Active thrust sheet deformation over multiple rupture cycles: A quantitative basis for relating terrace folds to fault slip rates

Many recent thrust fault earthquakes have involved coseismic surface faulting and folding, revealing the multifaceted nature of active thrust sheet deformation. We integrate records of surface deformation, subsurface structure and geochronology to investigate active surface deformation over multiple rupture cycles across the Southern Junggar Thrust (SJT) in the southern Junggar basin, NW China. Fluvial terrace geometries – extracted from a 1-m digital elevation model – reveal records of surface faulting across a prominent fault scarp. In addition, terraces exhibit progressive folding across fold scarps. Fault and fold scarps are spatially coincident with a surface-emergent SJT splay and subsurface fault bends along the SJT, respectively, constrained by seismic reflection data. We quantify the magnitude of fault slip at depth implied by fold scarps along Holocene-aged terraces. Our method yields results consistent with independent estimates of slip implied by fault scarp relief for the same terraces. Four late Quaternary terrace records are less continuous, preserved only as fold scarps that suggest folding kinematics involving a component of limb rotation. We develop a new method for quantifying fault slip at depth from terrace folds using a mechanical forward modeling approach. Our analysis yields quantitative relations between fold dip and fault slip, allowing us to quantify SJT fault slip from terrace folds from ~250 ka- present. SJT fault slip rate has decelerated from ~7.0 mm/yr in the Late Quaternary to ~1.3 mm/yr throughout the Holocene. These results provide new insight into the kinematics of fault-bend folding for natural structures and define new methods to accurately estimate fault slip and slip rates from terrace folds in active thrust sheets

Present Effects of Past Wildfires on Leaf Litter Breakdown in Stream Ecosystems

We investigated the present effects from a 10-year-old wildfire on leaf litter breakdown rates in 3 headwater streams in central Idaho. These systems experienced a massive debris flow one year after the fire. Based on soil instability and burn patterns, we identified 3 stream conditions: unburned, burned only, and burned/scoured. We placed leaf bags containing willow leaves (Salix sp.) in each stream type and removed bags at various time intervals until all bags were collected 100 days after their introduction. Leaf material was dried and weighed, and decay rate coefficients were calculated. Macroinvertebrates colonizing the bags were enumerated and identified, and selected taxa were placed into trophic groups. We found that the unburned stream had the fastest leaf litter breakdown rate, the lowest level of incident light reaching the stream, and the largest amount of benthic organic matter. The burned/scoured stream was nearly opposite in all respects. Numbers of 2 detritivore invertebrate taxa, Serratella tibialis and Zapada oregonensis, were highest in the unburned stream but lowest in the burned/scoured stream. A third taxon, Baetis sp., showed the opposite relationship. Presence of predatory invertebrates did not affect detritivore abundance or leaf decay rate in the bags. Our research suggests that recovery response variables of some stream systems may not have returned to prefire levels even a decade after the initial wildfire. In this study, the recovery of our streams appears to be connected to the return of the riparian zone, though fire-induced debris flows may slow or alter final recovery of the stream system

Metal Surface Energy: Persistent Cancellation of Short-Range Correlation Effects beyond the Random-Phase Approximation

The role that non-local short-range correlation plays at metal surfaces is investigated by analyzing the correlation surface energy into contributions from dynamical density fluctuations of various two-dimensional wave vectors. Although short-range correlation is known to yield considerable correction to the ground-state energy of both uniform and non-uniform systems, short-range correlation effects on intermediate and short-wavelength contributions to the surface formation energy are found to compensate one another. As a result, our calculated surface energies, which are based on a non-local exchange-correlation kernel that provides accurate total energies of a uniform electron gas, are found to be very close to those obtained in the random-phase approximation and support the conclusion that the error introduced by the local-density approximation is small.Comment: 5 pages, 1 figure, to appear in Phys. Rev.

