift, with patch extinction occurring when ratios exceeded a critical ratio of ~0.7. Monitoring dynamics of this critical ratio using aerial imagery provides a novel and cost‐effective indicator of kelp ecosystem resilience for preventing further losses. Targeted culling/harvesting of overgrazing sea urchins along patch edges will enhance native kelp survival and decrease perimeter‐to‐area ratio of remnant kelp patches; reducing risk of phase‐shift to sediment‐trapping turfs and invasive kelp, dually promoting recovery of kelp ecosystems. [ABSTRACT FROM AUTHOR]

Channel estimation (CE) is a crucial phase in wireless communication systems, especially in cell-free (CF) massive multiple input multiple output (M-MIMO) since it is a dynamic wireless network. Therefore, this work is introduced to study CE for the CF M-MIMO system in the uplink phase, wherein the performance of different estimators are evaluated, discussed, and compared in various situations. We assume the scenario in which each access point has prior knowledge of the channel statistics. The phase-aware-minimum mean square error (PA-MMSE) estimator, the non-phase-aware-MMSE (NPA-MMSE) estimator, and the least-squares estimator are the three estimators which are exploited in this work. Besides, we consider the Rician fading channel in which the line-of-sight path is realized with a phase-shift that models the users' mobility where the considered phase-shift follows a uniform distribution. On the other hand, the mean-squared error metric is employed in order to evaluate the performance of each estimator, where an analytical and simulated result is provided for the PA-MMSE estimator and the NPA-MMSE estimator in order to assert our numerical results. [ABSTRACT FROM AUTHOR]

In the field of power electronics-based electrical power conversion, the Dual Active Bridge (DAB) topology has become very popular in recent years due to its characteristics (e.g., bidirectional operation and galvanic isolation), which are particularly suitable to applications such as interface to renewable energy sources, battery storage systems and in smart grids. Although this converter type has been extensively investigated, its analysis and control still pose many challenges, due to the multiple control variables that affect the complex behavior of the converter. This paper presents a theoretical model of the single-phase DAB converter. The proposed model is very general, i.e., it can consider any modulation technique and operating condition. In particular, the converter is seen as composed by four legs, each capable of generating voltage on the inductor, and by the two output legs, which can steer the resulting inductor current to the load. Three variables are considered as the control inputs, i.e., the phase-shifts with respect to one leg. This approach results in a very simple yet accurate closed-form algorithm for obtaining the inductor current waveform. Moreover, a novel analytical model is proposed for calculating the average output current, based on the phase-shift values, independently of the output voltage. It is also shown that average output current can be varied cycle-by-cycle, with no further dynamics. In fact, average output current is not affected by the initial value of inductor current or by DC offset (which may arise during transients). The proposed models can be exploited at several stages of development of a DAB: during the design stage, for fast iteration, when selecting its operating points and when designing the control. In fact, based on the analytical results, a novel control loop is proposed, which adopts a "fictitious" (i.e., open-loop) inner current regulation loop, which can be applied to any modulation scheme (e.g., Single Phase-Shift, Triple Phase-Shift, etc.). The main advantage of this control scheme is that the simple dynamics of the output voltage versus the average output current can be decoupled from the complicated relationship between the phase-shifts and the output current. Moreover, a Finite Control Set (FCS) method is proposed, which selects the optimal operating points for each operating condition and control request, ensuring full Zero-Voltage Switching (ZVS) in all cases. The analytical results obtained and control methods proposed are verified through simulations and extensive experimental tests. [ABSTRACT FROM AUTHOR]

This paper proposes a 300 kW 24-slot/10-pole 6-phase stator-shifted fractional-slot concentrated winding spoke-type ferrite permanent magnet machine for electric truck applications. The proposed motor consists of a stator with dual three-phase windings positioned 75 degrees apart to reduce higher-order MMF harmonic order, and a rotor with an inexpensive and high-resistance ferrite permanent magnet in the spoke configuration. The simulated result of the stator-shifted machine is compared with a fabricated stator-shifted machine, and the results show good agreement with each other. To further reduce the torque ripple from 2.5 to 0.9% while maintaining a high maximum torque of 2980 Nm, circular voids with a diameter of 11 mm are embedded in the rotor. The proposed motor is evaluated for irreversible demagnetization, mechanical and thermal stability, and fault tolerant ability. To assess the proposed motor performance, the electric truck simulation model is constructed using MATLAB/Simulink and used to compare with the reported 12-slot/10-pole rare-earth permanent magnet-based machine. Compared to a previously reported six-phase rare-earth permanent magnet based flat-type machine, the proposed motor can save 4.3 kWh of energy with a USD 2512 lower cost while retaining a similar motor performance. [ABSTRACT FROM AUTHOR]

