A geometric model of multi-scale orientation preference maps via Gabor functions

In this paper we present a new model for the generation of orientation preference maps in the primary visual cortex (V1), considering both orientation and scale features. First we undertake to model the functional architecture of V1 by interpreting it as a principal fiber bundle over the 2-dimensional retinal plane by introducing intrinsic variables orientation and scale. The intrinsic variables constitute a fiber on each point of the retinal plane and the set of receptive profiles of simple cells is located on the fiber. Each receptive profile on the fiber is mathematically interpreted as a rotated Gabor function derived from an uncertainty principle. The visual stimulus is lifted in a 4-dimensional space, characterized by coordinate variables, position, orientation and scale, through a linear filtering of the stimulus with Gabor functions. Orientation preference maps are then obtained by mapping the orientation value found from the lifting of a noise stimulus onto the 2-dimensional retinal plane. This corresponds to a Bargmann transform in the reducible representation of the $\text{SE}(2)=\mathbb{R}^2\times S^1$ group. A comparison will be provided with a previous model based on the Bargman transform in the irreducible representation of the $\text{SE}(2)$ group, outlining that the new model is more physiologically motivated. Then we present simulation results related to the construction of the orientation preference map by using Gabor filters with different scales and compare those results to the relevant neurophysiological findings in the literature

A Data-Driven Air Transportation Delay Propagation Model Using Epidemic Process Models

In air transport network management, in addition to defining the performance behavior of the system’s components, identification of their interaction dynamics is a delicate issue in both strategic and tactical decision-making process so as to decide which elements of the system are “controlled” and how. This paper introduces a novel delay propagation model utilizing epidemic spreading process, which enables the definition of novel performance indicators and interaction rates of the elements of the air transportation network. In order to understand the behavior of the delay propagation over the network at different levels, we have constructed two different data-driven epidemic models approximating the dynamics of the system: (a) flight-based epidemic model and (b) airport-based epidemic model. The flight-based epidemic model utilizing SIS epidemic model focuses on the individual flights where each flight can be in susceptible or infected states. The airport-centric epidemic model, in addition to the flight-to-flight interactions, allows us to define the collective behavior of the airports, which are modeled as metapopulations. In network model construction, we have utilized historical flight-track data of Europe and performed analysis for certain days involving certain disturbances. Through this effort, we have validated the proposed delay propagation models under disruptive events

Effects of egg weight and length of storage on hatchability and subsequent growth performance of quail

This study was to investigate the effects of hatching egg weight and length of storage period on hatchability and subsequent growth performance of quail. A total of 2304 eggs was collected from a quail flock, aged 17 weeks. The eggs were divided into four groups on the basis of storage periods of 1, 3, 5 or 7 days. Prior to egg storage, the eggs in each group were classified according to egg weight, as small: 12.51 g. Hatchability of total and of fertile eggs increased significantly with an increase in egg weight but was not affected by duration of egg storage. There were no significant effects of egg storage period on body weight and feed conversion ratio of the progeny at six weeks of age. The average body weight of the quail produced from heavier eggs (large and jumbo) was significantly higher than those from the smaller eggs. It is recommended that the storage period should be no longer than 3 days. Eggs heavier than 11.50 g were found to be the most suitable for successful hatching and subsequent growth performance. Keywords: Quail, Egg weight, Storage period, Hatchability, Growth performance South African Journal of Animal Science Vol.33(4) 2003: 242-24

A sub-Riemannian model of the visual cortex with frequency and phase

In this paper we present a novel model of the primary visual cortex (V1) based on orientation, frequency and phase selective behavior of the V1 simple cells. We start from the first level mechanisms of visual perception: receptive profiles. The model interprets V1 as a fiber bundle over the 2-dimensional retinal plane by introducing orientation, frequency and phase as intrinsic variables. Each receptive profile on the fiber is mathematically interpreted as a rotated, frequency modulated and phase shifted Gabor function. We start from the Gabor function and show that it induces in a natural way the model geometry and the associated horizontal connectivity modeling the neural connectivity patterns in V1. We provide an image enhancement algorithm employing the model framework. The algorithm is capable of exploiting not only orientation but also frequency and phase information existing intrinsically in a 2-dimensional input image. We provide the experimental results corresponding to the enhancement algorithm

Damping properties of open pore aluminum foams produced by vacuum casting and NaCl dissolution process

