scholarly journals Stochastic Modeling of Density-Dependent Diploid Populations and the Extinction Vortex

2014 ◽  
Vol 46 (2) ◽  
pp. 446-477 ◽  
Author(s):  
Camille Coron
Keyword(s):  
Resource Competition ◽  
Adaptive Dynamics ◽  
Three Dimensional ◽  
Death Process ◽  
Fixation Rate ◽  
One Dimensional ◽  
Rare Mutations ◽  
Recurrence Relationship ◽  
Extinction Vortex

We model and study the genetic evolution and conservation of a population of diploid hermaphroditic organisms, evolving continuously in time and subject to resource competition. In the absence of mutations, the population follows a three-type, nonlinear birth-and-death process, in which birth rates are designed to integrate Mendelian reproduction. We are interested in the long-term genetic behavior of the population (adaptive dynamics), and in particular we compute the fixation probability of a slightly nonneutral allele in the absence of mutations, which involves finding the unique subpolynomial solution of a nonlinear three-dimensional recurrence relationship. This equation is simplified to a one-dimensional relationship which is proved to admit exactly one bounded solution. Adding rare mutations and rescaling time, we study the successive mutation fixations in the population, which are given by the jumps of a limiting Markov process on the genotypes space. At this time scale, we prove that the fixation rate of deleterious mutations increases with the number of already fixed mutations, which creates a vicious circle called the extinction vortex.

scholarly journals Stochastic Modeling of Density-Dependent Diploid Populations and the Extinction Vortex

2014 ◽  
Vol 46 (02) ◽  
pp. 446-477 ◽  
Author(s):  
Camille Coron
Keyword(s):  
Resource Competition ◽  
Adaptive Dynamics ◽  
Three Dimensional ◽  
Death Process ◽  
Fixation Rate ◽  
One Dimensional ◽  
Rare Mutations ◽  
Recurrence Relationship ◽  
Extinction Vortex

We model and study the genetic evolution and conservation of a population of diploid hermaphroditic organisms, evolving continuously in time and subject to resource competition. In the absence of mutations, the population follows a three-type, nonlinear birth-and-death process, in which birth rates are designed to integrate Mendelian reproduction. We are interested in the long-term genetic behavior of the population (adaptive dynamics), and in particular we compute the fixation probability of a slightly nonneutral allele in the absence of mutations, which involves finding the unique subpolynomial solution of a nonlinear three-dimensional recurrence relationship. This equation is simplified to a one-dimensional relationship which is proved to admit exactly one bounded solution. Adding rare mutations and rescaling time, we study the successive mutation fixations in the population, which are given by the jumps of a limiting Markov process on the genotypes space. At this time scale, we prove that the fixation rate of deleterious mutations increases with the number of already fixed mutations, which creates a vicious circle called the extinction vortex.

Investigation of Carbon Budget Around Artificial Upwelling Generator by a Coupled Physical-Biological Model

2007 ◽  
Author(s):  
Shigeru Tabeta ◽  
Haruki Yoshimoto
Keyword(s):  
Carbon Budget ◽  
Three Dimensional ◽  
Ecosystem Model ◽  
Biological Model ◽  
Target Area ◽  
Biological Pump ◽  
One Dimensional ◽  
Carbon Cycles ◽  
Fish Catch

There are several projects of generating upwelling by artificial structures to enhance the primary production expecting fish catch increase. From the view point of global environment, CO2 budget between atmosphere and ocean due to such technologies are also interesting. In this study, a coupled physical-biological model was developed to simulate the nitrogen and carbon cycles around artificial upwelling generator. The model is focusing on the degradation of particulate organic matter, because the process should much affects on the efficiency of the biological pump. The model is tuned by using the experimental data and applied to simulate the material cycle in the target area which is located north of Ikitsuki Island located northwest of Kyusyu, Japan, where an artificial seabed mound is installed to generate upwelling. The long-term carbon budget is also estimated by vertical one-dimensional ecosystem model using the parameters determined from the results of the three-dimensional coupled physical-biological model.

