Physics of Psychophysics: two coupled square lattices of spiking neurons have huge dynamic range at criticality

Psychophysics try to relate physical input magnitudes to psychological or neural correlates. Microscopic models to account for macroscopic psychophysical laws, in the sense of statistical physics, are an almost unexplored area. Here we examine a sensory epithelium composed of two connected square lattices of stochastic integrate-and-fire cells. With one square lattice we obtain a Stevens's law $\rho \propto h^m$ with Stevens's exponent $m = 0.254$ and a sigmoidal saturation, where $\rho$ is the neuronal network activity and $h$ is the input intensity (external field). We relate Stevens's power law exponent with the field critical exponent as $m = 1/\delta_h = \beta/\sigma$. We also show that this system pertains to the Directed Percolation (DP) universality class (or perhaps the Compact-DP class). With stacked two layers of square lattices, and a fraction of connectivity between the first and second layer, we obtain at the output layer $\rho_ 2 \propto h^{m_2}$, with $m_2 = 0.08 \approx m^2$, which corresponds to a huge dynamic range. This enhancement of the dynamic range only occurs when the layers are close to their critical point.Comment: 22 pages, 7 figures, accepted by Physical Review Researc

Lung diffusion in a 14-day swimming altitude training camp at 1850 meters

Swimming exercise at sea level causes a transient decrease in lung diffusing capacity for carbon monoxide (DLCO). The exposure to hypobaric hypoxia can affect lung gas exchange, and hypoxic pulmonary vasoconstriction may elicit pulmonary oedema. The purpose of this study is to evaluate whether there are changes in DLCO during a 14-day altitude training camp (1850 m) in elite swimmers and the acute effects of a combined training session of swimming in moderate hypoxia and 44-min cycling in acute normobaric severe hypoxia (3000 m). Participants were eight international level swimmers (5 females and 3 males; 17-24 years old; 173.5 ± 5.5 cm; 64.4 ± 5.3 kg) with a training volume of 80 km per week. The single-breath method was used to measure the changes in DLCO and functional gas exchange parameters. No changes in DLCO after a 14-day altitude training camp at 1850 m were detected but a decrease in alveolar volume (VA; 7.13 ± 1.61 vs. 6.50 ± 1.59 L; p = 0.005; d = 0.396) and an increase in the transfer coefficient of the lung for carbon monoxide (KCO; 6.23 ± 1.03 vs. 6.83 ± 1.31 mL·min−1·mmHg−1·L−1; p = 0.038; d = 0.509) after the altitude camp were observed. During the acute hypoxia combined session, there were no changes in DLCO after swimming training at 1850 m, but there was a decrease in DLCO after cycling at a simulated altitude of 3000 m (40.6 ± 10.8 vs. 36.8 ± 11.2 mL·min−1·mmHg−1; p = 0.044; d = 0.341). A training camp at moderate altitude did not alter pulmonary diffusing capacity in elite swimmers, although a cycling session at a higher simulated altitude caused a certain degree of impairment of the alveolar-capillary gas exchange

Welfare and Output in third-degree price discrimination: A note

One main result about the welfare effects of third-degree price discrimination by a monopolist is that an increase in total output is a necessary condition for welfare improvement. This note provides two examples showing that this proposition cannot be generalized to an oligopoly with heterogenous firms. In these examples, price discrimination makes competition more favorable to the low cost firm. This fact induces a cost saving that overcome the welfare loss from consumer misallocations associated to price discrimination

Investigation of low latitude scintillations in Brazil within the cigala project

Ionospheric scintillations are fluctuations in the phase and amplitude of the signals from GNSS satellites occurring when they cross regions of electron density irregularities in the ionosphere. Such disturbances can cause serious degradation on GNSS system performance, including integrity, accuracy and availability. The two indices internationally adopted to characterize ionospheric scintillations are: the amplitude scintillation index, S4, which is the standard deviation of the received power normalized by its mean value, and the phase scintillation index, σΦ, which is the standard deviation of the de-trended carrier phase. At low latitudes scintillations occur very frequently and can be intense. This is because the low latitudes show a characteristic feature of the plasma density, known as the equatorial anomaly, EA, for which a plasma density enhancement is produced and seen as crests on either side of the magnetic equator. It is a region in which the electron density is considerably high and inhomogeneous, producing ionospheric irregularities causing scintillations. The upcoming solar maximum, which is expected to reach its peak around May 2013, occurs at a time when our reliance on high-precision GNSS (such as GPS, GLONASS and the forthcoming GALILEO) has reached unprecedented proportions. Understanding and monitoring of scintillations are essential, so that warnings and forecast information can be made available to GNSS end users, either for global system or local augmentation network administrators in order to guarantee the necessary levels of accuracy, integrity and availability of high precision and/or safety-of-life applications. Especially when facing severe geospatial perturbations, receiver-level mitigations are also needed to minimize adverse effects on satellite signals tracking availability and accuracy. In this context, the challenge of the CIGALA (Concept for Ionospheric scintillation mitiGAtion for professional GNSS in Latin America) project, co-funded by the European GNSS Agency (GSA) through the European 7th Framework Program, is to understand the causes of ionospheric disturbances and model their effects in order to develop novel counter-measure techniques to be implemented in professional multi-frequency GNSS receivers. This paper describes the scientific advancements made within the project to understand and characterize ionospheric scintillation in Brazil by means of historical and new datasets

