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This work presents evidence of seasonal and inter-annual variations of the earthquake occurrence rate in the Azores Triple Junction, on the Mid-Atlantic Ridge (MAR). Annual cycles in microearthquakes are relatively common in intraplate continental regions affected by large hydrological loads, but this is the first time that earthquake seasonality is recognized near mid-ocean ridges. First, we benchmark the methodology by matching the published results of earthquake seasonality in the intraplate New Madrid Seismic Zone (USA). Next, we analyze the Azores earthquake catalogue, from 2008 to 2018, separately for oceanic and island regions. The results demonstrate that the seasonal modulation of the seismicity rate is only observed in the ocean, especially in the vicinity of the triple junction, with more earthquakes occurring during the summer months from May to August. Monte Carlo simulations show that the probability of observing such seasonality by chance is less than 1% for the magnitude band from 3.3 to 4.5, well above the detection threshold and magnitude of completeness of the seismic catalogue. The methodology includes a Jack-Knife approach, which shows that the oceanic seasonality is not the consequence of abnormal or extreme events. Although we speculate about possible earthquake triggering processes, it remains a challenge to definitely establish the mechanism responsible for the observed earthquake seasonal modulation in the Azores.

Fogo is a volcanic island located in the Cape Verde Archipelago and is one of the most active volcanoes on Earth, with numerous historical eruptions. Fogo has been widely studied from different perspectives, yet detailed characterization of its seismic structure is still missing, since previous seismic studies chiefly focused on regional features or on magmatic-induced seismicity.Seismic tomography has proven to be a powerful tool to determine the velocity structure in volcanic environments. The energy necessary to perform such studies can be obtained from the seismicity in volcano's vicinity or from ambient seismic noise. At short periods, it is challenging to get good surface wave dispersion measurements on waveforms resultant from earthquakes due to attenuation and scattering; waveforms retrieved from ambient noise cross-correlations are, however, especially useful to image crustal structure.In this study we used 14 seismic stations from three different networks deployed on Fogo. Ambient noise cross-correlations were computed for all possible inter-station pairs among the same network, through the phase cross-correlation technique. The empirical Green’s functions (EGF) were then obtained through the time-frequency phase-weighted stack. To decompose the EGFs in the time-frequency domain and thus obtain the dispersion curves of the Rayleigh waves, we applied the multiple filtering analysis (MFA). The Rayleigh wave fundamental mode group velocity curves were then picked manually and visually inspected for periods between 1 to 10 s. Tomographic inversions of the previously obtained group-velocity measurements were performed using the Fast Marching Surface Tomography package (FMST). To obtain the depth structure beneath Fogo, we extracted the values of velocity, from the set of 2D group-velocity maps, for 608 points of the grid, which are, in practical terms, local dispersion curves. The further inversion of these curves enables the construction of 1D S-wave velocity profiles for each node as a function of depth. The resulting 3D shear-wave velocity model shows two clear high-velocity anomalies: a stronger, well-defined tabular anomaly located between ~5 and 9 km of depth and beneath the entire island footprint, and a weaker but distinct anomaly located at 3–4 km of depth and only extending beneath the southwestern island sector, being absent in the northeast where the lowest velocities are attained. We interpret these positive anomalies as the result of intrusions of denser, now cooled sills, pervasively below the island edifice (whose base is located at ~5 km) and within the underlying seafloor sediments and crust (where rheological, density and thermal contrasts favor the emplacement of such intrusions), and higher up within the island edifice, beneath the southwestern sector. This latter positive anomaly is consistent with surface deformation represented by the NW-SE Galinheiros normal fault, which cuts across the island and exhibits ~150 m of vertical displacement, with the southwestern block being elevated relatively to the northeastern one. This study presents the first 3D shear-wave velocity model for Fogo, providing new and better insights into the local volcano-tectonic structure.This is a contribution to project SIGHT (PTDC/CTA-GEF/30264/2017) and UIDB/50019/2020 – IDL, both funded by FCT.

A 3 day exercise simulating unrest and a large explosive eruption at Katla volcano, Iceland, was conducted in January 2016. A large volume of simulated data based on a complex, but realistic eruption scenario was compiled in advance and then transmitted to exercise participants in near-real time over the course of the exercise. The scenario was designed to test the expertise and procedures of the local institutions in charge of warning and responding to volcanic hazards, namely the volcano observatory, national civil protection, and the local university-science sector, as well as their interactions with the European science community and the London Volcanic Ash Advisory Centre. This exercise was the first of this magnitude and scope in Iceland and has revealed many successful developments introduced since the 2010 Eyjafjallajökull and 2011 Grímsvötn eruptions. Following the exercise, 90% of participants said that they felt better prepared for a future eruption. As with any exercise, it also identified areas where further development is required and improvements can be made to procedures. Seven key recommendations are made to further develop capability and enhance the collaboration between the volcano observatory, volcano research institutions and civil protection authorities. These recommendations cover topics including notification of responders, authoritative messaging, data sharing and media interaction, and are more broadly applicable to volcanic institutions elsewhere. Lessons and suggestions for how to run a large-scale volcanic exercise are given and could be adopted by those planning to rehearse their own response procedures., This work was funded by the European Community’s FP7 Programme grant 308377 (Project FUTUREVOLC).

