Typical Time Scale Research Articles

Collective memory in primate conflict implied by temporal scaling collapse

In biological systems, prolonged conflict is costly, whereas contained conflict permits strategic innovation and refinement. Causes of variation in conflict size and duration are not well understood. We use a well-studied primate society model system to study how conflicts grow. We find conflict duration is a ‘first to fight’ growth process that scales superlinearly, with the number of possible pairwise interactions. This is in contrast with a ‘first to fail’ process that characterizes peaceful durations. Rescaling conflict distributions reveals a universal curve, showing that the typical time scale of correlated interactions exceeds nearly all individual fights. This temporal correlation implies collective memory across pairwise interactions beyond those assumed in standard models of contagion growth or iterated evolutionary games. By accounting for memory, we make quantitative predictions for interventions that mitigate or enhance the spread of conflict. Managing conflict involves balancing the efficient use of limited resources with an intervention strategy that allows for conflict while keeping it contained and controlled.

What pebbles are made of: Interpretation of the V883 Ori disk

Recently, an Atacama Large Millimeter/submillimeter Array (ALMA) observation of the water snow line in the protoplanetary disk around the FU Orionis star V883 Ori was reported. The radial variation of the spectral index at mm-wavelengths around the snow line was interpreted as being due to a pileup of particles interior to the snow line. However, radial transport of solids in the outer disk operates on timescales much longer than the typical timescale of an FU Ori outburst ($10^{1}$--$10^{2}$ yr). Consequently, a steady-state pileup is unlikely. We argue that it is only necessary to consider water evaporation and re-coagulation of silicates to explain the recent ALMA observation of V883 Ori because these processes are short enough to have had their impact since the outburst. Our model requires the inner disk to have already been optically thick before the outburst, and our results suggest that the carbon content of pebbles is low.

Nanosecond pump-probe device for time-resolved serial femtosecond crystallography developed at SACLA.

X-ray free-electron lasers (XFELs) have opened new opportunities for time-resolved X-ray crystallography. Here a nanosecond optical-pump XFEL-probe device developed for time-resolved serial femtosecond crystallography (TR-SFX) studies of photo-induced reactions in proteins at the SPring-8 Angstrom Compact free-electron LAser (SACLA) is reported. The optical-fiber-based system is a good choice for a quick setup in a limited beam time and allows pump illumination from two directions to achieve high excitation efficiency of protein microcrystals. Two types of injectors are used: one for extruding highly viscous samples such as lipidic cubic phase (LCP) and the other for pulsed liquid droplets. Under standard sample flow conditions from the viscous-sample injector, delay times from nanoseconds to tens of milliseconds are accessible, typical time scales required to study large protein conformational changes. A first demonstration of a TR-SFX experiment on bacteriorhodopsin in bicelle using a setup with a droplet-type injector is also presented.

Cooling rate effects in sodium silicate glasses: Bridging the gap between molecular dynamics simulations and experiments.

Although molecular dynamics (MD) simulations are commonly used to predict the structure and properties of glasses, they are intrinsically limited to short time scales, necessitating the use of fast cooling rates. It is therefore challenging to compare results from MD simulations to experimental results for glasses cooled on typical laboratory time scales. Based on MD simulations of a sodium silicate glass with varying cooling rate (from 0.01 to 100 K/ps), here we show that thermal history primarily affects the medium-range order structure, while the short-range order is largely unaffected over the range of cooling rates simulated. This results in a decoupling between the enthalpy and volume relaxation functions, where the enthalpy quickly plateaus as the cooling rate decreases, whereas density exhibits a slower relaxation. Finally, we show that, using the proper extrapolation method, the outcomes of MD simulations can be meaningfully compared to experimental values when extrapolated to slower cooling rates.

2-qubit quantum state transfer in spin chains and cold atoms with weak links

In this paper we discuss the implementation of 2-qubit quantum state transfer (QST) in inhomogeneous spin chains where the sender and the receiver blocks are coupled through the bulk channel via weak links. The fidelity and the typical timescale of the QST are discussed as a function of the parameters of the weak links. Given the possibility of implementing with cold atoms in optical lattices a variety of condensed matter systems, including spin systems, we also discuss the possible implementation of the discussed 2-qubit QST with cold gases with weak links, together with a discussion of the applications and limitations of the presented results.

