Odor-driven attractor dynamics in the antennal lobe allow for simple and rapid olfactory pattern classification

The antennal lobe plays a central role for odor processing in insects, as demonstrated by electrophysiological and imaging experiments. Here we analyze the detailed temporal evolution of glomerular activity patterns in the antennal lobe of honeybees. We represent these spatiotemporal patterns as trajectories in a multidimensional space, where each dimension accounts for the activity of one glomerulus. Our data show that the trajectories reach odor-specific steady states (attractors) that correspond to stable activity patterns at about 1 second after stimulus onset. As revealed by a detailed mathematical investigation, the trajectories are characterized by different phases: response onset, steady-state plateau, response offset, and periods of spontaneous activity. An analysis based on support-vector machines quantifies the odor specificity of the attractors and the optimal time needed for odor discrimination. The results support the hypothesis of a spatial olfactory code in the antennal lobe and suggest a perceptron-like readout mechanism that is biologically implemented in a downstream network, such as the mushroom body

Sensory memory for odors is encoded in spontaneous correlated activity between olfactory glomeruli

Sensory memory is a short-lived persistence of a sensory stimulus in the nervous system, such as iconic memory in the visual system. However, little is known about the mechanisms underlying olfactory sensory memory. We have therefore analyzed the effect of odor stimuli on the first odor-processing network in the honeybee brain, the antennal lobe, which corresponds to the vertebrate olfactory bulb. We stained output neurons with a calcium-sensitive dye and measured across-glomerular patterns of spontaneous activity before and after a stimulus. Such a single-odor presentation changed the relative timing of spontaneous activity across glomeruli in accordance with Hebb's theory of learning. Moreover, during the first few minutes after odor presentation, correlations between the spontaneous activity fluctuations suffice to reconstruct the stimulus. As spontaneous activity is ubiquitous in the brain, modifiable fluctuations could provide an ideal substrate for Hebbian reverberations and sensory memory in other neural systems

Nonequilibrium chiral perturbation theory and pion decay functions

We extend chiral perturbation theory to study a meson gas out of thermal equilibrium. Assuming that the system is initially in equilibrium at T-i < T-c and working within the Schwinger-Keldysh contour technique, we define consistently the time-dependent temporal and spatial pion decay functions, the counterparts of the pion decay constants, and calculate them to next to leading order. The link with curved space-time QFT allows to establish nonequilibrium renormalisation. The short-time behaviour and the applicability of our model to a heavy-ion collision plasma are also discussed in this work

Improving classification for brain computer interfaces using transitions and a moving window

Proceeding of: Biosignals 2009. International Conference on Bio-inspired Systems and Signal Processing, BIOSTEC 2009. Porto (Portugal), 14-17 January 2009The context of this paper is the brain-computer interface (BCI), and in particular the classification of signals with machine learning methods. In this paper we intend to improve classification accuracy by taking advantage of a feature of BCIs: instances run in sequences belonging to the same class. In that case, the classiffication problem can be reformulated into two subproblems: detecting class transitions and determining the class for sequences of instances between transitions. We detect a transition when the Euclidean distance between the power spectra at two different times is larger than a threshold. To tackle the second problem, instances are classified by taking into account, not just the prediction for that instance, but a moving window of predictions for previous instances. Experimental results show that our transition detection method improves results for datasets of two out of three subjects of the BCI III competition. If the moving window is used, classification accuracy is further improved, depending on the window size.Publicad

The impact of body image on the WTP values for reduced-fat and low-salt content potato chips among obese and non-obese consumers

The aim of this study is to assess the influence of body image on consumers’ willingness to pay (WTP) for potato chips carrying nutritional claims among obese and non-obese people. About 309 and grouped in: (i) non-obese with good body image; (ii) non-obese with body image dissatisfaction; and grouped in: (i) non-obese with good body image; (ii) non-obese with body image dissatisfaction; (iii) obese with good body image; (iv) obese with body image dissatisfaction. Results indicate differences in consumers’ willingness to pay among consumer groups. Body image dissatisfaction of normal people did not influence the WTP for healthier chips. Obese people with body image dissatisfaction were willing to pay more for healthier chips (i.e., low-salt content potato chips) than normal ones with body image dissatisfaction. Examining the role of knowledge in the light of how this could impact on body image is relevant to improve the health status of individuals and their diet. Knowledge about nutrition could improve the body image of obese people

Tiazol: Fragmento polifacético en el estudio y modulación de las propiedades ópticas no lineales (ONL)