International audience; Melatonin, a major signal of the circadian system, is also involved in brain functions such as learning and memory. Chronic melatonin treatment is known to improve memory performances, but the respective contribution of its central receptors, MT1 and MT2, is still unclear. Here, we used new single receptor deficient MT1-/and MT2-/mice to investigate the contribution of each receptor in the positive effect of chronic melatonin treatment on long-term recognition memory. The lack of MT2 receptor precluded memory-enhancing effect of melatonin in the object recognition task and to a lesser extent in the object location task, whereas the lack of MT1 receptor mitigated its effect in the object location task only. Our findings support a key role of MT2 in mediating melatonin's beneficial action on long-term object recognition memory, whereas MT1 may contribute to the effect on object location memory.

Melatonin, a major signal of the circadian system, is also involved in brain functions such as learning and memory. Chronic melatonin treatment is known to improve memory performances, but the respective contribution of its central receptors, MT

International audience; Volcanoes are complex systems that evolve in space and time as a result of their eruptive activity. Volcanic eruptions represent the ultimate expression of a complex interplay between internal and external processes that span across different time scales. Deciphering how internal and external processes interact at the time scale of eruptions may provide key insights on the temporal evolution of eruptions and also help to better evaluate associated volcanic hazards. Studies of the tidal influence on volcanic activity have fallen within this context, although the cause-effect relationship between tides and eruptions is still unclear. In this study, we used Singular Spectrum Analysis to analyze three time-series, namely the seismic tremor, SO2 emission and lava volume flow rate, which cover the first month of effusive activity at Fogo volcano, Cape Verde, in 2014-2015. We detect 9 tidal periodicities and up to 5 in each time-series ranging from semi-diurnal to fortnightly periods. We show that the movement of magma at crustal depths and at surface as well as gas emission during the effusive eruption are all modulated by lunisolar gravitational forces. We highlight the relevance of the volcano location on Earth, which together with the timing of the eruption, associated with a specific astronomical configuration, result in a specific combination of tides that directly influence the volcano eruptive activity. With this data set, we further investigate the response of Fogo volcano to this external forcing. We show that during the 2014-2015 eruption, Fogo volcano acted as a bandpass filter to quasi-permanent tidal oscillations.

Following publication of the original article Witham et al., 2020, it was noticed a mistake of copyright holder name.

Deciphering eruptive dynamics in near-real time is essential when dealing with hazard assessment and population evacuation. Recognition of specific patterns in time-series measured during volcanic activity may help decipher distinctive behavior at active volcanoes, providing insights into the underlying driving mechanisms. Multi-parameter data sets usually agree on the overall trend characterizing the temporal evolution of an eruption providing insights into the first-order eruptive dynamics. However, second-order variations detected in different data sets remain often poorly understood. The 2014-2015 Holuhraun eruption (Iceland) offers an excellent opportunity to investigate the dynamics of a long-lasting effusive eruption. We analyze the seismic tremor and the volcanic radiated power emitted by the lava field during the 6 months of the eruption using Singular Spectrum Analysis (SSA). In both geophysical time-series, we identify periods from ∼5 to ∼32 days coinciding with periods of Earth tides. Here we show that ∼50% of both signals are composed of tidal periods suggesting that magma movements follow frequencies imposed by lunisolar forces within the crust and at Earth's surface.

Publisher's version (útgefin grein), Large volume effusive eruptions with relatively minor observed precursory signals are at odds with widely used models to interpret volcano deformation. Here we propose a new modelling framework that resolves this discrepancy by accounting for magma buoyancy, viscoelastic crustal properties, and sustained magma channels. At low magma accumulation rates, the stability of deep magma bodies is governed by the magma-host rock density contrast and the magma body thickness. During eruptions, inelastic processes including magma mush erosion and thermal effects, can form a sustained channel that supports magma flow, driven by the pressure difference between the magma body and surface vents. At failure onset, it may be difficult to forecast the final eruption volume; pressure in a magma body may drop well below the lithostatic load, create under-pressure and initiate a caldera collapse, despite only modest precursors., The research presented here has benefitted from extended visits of FS during a sabbatical term to, and discussion with scientists at, the University of Leeds, ISTerre University of Savoie Mont-Blanc, USGS Cascades Volcano Observatory, and Geological Survey of Japan. We acknowledge reviews by Philip Benson and Luca Caricchi that helped to significantly improve the paper, as well as reviews of an early version of the paper by two anonymous reviewers. Financial support from the H2020 project EUROVOLC funded by the European Commission is acknowledged (grant number 731070). F.S. acknowledges support from the University of Iceland Research Fund, and R.G. acknowledges partial support through NSF grant EAR-1464546. Fissure swarms, central volcanoes and caldera outlines shown in Fig. 1 are reproduced from publications referred to (refs. 42,76) with permissions from Elsevier, and we acknowledge the use of ArticDEM (ref. 77) to plot surface and ice topography shown in Fig. 1. COMET is the NERC Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics, a partnership between UK Universities and the British Geological Survey.