Statistical link between external climate forcings and modes of ocean variability

In this study we investigate statistical link between external climate forcings and modes of ocean variability on inter-annual (3-year) to centennial (100-year) timescales using de-trended semi-partial-cross-correlation analysis technique. To investigate this link we employ observations (AD 1854–1999), climate proxies (AD 1600–1999), and coupled Atmosphere-Ocean-Chemistry Climate Model simulations with SOCOL-MPIOM (AD 1600–1999). We find robust statistical evidence that Atlantic multi-decadal oscillation (AMO) has intrinsic positive correlation with solar activity in all datasets employed. The strength of the relationship between AMO and solar activity is modulated by volcanic eruptions and complex interaction among modes of ocean variability. The observational dataset reveals that El Nino southern oscillation (ENSO) has statistically significant negative intrinsic correlation with solar activity on decadal to multi-decadal timescales (16–27-year) whereas there is no evidence of a link on a typical ENSO timescale (2–7-year). In the observational dataset, the volcanic eruptions do not have a link with AMO on a typical AMO timescale (55–80-year) however the long-term datasets (proxies and SOCOL-MPIOM output) show that volcanic eruptions have intrinsic negative correlation with AMO on inter-annual to multi-decadal timescales. The Pacific decadal oscillation has no link with solar activity, however, it has positive intrinsic correlation with volcanic eruptions on multi-decadal timescales (47–54-year) in reconstruction and decadal to multi-decadal timescales (16–32-year) in climate model simulations. We also find evidence of a link between volcanic eruptions and ENSO, however, the sign of relationship is not consistent between observations/proxies and climate model simulations.

Nature does not rely on long-lived electronic quantum coherence for photosynthetic energy transfer

During the first steps of photosynthesis, the energy of impinging solar photons is transformed into electronic excitation energy of the light-harvesting biomolecular complexes. The subsequent energy transfer to the reaction center is commonly rationalized in terms of excitons moving on a grid of biomolecular chromophores on typical timescales [Formula: see text]100 fs. Today's understanding of the energy transfer includes the fact that the excitons are delocalized over a few neighboring sites, but the role of quantum coherence is considered as irrelevant for the transfer dynamics because it typically decays within a few tens of femtoseconds. This orthodox picture of incoherent energy transfer between clusters of a few pigments sharing delocalized excitons has been challenged by ultrafast optical spectroscopy experiments with the Fenna-Matthews-Olson protein, in which interference oscillatory signals up to 1.5 ps were reported and interpreted as direct evidence of exceptionally long-lived electronic quantum coherence. Here, we show that the optical 2D photon echo spectra of this complex at ambient temperature in aqueous solution do not provide evidence of any long-lived electronic quantum coherence, but confirm the orthodox view of rapidly decaying electronic quantum coherence on a timescale of 60 fs. Our results can be considered as generic and give no hint that electronic quantum coherence plays any biofunctional role in real photoactive biomolecular complexes. Because in this structurally well-defined protein the distances between bacteriochlorophylls are comparable to those of other light-harvesting complexes, we anticipate that this finding is general and directly applies to even larger photoactive biomolecular complexes.

Molecular clumps photoevaporation in ionized regions

We study the photoevaporation of molecular clumps exposed to a UV radiation field including hydrogen-ionizing photons ($h\nu > 13.6$ eV) produced by massive stars or quasars. We follow the propagation and collision of shock waves inside clumps and take into account self-shielding effects, determining the evolution of clump size and density with time. The structure of the ionization-photodissociation region (iPDR) is obtained for different initial clump masses ($M=0.01 - 10^4\,{\rm M}_\odot$) and impinging fluxes ($G_0=10^2 - 10^5$ in units of the Habing flux). The cases of molecular clumps engulfed in the HII region of an OB star and clumps carried within quasar outflows are treated separately. We find that the clump undergoes in both cases an initial shock-contraction phase and a following expansion phase, which lets the radiation penetrate in until the clump is completely evaporated. Typical evaporation time-scales are $\simeq 0.01$ Myr in the stellar case and 0.1 Myr in the quasar case, where the clump mass is 0.1 ${\rm M}_\odot$ and $10^3\,{\rm M}_\odot$ respectively. We find that clump lifetimes in quasar outflows are compatible with their observed extension, suggesting that photoevaporation is the main mechanism regulating the size of molecular outflows.

Prethermalization at Low Temperature: The Scent of Long-Range Order.