Distinguishing circumstellar from stellar photometric variability in Eta Carinae

The interacting binary Eta Carinae remains one of the most enigmatic massive stars in our Galaxy despite over four centuries of observations. In this work, its light curve from the ultraviolet to the near-infrared is analysed using spatially resolved HST observations and intense monitoring at the La Plata Observatory, combined with previously published photometry. We have developed a method to separate the central stellar object in the ground-based images using HST photometry and applying it to the more numerous ground-based data, which supports the hypothesis that the central source is brightening faster than the almost-constant Homunculus. After detrending from long-term brightening, the light curve shows periodic orbital modulation (V ∼ 0.6 mag) attributed to the wind–wind collision cavity as it sweeps around the primary star and it shows variable projected area to our line-of-sight. Two quasi-periodic components with time-scales of 2–3 and 8–10 yr and low amplitude, V < 0.2 mag, are superimposed on the brightening light curve, being the only stellar component of variability found, which indicates minimal stellar instability. Moreover, the light-curve analysis shows no evidence of ‘shell ejections’ at periastron. We propose that the long-term brightening of the stellar core is due to the dissipation of a dusty clump in front of the central star, which works like a natural coronagraph. Thus, the central stars appear to be more stable than previously thought since the dominant variability originates from a changing circumstellar medium. We predict that the brightening phase, due mainly to dust dissipation, will be completed around 2032 ± 4 yr, when the star will be brighter than in the 1600s by up to V ∼ 1 mag.Fil: Damineli, A.. Universidade do Sao Paulo. Instituto de Astronomia, Geofísica e Ciências Atmosféricas; BrasilFil: Fernandez Lajus, Eduardo Eusebio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Almeida, L.A.. Universidade do Sao Paulo. Instituto de Astronomia, Geofísica e Ciências Atmosféricas; Brasil. Universidade Federal do Rio Grande do Norte; BrasilFil: Corcoran, M.F.. National Aeronautics and Space Administration; Estados Unidos. The Catholic University of America; Estados UnidosFil: Damineli, D.S.C.. University of Maryland; Estados UnidosFil: Gull, T.R.. National Aeronautics and Space Administration; Estados UnidosFil: Hamaguchi, K. National Aeronautics and Space Administration; Estados Unidos. University of Maryland; Estados UnidosFil: Hillier, D.J.. University of Pittsburgh; Estados UnidosFil: Jablonski, F.J.. Centro de Previsao de Tempo e Estudos Climáticos. Instituto Nacional de Pesquisas Espaciais; BrasilFil: Madura, T.I.. San Jose State University; Estados UnidosFil: Moffat, A.F.J.. Université du Québec a Montreal; CanadáFil: Navarete, F.. Universidade do Sao Paulo. Instituto de Astronomia, Geofísica e Ciências Atmosféricas; BrasilFil: Richardson, N.D.. University Of Toledo (utoledo); Estados UnidosFil: Ruiz, G.F.. Universidade do Sao Paulo. Instituto de Astronomia, Geofísica e Ciências Atmosféricas; BrasilFil: Salerno, N.E.. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Scalia, María Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Weigelt, G.. Max Planck Institute For Radio Astronomy; Alemani

Active Brownian Particles. From Individual to Collective Stochastic Dynamics

We review theoretical models of individual motility as well as collective dynamics and pattern formation of active particles. We focus on simple models of active dynamics with a particular emphasis on nonlinear and stochastic dynamics of such self-propelled entities in the framework of statistical mechanics. Examples of such active units in complex physico-chemical and biological systems are chemically powered nano-rods, localized patterns in reaction-diffusion system, motile cells or macroscopic animals. Based on the description of individual motion of point-like active particles by stochastic differential equations, we discuss different velocity-dependent friction functions, the impact of various types of fluctuations and calculate characteristic observables such as stationary velocity distributions or diffusion coefficients. Finally, we consider not only the free and confined individual active dynamics but also different types of interaction between active particles. The resulting collective dynamical behavior of large assemblies and aggregates of active units is discussed and an overview over some recent results on spatiotemporal pattern formation in such systems is given.Comment: 161 pages, Review, Eur Phys J Special-Topics, accepte

