Traditionally, mathematical modeling in population ecology is mainly focused on asymptotic behavior of the model, i.e. as given by the system attractors. Recently, however, transient regimes and ...especially long-term transients have been recognized as playing a crucial role in the dynamics of ecosystems. In particular, long-term transients are a potential explanation of ecological regime shifts, when an apparently healthy population suddenly collapses and goes extinct. In this paper, we show that the interplay between delay in maturation and a strong Allee effect can result in long-term transients in a single species system. We first derive a simple ‘conceptual’ model of the population dynamics that incorporates both a strong Allee effect and maturation delay. Unlike much of the previous work, our approach is not empirical since our model is derived from basic principles. We show that the model exhibits a high complexity in its asymptotic dynamics including multi-periodic and chaotic attractors. We then show the existence of long-term transient dynamics in the system, when the population size oscillates for a long time between locally stable stationary states before it eventually settles either at the persistence equilibrium or goes extinct. The parametric space of the model is found to have a complex structure with the basins of attraction corresponding to the persistence and extinction states being of a complicated shape. This impedes the prediction of the eventual fate of the population, as a small variation in the maturation delay or the initial population size can either bring the population to extinction or ensure its persistence.
•Long term transients (LTT) are known to play a crucial role in the dynamics of populations.•LTT can be an alternative mechanism of ecological regime shifts as compared to the classical attractor-based explanation.•Interplay between delay and the Allee effect can result in LTT leading to sudden regime shifts in a single species model.•Our model shows a high complexity both in terms of its asymptotic dynamics and the basins of attraction of final states.
Schur polynomials admit a somewhat mysterious deformation to Macdonald and Kerov polynomials, which do not have a direct group theory interpretation but do preserve most of the important properties ...of Schur functions. Nevertheless, the family of Schur–Macdonald functions is not sufficiently large: for various applications today, we need their not-yet-known analogues labeled by plane partitions, i.e., three-dimensional Young diagrams. Recently, a concrete way to obtain this generalization was proposed, and miraculous coincidences were described, raising hopes that it can lead in the right direction. But even in that case, much work is needed to convert the idea of generalized 3-Schur functions into a justified and effectively working theory. In particular, we can expect that Macdonald functions (and even all Kerov functions, given some luck) enter this theory on an equal footing with ordinary Schur functions. In detail, we describe how this works for Macdonald polynomials when the vector-valued times, which are associated with plane partitions and are arguments of the 3-Schur functions, are projected onto the ordinary scalar times under nonzero angles that depend on the Macdonald parameters q and t. We show that the cut-and-join operators smoothly interpolate between different limit cases. Most of the examples are restricted to level
2
.
—
Data obtained on carbonates and metaterrigenous rocks of the Devonian complex of the Sultan-Uizdag Range, northwestern Uzbekistan, which are carbonized in local deformation zones, are used in a ...generalized interpretation of the genesis of carbonaceous matter by means of decomposition of carbonates under the effect of seismogenic movements. The release of free carbon is facilitated by synchronous Fe–Mg metasomatism and by the reducing conditions in the presence of hydrogen. Based on literature data on experimental modeling of carbonization processes at high-speed shear deformations of carbonates in a hydrogen medium, a possible scenario is considered for the generation of hydrogen on the surfaces of quartz dislocations in the presence of water in metaterrigenous rocks in association with carbonates. The variation of carbon isotope composition over the volume of the carbonate and terrigenous rocks is extremely heterogeneous, with the
13
C isotope enriched in the fracture zones and
12
C enriched in the near-fracture volumes of decompression-damaged rocks. It is hypothesized that deformations can affect the fractionation of stable carbon isotopes. With regard for literature data, it is demonstrated that isotope exchange can proceed between the free carbon and carbonate carbon. Various aspects are discussed of the influence of mineral-phase and structural–textural transformations of carbonate rocks at their thermomechanical decomposition under shearing on the geomechanical behavior of the fracture, manifestations of mechanical instability in it, and causes of frictional weakening.
