Time Scale Of Process Research Articles

Quantifying the Effects of Non‐Hydrostatic Stress on Multi‐Component Minerals

AbstractMineral compositions are used to infer pressures, temperatures, and timescales of geological processes. The thermodynamic techniques underlying these inferences assume a uniform, constant pressure. Nonetheless, convergent margins generate significant non‐hydrostatic (unequal) stresses, violating the uniform pressure assumption and creating uncertainty. Materials scientists F. Larché and J. Cahn derived an equation suitable for non‐hydrostatically stressed geologic environments that links stress and equilibrium composition in elastic, multi‐component crystals. However, previous works have shown that for binary solid solutions with ideal mixing behavior, hundreds of MPa to GPa‐level stresses are required to shift mineral compositions by a few hundredths of a mole fraction, limiting the equation's applicability. Here, we apply Larché and Cahn's equation to garnet, clinopyroxene, and plagioclase solid solutions, incorporating for the first time non‐ideal mixing behavior and more than two endmembers. We show that non‐ideal mixing increases predicted stress‐induced composition changes by up to an order of magnitude. Further, incorporating additional solid solution endmembers changes the predicted stress‐induced composition shifts of the other endmembers being considered. Finally, we demonstrate that Larché and Cahn's approach yields positive entropy production, a requirement for any real process to occur. Our findings reveal that stresses between tens and a few hundred MPa can shift mineral compositions by several hundredths of a mole fraction. Consequently, mineral compositions could plausibly be used to infer stress states. We suggest that stress‐composition effects could develop via intracrystalline diffusion in any high‐grade metamorphic setting, but are most likely in hot, dry, and strong rocks such as lower crustal granulites.

Recent Progresses and Perspectives of UV Laser Annealing Technologies for Advanced CMOS Devices

The state-of-the-art CMOS technology has started to adopt three-dimensional (3D) integration approaches, enabling continuous chip density increment and performance improvement, while alleviating difficulties encountered in traditional planar scaling. This new device architecture, in addition to the efforts required for extracting the best material properties, imposes a challenge of reducing the thermal budget of processes to be applied everywhere in CMOS devices, so that conventional processes must be replaced without any compromise to device performance. Ultra-violet laser annealing (UV-LA) is then of prime importance to address such a requirement. First, the strongly limited absorption of UV light into materials allows surface-localized heat source generation. Second, the process timescale typically ranging from nanoseconds (ns) to microseconds (μs) efficiently restricts the heat diffusion in the vertical direction. In a given 3D stack, these specific features allow the actual process temperature to be elevated in the top-tier layer without introducing any drawback in the bottom-tier one. In addition, short-timescale UV-LA may have some advantages in materials engineering, enabling the nonequilibrium control of certain phenomenon such as crystallization, dopant activation, and diffusion. This paper reviews recent progress reported about the application of short-timescale UV-LA to different stages of CMOS integration, highlighting its potential of being a key enabler for next generation 3D-integrated CMOS devices.

Modes of massive nucleon transfer appearing in quasifission processes for collisions of superheavy nuclei

Background: It is challenging to distinguish between fusion-fission and quasifission experimentally. To determine the characteristics of quasifission processes associated with dominant phenomena in heavy-ion collisions is important for estimating precisely the fusion cross section, which is relevant to the synthesis of new elements. We classified fusion-fission and quasifission processes theoretically in the past for an accurate assessment of the fusion cross section [Y. Aritomo and M. Ohta, Nucl. Phys. A 744, 3 (2004)]. However, no detailed analysis focused on each process was performed.Purpose: In this work, we aimed to analyze the dynamical characteristics of quasifission processes in terms of the Langevin equation model. We specify the quasifission processes, and analyze the scission configuration. Finally, we clarify the origin of several modes included in quasifission.Method: The calculation framework is the multidimensional dynamical model of nucleus-nucleus collisions based on the Langevin equations.Results: It is shown that several quasifission modes exist leading to different fragment deformations. The timescale of the quasifission process differs for several different modes. Each scission configuration and total kinetic energy also differ.Conclusions: The different quasifission modes are caused by the neck relaxation controlling the mass drift toward symmetry. This means that it is possible to discuss the time-dependent functional form of the neck parameter $\ensuremath{\epsilon}$ for the quasifission process in the framework of the dynamical model based on Langevin equations.

