Turbulent luminance in impassioned van Gogh paintings

We show that the patterns of luminance in some impassioned van Gogh paintings display the mathematical structure of fluid turbulence. Specifically, we show that the probability distribution function (PDF) of luminance fluctuations of points (pixels) separated by a distance R compares notably well with the PDF of the velocity differences in a turbulent flow, as predicted by the statistical theory of A.N. Kolmogorov. We observe that turbulent paintings of van Gogh belong to his last period, during which episodes of prolonged psychotic agitation of this artist were frequent. Our approach suggests new tools that open the possibility of quantitative objective research for art representation

Delayed Self-Synchronization in Homoclinic Chaos

The chaotic spike train of a homoclinic dynamical system is self-synchronized by re-inserting a small fraction of the delayed output. Due to the sensitive nature of the homoclinic chaos to external perturbations, stabilization of very long periodic orbits is possible. On these orbits, the dynamics appears chaotic over a finite time, but then it repeats with a recurrence time that is slightly longer than the delay time. The effect, called delayed self-synchronization (DSS), displays analogies with neurodynamic events which occur in the build-up of long term memories.Comment: Submitted to Phys. Rev. Lett., 13 pages, 7 figure

Myofibroblast transdifferentiation is associated with changes in cellular and extracellular vesicle miRNA abundance

Transforming growth factor-beta 1 (TGF-β1), a pro-fibrotic tumour-derived factor promotes fibroblast differentiation in the tumour microenvironment and is thought to contribute to the development of pro-tumourigenic cancer-associated fibroblasts (CAFs) by promoting myofibroblast differentiation. miRNA dysregulation has been demonstrated in myofibroblast transdifferentiation and CAF activation, however, their expression varies among cell types and with the method of fibroblast induction. Here, the expression profile of miRNA in human primary oral fibroblasts treated with TGF-β1, to derive a myofibroblastic, CAF-like phenotype, was determined compared to untreated fibroblasts. Myofibroblast transdifferentiation was determined by the expression of alpha-smooth muscle actin (α-SMA) and fibronectin-1 extra domain A (FN-EDA1) using quantitative real-time PCR (qRT-PCR) and western blot. The formation of stress fibres was assessed by fluorescence microscopy, and associated changes in contractility were assessed using collagen contraction assays. Extracellular vesicles (EVs) were purified by using size exclusion chromatography and ultracentrifugation and their size and concentration were determined by nanoparticle tracking analysis. miRNA expression profiling in oral fibroblasts treated with TGF-β1 and their extracellular vesicles was carried out using tiling low-density array cards. The Database for Annotation, Visualization, and Integrated Discovery (DAVID) was used to perform functional and pathway enrichment analysis of target genes. In this study, TGF-β1 induced a myofibroblastic phenotype in normal oral fibroblasts as assessed by expression of molecular markers, the formation of stress fibres and increased contractility. TaqMan Low-Density Array (TLDA) analysis demonstrated that miR-503 and miR-708 were significantly upregulated, while miR-1276 was significantly downregulated in TGF-β1-treated oral fibroblasts (henceforth termed experimentally-derived CAF, eCAF). The gene functional enrichment analysis showed that the candidate miRNAs have the potential to modulate various pathways; including the Ras associated protein 1 (Rap1), PI3K-Akt, and tumour necrosis factor (TNF) signalling pathways. In addition, altered levels of several miRNAs were detected in eCAF EV, including miR-142 and miR-222. No differences in size or abundance of EV were detected between eCAF and normal oral fibroblast (NOF). Little overlap was observed between changes in cellular and EV miRNA profiles, suggesting the possibility of selective loading of EV miRNA. The study reveals miRNA expression signature could be involved in myofibroblast transdifferentiation and the miRNA cargo of their EV, providing novel insight into the involvement of miRNA in CAF development and function

High speed synchrotron X-ray imaging studies of the ultrasound shockwave and enhanced flow during metal solidification processes

