scholarly journals Demographic inference under the coalescent in a spatial continuum

2016 ◽  
Author(s):  
Stephane Guindon ◽  
Hongbin Guo ◽  
David Welch
Keyword(s):  
Genetic Diversity ◽  
Spatial Data ◽  
Null Model ◽  
Theoretical Work ◽  
Spatial Density ◽  
Recent Theoretical Work ◽  
The Usa ◽  
Demographic Inference ◽  
Two Parameters ◽  
Spatial Continuum

Understanding population dynamics from the analysis of molecular and spatial data requires sound statistical modeling. Current approaches assume that populations are naturally partitioned into discrete demes, thereby failing to be relevant in cases where individuals are scattered on a spatial continuum. Other models predict the formation of increasingly tight clusters of individuals in space, which, again, conflicts with biological evidence. Building on recent theoretical work, we introduce a new genealogy-based inference framework that alleviates these issues. This approach effectively implements a stochastic model in which the distribution of individuals is homogeneous and stationary, thereby providing a relevant null model for the fluctuation of genetic diversity in time and space. Importantly, the spatial density of individuals in a population and their range of dispersal during the course of evolution are two parameters that can be inferred separately with this method. The validity of the new inference framework is confirmed with extensive simulations and the analysis of influenza sequences collected over five seasons in the USA.

The light-scattering Mueller matrices for Rayleigh and Rayleigh-Gans-Debye approximation

1990 ◽  
Vol 55 (12) ◽  
pp. 2889-2897
Author(s):  
Jaroslav Holoubek
Keyword(s):  
Light Scattering ◽  
Theoretical Work ◽  
Matrix Elements ◽  
Elastic Light Scattering ◽  
Yield Information ◽  
Recent Theoretical Work ◽  
Particle Parameters ◽  
Complete Set ◽  
Single Matrix ◽  
Scattering Matrix Elements

Recent theoretical work has shown that the complete set of polarized elastic light-scattering studies should yield information about scatterer structure that has so far hardly been utilized. We present here calculations of angular dependences of light-scattering matrix elements for spheres near the Rayleigh and Rayleigh-Gans-Debye limits. The significance of single matrix elements is documented on examples that show how different matrix elements respond to changes in particle parameters. It appears that in the small-particle limit (Rg/λ < 0.1) we do not loose much information by ignoring "large particle" observables.

scholarly journals Magnetospheric Structure of Rotation-Powered Neutron Stars

1992 ◽  
Vol 128 ◽  
pp. 56-77 ◽  
Author(s):  
Jonathan Arons
Keyword(s):  
Radio Emission ◽  
Gamma Radiation ◽  
Heavy Ions ◽  
Theoretical Work ◽  
Future Research ◽  
Observational Constraints ◽  
Polar Caps ◽  
Recent Theoretical Work ◽  
Density Flow ◽  
Promising Avenue

AbstractI survey recent theoretical work on the structure of the magnetospheres of rotation-powered pulsars, within the observational constraints set by their observed spindown, their ability to power synchrotron nebulae and their ability to produce beamed collective radio emission, while putting only a small fraction of their energy into incoherent X- and gamma radiation. I find no single theory has yet given a consistent description of the magnetosphere, but I conclude that models based on a dense outflow of pairs from the polar caps, permeated by a lower density flow of heavy ions, are the most promising avenue for future research.

scholarly journals Molecular Analysis of a Plum pox virus W Isolate in Plum Germplasm Hand Carried into the USA from the Ukraine Shows a Close Relationship to a Latvian Isolate

Plant Disease ◽  
2013 ◽  
Vol 97 (1) ◽  
pp. 44-52 ◽  
Author(s):  
Vessela Mavrodieva ◽  
Delano James ◽  
Karen Williams ◽  
Sarika Negi ◽  
Aniko Varga ◽  
...  
Keyword(s):  
United States ◽  
Genetic Diversity ◽  
The United States ◽  
Common Source ◽  
Plum Pox Virus ◽  
High Genetic Diversity ◽  
Close Relationship ◽  
The Usa ◽  
Sequence Identities ◽  
Germplasm Accessions

