Dynamics Of Components Research Articles

Stochastic and deterministic kinetic energy backscatter parameterizations for simulation of the two-dimensional turbulence

AbstractThe problem of modelling 2D isotropic turbulence in a periodic rectangular domain excited by the forcing pattern of prescribed spatial scale is considered. This setting could be viewed as the simplest analogue of the large scale quasi-2D circulation of the ocean and the atmosphere. Since the direct numerical simulation (DNS) of this problem is usually not possible due to the high computational costs we explore several possibilities to construct coarse approximation models and corresponding subgrid closures (deterministic or stochastic). The necessity of subgrid closures is especially important when the forcing scale is close to the cutoff scale of the coarse model that leads to the significant weakening of the inverse energy cascade and large scale component of the system dynamics.The construction of closures is based on thea priorianalysis of the DNS solution and takes into account the form of a spatial approximation scheme used in a particular coarse model. We show that the statistics of a coarse model could be significantly improved provided a proper combination of deterministic and stochastic closures is used. As a result we are able to restore the shape of the energy spectra of the model. In addition the lagged auto correlations of the model solution as well as its sensitivity to external perturbations fit the characteristics of the DNS model much better.

Identifying Protein Conformational Dynamics Using Spin‐label ESR

Spin-label electron spin resonance (ESR) has emerged as a powerful tool to characterize protein dynamics. One recent advance is the development of ESR for resolving dynamical components that occur or coexist during a biological process. It has been applied to study the complex structural and dynamical aspects of membranes and proteins, such as conformational changes in protein during translocation from cytosol to membrane, conformational exchange between equilibria in response to protein-protein and protein-ligand interactions in either soluble or membrane environments, protein oligomerization, and temperature- or hydration-dependent protein dynamics. As these topics are challenging but urgent for understanding the function of a protein on the molecular level, the newly developed ESR methods to capture individual dynamical components, even in low-populated states, have become a great complement to other existing biophysical tools.

Energy propagation through dense granular systems

We discuss affine and non-affine components of particle dynamics in the context of energy propagation through dense granular matter as a consequence of externally imposed boundary perturbation. Earlier work (Kondic et al. in Phys Rev E 79:041304, 2009) has shown that the frequency and the wavenumber of the imposed perturbations strongly influence propagation, and in particular that the frequencies and wavenumbers that lead to well-defined propagation are limited from above. The present work shows that strong non-affine component of particle dynamics is associated with dispersion and loss of coherence.

Dispersal of juvenile bobcats in a recolonizing population

ABSTRACTNatural recolonization of bobcat (Lynx rufus) populations in the midwestern United States presents challenges for managers with limited knowledge of the species’ population dynamics in a highly fragmented agricultural landscape. Dispersal is a component of population dynamics of a recolonizing population, which is likely influenced by landscape features. To better understand population expansion, we examined dispersal characteristics of juvenile (<2 yr) bobcats in recently recolonized south‐central Iowa, USA, from 2003–2009. We radio‐collared and tracked dispersal fates of 61 individuals (34 males, 27 females), with 29 (22 males, 7 females) dispersing by approximately 2 years of age and the rest remaining philopatric. Most (65%) juvenile males dispersed, whereas only 26% of females dispersed. Initiation of dispersal varied, but none occurred in July–August. Dispersal duration ranged from 4–240 days. Average age at dispersal was 16.9 ± 1.1 (SE) months. Dispersal was most prevalent in an east‐west direction and straight‐line distances ranged from 6.6–203.2 km ( = 57.9 km). On average, males dispersed 44 km farther than females. Land cover composition was similar in natal and post‐dispersal core ranges and consisted predominantly (70%) of forest and grassland. Lower abundance of forest and grassland in areas north of the study area may ultimately limit the ability of juvenile bobcats to successfully disperse and expand throughout the Corn Belt of Iowa. © 2019 The Wildlife Society.

Can dark energy be expressed as a power series of the Hubble parameter?