A Hidden Relaxation Process in Poly(2-vinylpyridine) Homopolymers, Copolymers, and Nanocomposites

In broadband dielectric spectroscopy experiments, we find that introducing an air gap between the top electrode and the polymer sample reduces DC conductivity substantially, allowing the study of low-frequency relaxations, whose signal would otherwise be hidden by the DC conductivity signal. An extra process slower than the α-relaxation process is observed in poly(2-vinylpyridine) (P2VP), consistent with some earlier reports. This “slower process” was studied in two heterogeneous systems to examine the interaction between the 2VP and other species to elucidate the mechanism behind the slower process signal. In a random copolymer of styrene and 2VP, the relaxation strength of the slower process relative to the α-process increases substantially at low 2VP mole fractions. Additionally, in a composite of P2VP and octa(aminophenyl) silsesquioxane (OAPS), the presence of OAPS increases both the strength and timescale of the slower process, leaving the α-relaxation process relatively unchanged. This suggests that the slower process could be caused by cooperative polymer relaxation coupled to the transport of heterogeneous components and impurities. Further studies are needed to probe the molecular-level mechanism of this slower process and its effect on interfacial properties.

(Invited) Discovering Bottlenecks and Opportunities in Hybrid Solar Light Harvesting Systems By Ultrafast X-Ray Spectroscopy

A prerequisite for advancing hybrid solar light harvesting systems is a comprehensive understanding of photoinduced electronic dynamics across a wide range of spatial and temporal scales. Time-resolved spectroscopy techniques in the optical domain have proven instrumental in identifying critical timescales of fundamental processes, such as interfacial charge transfer, charge migration, and carrier lifetimes, which are intimately linked to a system's performance. New light source and instrument developments open opportunities to extend such studies into the X-ray regime. Due to their inherent elemental specificity and sensitivity to local electronic environments, time-domain X-ray spectroscopy techniques are uniquely suited to gain a microscopic picture of dynamics from well-defined reporter sites within often complex nanoscale light harvesting architectures. We will present new insights into fundamental photoinduced dynamics in several archetypical heterostructures based on femtosecond and picosecond time-resolved X-ray photoemission spectroscopy (TRXPS).The photoinduced transient charge redistribution in the model hybrid system of nanoporous zinc oxide (ZnO) sensitized by ruthenium bipyridyl chromophores is probed independently from the viewpoints of the molecular electron donor and the semiconductor acceptor.[1] Charge injection from the chromophore into the semiconductor is found to proceed via a transiently populated interfacial charge transfer (ICT) complex on an overall timescale of ~300 ps. Our results show that, even after release from the ICT states into the ZnO conduction band, the injected electrons remain localized within less than 6 nm from the interface, due to enhanced downward band-bending by the photo-injected charge carriers. This spatial confinement suggests that light-induced charge generation and transport in nanoscale ZnO photocatalytic devices proceeds predominantly within the defect-rich surface region, which may lead to enhanced surface recombination and explain their lower performance compared to titanium dioxide (TiO2)-based systems. The quantitative nature and surface sensitivity of TRXPS also provides direct access to the spatial separation of the holes remaining on the bipyridyl chromophores after charge injection from the semiconductor surface with sub-nm precision.Complementary femtosecond and picosecond TRXPS studies of photoinduced dynamics in copper-phthalocyanine(CuPc)-C60 heterojunctions provide a deeper understanding of both exciton migration pathways toward the interface as well as the absolute efficiency by which ICT states dissociate into separate charges.[2] The measurements reveal surprisingly efficient charge generation from triplet excitons and from the lowest lying ICT states, both of which were previously believed to be inactive during light-to-charge conversion.Photoinduced charge transfer dynamics between spherical gold nanoparticles (AuNPs) and a nanoporous film of TiO2 is monitored by picosecond TRXPS, providing direct access to the absolute photon-to-charge conversion efficiency and subsequent electron-hole recombination dynamics.[3] Preliminary results will be presented for the extension of the measurements into the ambient pressure regime, taking a first step toward the study of photoinduced interfacial chemistry by TRXPS in this model system for nanoplasmonic light harvesting applications.[1] S. Neppl et al., “Nanoscale Confinement of Photo-Injected Electrons at Hybrid Interfaces”, J. Phys. Chem. Lett. 12, 11951 (2021).[2] F. Roth et al., “Direct observation of charge separation in an organic light harvesting system by femtosecond time-resolved XPS”, Nat. Commun. 12, 1196 (2021).[3] M. Borgwardt et al., “Photoinduced Charge Carrier Dynamics and Electron Injection Efficiencies in Au Nanoparticle-Sensitized TiO2 Determined with Picosecond Time-Resolved X-ray Photoelectron Spectroscopy”, J. Phys. Chem. Lett. 11, 5476 (2020). Figure 1