Nonequilibrium time evolution in isolated many-body quantum systems generally results in thermalization. However, the relaxation process can be very slow, and quasistationary nonthermal plateaux are often observed at intermediate times. The paradigmatic example is a quantum quench in an integrable model with weak integrability breaking; for a long time, the state cannot escape the constraints imposed by the approximate integrability. We unveil a new mechanism of prethermalization, based on the presence of a symmetry of the prequench Hamiltonian, which is spontaneously broken at zero temperature and is explicitly broken by the postquench Hamiltonian. The typical time scale of the phenomenon is proportional to the thermal correlation length of the initial state, which diverges as the temperature is lowered. We show that the prethermal quasistationary state can be approximated by a mixed state that violates cluster decomposition property. We consider two examples: the transverse-field Ising chain, where the full-time evolution is computed analytically, and the (nonintegrable) anisotropic next-nearest-neighbor Ising model, which is investigated numerically.

Measuring surface magnetic fields of red supergiant stars

Context.Red supergiant (RSG) stars are very massive cool evolved stars. Recently, a weak magnetic field was measured at the surface ofαOri and this is so far the only M-type supergiant for which a direct detection of a surface magnetic field has been reported.Aims.By extending the search for surface magnetic field in a sample of late-type supergiants, we want to determine whether the surface magnetic field detected onαOri is a common feature among the M-type supergiants.Methods.With the spectropolarimeter Narval at TélescopeBernard-Lyotwe undertook a search for surface magnetic fields in a sample of cool supergiant stars, and we analysed circular polarisation spectra using the least-squares deconvolution technique.Results.We detect weak Zeeman signatures of stellar origin in the targets CE Tau,α1Her andμCep. For the latter star, we also show that cross-talk from the strong linear polarisation signals detected on this star must be taken into account. For CE Tau andμCep, the longitudinal component of the detected surface fields is at the Gauss-level, such as inαOri. We measured a longitudinal field almost an order of magnitude stronger forα1Her. We also report variability of the longitudinal magnetic field of CE Tau andα1Her, with changes in good agreement with the typical atmospheric dynamics time-scales. We also report a non-detection of magnetic field at the surface of the yellow supergiant starρCas.Conclusions.The two RSG stars of our sample, CE Tau andμCep, display magnetic fields very similar to that ofαOri. The non-detection of a magnetic field on the post-RSG starρCas suggests that the magnetic field disappears, or at least becomes undetectable with present methods, at later evolutionary stages. Our analysis ofα1Her supports the proposed reclassification of the star as an M-type asymptotic giant branch star.

Electromagnetic interaction between a rising spherical particle in a conducting liquid and a localized magnetic field

Lorentz force velocimetry (LFV) is a non-contact electromagnetic flow measurement technique for electrically conductive liquids. It is based on measuring the flow-induced force acting on an external permanent magnet. Motivated by extending LFV to liquid metal two-phase flow measurement, in a first test we consider the free rising of a non-conductive spherical particle in a thin tube of liquid metal (GaInSn) initially at rest. Here the measured force is due to the displacement flow induced by the rising particle. In this paper, numerical results are presented for three different analytical solutions of flows around a moving sphere under a localized magnetic field. This simplification is made since the hydrodynamic flow is difficult to measure or to compute. The Lorentz forces are compared to experiments. The aim of the present work is to check if our simple numerical model can provide Lorentz forces comparable to the experiments. The results show that the peak values of the Lorentz force from the analytical velocity fields provide us an upper limit to the measurement results. In the case of viscous flow around a moving sphere we recover the typical time-scale of Lorentz force signals.

Phototaxis beyond turning: persistent accumulation and response acclimation of the microalga Chlamydomonas reinhardtii

Phototaxis is an important reaction to light displayed by a wide range of motile microorganisms. Flagellated eukaryotic microalgae in particular, like the model organism Chlamydomonas reinhardtii, steer either towards or away from light by a rapid and precisely timed modulation of their flagellar activity. Cell steering, however, is only the beginning of a much longer process which ultimately allows cells to determine their light exposure history. This process is not well understood. Here we present a first quantitative study of the long timescale phototactic motility of Chlamydomonas at both single cell and population levels. Our results reveal that the phototactic strategy adopted by these microorganisms leads to an efficient exposure to light, and that the phototactic response is modulated over typical timescales of tens of seconds. The adaptation dynamics for phototaxis and chlorophyll fluorescence show a striking quantitative agreement, suggesting that photosynthesis controls quantitatively how cells navigate a light field.