In this work we examine the possibility that the dark energy (DE) density, $\rho_{de}$ can be dynamical and appear as a power series expansion of the Hubble rate (and its derivatives), i.e.$\rho_{de}(H,\dot{H},...)$. For the present universe, however, only the terms $H$, $\dot{H}$ and $H^2$ can be relevant, together with an additive constant term. We fit these models to the current cosmological data on the main observables SNIa+$H(z)$+BAO+LSS+CMB+BBN. Our analysis involves both the background as well as the cosmic perturbation equations. The latter include, apart from the matter density perturbations, also the DE density perturbations. We assume that matter and dynamical DE are separately self-conserved. As a result the equation of state of the DE becomes a nontrivial function of the cosmological redshift, $w_D=w_D(z)$. The particular subset of DE models of this type having no additive constant term in $\rho_{de}$ include the so-called entropic-force and QCD-ghost DE models, as well as the pure linear model $\rho_{de} \sim H$ all of which are strongly disfavored in our fitting analysis. In contrast, the models that include the additive term plus one or both of the dynamical components $\dot{H}$ and $H^2$ appear more favored than the $\Lambda$CDM. In particular, the dynamical DE models provide a value of $\sigma_8\simeq 0.74-0.77$ which is substantially lower than that of the $\Lambda$CDM and hence more in accordance with the observations. This helps to significantly reduce the $\sigma_8$-tension in the structure formation data. At the same time the predicted value for $H_0$ is in between the local and Planck measurements, thus helping to alleviate this tension as well.

Generalized statistical dynamical theory of x-ray diffraction by imperfect multilayer crystal structures with defects

The generalized statistical dynamical theory of x-ray scattering by imperfect single crystals with randomly distributed Coulomb-type defects has been extended to characterize structure imperfections in the real multilayers of arbitrary thickness in Bragg diffraction geometry. The recurrence relations for the coherent amplitude reflection and transmission coefficients of such multilayers, which consist of any number of layers with constant strain and randomly distributed defects in each one, have been derived within the concept of the dynamical wave field, i.e., the so-called Ewald-Bethe-Laue approach, with rigorous accounting for boundary conditions at layer interfaces. The analytical expression for the differential dynamical diffuse component of the reflection coefficient of an imperfect multilayer system has been obtained as well. This expression establishes direct connection between the distribution of the diffuse scattering intensity in a momentum space and statistical characteristics of defects in each layer. In addition, the integrals from differential diffuse scattering intensity over the Ewald sphere and over vertical divergence have been found, which correspond to diffuse components in measurements of rocking curves and reciprocal space maps, respectively. The developed theory provides the dynamical description for the one- and two-dimensional angular distributions of the mutually consistent coherent and diffuse components of x-ray scattering intensities, which are measured by the high-resolution double- and triple-crystal diffractometers, respectively, from imperfect films, multilayer structures, superlattices, etc. Examples of simulated rocking curves for the imperfect superlattice with defects of several types and reciprocal space map for the ion-implanted sample of yttrium iron garnet film with defects are given and discussed.

Chemical and Biological Factors in Infectious Diseases The oral microbial flora

The wide concept of health does not benefit of a single definition, but of multiple definitions and this plurality is related to the knowledge assimilated and the socio-economic dynamics. This is due to the fact that health is an ongoing process, its notion changing with the passage of time. Thus, at international level, health is nowadays defined considering multiple criteria. In the last decade, the analysis of relevant statistical data presents an unfavourable evolution for the three major components of population dynamics: natality, mortality and external migration, accompanied by the deterioration of the entire demographic construction and tendencies of heading towards an imminent demographic drift. Humans protect themselves against the microbial aggression by using their inborn barriers and mechanisms that are completed and modulated by acquired barriers and mechanisms. For a microorganism to reach the internal environment and generate an infectious process, it must get through and overcome these barriers. In order to overcome these barriers, the infectious agent must first adhere to the surface of epithelial cells and then pass through the epithelium. Local defence mechanisms help limit the infection and present the antigen to the regional lymphatic ganglions, contributing at the initiation of the immune response. On the other hand, the infectious agent present in the lymphatic system causes lymphangitis and satellite adenitis, which stand as a filter in the infections� way. The study included 127 patients with bacterial infections that were studied from 2014 to 2018. Infection can be caused by certain species of germs whose main feature is pathogenicity. Specific infections are caused by a foreign infectious agent that has accidentally reached the oral cavity causing oral lesions (appear in the secondary phase of the general infection). Specific infections are individualized, caused by a single microbe (monomicrobial) while the non-specific ones are associated (polymicrobial).