Four of 19 Prunus germplasm accessions hand carried from the Ukraine into the United States without authorization were found to be infected with Plum pox virus (PPV). Of the three isolates characterized, isolates UKR 44189 and UKR 44191 were confirmed to be isolates of PPV strain W, and UKR 44188 was confirmed to be an isolate of PPV strain D. UKR 44189 and UKR 44191 are very closely related to the PPV strain W isolate LV-145bt (HQ670748) from Latvia. Nucleotide and amino acid sequence identities between these three isolates were greater than 99%. This indicates that the isolates are very closely related and likely originated from a common source. The high genetic diversity among PPV-W strain isolates allowed the identification of potential recombination events between PPV isolates. It appears also that GF 305 peach and Prunus tomentosa are not hosts for the PPV isolate UKR 44189.

Genetic Diversity among Calamus brandisii Becc. (Arecaceae) Populations in Kerala Part of Western Ghats

2021 ◽  
Vol 43 (1) ◽  
pp. 38-42
Author(s):  
Kavungal Priya ◽  
◽  
Indira . ◽  
Vadakkethil Balakrishnan Sreekumar ◽  
Renuka . ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Western Ghats ◽  
Rapd Markers ◽  
Gene Diversity ◽  
Issr Markers ◽  
High Genetic Diversity ◽  
Western Ghats Of India ◽  
The Mean ◽  
Two Parameters ◽  
Two Populations

Calamus brandisii Becc. is one of the endemic slender rattans found in the Western Ghats of India. The genetic diversity of two main populations available in Kerala was investigated using 20 RAPD and 9 ISSR markers. Two parameters viz., gene diversity and genetic diversity within and among populations were analyzed. ISSR analysis showed quite high genetic diversity in Pandimotta compared to Bonacaud population whereas in RAPD markers both these populations were moderately diverse. The percentage of total genetic differentiation (Gst) among two populations is relatively higher than the mean Gst value indicating high genetic diversity within the populations. The genetic distance between these two populations was 0.1739 with ISSR markers and 0.1971 with RAPD markers. Because of its high genetic diversity, Pandimotta population can be treated as an important population of gene diversity with potentially useful genes. This may be included in the high priority reservoir for genetic conservation also.

scholarly journals THE EXOTIC BARIUM BISMUTHATES

1996 ◽  
Vol 10 (08) ◽  
pp. 863-955 ◽  
Author(s):  
A. TARAPHDER ◽  
RAHUL PANDIT ◽  
H. R. KRISHNAMURTHY ◽  
T. V. RAMAKRISHNAN
Keyword(s):  
Bound States ◽  
Random Phase ◽  
Density Wave ◽  
Mean Field ◽  
Experimental Tests ◽  
Theoretical Work ◽  
Recent Theoretical Work ◽  
Effects Of Disorder ◽  
Exotic Physics ◽  
Transport Gaps

We review the remarkable properties, including superconductivity, charge-density-wave ordering and metal–insulator transitions, of lead- and potassium-doped barium bismuthate. We will discuss some of the early theoretical studies of these systems. Our recent theoretical work, on the negative-U, extended-Hubbard model for these systems, will also be described. Both the large- and intermediate-U regimes of this model were examined, using mean-field and random-phase approximations, particularly with a view to fitting various experimental properties of these bismuthates. On the basis of our studies, we point out possibilities for exotic physics in these systems. We also emphasize the different consequences of electronic and phonon-mediated mechanisms for the negative U. We show that, for an electronic mechanism, the semiconducting phases of these bismuthates must be unique, with their transport properties dominated by charge±2eCooperon bound states. This can explain the observed difference between the optical and transport gaps. We propose other experimental tests for this novel mechanism of charge transport and comment on the effects of disorder.

scholarly journals The Swiss joint information platform for natural hazards

2019 ◽  
Vol 1 ◽  
pp. 1-2
Author(s):  
Philipp Angehrn ◽  
Sabina Steiner ◽  
Christophe Lienert
Keyword(s):  
Natural Hazards ◽  
Spatial Data ◽  
Natural Hazard ◽  
Regional Scale ◽  
Measurement Data ◽  
User Feedback ◽  
Acceptance Testing ◽  
Spatial Density ◽  
Data Sets ◽  
Information Platform