This manuscript summarizes consensus reached by the International Anorectal Physiology Working Group (IAPWG) for the performance, terminology used, and interpretation of anorectal function testing ...including anorectal manometry (focused on high-resolution manometry), the rectal sensory test, and the balloon expulsion test. Based on these measurements, a classification system for disorders of anorectal function is proposed. Aim to provide information about methods of diagnosis and new classification of functional anorectal disorders to a wide range of specialists general practitioners, therapists, gastroenterologists, coloproctologists all who face the manifestations of these diseases in everyday practice and determine the diagnostic and therapeutic algorithm. Current paper provides agreed statements of IAPWG Consensus and comments (in italics) of Russian experts on real-world practice, mainly on methodology of examination. These comments in no way intended to detract from the provisions agreed by the international group of experts. We hope that these comments will help to improve the quality of examination based on the systematization of local experience with the use of the methods discussed and the results obtained. Key recommendations: the International Anorectal Physiology Working Group protocol for the performance of anorectal function testing recommends a standardized sequence of maneuvers to test rectoanal reflexes, anal tone and contractility, rectoanal coordination, and rectal sensation. Major findings not seen in healthy controls defined by the classification are as follows: rectoanal areflexia, anal hypotension and hypocontractility, rectal hyposensitivity, and hypersensitivity. Minor and inconclusive findings that can be present in health and require additional information prior to diagnosis include anal hypertension and dyssynergia.
Understanding how patterns and travelling waves form in chemical and biological reaction–diffusion models is an area which has been widely researched, yet is still experiencing fast development. ...Surprisingly enough, we still do not have a clear understanding about all possible types of dynamical regimes in classical reaction–diffusion models, such as Lotka–Volterra competition models with spatial dependence. In this study, we demonstrate some new types of wave propagation and pattern formation in a classical three species cyclic competition model with spatial diffusion, which have been so far missed in the literature. These new patterns are characterized by a high regularity in space, but are different from patterns previously known to exist in reaction–diffusion models, and may have important applications in improving our understanding of biological pattern formation and invasion theory. Finding these new patterns is made technically possible by using an automatic adaptive finite element method driven by a novel a posteriori error estimate which is proved to provide a reliable bound for the error of the numerical method. We demonstrate how this numerical framework allows us to easily explore the dynamical patterns in both two and three spatial dimensions.
The recently proposed Kameyama–Nawata–Tao–Zhang (KNTZ ) trick completed the long search for exclusive Racah matrices
and
for all rectangular representations. The success of this description is a ...remarkable achievement of modern knot theory and classical representation theory, which was initially considered a tool for knot calculus but instead turned out to be its direct beneficiary. We show that this approach in fact consists in converting the arborescent evolution matrix
into the triangular form
, and we demonstrate how this works and show how the previous puzzles and miracles of the differential expansions look from this standpoint. Our conjecture for the form of the triangular matrix
in the case of the nonrectangular representation
is completely new. No calculations are simplified in this case, but we explain how it all works and what remains to be done to completely prove the conjecture. The discussion can also be useful for extending the method to nonrectangular cases and for the related search for gauge-invariant arborescent vertices. As one more application, we present a puzzling, but experimentally supported, conjecture that the form of the differential expansion for all knots is completely described by a particular case of twist knots.
Structural elements of the Svecokarelide pericratonic zone in the Karelian Massif (SE Fennoscandia) were identified and described. They were formed after the major events of the Svecofennian ...tectogenesis. The age ranges of the orogenic stage and the post-orogenic extension collapse were dated, and the depth levels of the corresponding structures were determined. The differentiated exhumation process of deep complexes of the post-Proterozoic Savo–Ladoga movable zone was visualized. The approximate exhumation velocities of the deep material were estimated at certain stages of Precambrian evolution in the zone under consideration.
