Observational and theoretical studies of the evolving structure of baroclinic waves

Dynamical processes involved in comma cloud formation, and passive tracer evolution in a baroclinic wave are discussed. An analytical solution was obtained demonstrating the complex nongeostrophic flow pattern involved in the redistribution of low level constituents in a finite amplitude baroclinic wave, and in the formation of the typical humidity and cloud distributions in such a wave. Observational and theoretical studies of blocking weather patterns in middle latitude flows were studied. The differences in the energy and enstrophy cascades in blocking and nonblocking situations were shown. It was established that pronounced upscale flow of both of these quantities, from intermediate to planetary scales, occurs during blocking episodes. The upscale flux of enstrophy, in particular, suggests that the persistence of blocking periods may be due to reduced dissipation of the large scale circulation and therefore entail some above normal predictability

A Numerical Evaluation of the Stochastic Completeness of the Kinetic Coagulation Equation

The stochastic completeness of the kinetic coagulation equation depends on the extent of correlations between particle properties. Such correlations are induced by the coalescence process that causes spatial inhomogeneities in the number concentration of the particles, and are particularly strong in poorly mixed suspensions. A Monte Carlo simulation of the coalescence process is used to evaluate the suitability of the kinetic coagulation equation to simulate the coalescence process using Brownian diffusion, fluid shear and differential sedimentation collision kernels. It is demonstrated that the outcome of the kinetic equation matches well the true stochastic averages, unless the number concentration of particles involved is very small. In that case, the discrepancies between the two approaches are substantial in the large end of the particle size spectrum

Oscillators and relaxation phenomena in Pleistocene climate theory

Ice sheets appeared in the northern hemisphere around 3 million years ago and glacial-interglacial cycles have paced Earth's climate since then. Superimposed on these long glacial cycles comes an intricate pattern of millennial and sub-millennial variability, including Dansgaard-Oeschger and Heinrich events. There are numerous theories about theses oscillations. Here, we review a number of them in order to draw a parallel between climatic concepts and dynamical system concepts, including, in particular, the relaxation oscillator, excitability, slow-fast dynamics and homoclinic orbits. Namely, almost all theories of ice ages reviewed here feature a phenomenon of synchronisation between internal climate dynamics and the astronomical forcing. However, these theories differ in their bifurcation structure and this has an effect on the way the ice age phenomenon could grow 3 million years ago. All theories on rapid events reviewed here rely on the concept of a limit cycle in the ocean circulation, which may be excited by changes in the surface freshwater surface balance. The article also reviews basic effects of stochastic fluctuations on these models, including the phenomenon of phase dispersion, shortening of the limit cycle and stochastic resonance. It concludes with a more personal statement about the potential for inference with simple stochastic dynamical systems in palaeoclimate science. Keywords: palaeoclimates, dynamical systems, limit cycle, ice ages, Dansgaard-Oeschger eventsComment: Published in the Transactions of the Philosophical Transactions of the Royal Society (Series A, Physical Mathematical and Engineering Sciences), as a contribution to the Proceedings of the workshop on Stochastic Methods in Climate Modelling, Newton Institute (23-27 August). Philosophical Transactions of the Royal Society (Series A, Physical Mathematical and Engineering Sciences), vol. 370, pp. xx-xx (2012); Source codes available on request to author and on http://www.uclouvain.be/ito

Nonlinear problems of complex natural systems: Sun and climate dynamics

Universal role of the nonlinear one-third subharmonic resonance mechanism in generation of the strong fluctuations in such complex natural dynamical systems as global climate and global solar activity is discussed using wavelet regression detrended data. Role of the oceanic Rossby waves in the year-scale global temperature fluctuations and the nonlinear resonance contribution to the El Nino phenomenon have been discussed in detail. The large fluctuations of the reconstructed temperature on the millennial time-scales (Antarctic ice cores data for the past 400,000 years) are also shown to be dominated by the one-third subharmonic resonance, presumably related to Earth precession effect on the energy that the intertropical regions receive from the Sun. Effects of Galactic turbulence on the temperature fluctuations are discussed in this content. It is also shown that the one-third subharmonic resonance can be considered as a background for the 11-years solar cycle, and again the global (solar) rotation and chaotic propagating waves play significant role in this phenomenon. Finally, a multidecadal chaotic coherence between the detrended solar activity and global temperature has been briefly discussed.Comment: arXiv admin note: substantial text overlap with arXiv:1002.1024, arXiv:1004.4639, arXiv:1006.4591, arXiv:1003.294

INVESTIGATION OF THE RELATIONSHIP BETWEEN INFLAMMATORY SIGNALING PATHWAYS AND INDOLEAMINE 2,3-DIOXYGENASE IN GLIOBLASTOMA MULTIFORME

