Optimal decision bounds for probabilistic population codes and time varying evidence

Decision making under time constraints requires the decision maker to trade off between making quick, inaccurate decisions and gathering more evidence for more accurate, but slower decisions. We have previously shown that, under rather general settings, optimal behavior can be described by a time-dependent decision bound on the decision maker’s belief of being correct (Drugowitsch, Moreno-Bote, Pouget, 2009). In cases where the reliability of sensory information remains constant over time, we have shown how to design diffusion models (DMs) with time-changing boundaries that feature such behavior. Such theories can be easily mapped onto simple neural models of decision making with two perfectly anti-correlated neurons, where they predict the existence of a stopping bound on the most active neurons. It is unclear however how the stopping bound would be implemented with more realistic neural population codes, particularly when the reliability of the evidence changes over time.
Here we show that, under certain realistic conditions, we can apply the theory of optimal decision making to the biologically more plausible probabilistic population codes (PPCs; Ma et al. 2006). Our analysis shows that, with population codes, the optimal decision bounds are a function of the neural activity of all neurons in the population, rather than a previously postulated bound on its maximum activity. This theory predicts that the bound on the most active neurons would appear to shift depending on the firing rate of other neurons in the population, a puzzling behavior under the drift diffusion model as it would wrongly suggest that subjects change their stopping rule across conditions. This theory also applies to the case of time varying evidence, a case that cannot be handled by drift diffusion models without unrealistic assumptions

Amazon and the New World of Publishing

Comments on Chris Sagers, Apple, Antitrust, and Irony (Harvard University Press, 2018

Dispersal of _Aedes aegypti_: field study in temperate areas and statistical approach

We studied the dispersion of _Aedes aegypti_ during egg laying in natural conditions. Two independent experiments involving mosquitoes dispersing from urbanization towards adjacent un-urbanized areas were carried out and analyzed in statistical terms. We find relations between stochastic variables related to the egg laying mosquito activity (ELMA), useful to assess dispersion probabilities, despite the lack of knowledge of the total number of ovipositions in the zone. We propose to evaluate the activity as minus the logarithm of the fraction of negative ovitraps at different distances from buildings. We also estimate the average number of eggs laid per oviposition using a regression between the ELMA and the number of eggs found. Three zones with different oviposition activity were determined: a corridor surrounding the urbanized area, a second region between 10m and 25m and the third region extending from 30m to 45m from the urbanization. The landscape (plant cover) and the human activity in the area appear to have an influence in the dispersal of _Aedes aegypti_

Cleft Palate In Children And Adolescent: A Study Of Arch Expansion

Penggunaan alat untuk mengembangkan lelangit telah dikatakan berkesan dalam menghasilkan daya ringan yang berpanjangan untuk mengembangkan rahang maksila di kalangan pesakit-pesakit sumbing bibir dan lelangt yang mempunyai saiz maksila yang kecil. The use of palatal expansion appliances has been claimed to produce a light, continuous force, which is capable of expanding the maxilla and correcting dental arch width of cleft palate patients who have deficient maxilla

Development Of A Mathematical Model To Predict Thermal Performance And Cost Effectiveness Of Solar Air Heaters

Energy is a subject of vital importance because of our great dependence on them in all aspects of life including social, economy and even in defence. In Malaysia the analyses of solar radiation at several main towns show that solar radiation has potential for drying purpose. This research is concerned with developing an internet-based mathematical model which is able to predict the thermal performance and cost effectiveness for different types of solar air heaters. The data and knowledge collected from published sources on solar collectors, literature review and the field survey along with personal communications in the solar energy field is used to develop an internet based mathematical model given the code name Mathematical Modeling for Solar Air Heaters (MMSAH). This Mathematical Model incorporates knowledge and able to calculate the parameters required to predict the thermal efficiency and the cost effectiveness of solar air heaters. These parameters are absorber plate temperature, the temperature of the transport fluid inside the duct flow,the output temperature and the overall heat loss coefficient. It also can calculate the fan power consumption to obtain the net energy gain which is required in the cost effectiveness calculation. The solution procedure is performed for flat and V-groove absorber in single and double flow mode, with and without porous media. The thermal performance was determined over a wide range of operating conditions. The optimum operating parameters with respect to the efficiency, outlet temperature and cost effectiveness have been determined. For mass flow rate it lies in the range of 0.025 to 0.045 kg/s, for channel flow depth the recommended ranges are 0.025 to 0.035 m for flat plate collector, 0.06 to 0.08 m for V-groove absorber and 0.04 to 0.055 m for lower duct in double flow double duct solar air heater. The optimum collector length for reasonable thermal performance and minimum annual cost per unit thermal energy gain was found to be between 1 and 3 m. For flat plate collector type it is found that the system thermal efficiency increases by 10-12% in double flow mode without porous media than single flow. An increase of 18% after using porous media in the lower channel than the single flow. For V-groove absorber type it is found that the double flow mode is 4-5% more efficient than the single flow mode. Observation shows that using the porous media in double flow increase the air heater efficiency by more than 7% efficient than the air heater in single mode and a further 2-3% in double flow mode without porous media. It is found that the annual cost of the collector in the double duct double pass flat plate collector with porous media is higher than the annual cost of the collector in double duct double pass flat plate collector without porous media and that is a consequence of using the porous media in which increase the pressure drop lead to increase in annual running cost. However the cost of solar energy (cost-benefit ratio); the annual cost of the collector/the annual thermal energy gain in double flow duct double duct flat plate collector with porous media is less than the cost of solar energy in double flow duct double duct flat plate collector without porous media due to the higher useful energy gained from using porous media which subsequently increase the heat transfer area. Also it is found that the cost-benefit ratio was affected by the flow depth. The developed program is capable of handling Malaysian ambient conditions, collector characteristics, and material thermal properties. The criteria for solar collector in Malaysia were used as the input in the program to simulate the performance of the solar air heaters. To assess the accuracy of the developed program, the mathematical model was validated by comparing its output with experimental results. The comparison conducted showed a similar agreement with maximum error of 5%. The technique seems to be promising since a great correlation has been obtained between the experimental and the predicted results (97.5% < R2 < 99.76% and P < 0.001)