Effect of a Scale‐Aware Convective Parameterization Scheme on the Simulation of Convective Cells‐Related Heavy Rainfall in South Korea

AbstractIn this study, the effect of a scale‐aware convective parameterization scheme (CPS) on the simulation of heavy precipitation in the gray‐zone was investigated using the Weather Research and Forecasting (WRF) model. We performed WRF simulations with the Kain–Fritsch (KF) scheme (non‐scale‐aware), Multiscale Kain–Fritsch (MSKF) scheme (scale‐aware), and explicit convection (i.e., no CPS). The MSKF scheme uses a scale‐aware parameter that modulates the convective available potential energy (CAPE) timescale and entrainment process in the KF scheme as a function of the horizontal grid spacing. The results of this study show that WRF simulations using explicitly resolved convection lead to overestimations and erroneous precipitation locations in the gray‐zone because the convection and atmospheric instability cannot be appropriately triggered and reduced. The CPS without scale‐awareness in the gray‐zone exaggerates the convection and distorts synoptic fields, leading to the erroneous simulation of heavy precipitation at high resolution. The MSKF scheme with scale‐awareness improves the simulation of convective cells‐related heavy rainfall by removing the atmospheric instability in the gray‐zone, reducing the role of the CPS, and increasing the role of the microphysics parameterization scheme (MPS) with decreasing grid spacing. In addition, the results of sensitivity experiments show that reducing the CAPE timescale leads to the faster development of convective cells, whereas decreasing the entrainment leads to precipitation overestimation. The modulated parameters in the scale‐aware MSKF scheme play a crucial role in balancing the effects of the CPS and MPS in the gray‐zone.

Anisotropic cosmic ray diffusion in isotropic Kolmogorov turbulence

ABSTRACT Understanding the time-scales for diffusive processes and their degree of anisotropy is essential for modelling cosmic ray transport in turbulent magnetic fields. We show that the diffusion time-scales are isotropic over a large range of energy and turbulence levels, notwithstanding the high degree of anisotropy exhibited by the components of the diffusion tensor for cases with an ordered magnetic field component. The predictive power of the classical scattering relation as a description for the relation between the parallel and perpendicular diffusion coefficients is discussed and compared to numerical simulations. Very good agreement for a large parameter space is found, transforming classical scattering relation predictions into a computational prescription for the perpendicular component. We discuss and compare these findings, in particular, the time-scales to become diffusive with the time-scales that particles reside in astronomical environments, the so-called escape time-scales. The results show that, especially at high energies, the escape times obtained from diffusion coefficients may exceed the time-scales required for diffusion. In these cases, the escape time cannot be determined by the diffusion coefficients.

Diffusion chronometry of volcanic rocks: looking backward and forward

Diffusion of elements that result in compositional zoning in minerals in volcanic rocks may be used to determine the timescales of various volcanic processes (e.g., residence times in different reservoirs, ascent rates of magmas). Here, we introduce the tool and discuss the reasons for its gain in popularity in recent times, followed by a summary of various applications and some main inferences from those applications. Some specialized topics that include the role of diffusion anisotropy, isotopic fractionation by diffusion, image analysis as a tool for expediting applications, and the sources of uncertainties in the method are discussed. We point to the connection between timescales obtained from diffusion chronometry to those obtained from geochronology as well as various monitoring tools. A listing of directions in which we feel most progress is necessary/will be forthcoming is provided in the end.