From stand to landscape: modelling post-fire regeneration and species growth

Landscape models are comprehensive tools that allow for an understanding of landscape dynamics and a means of deriving future projections in the context of global change. Vegetation and ecological processes such as growth, death or regeneration are essential components of forest landscape dynamics, but their inclusion in landscape-level modelling frameworks is not straightforward as there is a trade-off between model feasibility, desirable complexity and the inclusion of relevant ecological processes. If models are to project future landscape dynamics, climatic influence on vegetation processes needs to be integrated; however, this usually leads to a major increment in model complexity. Here, a post-fire regeneration model (in terms of tree species) and a growth model (in terms of basal areas) is presented for Mediterranean forests including climate influences on such processes. The model captures vegetation dynamics at the stand level and accounts for post-fire regeneration and vegetation growth at the landscape level, with inclusion of the dynamically influencing effect of climate. The model was calibrated with 7709 inventory data plots and validated with 233 burned plots in the Mediterranean region of Catalonia (NE Spain). Results show that our model is able to accurately predict tree species post-fire regeneration and biomass growth. They also show that integration of climatic information represents a significant improvement on the predictive accuracy of the model. Overall, this study presents a generic approach to extend local vegetation dynamics information to the landscape level; furthermore, allowing the projection of vegetation dynamics under changing climatic conditions.

Eco-Evolutionary Dynamics of Sexual Dimorphism

Sexual dimorphism is widespread, but we have a limited understanding of its significance for communities and ecosystems. Several new experiments demonstrate that sexual dimorphism can have far-reaching ecological effects. These results suggest that sexual dimorphism and sexual selection are potent, but largely overlooked components of eco-evolutionary dynamics.

The relationship between the components of the Argentina economic dynamics and the financial capital between 2002 and 2012

The combination of certain economic policies and a positive external situation contributed to high growth rates of the Argentine economy and a lower external debt during the first years of post-convertibility. The objective of this paper is to verify if the financial capital kept a central position in the Argentine economic process in the first decade of post-convertibility, by analysing the relations between the financial capital and the different areas of the economic dynamics. This central position was characterized by the ability of the financial capital to condition policy making decisions, partial disconnection with productive activity and high profitability. The study was carried out through a historical structural approach, limiting the areas of economic dynamics to its most relevant variables in the explanation of the functioning of Argentine economy.

Factors Determining Trade Credit Dynamics During Crisis: Panel Data Analysis for Macedonian Firms

The study is aimed at determining the factors influencing the trade credits dynamics for twenty three firms registered on the Macedonian Stock Exchange, as well as at checking for crisis effects from 2011 to 2015. The study includes a review of the literature on commercial credit factors; elaborately analyzed descriptive statistics of the collected data and dependent variable variance; tests for unobservable effects and their functional form; evaluation of panel regression and interpretation of the results. The authors have proved that net trade credits for these firms depends mainly on the growth potential of lagging firms and their vulnerability, and the crisis effects are significant only for the latter factor. Moreover, the overall efficiency of firms’ assets and their ability to convert income into cash does not have a significant impact in the crisis and post-crisis periods. The growth opportunities and profitability demonstrate a negative impact, meaning that growing and more profitable firms on average tend to expand and receive more trade credits than counterparties. Profitability has a significant impact on trade credit and the effect is seen during the first year after the crisis. Thus, the dynamics of trade credits of registered Macedonian firms is largely determined by the internal factors of a firm, and not by the external macroeconomic situation. Therefore, better financial management is suggested to improve the trade credit policy. One of the directions for further research is the evaluation of the autoregressive component of the trade credit dynamics, as well as including spatial effects in the regression equation.