The highly dynamic behaviour of ultrasonic bubble implosion in liquid metal, the multiphase liquid metal flow containing bubbles and particles, and the interaction between ultrasonic waves and semisolid phases during solidification of metal were studied in situ using the complementary ultrafast and high speed synchrotron X-ray imaging facilities housed respectively at the Advanced Photon Source, Argonne National Laboratory, US, and Diamond Light Source, UK. Real-time ultrafast X-ray imaging of 135,780 frames per second (fps) revealed that ultrasonic bubble implosion in a liquid Bi-8 wt. %Zn alloy can occur in a single wave period (30 kHz), and the effective region affected by the shockwave at implosion was 3.5 times the original bubble diameter. Furthermore, ultrasound bubbles in liquid metal move faster than the primary particles, and the velocity of bubbles is 70 ~ 100% higher than that of the primary particles present in the same locations close to the sonotrode. Ultrasound waves can very effectively create a strong swirling flow in a semisolid melt in less than one second. The energetic flow can detach solid particles from the liquid-solid interface and redistribute them back into the bulk liquid very effectively

Explaining motivation in language learning: a framework for evaluation and research

Researching motivation in language learning is complex and multi-faceted. Various models of learner motivation have been proposed in the literature, but no one model supplies a complex and coherent framework for investigating a range of motivational characteristics. Building on previous models I propose such a methodological framework, based on a complex dynamic systems perspective, which re-conceptualises the investigation of motivation in SLA in qualitative and mixed method approaches by offering one flexible tool for case study approaches. This new framework has been tried and tested in three locations in England and reported as case studies. The study aimed to address the following research questions: (1) in what ways does CLIL impact on learner motivation? (2) what are the main elements of CLIL that enhance motivation? Overall analysis of the results found that where expectations of success were high and where the teaching was effective, CLIL had a positive impact on motivation and progress. The framework is designed to be flexible enough to be used to investigate language learning in a range of national contexts. It is hoped that the proposed framework, reported here together with exemplification and commentary from the English study, will enable researchers in a wide range of language learning contexts to investigate learner motivation in a systematic and in-depth manner

Cellular Array Morphology During Directional Solidification

Cellular array morphology has been examined in the shallow cell, deep cell, and cell-to-dendrite transition regime in Pb-2.2 wt pct Sb and Al-4.1 wt pct Cu alloy single-crystal samples that were directionally solidified along [100]. Statistical analysis of the cellular spacing distribution on transverse sections has been carried out using minimum spanning tree (MST), Voronoi polygons, radial distribution factor, and fast Fourier transform (FFT) techniques. The frequency distribution of the number of nearest neighbors and the MST parameters suggest that the arrangement of cells may be visualized as a hexagonal tessellation with superimposed 50 pct random noise. However, the power spectrum of the Fourier transform of the cell centers shows a diffused single-ring pattern that does not agree with the power spectrum from the hexagonal tessellation having a 50 pct superimposed random (uniformly distributed or Gaussian) noise. The radial distribution factor obtained from the cells is similar to that of liquids. An overall steady-state distribution in terms of the mean primary spacing is achieved after directional solidification of about three mushy-zone lengths. However, the process of nearest-neighbor interaction continues throughout directional solidification, as indicated by about 14 pct of the cells undergoing submerging in the shallow cell regime or by an increasing first and second nearest-neighbor ordering along the growth direction for the cells at the cell-to-dendrite transition. The nature of cell distribution in the Al-Cu alloy appears to be the same as that in the Pb-Sb. The ratio between the upper and lower limits of the primary spacing, as defined by the largest and the smallest 10 pct of the population, respectively, is constant: 1.43 +/- 0.11. It does not depend upon the solidification processing conditions

Dark energy as a mirage

Motivated by the observed cosmic matter distribution, we present the following conjecture: due to the formation of voids and opaque structures, the average matter density on the path of the light from the well-observed objects changes from Omega_M ~ 1 in the homogeneous early universe to Omega_M ~ 0 in the clumpy late universe, so that the average expansion rate increases along our line of sight from EdS expansion Ht ~ 2/3 at high redshifts to free expansion Ht ~ 1 at low redshifts. To calculate the modified observable distance-redshift relations, we introduce a generalized Dyer-Roeder method that allows for two crucial physical properties of the universe: inhomogeneities in the expansion rate and the growth of the nonlinear structures. By treating the transition redshift to the void-dominated era as a free parameter, we find a phenomenological fit to the observations from the CMB anisotropy, the position of the baryon oscillation peak, the magnitude-redshift relations of type Ia supernovae, the local Hubble flow and the nucleosynthesis, resulting in a concordant model of the universe with 90% dark matter, 10% baryons, no dark energy, 15 Gyr as the age of the universe and a natural value for the transition redshift z_0=0.35. Unlike a large local void, the model respects the cosmological principle, further offering an explanation for the late onset of the perceived acceleration as a consequence of the forming nonlinear structures. Additional tests, such as quantitative predictions for angular deviations due to an anisotropic void distribution and a theoretical derivation of the model, can vindicate or falsify the interpretation that light propagation in voids is responsible for the perceived acceleration.Comment: 33 pages, 2 figs; v2: minor clarifications, results unchanged; v3: matches the version published in General Relativity and Gravitatio