The 6-month long eruption at Holuhraun (August 2014–February 2015) in the Bárðarbunga-Veiðivötn volcanic system was the largest effusive eruption in Iceland since the 1783–1784 CE Laki eruption. The lava flow field covered ~84 km2 and has an estimated bulk (i.e., including vesicles) volume of ~1.44 km3. The eruption had an average discharge rate of ~90 m3/s making it the longest effusive eruption in modern times to sustain such high average flux. The first phase of the eruption (August 31, 2014 to mid-October 2014) had a discharge rate of ~350 to 100 m3/s and was typified by lava transport via open channels and the formation of four lava flows, no. 1–4,which were emplaced side by side. The eruption began on a 1.8 km long fissure, feeding partly incandescent sheets of slabby pāhoehoe up to 500 m wide. By the following day the lava transport got confined to open channels and the dominant lava morphology changed to rubbly pāhoehoe and ‘a’ā. The latter became the dominating morphology of lava flows no. 1–8. The second phase of the eruption (Mid-October to end November) had a discharge of ~100–50 m3/s. During this time the lava transport system changed, via the formation of a b1 km2 lava pond ~1 km east of the vent. The pond most likely formed in a topographical low created by a the pre-existing Holuhraun and the newHoluhraun lava flow fields. This pond became themain point of lava distribution, controlling the emplacement of subsequent flows (i.e. no. 5–8). Towards the end of this phase inflation plateaus developed in lava flowno. 1. These inflation plateaus were the surface manifestation of a growing lava tube system, which formed as lava ponded in the open lava channels creating sufficient lavastatic pressure in the fluid lava to lift the roof of the lava channels. This allowed new lava into the previously active lava channel lifting the channel roof via inflation. The final (third) phase, lasting from December to end-February 2015 had a mean discharge rate of ~50 m3/s. In this phase the lava transport was mainly confined to lava tubes within lava flows no. 1–2, which fed breakouts that resurfaced N19 km2 of the flow field. The primary lava morphology from this phase was spiny pāhoehoe, which superimposed on the ‘a’ā lava flows no. 1–3 and extended the entire length of the flow field (i.e. 17 km). Thismade the 2014–2015 Holuhraun a paired flow field,where both lava morphologies had similar length. We suggest that the similar length is a consequence of the pāhoehoe is fed from the tube systemutilizing the existing ‘a’ā lava channels, and thereby are controlled by the initial length of the ‘a’ā flows., The work was financed with crisis response funding from the Icelandic Government along with European Community's Seventh Framework Programme Grant No. 308377 (Project FUTUREVOLC) and along with the Icelandic Research fund, Rannis, Grant of Excellence No. 152266-052 (Project EMMIRS). Furthermore, Vinur Vatnajökuls are thanked for support.

Lava flows contract as they cool, causing progressive subsidence of the flow surface. Here we study this process by measuring and modelling the deformation of emplaced lava flows and the surrounding substrate. The temporal trend of vertical lava movements was investigated using interferometric analysis of synthetic aperture radar (InSAR) images from the 1991 and 2000 Hekla eruptions, covering periods of 23 and 12 years, respectively. Data from six tracks from three satellites, including both ascending and descending passes, were used to create 99 interferograms, from which trends of accumulated subsidence and subsidence velocities were derived. Subsidence rates are similar for both lava flows and decay approximately exponentially from about 20 mm/year five years after emplacement to about 2 mm/year 15 years after emplacement. A one-dimensional, semi-analytical model was fitted to the observed subsidence rates, with subsidence due to phase change calculated analytically, and subsidence due to thermal contraction calculated numerically using dilatometic constraints obtained experimentally. The initial thicknesses of the 1991 and 2000 lava fields, D1991 and D2000, scaled thermal expansivity, γα, and thermal diffusivity, κ, are the crucial parameters influencing lava subsidence and subsidence rate. Inversion for these parameters reveal linear correlations between them. Best fitting results of inversions for D1991 range from 10 m to 27 m, for D2000 from 10 m to 30 m, γα = (9 − 24) × 10−6K−1, and κ = (1 − 7) × 10−7m2s−1.