Towards Machine Wald

The past century has seen a steady increase in the need of estimating and predicting complex systems and making (possibly critical) decisions with limited information. Although computers have made possible the numerical evaluation of sophisticated statistical models, these models are still designed \emph{by humans} because there is currently no known recipe or algorithm for dividing the design of a statistical model into a sequence of arithmetic operations. Indeed enabling computers to \emph{think} as \emph{humans} have the ability to do when faced with uncertainty is challenging in several major ways: (1) Finding optimal statistical models remains to be formulated as a well posed problem when information on the system of interest is incomplete and comes in the form of a complex combination of sample data, partial knowledge of constitutive relations and a limited description of the distribution of input random variables. (2) The space of admissible scenarios along with the space of relevant information, assumptions, and/or beliefs, tend to be infinite dimensional, whereas calculus on a computer is necessarily discrete and finite. With this purpose, this paper explores the foundations of a rigorous framework for the scientific computation of optimal statistical estimators/models and reviews their connections with Decision Theory, Machine Learning, Bayesian Inference, Stochastic Optimization, Robust Optimization, Optimal Uncertainty Quantification and Information Based Complexity.Comment: 37 page

Thermally Triggered Hydrogel Injection Into Bovine Intervertebral Disc Tissue Explants Induces Differentiation Of Mesenchymal Stem Cells And Restores Mechanical Function.

We previously reported a synthetic Laponite® crosslinked pNIPAM-co-DMAc (L-pNIPAM-co-DMAc) hydrogel which promotes differentiation of mesenchymal stem cells (MSCs) to nucleus pulposus (NP) cells without additional growth factors. The clinical success of this hydrogel is dependent on: integration with surrounding tissue; the capacity to restore mechanical function; as well as supporting the viability and differentiation of delivered MSCs. Bovine NP tissue explants were injected with media (control), human MSCs (hMSCs) alone, acellular L-pNIPAM-co-DMAc hydrogel or hMSCs incorporated within the L-pNIPAM-co-DMAc hydrogel and maintained at 5% O2 for 6 weeks. Viability of native NP cells and delivered MSCs was maintained. Furthermore hMSCs delivered via the L-pNIPAM-co-DMAc hydrogel differentiated and produced NP matrix components: aggrecan, collagen type II and chondroitin sulphate, with integration of the hydrogel with native NP tissue. In addition L-pNIPAM-co-DMAc hydrogel injected into collagenase digested bovine discs filled micro and macro fissures, were maintained within the disc during loading and restored IVD stiffness. The mechanical support of the L-pNIPAM-co-DMAc hydrogel, to restore disc height, could provide immediate symptomatic pain relief, whilst the delivery of MSCs over time regenerates the NP extracellular matrix; thus the L-pNIPAM-co-DMAc hydrogel could provide a combined cellular and mechanical repair approach

Luminescence spectra and kinetics of disordered solid solutions

We have studied both theoretically and experimentally the luminescence spectra and kinetics of crystalline, disordered solid solutions after pulsed excitation. First, we present the model calculations of the steady-state luminescence band shape caused by recombination of excitons localized in the wells of random potential induced by disorder. Classification of optically active tail states of the main exciton band into two groups is proposed. The majority of the states responsible for the optical absorption corresponds to the group of extended states belonging to the percolation cluster, whereas only a relatively small group of “radiative” states forms the steady-state luminescence band. The continuum percolation theory is applied to distinguish the “radiative” localized states, which are isolated in space and have no ways for nonradiative transitions along the tail states. It is found that the analysis of the exciton-phonon interaction gives the information about the character of the localization of excitons. We have shown that the model used describes quite well the experimental cw spectra of CdS(1−c)Sec and ZnSe(1−c)Tec solid solutions. Further, the experimental results are presented for the temporal evolution of the luminescence band. It is shown that the changes of band shape with time come from the interplay of population dynamics of extended states and spatially isolated “radiative” states. Finally, the measurements of the decay of the spectrally integrated luminescence intensity at long delay times are presented. It is shown that the observed temporal behavior can be described in terms of relaxation of separated pairs followed by subsequent exciton formation and radiative recombination. Electron tunneling processes are supposed to be responsible for the luminescence in the long-time limit at excitation below the exciton mobility edge. At excitation by photons with higher energies the diffusion of electrons can account for the observed behavior of the luminescence

Tau Ori and Tau Lib: Two New Massive Heartbeat Binaries

We report the discovery of two massive eccentric systems with BRITE data, tau Ori and tau Lib, showing heartbeat effects close to the periastron passage. τ Lib exhibits shallow eclipses that will soon vanish due to the apsidal motion in the system. In neither system, tidally excited oscillations were detected