Computations of Viking Lander Capsule Hypersonic Aerodynamics with Comparisons to Ground and Flight Data

Comparisons are made between the LAURA Navier-Stokes code and Viking Lander Capsule hypersonic aerodynamics data from ground and flight measurements. Wind tunnel data are available for a 3.48 percent scale model at Mach 6 and a 2.75 percent scale model at Mach 10.35, both under perfect gas air conditions. Viking Lander 1 aerodynamics flight data also exist from on-board instrumentation for velocities between 2900 and 4400 m/sec (Mach 14 to 23.3). LAURA flowfield solutions are obtained for the geometry as tested or flown, including sting effects at tunnel conditions and finite-rate chemistry effects in flight. Using the flight vehicle center-of-gravity location (trim angle approx. equals -11.1 deg), the computed trim angle at tunnel conditions is within 0.31 degrees of the angle derived from Mach 6 data and 0.13 degrees from the Mach 10.35 trim angle. LAURA Mach 6 trim lift and drag force coefficients are within 2 percent of measured data, and computed trim lift-to-drag ratio is within 4 percent of the data. Computed trim lift and drag force coefficients at Mach 10.35 are within 5 percent and 3 percent, respectively, of wind tunnel data. Computed trim lift-to-drag ratio is within 2 percent of the Mach 10.35 data. Using the nominal density profile and center-of-gravity location, LAURA trim angle at flight conditions is within 0.5 degrees of the total angle measured from on-board instrumentation. LAURA trim lift and drag force coefficients at flight conditions are within 7 and 5 percent, respectively, of the flight data. Computed trim lift-to-drag ratio is within 4 percent of the data. Computed aerodynamics sensitivities to center-of-gravity location, atmospheric density, and grid refinement are generally small. The results will enable a better estimate of aerodynamics uncertainties for future Mars entry vehicles where non-zero angle-of-attack is required

Rings and bars: unmasking secular evolution of galaxies

Secular evolution gradually shapes galaxies by internal processes, in contrast to early cosmological evolution which is more rapid. An important driver of secular evolution is the flow of gas from the disk into the central regions, often under the influence of a bar. In this paper, we review several new observational results on bars and nuclear rings in galaxies. They show that these components are intimately linked to each other, and to the properties of their host galaxy. We briefly discuss how upcoming observations, e.g., imaging from the Spitzer Survey of Stellar Structure in Galaxies (S4G), will lead to significant further advances in this area of research.Comment: Invited review at "Galaxies and their Masks", celebrating Ken Freeman's 70-th birthday, Sossusvlei, Namibia, April 2010. To be published by Springer, New York, editors D.L. Block, K.C. Freeman, & I. Puerari; minor change

The Fueling and Evolution of AGN: Internal and External Triggers

In this chapter, I review the fueling and evolution of active galactic nuclei (AGN) under the influence of internal and external triggers, namely intrinsic properties of host galaxies (morphological or Hubble type, color, presence of bars and other non-axisymmetric features, etc) and external factors such as environment and interactions. The most daunting challenge in fueling AGN is arguably the angular momentum problem as even matter located at a radius of a few hundred pc must lose more than 99.99 % of its specific angular momentum before it is fit for consumption by a BH. I review mass accretion rates, angular momentum requirements, the effectiveness of different fueling mechanisms, and the growth and mass density of black BHs at different epochs. I discuss connections between the nuclear and larger-scale properties of AGN, both locally and at intermediate redshifts, outlining some recent results from the GEMS and GOODS HST surveys.Comment: Invited Review Chapter to appear in LNP Volume on "AGN Physics on All Scales", Chapter 6, in press. 40 pages, 12 figures. Typo in Eq 5 correcte