Restricted feeding during the resting period causes pronounced shifts in a number of peripheral clocks, but not the central clock in the suprachiasmatic nucleus (SCN). By contrast, daily caloric restriction impacts also the light-entrained SCN clock, as indicated by shifted oscillations of clock (PER1) and clock-controlled (vasopressin) proteins. To determine if these SCN changes are due to the metabolic or timing cues of the restricted feeding, mice were challenged with an ultradian 6-meals schedule (1 food access every 4 h) to abolish the daily periodicity of feeding. Mice fed with ultradian feeding that lost 10% body mass (i.e. hypocaloric) became more diurnal, hypothermic in late night, and displayed larger (3.5 h) advance of body temperature rhythm, more reduced PER1 expression in the SCN, and further modified gene expression in the liver (e.g. larger phase-advance of Per2 and up-regulated levels of Pgc-1α). While glucose rhythmicity was lost under ultradian feeding, the phase of daily rhythms in liver glycogen and plasma corticosterone (albeit increased in amplitude) remained unchanged. In conclusion, the additional impact of hypocaloric conditions on the SCN are mainly due to the metabolic and not the timing effects of restricted daytime feeding.

Circadian rhythms in nocturnal and diurnal mammals are primarily synchronized to local time by the light/dark cycle. However, nonphotic factors, such as behavioral arousal and metabolic cues, can also phase shift the master clock in the suprachiasmatic nuclei (SCNs) and/or reduce the synchronizing effects of light in nocturnal rodents. In diurnal rodents, the role of arousal or insufficient sleep in these functions is still poorly understood. In the present study, diurnal Sudanian grass rats,Arvicanthis ansorgei, were aroused at night by sleep deprivation (gentle handling) or caffeine treatment that both prevented sleep. Phase shifts of locomotor activity were analyzed in grass rats transferred from a light/dark cycle to constant darkness and aroused in early night or late night. Early night, but not late night, sleep deprivation induced a significant phase shift. Caffeine on its own induced no phase shifts. Both sleep deprivation and caffeine treatment potentiated light-induced phase delays and phase advances in response to a 30 min light pulse, respectively. Sleep deprivation in early night, but not late night, potentiated light-induced c-Fos expression in the ventral SCN. Caffeine treatment in midnight triggered c-Fos expression in dorsal SCN. Both sleep deprivation and caffeine treatment potentiated light-induced c-Fos expression in calbindin-containing cells of the ventral SCN in early and late night. These findings indicate that, in contrast to nocturnal rodents, behavioral arousal induced either by sleep deprivation or caffeine during the sleeping period potentiates light resetting of the master circadian clock in diurnal rodents, and activation of calbindin-containing suprachiasmatic cells may be involved in this effect.SIGNIFICANCE STATEMENTArousing stimuli have the ability to regulate circadian rhythms in mammals. Behavioral arousal in the sleeping period phase shifts the master clock in the suprachiasmatic nuclei and/or slows down the photic entrainment in nocturnal animals. How these stimuli act in diurnal species remains to be established. Our study in a diurnal rodent, the Grass rat, indicates that sleep deprivation in the early rest period induces phase delays of circadian locomotor activity rhythm. Contrary to nocturnal rodents, both sleep deprivation and caffeine-induced arousal potentiate the photic entrainment in a diurnal rodent. Such enhanced light-induced circadian responses could be relevant for developing chronotherapeutic strategies.

A volcanic eruption initiated on 23/Nov/2014 on Fogo Island in Cape Verde (14.91°N, 24.38°W, Figure 1 ) lasted for 78 days until 08/Feb/2015 [1] – [4] . Volcanic eruptions are phenomena with strong heat fluxes due to the release of lava and gases that can be suitably monitored through thermal remote sensing and its principles [5] . The sensors acquiring such type of data have generally a high temporal resolution but a low spatial one. But at the same time, non-thermal imagery captured by other sensors can also be very useful to better understand the ongoing event and track its temporal evolution [6] . Therefore, we propose a methodology to reconstruct the 2014-2015 Fogo eruption based on multi-platform imagery.