Earth-like worlds on eccentric orbits: excursions beyond the habitable zone

2002 ◽  
Vol 1 (1) ◽  
pp. 61-69 ◽  
Author(s):  
Darren M. Williams ◽  
David Pollard
Keyword(s):  
General Circulation ◽  
Climate Model ◽  
Three Dimensional ◽  
Balance Model ◽  
Seasonal Temperature ◽  
Habitable Zone ◽  
One Dimensional ◽  
Climate Stability ◽  
Eccentric Orbits

Many of the recently discovered extrasolar giant planets move around their stars on highly eccentric orbits, and some with e [ges ] 0·7. Systems with planets within or near the habitable zone (HZ) will possibly harbour life on terrestrial-type moons if the seasonal temperature extremes resulting from the large orbital eccentricities of the planets are not too severe. Here we use a three-dimensional general-circulation climate model and a one-dimensional energy-balance model to examine the climates of either bound or isolated earths on extremely elliptical orbits near the HZ. While such worlds are susceptible to large variations in surface temperature, long-term climate stability depends primarily on the average stellar flux received over an entire orbit, not the length of the time spent within the HZ.

scholarly journals EVOLUTIONARY DYNAMICS CAN BE CHAOTIC: A FIRST EXAMPLE

2010 ◽  
Vol 20 (11) ◽  
pp. 3473-3485 ◽  
Author(s):  
FABIO DERCOLE ◽  
SERGIO RINALDI
Keyword(s):  
Bifurcation Analysis ◽  
Food Chain ◽  
Evolutionary Dynamics ◽  
Adaptive Dynamics ◽  
Three Dimensional ◽  
Phenotypic Trait ◽  
Predator Species ◽  
Evolutionary Trajectories ◽  
Trait Space

We present in this paper the first example of chaotic evolutionary dynamics in biology. We consider a Lotka–Volterra tritrophic food chain composed of a resource, its consumer, and a predator species, each characterized by a single adaptive phenotypic trait, and we show that for suitable modeling and parameter choices the evolutionary trajectories approach a strange attractor in the three-dimensional trait space. The study is performed through the bifurcation analysis of the so-called canonical equation of Adaptive Dynamics, the most appropriate modeling approach to long-term evolutionary dynamics.

scholarly journals Long-term evolution of surviving companion stars of Type Iax supernovae

2020 ◽  
Vol 500 (1) ◽  
pp. 301-309
Author(s):  
Zheng-Wei Liu ◽  
Yaotian Zeng
Keyword(s):  
Stellar Evolution ◽  
Main Sequence ◽  
Three Dimensional ◽  
Late Time ◽  
One Dimensional ◽  
Term Evolution ◽  
Post Impact ◽  
Explosion Mechanism ◽  
Hydrodynamical Simulations

ABSTRACT The nature of the progenitors and explosion mechanism of Type Iax supernovae (SNe Iax) remain a mystery. The single-degenerate (SD) systems that involve the incomplete pure deflagration explosions of near-Chandrasekhar-mass white dwarfs (WDs) have recently been proposed for producing SNe Iax in which non-degenerate companions are expected to survive from SN explosions. In this work, we concentrate on the main-sequence (MS) donor SD progenitor systems. By mapping the computed companion models from three-dimensional hydrodynamical simulations of ejecta-companion interaction into a one-dimensional stellar evolution code mesa, we investigate the long-term appearance and observational signatures of surviving MS companions of SNe Iax by tracing their post-impact evolution. Depending on different MS companion models, it is found that the shocked surviving companion stars can significantly expand and evolve to be more luminous (5–$500\, L_{\odot }$) for a time-scale of 10–104 yr. Comparing with the late-time light curve of an observed SN Iax (SN 2005hk), it is suggested that surviving MS companions of SNe Iax would expect to be visible about 1000 d after the explosion when SN itself has been faded.

Structure and function of neural networks in the retina

1988 ◽  
Vol 46 ◽  
pp. 26-27
Author(s):  
Peter Sterling
Keyword(s):  
Ganglion Cells ◽  
Three Dimensional ◽  
Structure And Function ◽  
Synaptic Connections ◽  
Visual Axis ◽  
One Dimensional ◽  
Cat Retina ◽  
Ultrathin Sections ◽  
And Function ◽  
Insight Into

The synaptic connections in cat retina that link photoreceptors to ganglion cells have been analyzed quantitatively. Our approach has been to prepare serial, ultrathin sections and photograph en montage at low magnification (˜2000X) in the electron microscope. Six series, 100-300 sections long, have been prepared over the last decade. They derive from different cats but always from the same region of retina, about one degree from the center of the visual axis. The material has been analyzed by reconstructing adjacent neurons in each array and then identifying systematically the synaptic connections between arrays. Most reconstructions were done manually by tracing the outlines of processes in successive sections onto acetate sheets aligned on a cartoonist's jig. The tracings were then digitized, stacked by computer, and printed with the hidden lines removed. The results have provided rather than the usual one-dimensional account of pathways, a three-dimensional account of circuits. From this has emerged insight into the functional architecture.