Microsecond non-melt UV laser annealing for future 3D-stacked CMOS

Three-dimensional (3D) CMOS technology encourages the use of UV laser annealing (UV-LA) because the shallow absorption of UV light into materials and the process timescale typically from nanoseconds (ns) to microseconds (μs) strongly limit the vertical heat diffusion. In this work, μs UV-LA solid phase epitaxial regrowth demonstrated an active carrier concentration surpassing 1 × 1021 at cm−3 in an arsenic ion-implanted silicon-on-insulator substrate. After the subsequent ns UV-LA known for improving CMOS interconnect, only a slight (∼5%) sheet resistance increase was observed. The results open a possibility to integrate UV-LA at different stages of 3D-stacked CMOS.

Adsorption of Polar Species at Crude Oil-Water Interfaces: the Chemoelastic Behavior.

We investigate the formation and properties of crude oil/water interfacial films. The time evolution of interfacial tension suggests the presence of short and long timescale processes reflecting the competition between different populations of surface-active molecules. We measure both the time-dependent shear and extensional interfacial rheology moduli. Late-time interface rheology is dominated by elasticity, which results in visible wrinkles on the crude oil drop surface upon interface disturbance. We also find that the chemical composition of the interfacial films is affected by the composition of the aqueous phase that it has contacted. For example, sulfate ions promote films enriched with carboxylic groups and condensed aromatics. Finally, we perform solution exchange experiments and monitor the late-time film composition upon the exchange. We detect the film composition change upon replacing chloride solutions with sulfate-enriched ones. To the best of our knowledge, we are the first to report the composition alteration of aged crude oil films. This finding might foreshadow an essential crude oil recovery mechanism.

Diffuser: A user-friendly program for diffusion chronometry with robust uncertainty estimation

Chemical diffusion in minerals has shown great potential to quantify timescales of geological processes. The presence of chemical gradients, along with favorable temperature and time conditions, lead to the formation of measurable diffusion profiles. Temporal information can be extracted from measured diffusion profiles using either analytical or numerical solutions of Fick's second law. Currently, there is a lack of widely adopted programs for diffusion studies. In addition, the uncertainties associated with timescales derived from diffusion chronometry are critical for geological studies, but are not always robustly evaluated. In many cases, only uncertainties in curve fitting parameters and temperature are considered, whereas other uncertainties, such as those associated with the experimentally determined diffusion coefficients themselves, are rarely propagated into the calculated timescales. Ignoring these uncertainties reduces the reproducibility and intercomparability of results. In response to these challenges, we present Diffuser, a user-friendly program to standardize diffusion chronometry with transparent and robust propagation of uncertainties. Using analytical and numerical methods, our program provides an automatic, visual, and efficient curve fit to extract chronological information from diffusion profiles. The method is complemented by an algorithm to propagate all uncertainties (i.e., measurement, temperature, curve fitting, and diffusion coefficient) to derived timescales. Three examples are provided to highlight how the program can recover timescales with internal consistency, efficient computing, and easy-to-use features. Our freely available and user-friendly program will hopefully increase the accessibility and consistency of diffusion modeling and thereby to facilitate more high-quality diffusion studies.

Insights into the temporal evolution of magma plumbing systems from compositional zoning in clinopyroxene crystals from the Agnano-Monte Spina Plinian eruption (Campi Flegrei, Italy)