International audience; The cerebellum contains a circadian clock, generating internal temporal signals. The daily oscillations of cerebellar proteins were investigated in mice using a large-scale two-dimensional difference in gel electrophoresis (2D-DIGE). Analysis of 2D-DIGE gels highlighted the rhythmic variation in the intensity of 27/588 protein spots (5%) over 24 h based on cosinor regression. Notably, the rhythmic expression of most abundant cerebellar proteins was clustered in two main phases (i.e., midday and midnight), leading to bimodal distribution. Only six proteins identified here to be rhythmic in the cerebellum are also known to oscillate in the suprachiasmatic nuclei, including two proteins involved in the synapse activity (Synapsin 2 [SYN2] and vesicle-fusing ATPase [NSF]), two others participating in carbohydrate metabolism (triosephosphate isomerase (TPI1] and alpha-enolase [ENO1]), Glutamine synthetase (GLUL), as well as Tubulin alpha (TUBA4A). Most oscillating cerebellar proteins were not previously identified in circadian proteomic analyses of any tissue. Strikingly, the daily accumulation of mitochondrial proteins was clustered to the mid-resting phase, as previously observed for distinct mitochondrial proteins in the liver. Moreover, a number of rhythmic proteins, such as SYN2, NSF and TPI1, were associated with non-rhythmic mRNAs, indicating widespread post-transcriptional control in cerebellar oscillations. Thus, this study highlights extensive rhythmic aspects of the cerebellar proteome.

We report how data from satellite and aerial synthetic aperture radar (SAR) observations were integrated into monitoring of the 2014–2015 Holuhraun eruption in the Bárðarbunga volcanic system, the largest effusive eruption in Iceland since the 1783–84 Laki eruption. A lava field formed in one of the most remote areas in Iceland, after the propagation of a ∼50 km-long dyke beneath the Vatnajökull ice cap, where the Bárðarbunga caldera is located. Due to the 6 month duration of the eruption, mainly in wintertime, daily monitoring was particularly challenging. During the eruption, the European volcanological project FutureVolc was ongoing, allowing collaboration of many European experts on volcano monitoring activities. Icelandic volcanoes are also a permanent Supersite within the Geohazard Supersites and Natural Laboratories (GSNL) initiative, with support from the Committee on Earth Observation Satellite (CEOS) in the form of a large collection of SAR images. SAR data were acquired by Cosmo-SkyMed (CSK) and TerraSAR-X (TSX) satellites and complemented by aerial SAR images. The large set of SAR satellite data significantly contributed to the daily monitoring during the unrest at Bárðarbunga caldera, the Holuhraun eruption and the year following the eruption. Detection of surface changes using both SAR amplitude and phase information was conducted throughout the whole duration of the volcano-tectonic event, and in the following months, to quantify and track the evolution of volcanic processes at Holuhraun and geothermal activity at Bárðarbunga volcano. Combination of SAR data with other data sets, e.g., satellite optical images and geodetic Global Positioning System (GPS) measurements, was essential for the evaluation of the volcanic hazard in the whole area. International collaboration within the FutureVolc project formed the basis for successful analyses and interpretation of the large SAR data set. Information was provided at Scientific Advisory Board meetings of the Icelandic Civil Protection and used in decision-making, as well as for supporting field-deployment and air-based surveys.

he 2014–2015 Bárðarbunga fissure eruption at Holuhraun in central Iceland was distinguished by the high emission of gases, in total 9.6 Mt SO2, with almost no tephra. This work collates all ground-based measurements of this extraordinary eruption cloud made under particularly challenging conditions: remote location, optically dense cloud with high SO2 column amounts, low UV intensity, frequent clouds and precipitation, an extensive and hot lava field, developing ramparts, and high-latitude winter conditions. Semi-continuous measurements of SO2 flux with three scanning DOAS instruments were augmented by car traverses along the ring-road and along the lava. The ratios of other gases/SO2 were measured by OP-FTIR, MultiGAS, and filter packs. Ratios of SO2/HCl = 30–110 and SO2/HF = 30–130 show a halogen-poor eruption cloud. Scientists on-site reported extremely minor tephra production during the eruption. OPC and filter packs showed low particle concentrations similar to non-eruption cloud conditions. Three weather radars detected a droplet-rich eruption cloud. Top of eruption cloud heights of 0.3–5.5 km agl were measured with ground- and aircraft-based visual observations, web camera and NicAIR II infrared images, triangulation of scanning DOAS instruments, and the location of SO2 peaks measured by DOAS traverses. Cloud height and emission rate measurements were critical for initializing gas dispersal simulations for hazard forecasting., his work was greatly supported by the FUTUREVOLC project funded by the European Union's Seventh Program for research, technological development, and demonstration under grant agreement No 308377. BG and SA acknowledge a grant from the Swedish Research Council FORMAS. EI acknowledges NERC urgency grant NE/M021130/1.

Improving our understanding of volcanic hazards requires better knowledge of the location, volume and properties of magma bodies in the roots of active volcanoes, as well as information on melt supply and magma transfer. This requires a good understanding of both the geometric structure of the volcanic and igneous plumbing system, as well as observations of sub-surface magma movements and their interpretation. Arrival of new magma in volcano roots often causes volcanic unrest expressed by one or more of the following: increased seismicity, ground deformation, volcanic gas release and ground temperature changes. Recent eruptions and magmatic events in Iceland have provided opportunities to apply repeated geodetic observations at volcanoes to measure ground deformation and interpret these measurements together with seismic observations in terms of subsurface magmatic processes.