A New Approach on Proving Collatz Conjecture

Collatz Conjecture (3x+1 problem) states any natural number x will return to 1 after 3⁎x+1 computation (when x is odd) and x/2 computation (when x is even). In this paper, we propose a new approach for possibly proving Collatz Conjecture (CC). We propose Reduced Collatz Conjecture (RCC)—any natural number x will return to an integer that is less than x. We prove that RCC is equivalent to CC. For proving RCC, we propose exploring laws of Reduced Collatz Dynamics (RCD), i.e., from a starting integer to the first integer less than the starting integer. RCC can also be stated as follows: RCD of any natural number exists. We prove that RCD is the components of original Collatz dynamics (from a starting integer to 1); i.e., RCD is more primitive and presents better properties. We prove that RCD presents unified structure in terms of (3⁎x+1)/2 and x/2, because 3⁎x+1 is always followed by x/2. The number of forthcoming (3⁎x+1)/2 computations can be determined directly by inputting x. We propose an induction method for proving RCC. We also discover that some starting integers present RCD with short lengths no more than 7. Hence, partial natural numbers are proved to guarantee RCC in this paper, e.g., 0 module 2; 1 module 4; 3 module 16; 11 or 23 module 32; 7, 15, or 59 module 128. The future work for proving CC can follow this direction, to prove that RCD of left portion of natural numbers exists.

Enhanced Himalayan Glacial Melting During YD and H1 Recorded in the Northern Bay of Bengal

AbstractOcean‐land thermal feedback mechanisms in the Indian Summer Monsoon (ISM) domain are an important but not well understood component of regional climate dynamics. Here we present a δ18O record analyzed in the mixed‐layer dwelling planktonic foraminifer Globigerinoides ruber (sensu stricto) from the northernmost Bay of Bengal (BoB). The δ18O time series provides a spatially integrated measure of monsoonal precipitation and Himalayan meltwater runoff into the northern BoB and reveals two brief episodes of anomalously low δ18O values between 16.3±0.4 and 16±0.5 and 12.6±0.4 and 12.3±0.4 thousand years before present. The timing of these events is centered at Heinrich event 1 and the Younger Dryas, well‐known phases of weak northern hemisphere monsoon systems. Numerical climate model experiments, simulating Heinrich event‐like conditions, suggest a surface warming over the monsoon‐dominated Himalaya and foreland in response to ISM weakening. Corroborating the simulation results, our analysis of published moraine exposure ages in the monsoon‐dominated Himalaya indicates enhanced glacier retreats that, considering age model uncertainties, coincide and overlap with the episodes of anomalously low δ18O values in the northernmost BoB. Our climate proxy and simulation results provide insights into past regional climate dynamics, suggesting reduced cloud cover, increased solar radiation, and air warming of the Himalaya and foreland areas and, as a result, glacier mass losses in response to weakened ISM.

Non-averaged regularized formulations as an alternative to semi-analytical orbit propagation methods

This paper is concerned with the comparison of semi-analytical and non-averaged propagation methods for Earth satellite orbits. We analyse the total integration error for semi-analytical methods and propose a novel decomposition into dynamical, model truncation, short-periodic, and numerical error components. The first three are attributable to distinct approximations required by the method of averaging, which fundamentally limit the attainable accuracy. In contrast, numerical error, the only component present in non-averaged methods, can be significantly mitigated by employing adaptive numerical algorithms and regularized formulations of the equations of motion. We present a collection of non-averaged methods based on the integration of existing regularized formulations of the equations of motion through an adaptive solver. We implemented the collection in the orbit propagation code THALASSA, which we make publicly available, and we compared the non-averaged methods to the semi-analytical method implemented in the orbit propagation tool STELA through numerical tests involving long-term propagations (on the order of decades) of LEO, GTO, and high-altitude HEO orbits. For the test cases considered, regularized non-averaged methods were found to be up to two times slower than semi-analytical for the LEO orbit, to have comparable speed for the GTO, and to be ten times as fast for the HEO (for the same accuracy). We show for the first time that efficient implementations of non-averaged regularized formulations of the equations of motion, and especially of non-singular element methods, are attractive candidates for the long-term study of high-altitude and highly elliptical Earth satellite orbits.