Pervasive tumors appear to evade immune detection through manipulation of the immune response, though precisely how this occurs is not well understood. A further understanding of these details may be achieved through the study of inflammation-driven tumors. While inflammatory cytokines increase blood flow to sites of inflammation for increased delivery of oxygen and nutrients, immune cells are also recruited and activated. Interferon-γ, an inflammatory cytokine, may suppress the actions of effector T cells through induction of indoleamine 2,3-dioxygenase-1 (IDO-1). IDO is involved in tryptophan metabolism and stimulates the recruitment and maturation of T regulatory lymphocytes while suppressing the activity and proliferation of T effector cells. IFN-γ appears to induce IDO-1 expression through NF-κB and JAK-STAT signaling pathways, though the precise signaling cascades are unclear. Here we investigate the relationship between IFN-γ and IDO in glioblastoma, an aggressive cancer of the brain with very poor prognosis. Reporter assays indicate that IFN-γ does increase transcriptional activation at the IDO-1 promoter, while protein analysis does not indicate a change of IDO-1 expression at the protein level. IFN-γ does appear to negatively affect transcriptional activation of the canonical NF-κB pathway, as seen by a loss in p65 phosphorylation, suggesting that IFN-γ signals independently, perhaps in opposition to, the canonical NF-κB transcriptional cascade

Listener expectations and the perceptual accommodation of talker variability: A pre-registered replication

Published: 04 May 2021Researchers have hypothesized that in order to accommodate variability in how talkers produce their speech sounds, listeners must perform a process of talker normalization. Consistent with this proposal, several studies have shown that spoken word recognition is slowed when speech is produced by multiple talkers compared with when all speech is produced by one talker (a multitalker processing cost). Nusbaum and colleagues have argued that talker normalization is modulated by attention (e.g., Nusbaum & Morin, 1992, Speech Perception, Production and Linguistic Structure, pp. 113–134). Some of the strongest evidence for this claim is from a speeded monitoring study where a group of participants who expected to hear two talkers showed a multitalker processing cost, but a separate group who expected one talker did not (Magnuson & Nusbaum, 2007, Journal of Experimental Psychology, 33[2], 391–409). In that study, however, the sample size was small and the crucial interaction was not significant. In this registered report, we present the results of a well-powered attempt to replicate those findings. In contrast to the previous study, we did not observe multitalker processing costs in either of our groups. To rule out the possibility that the null result was due to task constraints, we conducted a second experiment using a speeded classification task. As in Experiment 1, we found no influence of expectations on talker normalization, with no multitalker processing cost observed in either group. Our data suggest that the previous findings of Magnuson and Nusbaum (2007) be regarded with skepticism and that talker normalization may not be permeable to high-level expectations.This research was supported by NSF 1754284, NSF IGERT 1144399 & NSF NRT 1747486 (PI: JSM) and NSF BCS 1554810 & NIH R01 DC013064 (PI: EBM). This research was also supported in part by the Basque Government through the BERC 2018- 2021 program and by the Agencia Estatal de Investigación through BCBL Severo Ochoa excellence accreditation SEV-2015-0490. SL was supported by an NSF Graduate Research Fellowshi

Using eddy covariance to measure the dependence of air–sea CO2 exchange rate on friction velocity

Parameterisation of the air–sea gas transfer velocity of CO2 and other trace gases under open-ocean conditions has been a focus of air–sea interaction research and is required for accurately determining ocean carbon uptake. Ships are the most widely used platform for air–sea flux measurements but the quality of the data can be compromised by airflow distortion and sensor cross-sensitivity effects. Recent improvements in the understanding of these effects have led to enhanced corrections to the shipboard eddy covariance (EC) measurements. Here, we present a revised analysis of eddy covariance measurements of air–sea CO2 and momentum fluxes from the Southern Ocean Surface Ocean Aerosol Production (SOAP) study. We show that it is possible to significantly reduce the scatter in the EC data and achieve consistency between measurements taken on station and with the ship underway. The gas transfer velocities from the EC measurements correlate better with the EC friction velocity (u*) than with mean wind speeds derived from shipboard measurements corrected with an airflow distortion model. For the observed range of wind speeds (u10 N = 3–23 m s−1), the transfer velocities can be parameterised with a linear fit to u*. The SOAP data are compared to previous gas transfer parameterisations using u10 N computed from the EC friction velocity with the drag coefficient from the Coupled Ocean–Atmosphere Response Experiment (COARE) model version 3.5. The SOAP results are consistent with previous gas transfer studies, but at high wind speeds they do not support the sharp increase in gas transfer associated with bubble-mediated transfer predicted by physically based models