The nuclear receptor REV-ERBα is part of the molecular clock mechanism and thought to be involved in a variety of biological processes within metabolically active peripheral tissues as well. To investigate whether Rev-erbα (also known as Nr1d1) in the brain plays a role in the daily variations of energy metabolism, feeding behaviour and the sleep-wake cycle, we studied mice with global (GKO) or brain (BKO) deletion of Rev-erbα. Mice were studied both in a light-dark cycle and constant darkness, and 24-h variations of Respiratory quotient (RQ) and energy expenditure, as well as the temporal patterns of rest-activity and feeding behavior were recorded. The RQ increase of GKO mice was not detected in BKO animals, indicating a peripheral origin for this metabolic alteration. Arrhythmic patterns of locomotor activity were only found in BKO mice. By contrast, the circadian rhythm of food intake was lost both in GKO and BKO mice, mostly by increasing the number of daytime meals. These changes in the circadian pattern of feeding behaviour were, to some extent, correlated with a loss of rhythmicity of hypothalamic Hcrt (also named Orx) mRNA levels. Together, these findings highlight that Rev-erbα in the brain is involved in the temporal partitioning of feeding and sleep, whereas its effects on energy metabolism are mainly exerted through its peripheral expression. This article is protected by copyright. All rights reserved.

Chronic jet lag or shift work is deleterious to human metabolic health, in that such circadian desynchronization is associated with being overweight and the prevalence of altered glucose metabolism. Similar metabolic changes are observed with age, suggesting that chronic jet lag and accelerated cell aging are intimately related, but the association remains to be determined. We addressed whether jet lag induces metabolic and cell aging impairments in young grass rats (2-3 mo old), using control old grass rats (12-18 mo old) as an aging reference. Desynchronized young and control old subjects had impaired glucose tolerance (+60 and +280%) when compared with control young animals. Despite no significant variation in liver DNA damage, shorter telomeres were characterized, not only in old animal liver cells (-18%), but also at an intermediate level in desynchronized young rats (-9%). The same pattern was found for deacetylase sirtuin (SIRT)-1 (-57 and -29%), confirming that jet-lagged young rats have an intermediate aging profile. Our data indicate that an experimental circadian desynchronization in young animals is associated with a precocious aging profile based on 3 well-known markers, as well as a prediabetic phenotype. Such chronic jet lag-induced alterations observed in a diurnal species constitute proof of principle of the need to develop preventive treatments in jet-lagged persons and shift workers.

Stress transfer associated with an earthquake, which may result in the seismic triggering of aftershocks (earthquake–earthquake interactions) and/or increased volcanic activity (earthquake–volcano interactions), is a well-documented phenomenon. However limited studies have been undertaken concerning volcanic triggering of activity at neighbouring volcanoes (volcano–volcano interactions). Here we present new deformation and stress modelling results utilising a wealth of diverse geodetic observations acquired during the 2014–2015 unrest and eruption within the Bardarbunga volcanic system. These comprise a combination of InSAR, GPS, LiDAR, radar profiling and optical satellite measurements. We find a strong correlation between the locations of increased seismicity at nearby Tungnafellsjokull volcano and regions of increased tensile and Coulomb stress changes. Our results suggest that stress transfer during this major event has resulted in earthquake triggering at the neighbouring Tungnafellsjokull volcano by unclamping faults within the associated fissure swarm. This work has immediate application to volcano monitoring; to distinguish the difference between stress transfer and new intrusive activity.

International audience; Measuring displacement-length profiles along normal faults provides crucial information on fault growth processes. Here, based on satellite imagery and topography we analyze 357 normal faults distributed along the active rift of Dabbahu-Manda-Hararo (DMH), Afar, which offers a unique opportunity to investigate the influence of magmatism on fault growth processes. Our measurements reveal a large variety of slip profiles that are not consistent with elastic deformation. Their analysis contributes towards a better understanding of the lateral propagation of faults, especially when nucleation points and existence of barriers are included. Using the fault growth model of Manighetti et al. (2001), we determine the preferred direction of lateral propagation for each fault. Our results suggest that lateral propagation of faults is easier away from areas where magma has been stored for long time at crustal depth, and has thus modified the thermo-mechanical properties of the host-rock. However, these areas correspond also to areas where the initiation of fault growth appears as easiest along the rift. In combining these results with the analysis of rift width and the position of magma reservoirs along DMH rift, we show that fault growth keeps track of the magma presence and/or movement in the crust.