<p><strong>Abstract.</strong> The Swiss Joint Information Platform for Natural Hazards (GIN) has been realized from 2008 to 2010 as part of the Swiss federal government’s OWARNA project, which aimed at optimizing warning and alerting procedures against natural hazard. The first online-version of the platform went productive in 2011 with the primary goal of providing measured and forecast natural hazard data in form of processed cartographic, graphic and other multimedia products to professional users &amp;ndash; before, during and after natural hazard events. In Switzerland water-, weather-, snow- and earthquake-related hazards are the most relevant ones.</p><p>In 2013, an online survey showed that the platform does not fully meet user expectations, particularly as to user experience and usability of its cartographic, web-based user interface. Revaluation and redesign of the overall platform were necessary in order to improve map legibility, caused by the complexity of data, large data amounts, and high spatial density of online, real-time measurement data locations. A new web design and user interaction concept have been developed in 2014 and eventually put online in June 2017. User acceptance testing by means of surveys and direct user feedback sessions were key factors in this perennial redesign process. The GIN platform now features important novel technical and graphical elements: The starting page is based on a dashboard containing virtual dossiers (Fig. 1), with which users configure their desired information, data, and map bundles individually, or use predefined adaptable views on various existing data sets. In addition, there is a new overall spatial search function to query data parameters. A responsive approach further improves the usability of the platform. The focus of these new features is on multi-views involving maps, diagrams, tables, text products, as well as selected geographical areas on maps, and fast data queries (Fig. 2). Current user feedback suggests that the new GIN platform design is well received, and that it is moving closer to its very goal: online monitoring and management of natural hazard events by enhanced usability, more targeted and higher personalization.</p><p>Several Swiss Cantons (i.e., the political entities in Switzerland below the federation) actively participated, and still participate, in the conceptual GIN platform development process through advisory board meetings and consultations. On the operational level, Cantons actively provide and contribute further natural hazard information and measurement data from their own natural hazard monitoring networks. These additional Cantonal regional-scale data sets help to fill spatial data gaps, where no Federal data is available. GIN thusly integrates natural hazard data from Federal and Cantonal levels (and partly even private level), which adds value to all stakeholders on various political levels involved in natural hazard management (Federal, Cantonal, Regional, Communal crisis committees). Stakeholders not only use GIN’s ample database and cartographic product portfolio to accomplish their early warning and crisis management tasks, but also benefit from seamless, secure and reliable IT-services, provided by the Swiss Federal Government. With the new GIN platform, Switzerland has a powerful, integrative, and comprehensive tool for monitoring and responding to natural hazard events.</p>

scholarly journals Landauer in the age of synthetic biology: energy consumption and information processing in biochemical networks

2015 ◽  
Author(s):  
Pankaj Mehta ◽  
Alex H Lang ◽  
David J Schwab
Keyword(s):  
Information Processing ◽  
Energy Consumption ◽  
Synthetic Biology ◽  
Protein Modification ◽  
Theoretical Work ◽  
Biochemical Networks ◽  
Fundamental Physics ◽  
Recent Theoretical Work ◽  
Cellular Circuits ◽  
Molecular Components

A central goal of synthetic biology is to design sophisticated synthetic cellular circuits that can perform complex computations and information processing tasks in response to specific inputs. The tremendous advances in our ability to understand and manipulate cellular information processing networks raises several fundamental physics questions: How do the molecular components of cellu- lar circuits exploit energy consumption to improve information processing? Can one utilize ideas from thermodynamics to improve the design of synthetic cellular circuits and modules? Here, we summarize recent theoretical work addressing these questions. Energy consumption in cellular cir- cuits serves five basic purposes: (1) increasing specificity, (2) manipulating dynamics, (3) reducing variability, (4) amplifying signal, and (5) erasing memory. We demonstrate these ideas using several simple examples and discuss the implications of these theoretical ideas for the emerging field of synthetic biology. We conclude by discussing how it may be possible to overcome these limitations using “post-translational” synthetic biology that exploits reversible protein modification.

scholarly journals Mixed-polarity random-dot stereograms alter GABA and Glx concentration in the early visual cortex