Kelp and macroalgal forests provide the ecological foundations of many temperate rocky reef ecosystems, but have regionally declined, often due to sea urchin overgrazing and the formation of urchin barrens. Sea urchin removal has long been used to investigate kelp-sea urchin dynamics and is increasingly being promoted for kelp forest restoration. In this review, we assess the methods and outcomes of sea urchin removal experiments to evaluate their potential use and feasibility as a tool for restoring macroalgal forests. Seventy-nine sea urchin removal projects were reviewed from temperate subtidal rocky reef systems between 1975 and 2020. Removal methods were often not reported (35%), but included manual culling, including crushing (25%) and chemical application (quicklime, 9%), or relocating sea urchins (13%). Only a small percentage of removals were large in scale (16% > 10 ha) and 92% of these utilized culling. Culling is often the most practical method of urchin removal, but all methods can be effective and we encourage development of new approaches that harvest and utilize low-quality urchins. Urchin removal led to an increase in macroalgae in 70% of studies, and a further 21% showed partial increases (e.g., at one or more sites or set of conditions). Restoration effectiveness is increased by removing essentially all sea urchins from discrete areas of urchin barrens. Sea urchin removal provides a simple, relatively cheap, and effective method that promotes kelp recovery within urchin barrens. However, sea urchin removal does not address the underlying cause of elevated sea urchin populations and is unlikely to provide a long-term solution to restore kelp forests and full ecosystem function on its own. We therefore suggest that if sea urchin removal is considered as a tool for kelp forest restoration, it should be incorporated with other management measures that aim to increase kelp forest resilience and biodiversity (e.g., marine protected areas, predator protection or enhancement). This will ensure that kelp restoration efforts have the greatest ecological, socio-economic and cultural outcomes in the long-term.

Though the merits of matrix-based dual-active-bridge (MB-DAB) ac–dc converter as a submodule for grid-connected multilevel medium-voltage ac (MVac)–low-voltage dc (LVdc) conversion have been presented in recent literature, its operational challenges in the cascaded configuration have not been explored. The objective of this article is to present the inevitable challenge of unequal power routing through the submodules of cascaded matrix-based dual-active-bridge (CMB-DAB) and its mitigation. The detailed and simplified small-signal model of the CMB-DAB converter along with the proposed power balance control (PBC) strategy required to eliminate the power imbalance issue are explained comprehensively. The simulation results for a 3-cell 52.65-kVA CMB-DAB converter along with scaled-down 5.85 kVA experimental results are presented, to demonstrate the unavoidable power imbalance issue and the proposed PBC strategy as a mitigation technique. The proposed scheme is observed to perform seamlessly with the conventional LVdc bus voltage control and remediate power-routing imbalance issue during the steady-state, load-change and hot plug-in/hot plug-out operations. [ABSTRACT FROM AUTHOR]

Li M, Luo H, Zhang W, et al. Int J Nanomedicine. 2018;13:3907–3920. The Editor and Publisher of International Journal of Nanomedicine wish to retract the published article. Concerns were raised regarding the alleged duplication of images in Figure 6. Specifically, Figure 6A, Non-targeted group, appears to have been duplicated with Figure 6A, Antagonized group. The authors responded to our queries and provided some of the original data relating to Figure 6. However, the Editor determined that current and previous concerns relating to this article have raised doubts about the validity of the findings and requested for the article to be retracted. The authors have been informed of this decision. Our decision-making was informed by our policy on publishing ethics and integrity and the COPE guidelines on retraction. The retracted article will remain online to maintain the scholarly record, but it will be digitally watermarked on each page as “Retracted”. This retraction relates to this paper

Calcium signaling is pivotal to the circadian clockwork in the suprachiasmatic nucleus (SCN), particularly in rhythm entrainment to environmental light-dark cycles. Here, we show that a small G-protein Gem, an endogenous inhibitor of high-voltage-activated voltage-dependent calcium channels (VDCCs), is rapidly induced by light in SCN neurons via the calcium (Ca2+)-mediated CREB/CRE transcriptional pathway. Gem attenuates light-induced calcium signaling through its interaction with VDCCs. The phase-shift magnitude of locomotor activity rhythms by light, at night, increases in Gem -deficient (Gem −/− ) mice. Similarly, in SCN slices from Gem −/− mice, depolarizing stimuli induce larger phase shifts of clock gene transcription rhythms that are normalized by the application of an L-type VDCC blocker, nifedipine. Voltage-clamp recordings from SCN neurons reveal that Ca2+ currents through L-type channels increase in Gem −/− mice. Our findings suggest that transcriptionally activated Gem feeds back to suppress excessive light-evoked L-type VDCC activation, adjusting the light-induced phase-shift magnitude to an appropriate level in mammals. [Display omitted] • A light exposure induces a small G-protein Gem in the suprachiasmatic nucleus • Magnitude of light-induced phase shift is accelerated in Gem-knockout mice • Ca2+ currents through high-voltage VDCCs are increased in Gem-knockout mice • Induced Gem feeds back to reduce Ca2+ entry and the magnitude of phase shift A light exposure shifts the circadian rhythms phase dependently. Here, Matsuo et al. report that light-induced immediate-early gene Gem in the master clock in the suprachiasmatic nucleus feeds back to suppress excessive Ca2+ entry through L-type voltage-dependent calcium channels, adjusting the phase-shift magnitude to an appropriate level in mammals. [ABSTRACT FROM AUTHOR]

The neurohormone melatonin facilitates entrainment of biological rhythms to environmental light-dark conditions as well as phase-shifts of circadian rhythms in constant conditions via activation of the MT 1 and/or MT 2 receptors expressed within the suprachiasmatic nucleus of the hypothalamus. The efficacy of melatonin and related agonists to modulate biological rhythms can be assessed using two well-validated mouse models of rhythmic behaviors. These models serve as predictive measures of therapeutic efficacy for treatment of circadian phase disorders caused by internal (e.g., clock gene mutations, blindness, depression, seasonal affective disorder) or external (e.g., shift work, travel across time zones) causes in humans. Here we provide background and detailed protocols for quantitative assessment of the magnitude and efficacy of melatonin receptor ligands in mouse circadian phase-shift and re-entrainment paradigms. The utility of these models in the discovery of novel therapeutics acting on melatonin receptors will also be discussed., (© 2022. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)