The complex sequential compositional zoning of clinopyroxene crystals erupted <5 ka during the Agnano-Monte Spina (A-MS) eruption, which is considered to be the reference event for a future large-scale explosive eruption at Campi Flegrei caldera (Italy), has been characterized in detail. Concentration profiles (20–800 μm long, spacing 2.5–10 μm) of major (Si, Ti, Al, Fe, Mg and Ca) and minor (Mn, Na, Ni and Cr) elements were measured along different directions in the clinopyroxene crystals. The zoning patterns of Fe–Mg and selected elements (e.g., Al, Ti) often consist of two or more compositional plateaus with both sharp and/or slightly diffuse boundaries between the plateaus. Each compositional population results from a growth stage in a distinct Magmatic Environment (ME), which is identified as a defined set of intensive thermodynamic variables (pressure, temperature, bulk composition and fugacity of fluids including oxygen). The large range of chemical compositions of clinopyroxenes reveals the existence of at least four MEs that are characterized by different compositional populations; two of these are dominant. The variation in zoning pattern from one plateau composition to another fingerprints the transfer of the crystal from one ME to another. In combination with Sr isotopic data and thermobarometric estimates, our systematic characterization of clinopyroxene zoning patterns suggests recharge by deep mafic magmas (ME0: Mg# = 85–92) of an evolved shallow reservoir (ME2: Mg# = 70–78). Such a process also led to the formation of a compositionally intermediate environment (ME1: Mg# = 84–80), that is detected in the clinopyroxene zoning pattern.A new method has been developed in this work to evaluate the effective diffusive modifications that affect the concentration profiles of zoned crystals. The application of different diffusion modeling methods indicates that deep and shallow reservoirs beneath the Campi Flegrei caldera were connected to each other over several tens of years until the amount of mafic recharge increased during the last 10–15 years before the A-MS eruption. This study highlights the complex relationships between events of magma recharge and the onset of eruption. Our results provide a contribution to the knowledge of timescales of magmatic processes that have recently occurred beneath the Campi Flegrei caldera, which is useful for risk assessment.

The coherence time of sunlight in the context of natural and artificial light-harvesting

The suggestion that quantum coherence might enhance biological processes such as photosynthesis is not only of fundamental importance but also leads to hopes of developing bio-inspired ‘green’ quantum technologies that mimic nature. A key question is how the timescale of coherent processes in molecular systems compare to that of the driving light source—the Sun. Across the quantum biology literature on light-harvesting, the coherence time quoted for sunlight spans about two orders of magnitude, ranging from 0.6 to ‘10s’ of femtoseconds. This difference can potentially be significant in deciding whether the induced light-matter coherence is long enough to affect dynamical processes following photoexcitation. Here we revisit the historic calculations of sunlight coherence starting with the black-body spectrum and then proceed to provide values for the more realistic case of atmospherically filtered light. We corroborate these values with interferometric measurements of the complex degree of temporal coherence from which we calculate the coherence time of atmospherically filtered sunlight as 1.12pm {0.04},{hbox { fs}}, as well as the coherence time in a chlorophyll analogous filtered case as 4.87pm {0.21},{hbox { fs}}.

Applying non-parametric Bayesian networks to estimate maximum daily river discharge: potential and challenges

Abstract. Non-parametric Bayesian networks (NPBNs) are graphical tools for statistical inference widely used for reliability analysis and risk assessment and present several advantages, such as the embedded uncertainty quantification and limited computational time for the inference process. However, their implementation in hydrological studies is still scarce. Hence, to increase our understanding of their applicability and extend their use in hydrology, we explore the potential of NPBNs to reproduce catchment-scale hydrological dynamics. Long-term data from 240 river catchments with contrasting climates across the United States from the Catchment Attributes and Meteorology for Large-sample Studies (CAMELS) data set will be used as actual means to test the utility of NPBNs as descriptive models and to evaluate them as predictive models for maximum daily river discharge in any given month. We analyse the performance of three networks, one unsaturated (hereafter UN-1), one saturated (hereafter SN-1), both defined only by hydro-meteorological variables and their bivariate correlations, and one saturated network (hereafter SN-C), consisting of the SN-1 network and including physical catchments' attributes. The results indicate that the UN-1 network is suitable for catchments with a positive dependence between precipitation and discharge, while the SN-1 network can also reproduce discharge in catchments with negative dependence. The latter can reproduce statistical characteristics of discharge (tested via the Kolmogorov–Smirnov statistic) and have a Nash–Sutcliffe efficiency (NSE) ≥0.5 in ∼40 % of the catchments analysed, receiving precipitation mainly in winter and located in energy-limited regions at low to moderate elevation. Further, the SN-C network, based on similarity of the catchments, can reproduce discharge statistics in ∼10 % of the catchments analysed. We show that once a NPBN is defined, it is straightforward to infer discharge and to extend the network itself with additional variables, i.e. going from the SN-1 network to the SN-C network. However, the results also suggest considerable challenges in defining a suitable NPBN, particularly for predictions in ungauged basins. These are mainly due to the discrepancies in the timescale of the different physical processes generating discharge, the presence of a “memory” in the system, and the Gaussian-copula assumption used for modelling multivariate dependence.