Los videojuegos, nuevas narrativas del siglo XXI.

85 p. Recuso Electr?nicoNuestro trabajo realiza una contextualizaci?n, acerca de los conceptos b?sicos del juego a trav?s de los planteamientos de Huizinga, que cimentaron la base para toda una serie de estudios referentes a los beneficios de la l?dica y el juego en el desarrollo cognitivo y emocional. De igual manera analizaremos el concepto de videojuego como tal y los beneficios descubiertos acerca de estos, haciendo una revisi?n de diferentes estudios dentro de los cuales encontramos los del Psic?logo Carlos Gonz?lez Tard?n, entre varios autores m?s. En el segundo cap?tulo, se desarrollar? un an?lisis narratol?gico a diferentes videojuegos, tomando como base los estudios realizados por Mart?nez y Scheffel en cuanto estudios narratol?gicos literarios y tambi?n las postulaciones de Gaudreault y Jost quienes desarrollaron todo un an?lisis narratol?gico al discurso cinematogr?fico. Posteriormente realizaremos en nuestro tercer cap?tulo una investigaci?n acerca del proceso creativo involucrado en la realizaci?n de argumentos y guiones dise?ados para los videojuegos,. Dentro de dicho proceso se analiz? la relaci?n de los fundamentos b?sicos de la producci?n narrativa, establecidos por Arist?teles, Vladimir Propp, Joseph Campbell y Lajos Egri, adem?s de su aplicaci?n en el campo de los videojuegos, de igual manera a trav?s de varios ejemplos se se plasma nuestra experiencia en la realizaci?n de los distintos formatos de guiones utilizados en la composici?n de nuestro propio videojuego. Finalizamos con algunas conclusiones referentes al tema, en la que a trav?s del resumen de los diferentes an?lisis y nuestra experiencia.Our work makes a contextualization about the basics of the game through approaches Huizinga, which cemented the basis for a series of studies on the benefits of fun and play in cognitive and emotional development. Similarly we discuss the concept of game as such and benefits discovered about these, by reviewing different studies within which are those of Psic?logo Tard?n Carlos Gonzalez, among several other authors. In the second chapter, different games narratological analysis, based on studies by Martinez and Scheffel as narratological literary studies and applications from Gaudreault and Jost who developed a whole narratological the cinematic discourse analysis will be developed. Then we will make our third chapter an investigation into the creative process involved in making arguments and scripts designed for video games ,. Within this process the relationship of the basic fundamentals of narrative production was analyzed, established by Aristotle, Vladimir Propp, Joseph Campbell and Lajos Egri, in addition to its application in the field of video games, equally through several examples our experience is reflected in the performance of various script formats used in the composition of our own game. We conclude with some conclusions concerning the topic, which through the summary of the different analyzes and our experience. Keywords: Narratolog?a, Video Games, Story, Education

Ge-substitutional defects and the r3xr3 <--> 3x3 transition in alpha--SnGe(111)

The structure and energetics of Ge substitutional defects on the alpha-Sn/Ge(111) surface are analyzed using Density Functional Theory (DFT) molecular dynamics (MD) simulations. An isolated Ge defect induces a very local distortion of the 3x3 reconstruction, confined to a significant downwards displacement (-0.31 A) at the defect site and a modest upward displacement (0.05 A) of the three Sn nearest neighbours with partially occupied dangling bonds. Dynamical fluctuations between the two degenerate ground states yield the six-fold symmetry observed around a defect in the experiments at room temperature. Defect-defect interactions are controlled by the energetics of the deformation of the 3x3 structure: They are negligible for defects on the honeycomb lattice and quite large for a third defect on the hexagonal lattice, explaining the low temperature defect ordering.Comment: 4 pages, Revtex, 7 Encapsulated Postscript figures, uses epsf.sty. Submitted to Phys. Rev. Let