Observation of Tropical Cyclone‐Induced Shallow Water Currents in Taiwan Strait

AbstractThe data from three stations equipped with Acoustic Doppler Current Profilers (ADCPs) deployed in the shallow water of the Taiwan Strait (TWS) were used to study the shallow coastal ocean response to five quasi‐continuous tropical cyclone (TC) events in the late summer 2006. We revealed that, in the forced stage, when the large and strong TC (Bilis) transited, the geostrophic currents were formed which dominated the whole event, while the strong but relatively small one (Saomai) or the weak one (Bopha) primarily leaded to the generation of Ekman currents. In the relaxation stage, the barotropic subinertial waves and/or the baroclinic near‐inertial oscillations (NIOs) were triggered. Typically, during the transit of the Saomai, subinertial waves were induced which demonstrated a period of 2.8–4.1 days and a mean alongshore phase velocity of 14.9 ± 3.2 m/s in the form of free‐barotropic continental shelf waves. However, the NIOs are only notable in the area in which the water column is stably stratified and also where the wind stress is dominated by the clockwise component and accompanied by high‐frequency (near‐inertial) variations. We also demonstrated that, due to the damping effects, the nonlinear wave‐wave interaction (e.g., between NIO and semidiurnal tide in our case), together with the well‐known bottom friction, led to the rapid decay of the observed TC‐induced near‐inertial currents, giving a typical e‐folding time scale of 1–3 inertial periods. Moreover, such nonlinear wave‐wave interaction was even found to play a major role during the spring tide in TWS.

Assessment of different formation scenarios for the ring system of (10199) Chariklo

The discovery that the centaur (10199) Chariklo possesses a ring system opens questions about their origin. We here asses the plausibility of different scenarios for the origin of the observed ring system. We first consider the possibility that the material of the ring originated in the disruption of a satellite that had reached a critical distance from the centaur. We discuss the conditions for the putative satellite to approach the centaur as a consequence of tidal interaction. A three-body encounter is also considered as a transport mechanism. In addition, we study the case in which the ring is formed by the ejecta of a cratering collision on the centaur and we constrain the collision parameters and the size of the resulting crater of the event. Finally, we consider that the ring material originates from a catastrophic collision between a background object and a satellite located at a distance corresponding to the the current location of the ring. We compute the typical timescales for these scenarios. We estimate that in order to be tidally disrupted a satellite would have had to be larger than approximately 6.5 km at the location of the rings. However the tidal interaction is rather weak for objects of the size of outer solar system bodies at the ring location, therefore we considered other more effective mechanisms by which a satellite migt have approached the centaur. Collisonal scenarios are both physically plausible for the formation, but semianalytical estimations indicate that the probability of the corresponding collisions is low under current conditions

Energy Invariance in Capillary Systems.

We demonstrate the continuous translational invariance of the energy of a capillary surface in contact with reconfigurable solid boundaries. We present a theoretical approach to find the energy-invariant equilibria of spherical capillary surfaces in contact with solid boundaries of arbitrary shape and examine the implications of dynamic frictional forces upon a reconfiguration of the boundaries. Experimentally, we realize our ideas by manipulating the position of a droplet in a wedge geometry using lubricant-impregnated solid surfaces, which eliminate the contact-angle hysteresis and provide a test bed for quantifying dissipative losses out of equilibrium. Our experiments show that dissipative energy losses for an otherwise energy-invariant reconfiguration are relatively small, provided that the actuation time scale is longer than the typical relaxation time scale of the capillary surface. We discuss the wider applicability of our ideas as a pathway for liquid manipulation at no potential energy cost in low-pinning, low-friction situations.

Long-Lived Hot Carriers in Formamidinium Lead Iodide Nanocrystals

The efficient harvesting of hot carrier energy in semiconductors is typically inhibited by their ultrafast thermalization process. Recently, highly promising experiments reported on the slowdown of the intraband relaxation in hybrid metal halide perovskites. In this work, we report on the presence of long-lived hot carriers in weakly confined colloidal nanocrystals (NCs) of formamidinium lead iodide perovskite (FAPbI3). The effect is apparent from the excitation-dependent lengthening of the rise time and broadening of the high-energy tail of the transient absorption bleaching signal, yielding a retardation of the carrier relaxation by 2 orders of magnitude compared to typical time scales in colloidal semiconductor NCs. Three distinct cooling stages are observed, occurring at sub-picosecond, ∼5 ps, and ∼40 ps time scales, which we attribute to scattering from LO-phonons, contribution from a hot phonon bottleneck effect and Auger heating, respectively. Thermalization appears also influenced by the FAPbI3 NC...