Using GPS collars to investigate the frequency and behavioural outcomes of intraspecific interactions among carnivores: A case study of male cheetahs in the Maasai Mara, Kenya.

Intraspecific interactions between individuals or groups of individuals of the same species are an important component of population dynamics. Interactions can be static, such as spatial overlap, or dynamic based on the interactions of movements, and can be mediated through communication, such as the deployment of scent marks. Interactions and their behavioural outcomes can be difficult to determine, especially for species that live at low densities. With the use of GPS collars we quantify both static and dynamic interactions between male cheetahs (Acinonyx jubatus) and the behavioural outcomes. The 99% home-ranges of males overlapped significantly while there was little overlap of the 50% home-ranges. Despite this overlap, male cheetahs rarely came into close proximity of one another, possibly because presence was communicated through frequent visits to marking posts. The minimum distance between individuals in a dyad ranged from 89m to 196m but the average proximity between individuals ranged from 17,145 ± 6,865m to 26,367 ± 11,288m. Possible interactions took place more frequently at night than by day and occurred mostly in the 50% home-range of one individual of a dyad or where cores of both individuals overlapped. After a possible encounter male cheetahs stayed in close proximity to each other for up to 6 hours, which could be the result of a territory defence strategy or the presence of a receptive female. We believe that one of the encounters between a singleton and a 5-male coalition resulted in the death of the singleton. Our results give new insights into cheetah interactions, which could help our understanding of ecological processes such as disease transmission.

Multiple mechanisms confer stability to isolated populations of a rare endemic plant

AbstractThe persistence of small populations remains a puzzle for ecology and conservation. Especially interesting is how naturally small, isolated populations are able to persist in the face of multiple environmental forces that create fluctuating conditions and should, theory predicts, lead to high probabilities of extirpation. We used a combination of long‐term census data and a five‐year demographic study of a naturally rare, endemic plant, Yermo xanthocephalus, to evaluate the importance of several possible mechanisms for small population persistence: negative density dependence, vital rate buffering, demographic compensation, asynchrony in dynamics among sub‐populations, and source–sink dynamics. These non‐exclusive explanations for population persistence all have been shown to operate in some systems, but have rarely if ever been simultaneously examined for the same population or species. We hypothesized that asynchrony in dynamics and demographic compensation would be more powerful than the other three mechanisms. We found partial support for our hypothesis: density dependence, asynchrony among population segments, and source–sink patterns appear to be the most important mechanisms maintaining population viability in this species. Importantly, these processes all appear to operate strongly at very fine spatial scales for Yermo, allowing the only two, extremely small, populations to persist. We also found considerable differences in the results of our census and demographic analyses. In general, we estimated substantially greater chances of population survival from the census data than from the shorter‐term demographic studies. In part, this difference is due to drier than average climate conditions during the years of the demographic work. These results emphasize that while demographic information is necessary to understand various components of population dynamics, longer term studies, even if much less detailed, can be more powerful in uncovering some mechanisms that may be critical in stabilizing population numbers, especially in variable environments.