The root-zone soil moisture spectrum in a mediterranean ecosystem

Storage of water within soil pores of the root zone introduce memory effects in the dynamics of soil moisture that are considerably longer than the integral timescale of many atmospheric processes. Thus, hydro-climatic states can be “sustained” through land-surface heat and water vapor fluxes primarily because they can “feed off” on this long-term soil moisture memory. Root-zone soil moisture memory is only but one feature characterizing the spectrum of soil moisture dynamics, which is analyzed here using a combination of long-term measurements and models. In particular, the spectrum of root-zone soil moisture content in a Mediterranean ecosystem is examined using 14-years of half-hourly measurements. A distinguishing hydro-climatic feature in such ecosystems is that sources (mainly rainfall) and sinks (mainly evapotranspiration) of soil moisture are roughly out of phase with each other. For over 4 decades of time scales and 7 decades of energy, the canonical shape of the measured soil moisture spectrum is shown to be approximately Lorentzian determined by the soil moisture variance and its memory but with two exceptions: the occurrences of a peak at diurnal-to-daily time scales and a weaker peak at near annual time scales. Model calculations and spectral analysis demonstrate that diurnal and seasonal variations in hydroclimate forcing responsible for variability in evapotranspiration had minor impact on the normalized shape of the soil moisture spectrum. However, their impact was captured by adjustments in the temporal variance. These findings indicate that precipitation and not evapotranspiration variability dominates the multi-scaling properties of soil moisture variability consistent with prior climate model simulations. Furthermore, the soil moisture memory inferred by the annual peak of soil moisture (340 d) is consistent with climate model simulations, while the memory evaluated from the loss function of a linearized mass balance approach leads to a smaller value (50 d), highlighting the effect of weak non-stationarity on soil moisture variability.

Intrinsic timescales as an organizational principle of neural processing across the whole rhesus macaque brain.

Hierarchical temporal dynamics are a fundamental computational property of the brain; however, there are no whole brain, noninvasive investigations into timescales of neural processing in animal models. To that end, we used the spatial resolution and sensitivity of ultrahigh field functional magnetic resonance imaging (fMRI) performed at 10.5 T to probe timescales across the whole macaque brain. We uncovered within-species consistency between timescales estimated from fMRI and electrophysiology. Crucially, we extended existing electrophysiological hierarchies to whole-brain topographies. Our results validate the complementary use of hemodynamic and electrophysiological intrinsic timescales, establishing a basis for future translational work. Further, with these results in hand, we were able to show that one facet of the high-dimensional functional connectivity (FC) topography of any region in the brain is closely related to hierarchical temporal dynamics. We demonstrated that intrinsic timescales are organized along spatial gradients that closely match FC gradient topographies across the whole brain. We conclude that intrinsic timescales are a unifying organizational principle of neural processing across the whole brain.

Photon transport enhancement through a coupled-cavity QED system with dynamic modulation.

We investigate photonic transport through fiber optical cavities under tunable fast modulation, which is induced by modulating atom-cavity coupling in a cavity quantum electrodynamics (CQED) system. The modulation bandwidth exceeds the timescales of all other system processes, such as cavity decay and atom-cavity coupling, and allows control of the dynamics of photonic transport through the cavity array. The transmission as a function of the modulation frequency clearly shows enhancement peaks in single cavity and two coupled-cavity cases. In particular, in the coupled-cavity case, the position of the enhancement peak is shifted due to the delocalized cavity field in the coupled system.