Practical electron tomography

1995 ◽  
Vol 53 ◽  
pp. 742-743
Author(s):  
C.L. Woodcock
Keyword(s):  
Electron Tomography ◽  
Tomographic Reconstruction ◽  
Three Dimensional ◽  
3D Shape ◽  
Computational Resources ◽  
Shape Of Particles

Despite the potential of the technique, electron tomography has yet to be widely used by biologists. This is in part related to the rather daunting list of equipment and expertise that are required. Thanks to continuing advances in theory and instrumentation, tomography is now more feasible for the non-specialist. One barrier that has essentially disappeared is the expense of computational resources. In view of this progress, it is time to give more attention to practical issues that need to be considered when embarking on a tomographic project. The following recommendations and comments are derived from experience gained during two long-term collaborative projects.Tomographic reconstruction results in a three dimensional description of an individual EM specimen, most commonly a section, and is therefore applicable to problems in which ultrastructural details within the thickness of the specimen are obscured in single micrographs. Information that can be recovered using tomography includes the 3D shape of particles, and the arrangement and dispostion of overlapping fibrous and membranous structures.

Exploring the Multidimensional Facets of Authoritarianism: Authoritarian Aggression and Social Dominance Orientation

2008 ◽  
Vol 67 (1) ◽  
pp. 51-60 ◽  
Author(s):  
Stefano Passini
Keyword(s):  
Social Dominance ◽  
Factor Model ◽  
Three Dimensional ◽  
Social Dominance Orientation ◽  
Model Fit ◽  
Regression Analyses ◽  
One Dimensional ◽  
Confirmatory Factor ◽  
The One ◽  
Better Than

The relation between authoritarianism and social dominance orientation was analyzed, with authoritarianism measured using a three-dimensional scale. The implicit multidimensional structure (authoritarian submission, conventionalism, authoritarian aggression) of Altemeyer’s (1981, 1988) conceptualization of authoritarianism is inconsistent with its one-dimensional methodological operationalization. The dimensionality of authoritarianism was investigated using confirmatory factor analysis in a sample of 713 university students. As hypothesized, the three-factor model fit the data significantly better than the one-factor model. Regression analyses revealed that only authoritarian aggression was related to social dominance orientation. That is, only intolerance of deviance was related to high social dominance, whereas submissiveness was not.

Custom Presurgical Planning for Midfacial Reconstruction

2020 ◽  
Vol 36 (06) ◽  
pp. 696-702
Author(s):  
Nolan B. Seim ◽  
Enver Ozer ◽  
Sasha Valentin ◽  
Amit Agrawal ◽  
Mead VanPutten ◽  
...  
Keyword(s):  
Multidisciplinary Approach ◽  
Functional Performance ◽  
Three Dimensional ◽  
Free Tissue Transfer ◽  
Long Term Effects ◽  
Presurgical Planning ◽  
Dental Rehabilitation ◽  
Midface Reconstruction ◽  
Reconstructive Algorithm

AbstractResection and reconstruction of midface involve complex ablative and reconstructive tools in head and oncology and maxillofacial prosthodontics. This region is extraordinarily important for long-term aesthetic and functional performance. From a reconstructive standpoint, this region has always been known to present challenges to a reconstructive surgeon due to the complex three-dimensional anatomy, the variable defects created, combination of the medical and dental functionalities, and the distance from reliable donor vessels for free tissue transfer. Another challenge one faces is the unique features of each individual resection defect as well as individual patient factors making each preoperative planning session and reconstruction unique. Understanding the long-term effects on speech, swallowing, and vision, one should routinely utilize a multidisciplinary approach to resection and reconstruction, including head and neck reconstructive surgeons, prosthodontists, speech language pathologists, oculoplastic surgeons, dentists, and/or craniofacial teams as indicated and with each practice pattern. With this in mind, we present our planning and reconstructive algorithm in midface reconstruction, including a dedicated focus on dental rehabilitation via custom presurgical planning.

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