2019 ◽  
Author(s):  
Reuben Rideaux ◽  
Nuno Goncalves ◽  
Andrew E Welchman
Keyword(s):  
Visual Cortex ◽  
Three Dimensional ◽  
Theoretical Work ◽  
Dimensional Structure ◽  
Resonance Spectroscopy ◽  
Gaba Concentration ◽  
Recent Theoretical Work ◽  
Random Dot Stereograms ◽  
Mixed Polarity ◽  
Early Visual Cortex

ABSTRACTThe offset between images projected onto the left and right retinae (binocular disparity) provides a powerful cue to the three-dimensional structure of the environment. It was previously shown that depth judgements are better when images comprise both light and dark features, rather than only dark or only light elements. Since Harris and Parker (1995) discovered the “mixed-polarity benefit”, there has been limited evidence supporting their hypothesis that the benefit is due to separate bright and dark channels. Goncalves and Welchman (2017) observed that single- and mixed-polarity stereograms evoke different levels of positive and negative activity in a deep neural network trained on natural images to make depth judgements, which also showed the mixed-polarity benefit. Motivated by this discovery, here we seek to test the potential for changes in the balance of excitation and inhibition that are produced by viewing these stimuli. In particular, we use magnetic resonance spectroscopy to measure Glx and GABA concentration in the early visual cortex of adult humans while viewing single- and mixed-polarity random-dot stereograms (RDS). We find that observers’ Glx concentration is significantly higher while GABA concentration is significantly lower when viewing mixed-polarity RDS than when viewing single-polarity RDS. These results indicate that excitation and inhibition facilitate processing of single- and mixed-polarity stereograms in the early visual cortex to different extents, consistent with recent theoretical work (Goncalves & Welchman, 2017).

scholarly journals Imaging Mueller matrix determination of transparent, unpolarizing samples using a classically entangled polarization state

2018 ◽  
Vol 64 (4) ◽  
pp. 407
Author(s):  
Jacqueline Isamar Muro-Ríos ◽  
R. Espinosa-Luna
Keyword(s):  
Open Space ◽  
Polarization State ◽  
Theoretical Work ◽  
Mueller Matrix ◽  
Experimental Setup ◽  
Wave Plate ◽  
Recent Theoretical Work ◽  
Study Results ◽  
Theoretical Proposal

Inspired in a recent theoretical work for the determination of the Mueller matrix, using as incidence a single classically entangled polarization state (F. Töppel et al., New J. Phys. 16 (2014) 073019), an experimental setup is proposed and tested.  The open space and two wave plate retarders are used as the transparent, nondepolarizing samples under study. Results show some experimental improvements are necessary in order to implement accurately the theoretical proposal in which this work is based.

scholarly journals Task-evoked pupil responses reflect internal belief states

2018 ◽  
Author(s):  
O. Colizoli ◽  
J.W. de Gee ◽  
A.E. Urai ◽  
T.H. Donner
Keyword(s):  
Pupil Diameter ◽  
Theoretical Work ◽  
Prediction Errors ◽  
Decision Confidence ◽  
Uncertain Evidence ◽  
Recent Theoretical Work ◽  
The Face ◽  
Belief States ◽  
State Of The Environment ◽  
Made In

AbstractPerceptual decisions about the state of the environment are often made in the face of uncertain evidence. Internal uncertainty signals are considered important regulators of learning and decision-making. A growing body of work has implicated the brain’s arousal systems in uncertainty signaling. Here, we found that two specific computational variables, postulated by recent theoretical work, evoke boosts of arousal at different times during a perceptual decision: decision confidence (the observer’s internally estimated probability that a choice was correct given the evidence) before feedback, and prediction errors (deviations from expected reward) after feedback. We monitored pupil diameter, a peripheral marker of central arousal state, while subjects performed a challenging perceptual choice task with a delayed monetary reward. We quantified evoked pupil responses during decision formation and after reward-linked feedback. During both intervals, decision difficulty and accuracy had interacting effects on pupil responses. Pupil responses negatively scaled with decision confidence prior to feedback and scaled with uncertainty-dependent prediction errors after feedback. This pattern of pupil responses during both intervals was in line with a model using the observer’s graded belief about choice accuracy to anticipate rewards and compute prediction errors. We conclude that pupil-linked arousal systems are modulated by internal belief states.

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