Based on analytical data on the geochemistry of tectonic pseudotachylytes and their host rocks, the specific trends of redistribution of major, trace, and rare earth elements in the course of ...seismogenic frictional melting of the arkosic metaterrigenous rocks from three zones of regional metamorphism with different temperatures (greenschist, amphibolite, and granulite) in the Northern Ladoga region are discussed. Oppositely directed trends of changes in the contents of the oxides of major elements in the protolith–blastocataclasite–pseudotachylyte triad were revealed, and a unidirectional increase in the basicity of the frictional melt as compared with the protolith was established at the same time. Geochemical evidence for partial selective melting of the protoliths is discussed. The specific features of the fractionation of trace and rare-earth elements during the transition of the protolith into the melt, as well as during its subsequent partial recrystallization, are shown. The emergence of a peak of elevated europium contents relative to the protolith in the melt matrix of all three sampling points is noted. Based on changes in the concentrations of these elements in the zones of pseudotachylyte substrate generation and in the areas of its moving and injection, the estimates of their differential mobility during frictional melting in a dynamic slip zone are given.
•Sensitized Mn2+ luminescence is studied in lithium tetraborate.•Existence of complex luminescence centres is proposed.•Slow or ultrafast Mn2+ luminescence decays occur depending on the excitation ...energy.•Mechanisms for excitation transfer and luminescence decay acceleration are proposed.
Sub-nanosecond luminescence of Mn2+ in Mn-, Sn/Mn-, and Cu/Mn-doped Li2B4O7 ceramics is observed under laser excitation. Picosecond pulsed laser radiation (350–370 nm) generates the frequency-doubled radiation directly in a single microcrystal selected in a ceramic sample, with this secondary radiation falling within the impurity-induced VUV excitation bands of doped Li2B4O7. These excitation bands are attributed to the creation of an impurity-bound intra-anionic exciton in MeiO4–BO3–MnLi complex centres (Mei = Mn, Sn, or Cu). The exciton, in turn, interacts with a nearby Mn2+ ion due to mixing of the Mn2+ excited states with the excitonic states. Exciton annihilation involves Mn2+ energy levels as transient states and causes a sub-nanosecond radiative transition which is accelerated, being accompanied by rearrangement of the surrounding atoms. Excitation within the lower-energy bands is related to the other part of the complex luminescence centre, this is metal-to-ligand intra-anionic charge transfer, which makes an electron accessible to MnLi, while the hole is transferred only during relaxation of the excited structure. Mn2+ radiative transitions are not forced in the latter case, and slow Mn2+ luminescence decay is observed.
Chest MRI of patients with COVID-19 Vasilev, Yu A.; Sergunova, K.A.; Bazhin, A.V. ...
Magnetic resonance imaging,
06/2021, Volume:
79
Journal Article
Peer reviewed
Open access
During the pandemic of novel coronavirus infection (COVID-19), computed tomography (CT) showed its effectiveness in diagnosis of coronavirus infection. However, ionizing radiation during CT studies ...causes concern for patients who require dynamic observation, as well as for examination of children and young people. For this retrospective study, we included 15 suspected for COVID-19 patients who were hospitalized in April 2020, Russia. There were 4 adults with positive polymerase chain reaction (PCR) test for COVID-19. All patients underwent magnetic resonance imaging (MRI) examinations using MR-LUND PROTOCOL: Single-shot Fast Spin Echo (SSFSE), LAVA 3D and IDEAL 3D, Echo-planar imaging (EPI) diffusion-weighted imaging (DWI) and Fast Spin Echo (FSE) T2 weighted imaging (T2WI). On T2WI changes were identified in 9 (60,0%) patients, on DWI – in 5 (33,3%) patients. In 5 (33,3%) patients lesions of the parenchyma were visualized on T2WI and DWI simultaneously. At the same time, 4 (26.7%) patients had changes in lung tissue only on T2WI. (P(McNemar) = 0,125; OR = 0,00 (95%); kappa = 0,500). In those patients who had CT scan, the changes were comparable to MRI. The results showed that in case of CT is not available, it is advisable to conduct a chest MRI for patients with suspected or confirmed COVID-19. Considering that T2WI is a fluid-sensitive sequence, if imaging for the lung infiltration is required, we can recommend the abbreviated MRI protocol consisting of T2 and T1 WI. These data may be applicable for interpreting other studies, such as thoracic spine MRI, detecting signs of viral pneumonia of asymptomatic patients. MRI can detect features of viral pneumonia.
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