The elderly population shows various circadian disturbances, including dampened amplitude of rhythmicity and decreased responsiveness to light. The common poor folate status in the elderly might account for these aging-related circadian disturbances. To test this hypothesis, we investigated whether folate deficiency in mice affects circadian oscillations of the master clock in the suprachiasmatic nuclei, and the shifting responses to light. Mice fed a diet without folate for 6 weeks displayed markedly reduced (4.5-fold) erythrocyte folate concentration and increased (2.3-fold) homocysteinemia compared with control mice. Folate deficiency decreased the circadian amplitude of vasopressin and the clock protein PERIOD 2 (PER2) in the master clock, slowed the rate of re-entrainment of behavioral rhythms after delayed light-dark cycle and reduced light-induced phase-delays, without detectable morphologic changes in the retina, such as the number of melanopsinergic ganglion cells, that might have impaired photodetection. In conclusion, folate deficiency and consecutive hyperhomocysteinemia led to dampened PER2 and vasopressin oscillations in the master clock and reduced responsiveness to photic resetting, which constitute hallmarks of aging effects on circadian rhythmicity.

Foraging is costly in terms of time and energy. An endogenous food-entrainable system allows anticipation of predictable changes of food resources in nature. Yet the molecular mechanism that controls food anticipation in mammals remains elusive. Here we report that deletion of the clock component Rev-erbα impairs food entrainment in mice. Rev-erbα global knockout (GKO) mice subjected to restricted feeding showed reduced elevations of locomotor activity and body temperature prior to mealtime, regardless of the lighting conditions. The failure to properly anticipate food arrival was accompanied by a lack of phase-adjustment to mealtime of the clock protein PERIOD2 in the cerebellum, and by diminished expression of phosphorylated ERK 1/2 (p-ERK) during mealtime in the mediobasal hypothalamus and cerebellum. Furthermore, brain-specific knockout (BKO) mice for Rev-erbα display a defective suprachiasmatic clock, as evidenced by blunted daily activity under a light-dark cycle, altered free-running rhythm in constant darkness and impaired clock gene expression. Notably, brain deletion of Rev-erbα totally prevented food-anticipatory behaviour and thermogenesis. In response to restricted feeding, brain deletion of Rev-erbα impaired changes in clock gene expression in the hippocampus and cerebellum, but not in the liver. Our findings indicate that Rev-erbα is required for neural network-based prediction of food availability.

Growing evidence links metabolic disorders to circadian alterations. Genetically obese db/db mice, lacking the long isoform of leptin receptor, are a recognized model of type 2 diabetes. In this study, we aimed at characterizing the potential circadian alterations of db/db mice in comparison to db/+ control mice. By using telemetry devices, we first reported arrhythmicity in general activity of most db/db mice under both light-dark cycle and constant darkness, while their rhythm of body temperature is less dramatically disrupted. Water access restricted to nighttime restores significant rhythmicity in behaviorally arrhythmic db/db mice, indicating a masking effect of polydipsia when water is available ad libitum. Endogenous period of temperature rhythm under constant dark conditions is significantly increased (+30 min) in db/db compared with db/+ mice. Next, we studied the oscillations of clock proteins (PER1, PER2 and BMAL1) in the suprachiasmatic nuclei (SCN), the site of the master clock, and detected no difference according to the genotype. Furthermore, c-FOS and P-ERK1/2 expression in response to a light pulse in late night was significantly increased (+80 and +55%, respectively) in the SCN of these diabetic mice. We previously showed that, in addition to altered activity rhythms, db/db mice exhibit altered feeding rhythm. Therefore, we investigated daily patterns of clock protein expression in medial hypothalamic oscillators involved in feeding behavior (arcuate nucleus, ventro- and dorso-medial hypothalamic nuclei). Compared with db/+ mice, very subtle or no difference in oscillations of PER1 and BMAL1 is found in the medial hypothalamus. Although we did not find a clear link between altered hypothalamic clockwork and behavioral rhythms in db/db mice, our results highlight a lengthened endogenous period and altered photic integration in these genetically obese and diabetic mice. journal article research support, non-u.s. gov't 2016 May 2015 07 03 imported