Comparison of SWAT and GSSHA for High Time Resolution Prediction of Stream Flow and Sediment Concentration in a Small Agricultural Watershed

In this study, two hydrologic models, the Gridded Surface Subsurface Hydrologic Analysis (GSSHA) and the Soil and Water Assessment Tool (SWAT), were applied to predict stream flow and suspended sediment concentration (SSC) in a small agricultural watershed in Ishigaki Island, Japan, in which the typical time scale of flood event was several hours. The performances of these two models were compared in order to select the right model for the study watershed. Both models were calibrated and validated against hourly stream flow and SSC for half-month periods of 15 to 31 May 2011 and 17 March to 7 April 2013, respectively. The results showed that both models successfully estimated hourly stream flow and SSC in a satisfactory way. For the short-term simulations, the GSSHA model performed slightly better in simulating stream flow as compared to SWAT during both calibration and validation periods. GSSHA only gave better accuracy when predicting SSC during calibration, while SWAT performed slightly better during validation. For long-term simulations, both models yielded comparable results for long-term stream flow and SSC with acceptable agreement. However, SWAT predicted the overall variation of long-term SSC better than GSSHA.

Positive and Negative Eddy Feedbacks Acting on Midlatitude Jet Variability in a Three-Level Quasigeostrophic Model

Abstract The variability of midlatitude jets is investigated in a long-term integration of a dry three-level quasigeostrophic model on the sphere. As for most observed jets, the leading EOF of the zonal-mean wind corresponds to latitudinal shifts of the jet, and the second EOF to pulses of the jet speed. The first principal component (PC1) is also more persistent than the second one (PC2); this longer persistence arises from different eddy feedbacks both in the short term (i.e., within a few days following the peak of the PCs) and in the long term. The short-term eddy feedbacks come from two distinct mechanisms. First, a planetary waveguide effect acts as a negative feedback on both PCs. The positive phases of PC1 and PC2, which correspond to poleward-shifted and accelerated jets, respectively, are first driven then canceled by planetary waves reflecting on the equatorward flank of the jet. A similar process occurs for the negative phases when planetary waves reflect on the poleward flank of the jet. Second, synoptic waves also exert a short-term negative feedback on PC2: when the jet accelerates, the enhanced meridional wind shear increases the barotropic sink of eddy energy and depletes it very rapidly, therefore preventing synoptic eddies from maintaining the accelerated jet. Finally, at lags longer than their typical time scale, synoptic eddies drive a positive feedback on PC1 only. This feedback can be explained by a baroclinic mechanism in which the jet shift modifies the baroclinicity, causing, first, eddy heat flux anomalies and, then, momentum convergence anomalies. This feedback is absent for PC2, despite some changes in the baroclinicity.

Thermally induced group effects among energy piles

The behaviour of conventional pile groups (e.g. closely spaced) that are subjected to mechanical loads has been shown to be different from the behaviour of single isolated piles. The so-called ‘group effects’ are responsible for this behaviour and must be considered for an optimal design of pile foundations. In recent years, energy piles have shown potential to work as both structural supports and geothermal heat exchangers, and thus are subjected to both mechanical and thermal loads. An increasing amount of research has investigated the previously unexplored impact of thermal loads on the thermo-mechanical behaviour of energy piles. However, no field data over typical timescales of practical geothermal applications have been available to analyse the development and impact of thermally induced group effects between energy piles (e.g. closely spaced) on their thermo-mechanical behaviour. To investigate this problem, a full-scale in situ test of a group of energy piles and coupled three-dimensional thermo-mechanical finite-element analyses were performed and are presented in this paper. This work demonstrates that significant thermally induced group effects characterise closely spaced energy piles. Attention must be devoted to these effects throughout the design process (e.g. geotechnical, structural and energy) of energy piles because they play an important role in the serviceability performance of these foundations.

Stochastic fluctuations of permittivity coupling regulate seizure dynamics in partial epilepsy

Partial epilepsy is characterized by recurrent seizures that arise from a localized pathological brain region. During the onset of partial epilepsy, the seizure evolution commonly exhibits typical timescale separation phenomenon. This timescale separation behavior can be mimicked by a paradigmatic model termed as Epileptor, which consists of coupled fast-slow neural populations via a permittivity variable. By incorporating permittivity noise into the Epileptor model, we show here that stochastic fluctuations of permittivity coupling participate in the modulation of seizure dynamics in partial epilepsy. In particular, introducing a certain level of permittivity noise can make the model produce more comparable seizure-like events that capture the temporal variability in realistic partial seizures. Furthermore, we observe that with the help of permittivity noise our stochastic Epileptor model can trigger the seizure dynamics even when it operates in the theoretical nonepileptogenic regime. These findings establish a deep mechanistic understanding on how stochastic fluctuations of permittivity coupling shape the seizure dynamics in partial epilepsy, and provide insightful biological implications.