A lo largo de esta Tesis Doctoral se ha explorado el comportamiento de sistemas D-pi-A derivados de tiazol: En el Capítulo 2 se ha estudiado cómo influye la orientación del anillo de tiazol formando parte del espaciador de sistemas push-pull. Contrariamente a lo que se venía afirmando en la bibliografía, en base a los pocos estudios existentes hasta el momento, al analizar nuestras nuevas moléculas tanto de forma teórica como experimental, podemos concluir que no siempre se cumple que el derivado matched presenta propiedades ópticas no lineales de segundo orden superiores al análogo mismatched, sino que en general son similares y que la regioisomería del tiazol tiene un papel menos importante que los grupos dador y aceptor a la hora de optimizar la respuesta ONL. En el Capítulo 3 se ha analizado la gran capacidad aceptora que presenta la unidad de 4-fenil-2-dicianometiltiazol cuando se encuentra conectada con un dador proaromático. Adicionalmente, se ha observado cómo el carácter dipolar de moléculas derivadas de 4-fenil-2-dicianometiltiazol va aumentando considerablemente a medida que aumenta la proaromaticidad del dador usado (llegando a recorrer las 5 regiones de la curva de Marder), obteniéndose sistemas: i) predominantemente neutros con dadores aromáticos (dietilaminofenilo); ii) de tipo cianina con dadores moderadamente proaromáticos (1,3-ditiol-2-ilideno); iii) con gran carácter zwitteriónico con dadores fuertemente proaromáticos (benzotiazolilideno, 4-piridilideno o 4H-piranilideno). En el Capítulo 4 se ha estudiado la reacción de cicloadición [2+2] entre 4-etinil-N,N-dimetilanilina, y nuevos sistemas poliénicos D-pi-A (que pueden ser considerados como ¿alquenos confusos¿). Se ha comprobado que dicha reacción tiene lugar sobre el doble enlace situado más próximo al extremo dador de sistemas D-pi-A. Usando esta metodología podemos partiendo de un compuesto D-pi-A plano, obtener un análogo con un doble enlace y un anillo de DMA adicionales, encontrándose dicho anillo fuera del plano molecular. El interés que presenta esta aproximación recae en que el anillo adicional de DMA actúa aumentando la polaridad de los sistemas (respecto a un sistema igual, sin dicho fragmento) y resulta especialmente útil para sistemas situados en la zona C, D de la curva de Marder (nuevos sistemas derivados de pirano sintetizados en el Capítulo 3), ya que en éstos el aumento de polaridad lleva asociado un incremento de la actividad óptica no lineal de segundo orden

P-T conditions of mantle xenoliths from La Banya del Boc and Puig d’Adri volcanoes (Girona)

Several thermometers and one barometer are used in order to determine the P-T conditions of type I xenoliths enclosed in alkaline mafic lavas from the Catalan Neogene-Quaternary volcanism. Average temperatures from the different thermometers are similar and higher in harzburgites (1106- 1036º C) than in lherzolites (1043- 867º C), and one pyroxenite shows similar T to harzburgites (1078º C). Low standard deviation for the T estimates reflects equilibrium in most samples for the thermometric reactions. Pressure estimates show high uncertainty, except for few samples, the pyroxenite included, which give consistent values (15.0- 9.6 kbar) within the spinel lherzolite fiel

Novel types of anti-ecloud surfaces

In high power RF devices for space, secondary electron emission appears as the main parameter governing the multipactor effect and as well as the e-cloud in large accelerators. Critical experimental activities included development of coatings with low secondary electron emission yield (SEY) for steel (large accelerators) and aluminium (space applications). Coatings with surface roughness of high aspect ratio producing the so-call secondary emission suppression effect appear as the selected strategy. In this work a detailed study of the SEY of these technological coatings and also the experimental deposition methods (PVD and electrochemical) are presented. The coating-design approach selected for new low SEY coatings include rough metals (Ag, Au, Al), rough alloys (NEG), particulated and magnetized surfaces, and also graphene like coatings. It was found that surface roughness also mitigate the SEY deterioration due to aging processes.Comment: 4 pages, contribution to the Joint INFN-CERN-EuCARD-AccNet Workshop on Electron-Cloud Effects: ECLOUD'12; 5-9 Jun 2012, La Biodola, Isola d'Elba, Italy; CERN Yellow Report CERN-2013-002, pp.153-15

Perturbation expansion for 2-D Hubbard model

We develop an efficient method to calculate the third-order corrections to the self-energy of the hole-doped two-dimensional Hubbard model in space-time representation. Using the Dyson equation we evaluate the renormalized spectral function in various parts of the Brillouin zone and find significant modifications with respect to the second-order theory even for rather small values of the coupling constant U. The spectral function becomes unphysical for $U \simeq W$, where W is the half-width of the conduction band. Close to the Fermi surface and for U<W, the single-particle spectral weight is reduced in a finite energy interval around the Fermi energy. The increase of U opens a gap between the occupied and unoccupied parts of the spectral function.Comment: 17 pages, 11 Postscript figures, Phys. Rev. B, accepte

EFECTIVIDAD DEL TRATAMIENTO DEL SÍNDROME NEFRÓTICO CORTICORRESISTENTE EN PEDIATRÍA

El síndrome nefrótico idiopático es muy frecuente en niños, su evolución está determinada por la respuesta al tratamiento con corticoides y variedad histológica, pero existe un 15% - 27% son Síndrome Nefrótico Corticorresistentes (SNCR), en estos casos se utilizan terapias alternativas para lograr la remisión de la proteinuria. En el Hospital Infantil Manuel de Jesús Rivera (HIMJR) de Nicaragua, se aplica, ciclofosfamida + enalapril + prednisona (esquema 1) y ciclosporina A + enalapril + prednisona (esquema 2). Con el objetivo de analizar la efectividad de estos tratamientos y su relación con la variedad histológica, se realizó un estudio en setenta niños diagnosticados en este centro asistencial con el SNCR, en el periodo 2005–2012. El estudio fue descriptivo, observacional, retrospectivo y transversal, encontrándose los siguientes resultados: 57,1% escolares del sexo femenino, el 51,4% glomeruroesclerosis focal segmentaria (GSFS), lesión de cambios mínimos 32,8%, glomerulopatía membranosa 7,2%, membranoproliferativa 4,2% y no concluyente 4,2%. Los setenta pacientes en estudio recibieron el esquema 1, obteniendo remisión completa (RC) el 38,5%; remisión parcial (RP) el 7,1% y 54,2% sin remisión (SR) de la proteinuria, a los diecinueve niños sin remisión se les aplicó el esquema 2, obteniendo RC el 26,3%, RP el 42,1% y 31,5% SR de la proteinuria. En relación a la variedad histológica el 41,1% (14) de GSFS tratados con esquema 1, y el 36,3% (4) con esquema 2 obtuvieron RC. En Nicaragua se recomienda mantener el esquema 1 para tratar el SNCR, se instauran otras alternativas en casos sin remisión