Brothelande, E. et. al., In this contribution, we focus on one of the most active resurgences on Earth, that of the Yenkahe dome in the Siwi caldera (Tanna Island, Vanuatu), which is associated with the persistently active Yasur volcano. Gravity and magnetic surveys have been carried out over the past few years in the area, as well as electrical methods including electrical resistivity tomography (ERT), time domain electro-magnetics (TDEM) and self-potential (SP). These investigations were completed by thermometry, CO2 soil gas measurements, field observations and sampling. This multi-method approach allows geological structures within the caldera to be identified, as well as associated hydrothermal features. The global structure of the caldera is deduced from gravity data, which shows the caldera rim as a high density structure. Large lava fields, emplaced before and after the onset of resurgence, are evidenced by combined gravity, magnetic and resistivity signals. In the middle of the caldera, the Yenkahe dome apparently results from a combination of volcanic and tectonic events, showing that lava extrusion and resurgence have been operating simultaneously or alternately during the Siwi caldera post-collapse history. There is a clear distinction between the western and eastern parts of the dome. The western part is older and records the growth of an initial volcanic cone and the formation of a small caldera. This small caldera (paleo-Yasur caldera), partially filled with lava flows, is the present-day focus of volcanic activity and associated fluid circulation and alteration. The eastern part of the dome is presumably younger, and is characterized by intense, extensive hydrothermal alteration and activity. Its northern part is covered by lava flow piles and exhibits a shallow hydrothermal zone in ERT. The southern part has hydrothermal alteration and activity extending at least down to the base of the resurgent dome. This part of the dome is built up of low cohesion rock and is thus potentially prone to gravitational landslides. Lastly, while self-potential and temperature data suggest that widespread hydrothermal circulation occurs throughout almost all of the caldera, and possibly beyond, the most active parts of this hydrothermal system are associated with the dome. The presence of this active hydrothermal system is the clearest indicator that these methods can provide of a potential shallow magmatic body underneath the dome, This research was co-financed by the French Government “ANR ARC-Vanuatu: Programme Catastrophes Telluriques et Tsunamis” (ANR-06-CATT-02) and Laboratory of Excellence initiative n°ANR-10-LABX-0006, the Laboratoire Magmas et Volcans (LMV), the Laboratoire GéoSciences Réunion, the Région Auvergne and the European Regional Development Fund. Datasets are available at LMV. In addition, gravimetric data are available at International Gravimetric Bureau. This is Laboratory of Excellence ClerVolc contribution number 171 and IPGP contribution number 3654.

International audience; The rifting episode that occurred in Dabbahu–Manda–Hararo (Ethiopia) between 2005 and 2010 during which 14 dyke intrusions were emitted, was a unique opportunity to study interactions between tectonic deformation and magmatic processes. While magmatism has been shown to control primarily the spatial and temporal distribution of dyke intrusions during this accretion sequence, the role of faults in accommodating plate spreading in rift segments is poorly understood. During interdyking periods, transient ground deformation due to magma movement is generally observed. Investigating such a small-scale deformation and in particular the movement along faults during these periods will help understanding the factors that trigger fault movement in magmatic rifts. We analyse fault activity during three interdyking periods: 2006 December–June (d0–d1), 2007 January–July (d5–d6) and 2009 November–January (d10–d11). The time–space evolution of surface displacements along ∼700 faults is derived from pairs of ascending and descending SAR interferograms. Surface slip distributions are then compared with codyking ground deformation fields. The results show that faults are mainly activated above the areas affected by magma emplacement during interdyking periods. A detailed analysis of brittle deformation during the six months following the 2005 September intrusion shows asymmetric deformation on the rift shoulders, with significant opening on faults located to the west of the dyke. We explain this feature by the activation of westward dipping pre-existing faults, with block rotations in between. In addition, we observe that the strip encompassing the activated faults narrows by 30 per cent from co- to interdyking period. This suggests that magma keeps migrating to shallower depths after the dyke intrusion. During a rifting episode, activation of faults in a pre-existing fracture network therefore seems to be mainly controlled by deep magma processes.

Large volcanic eruptions on Earth commonly occur with a collapse of the roof of a crustal magma reservoir, forming a caldera. Only a few such collapses occur per century, and the lack of detailed observations has obscured insight into the mechanical interplay between collapse and eruption.We usemultiparameter geophysical and geochemical data to show that the 110-square kilometer and 65-meter-deep collapse of Bárdarbunga caldera in 2014–2015 was initiated through withdrawal of magma, and lateral migration through a 48-kilometers-long dike, from a 12-kilometers deep reservoir. Interaction between the pressure exerted by the subsiding reservoir roof and the physical properties of the subsurface flow path explain the gradual, near exponential decline of both collapse rate and the intensity of the 180-day- long eruption., Civil Protection Department of the National Commissioner of the Icelandic Police. European Community’s Seventh Framework Programme grant no. 308377 (Project FUTUREVOLC). EU Seventh Framework Marie Curie project NEMOH no. 289976 CO2Volc ERC grant no. 279802, the Research Fund of the University of Iceland, the Irish Research Council, the Helmholtz Alliance on Remote Sensing and Earth System Dynamics (EDA), Bayerisches Geoinstitut through their DFG core facility for high pressure research, and UNAM/CIC Intercambio Académico.