Dynamical Elliptical Diagnostics of the Antarctic Polar Vortex

Abstract Elliptical diagnostics provide dynamical and climatological information about the behavior of the Arctic and Antarctic stratospheric polar vortices. Here Kida’s model, describing the evolution of a uniform vortex in a linear, but possibly unsteady, background flow, is used to interpret the observed evolution of the Antarctic vortex in late winter during 1999–2018. Kida’s model has oscillatory solutions that can undergo an amplitude bifurcation, which serves as a simple model for the onset of vortex-splitting stratospheric sudden warmings (SSWs). A data assimilation method is used to find solutions of Kida’s equations consistent with the observations. A phase-plane analysis reveals large interannual variability in the amplitude of oscillations of the vortex. In 2002, the year of the only observed vortex-splitting Antarctic SSW, the system is found to cross a separatrix in phase space, associated with the SSW amplitude bifurcation, in late September. An output of the data assimilation is the linear background flow experienced by the vortex. The rotational component of this linear flow is consistent with the vortex being embedded in an anticyclonic background. The time-mean strain flow is weak but has a clear orientation, consistent with the presence of stationary forcing due to planetary-scale topography and land–sea contrast. The time-varying strain flow is comparatively large in magnitude, illustrating the relative importance of the planetary-scale component of the turbulent dynamics occurring at tropopause level. Unlike in the Northern Hemisphere, therefore, the direction of future Antarctic vortex splits will not necessarily align with the direction of the 2002 split.

Latent TB Infection (LTBI) – Mycobacterium tuberculosis pathogenesis and the dynamics of the granuloma battleground

Latent tuberculosis infection (LTBI) is established in over 90% of persons infected with Mycobacterium tuberculosis (Mtb), from whom new active TB cases will arise. Understanding the spatio-temporal dynamics of host immune responses in LTBI granulomas is essential to designing effective post-exposure therapies that inhibit progression to TB. Information arising from cancer studies and other modalities – where local chronic inflammation leads to immunopathology – can help provide insights into the biological pathways at play in LTBI granulomas. Translational studies using patient material as well as LTBI+ donor-derived tissue samples are instrumental in understanding the various components of granuloma dynamics, immunological landscapes therein and how this could help to identify therapeutic targets. Deep sequencing technologies may aid to decipher the genetic changes in lung granuloma and blood samples from LTBI+ individuals associated with progression to active TB disease. This may lead to advancement of development of targeted Host-Directed Therapies (HDTs) and their evaluation as adjunct TB therapies for improving treatment outcomes for LTBI and pulmonary TB.

Effects of Parameterized Boundary Layer Structure on Hurricane Rapid Intensification in Shear

Abstract This study investigates the role of the parameterized boundary layer structure in hurricane intensity change using two retrospective HWRF forecasts of Hurricane Earl (2010) in which the vertical eddy diffusivity Km was modified during physics upgrades. Earl undergoes rapid intensification (RI) in the low-Km forecast as observed in nature, while it weakens briefly before resuming a slow intensification at the RI onset in the high-Km forecast. Angular momentum budget analysis suggests that Km modulates the convergence of angular momentum in the boundary layer, which is a key component of the hurricane spinup dynamics. Reducing Km in the boundary layer causes enhancement of both the inflow and convergence, which in turn leads to stronger and more symmetric deep convection in the low-Km forecast than in the high-Km forecast. The deeper and stronger hurricane vortex with lower static stability in the low-Km forecast is more resilient to shear than that in the high-Km forecast. With a smaller vortex tilt in the low-Km forecast, downdrafts associated with the vortex tilt are reduced, bringing less low-entropy air from the midlevels to the boundary layer, resulting in a less stable boundary layer. Future physics upgrades in operational hurricane models should consider this chain of multiscale interactions to assess their impact on model RI forecasts.

Spatio-temporal neural networks for space-time data modeling and relation discovery

We introduce a dynamical spatio-temporal model formalized as a recurrent neural network for modeling time series of spatial processes, i.e., series of observations sharing temporal and spatial dependencies. The model learns these dependencies through a structured latent dynamical component, while a decoder predicts the observations from the latent representations. We consider several variants of this model, corresponding to different prior hypothesis about the spatial relations between the series. The model is used for the tasks of forecasting and data imputation. It is evaluated and compared to state-of-the-art baselines, on a variety of forecasting and imputation problems representative of different application areas: epidemiology, geo-spatial statistics, and car traffic prediction. The experiments also show that this approach is able to learn relevant spatial relations without prior information.