Generation of a human iPSC line from a patient with Leigh syndrome

Human iPSC line LND554SV.3 was generated from heteroplasmic fibroblasts of a patient with Leigh syndrome carrying a mutation in the MT-ND5 gene (m.13513G. >. A; p.D393N). Reprogramming factors Oct3/4, Sox2, Klf4, and cMyc were delivered using a non-integrative methodology that involves the use of Sendai virus.This work was supported by grants from the “Centro de Investigación Biomédica en Red en Enfermedades Raras” (CIBERER) (grant 13-717/132.05 to RG), the “Instituto de Salud Carlos III” [Fondo de Investigación Sanitaria and Regional Development Fund (ERDF/FEDER) funds PI10/0703 and PI13/00556 to RG and PI15/00484 to MEG], “Comunidad Autónoma de Madrid” (grant number S2010/BMD-2402 to RG); TG receives grant support from the Universidad Autónoma de Madrid (FPI-UAM) and FZD from the Ministerio de Educación, Cultura y Deporte (FPU13/00544). MEG is a staff scientist at the “Centro de Investigación Biomédica en Red en Enfermedades Raras” (CIBERER) at the “Centro de Investigación Biomédica en Red en Enfermedades Raras” (CIBERER)

Generation of a human control iPSC line with a European mitochondrial haplogroup U background

Human iPSC line N44SV.5 was generated from primary normal human dermal fibroblasts belonging to the European mitochondrial haplogroup U. For this purpose, reprogramming factors Oct3/4, Sox2, Klf4, and cMyc were delivered using a non-integrative methodology that involves the use of Sendai virus.This work was supported by grants from the “Centro de Investigación Biomédica en Red en enfermedades raras” (CIBERER) (grant 13-717/132.05 to RG), the “Instituto de Salud Carlos III” [Fondo de Investigación Sanitaria and Regional Development Fund (ERDF/FEDER) funds PI10/0703 and PI13/00556 to RG and PI15/00484 to MEG], “Comunidad Autónoma de Madrid” (grant number S2010/BMD-2402 to R.G); T.G. receives grant support from the Universidad Autónoma de Madrid, FPI-UAM and F.Z.D. from the Ministerio de Educación, Cultura y Deporte, grant number FPU13/00544. M.E.G. is staff scientist at the “Centro de Investigación Biomédica en Red en Enfermedades Raras” (CIBERER

Generation of a human iPSC line from a patient with a mitochondrial encephalopathy due to mutations in the GFM1 gene

Human iPSC line GFM1SV.25 was generated from fibroblasts of a child with a severe mitochondrial encephalopathy associated with mutations in the GFM1 gene, encoding the mitochondrial translation elongation factor G1. Reprogramming factors OCT3/4, SOX2, CMYC and KLF4 were delivered using a non integrative methodology that involves the use of Sendai virus.This work was supported by grants from the “Centro de Investigación Biomédica en Red en enfermedades raras” (CIBERER) (Grant 13-717/132.05 to RG), the “Instituto de Salud Carlos III” [Fondo de Investigación Sanitaria and Regional development fund (ERDF/FEDER) funds PI10/0703 and PI13/00556 to RG and PI15/00484 to MEG], “Comunidad Autónoma de Madrid” (Grant number S2010/BMD-2402 to RG); TG receives grant support from the Universidad Autónoma de Madrid (FPI-UAM) and FZD from the Ministerio de Educación, Cultura y Deporte (Grant FPU13/00544). MEG is staff scientist at the “Centro de Investigación Biomédica en Red en Enfermedades Raras” (CIBERER

Generation of a human iPSC line from a patient with a defect of intergenomic communication

Human iPSC line PG64SV.2 was generated from fibroblasts of a patient with a defect of intergenomic communication. This patient harbored a homozygous mutation (c.2243G>C; p.Trp748Ser) in the gene encoding the catalytic subunit of the mitochondrial DNA polymerase gamma gene (POLG). Reprogramming factors Oct3/4, Sox2, Klf4, and cMyc were delivered using a non integrative methodology that involves the use of Sendai virus.This work was supported by grants from the “Centro de Investigación Biomédica en Red en enfermedades raras” (CIBERER) (Grant 13-717/132.05 to RG), the “Instituto de Salud Carlos III” [Fondo de Investigación Sanitaria and Regional development fund (ERDF/FEDER) funds PI10/0703 and PI13/00556 to RG and PI15/00484 to MEG], “Comunidad Autónoma de Madrid” (Grant number S2010/BMD-2402 to RG); TG receives grant support from the Universidad Autónoma de Madrid (FPI-UAM) and FZD from the Ministerio de Educación, Cultura y Deporte (Grant FPU13/00544). MEG is staff scientist at the “Centro de Investigación Biomédica en Red en Enfermedades Raras” (CIBERER

Generation of a human iPSC line from a patient with an optic atrophy ‘plus’ phenotype due to a mutation in the OPA1 gene

AbstractHuman iPSC line Oex2054SV.4 was generated from fibroblasts of a patient with an optic atrophy ‘plus’ phenotype associated with a heterozygous mutation in the OPA1 gene. Reprogramming factors OCT3/4, SOX2, CMYC and KLF4 were delivered using a non-integrative methodology that involves the use of Sendai virus