Cyclicity of multistage anatexis of deeply subducted continental crust during the North Qaidam orogeny: Tracing the source, timescale, and evolution of pulsed melts

The most significant mass transfer processes at a convergent plate boundary are tectonic accretion and fluids/melts released from sites of generation to sites of accumulation. However, some crucial questions remain with regards to the source, timescale, and evolution of such anatectic processes, for example, single or multistage anatexis of deeply subducted continental crust. To better understand the processes involved in anatexis, we have quantified the timescale and nature of formation and evolution processes of multistage felsic veins within retrograde eclogite using zircon, monazite, and xenotime geochemistry and geochronology, whole-rock composition, and Sr-Nd-Hf isotope analysis from the Lüliangshan, North Qaidam orogen. The U–Pb dating of coexisting zircon, monazite, and xenotime gives three groups of ages at <i>ca.</i> 441 to 435, <i>ca.</i> 425, and <i>ca.</i> 413 to 409 Ma, respectively, which record at least three episodes of pulsed melts. The first stage of zircon formation is characterized by not only the absence of oscillatory zoning of different zircons in cathodoluminescence images but also some of them with flat HREE and without Eu anomalies, indicating they may form in anatectic melts under eclogite-facies conditions. The second and third phases of melts may have occurred under granulite- and amphibole-facies conditions during exhumation. Furthermore, two classes of felsic veins within the eclogite show wide variations of whole-rock composition, (⁸⁷Sr/⁸⁶Sr)_i, ε_Nd (t), and ε_Hf (t) values, which demonstrate that they were derived from fluid-present dehydration partial melting of different proportions of subducted gneiss and eclogite during different periods. These findings show that melts have systematic differences in chemical and isotopic signatures resulting from lithological diversity and depth of partial melting. Thus, small-scale melts released from the source can excellently explain the variability in whole-rock composition, accessory mineral growth zoning, and prominent isotope variability in syn-collisional heterogeneous granites. An additional implication is that as these melts escape their adjacent area of formation, they migrate and mix along channelized melt pathways, resulting in melt-rock and crust-mantle interaction and the triggering of syn- and post-collisional magmatism.

Microscopic observation of hidden Johari-Goldstein-β process in glycerol.

The Johari-Goldstein-β (JG-β) process is widely observed in a variety of glass-forming systems and recognized as an intrinsic process in deeply supercooled and glassy states. However, in some systems, e.g., glycerol, a clear sign of the JG-β process is often not apparent; for example, an isolated JG-β peak may not be observed in the dielectric relaxation spectrum. In this study, we directly investigated the angstrom-scale dynamics of glycerol through quasielastic scattering experiments using time-domain interferometry. The relaxation times of the local motions start to decouple from the timescale of the diffusion process and follow the established behavior of the JG-β process. This finding microscopically indicates the existence of the hidden JG-β process in glycerol. In addition, we succeeded in determining the decoupling temperature of the JG-β process by using the spatial-scale selectivity of the quasielastic scattering technique.

Cerebral cortical processing time is elongated in human brain evolution

An increase in number of neurons is presumed to underlie the enhancement of cognitive abilities in brain evolution. The evolution of human cognition is then expected to have accompanied a prolongation of net neural-processing time due to the accumulation of processing time of individual neurons over an expanded number of neurons. Here, we confirmed this prediction and quantified the amount of prolongation in vivo, using noninvasive measurements of brain responses to sounds in unanesthetized human and nonhuman primates. Latencies of the N1 component of auditory-evoked potentials recorded from the scalp were approximately 40, 50, 60, and 100 ms for the common marmoset, rhesus monkey, chimpanzee, and human, respectively. Importantly, the prominent increase in human N1 latency could not be explained by the physical lengthening of the auditory pathway, and therefore reflected an extended dwell time for auditory cortical processing. A longer time window for auditory cortical processing is advantageous for analyzing time-varying acoustic stimuli, such as those important for speech perception. A novel hypothesis concerning human brain evolution then emerges: the increase in cortical neuronal number widened the timescale of sensory cortical processing, the benefits of which outweighed the disadvantage of slow cognition and reaction.