In this study,damping ratios of 3 samples made of aluminum foam material, which have different-density pores, were calculated, the effects pore density on damping were examined. Experimental modal analysis method was used for examining of the effects of the pore density on damping. In experimental modal analysis method, frequency charts were obtained by driving to the sample with a hammer. Through these frequency charts, damping ratios of each 3 samples were calculated with ME’scope VES program. It was observed in calculated damping ratios that pore density has influences on damping; thus, damping accordingly increases as the number of pores increases. It is seen that critical damping constant decreases as the material structure changes in terms of volume and density

Damping properties of open pore aluminum foams produced by vacuum casting and NaCl dissolution process

In this study,damping ratios of 3 samples made of aluminum foam material, which have different-density pores, were calculated, the effects pore density on damping were examined. Experimental modal analysis method was used for examining of the effects of the pore density on damping. In experimental modal analysis method, frequency charts were obtained by driving to the sample with a hammer. Through these frequency charts, damping ratios of each 3 samples were calculated with ME’scope VES program. It was observed in calculated damping ratios that pore density has influences on damping; thus, damping accordingly increases as the number of pores increases. It is seen that critical damping constant decreases as the material structure changes in terms of volume and density

The use of short-term analysis of heart rate variability to assess autonomic function in obese children and its relationship with metabolic syndrome

Background: The cardiovascular autonomic nervous system in obese children is one of the main initiators of coronary heart disease and hypertension and may have a close relationship with insulin resistance. Heart rate variability is one non-invasive method to assess the cardiovascular autonomic system. In this method, low frequency parameters reflect sympathovagal activity, high frequency parameters reflect vagal activity and the ratio of these parameters reflects sympathovagal balance. Methods: In this study, a short-term analysis of heart rate variability was conducted in 66 obese children and 40 healthy controls. Results: While high frequency parameter values are lower in the obese group compared to the controls (16.02 &#177; 12.9 nu vs. 21.45 &#177; 13.6 nu, p = 0.046), the low frequency/high frequency ratio is found significantly higher (3.79 &#177; 2.34 vs. 2.25 &#177; 0.93, p < 0.001). A significant difference was not detected for the low frequency values (p = 0.787). Insulin resistance was found in 33 (50%) patients, dyslipidemia was found in 39 (59%) and hypertension was found in 18 (27%). Metabolic syndrome was detected in 39% patients in the obese group. Conclusions: We found that vagal activity was decreased in the obese group and the autonomic nervous system balance was impaired in favor of sympathetic activity in the short-term heart rate analysis. (Cardiol J 2012; 19, 5: 501-506

Investigating 5- to 9-Year-Old Children's Descriptions of Routine Tasks

Scripts provide insight into children's organization and perception of events (Reifel & Garza, 1983) and their understanding of relational terms (French, 1983). Previous work found that children are providing scripts at a young age, but five-year-old children still have difficulty sequencing actions (Verrier, 2000). Thus, this study investigates five- to nine-year-old children's descriptions of routine tasks to better understand children's script mastery and script organization. Sixty children and twelve adults looked at pictures of someone brushing their teeth and washing their hands to describe how they would perform these tasks. Adults provided standardized descriptions. Responses were coded for the number and type of steps provided as well as for the temporal terms included. Results found no age-related differences between the child groups, but adults included significantly more steps than the children. Also, contrary to the adults, children showed an interaction between the event type and step categories. Furthermore, participants used the temporal term then most frequently, and opportunities to use then were taken most at the transition points between step categories. Findings suggest that children structure their scripts similarly to adults but still do not include as many details. Also, participants identify distinct transition points within scripts and label them with the temporal term then. These findings are valuable because they may potentially contribute to research surrounding narratives and learning disabilities.Undergraduate Research Scholarship from the College of Arts and Sciences Honors CommitteeNational Science FoundationNo embargoAcademic Major: Speech and Hearing Scienc

Coherence resonance in neuronal populations: mean-field versus network model

The counter-intuitive phenomenon of coherence resonance describes a non-monotonic behavior of the regularity of noise-induced oscillations in the excitable regime, leading to an optimal response in terms of regularity of the excited oscillations for an intermediate noise intensity. We study this phenomenon in populations of FitzHugh-Nagumo (FHN) neurons with different coupling architectures. For networks of FHN systems in excitable regime, coherence resonance has been previously analyzed numerically. Here we focus on an analytical approach studying the mean-field limits of the locally and globally coupled populations. The mean-field limit refers to the averaged behavior of a complex network as the number of elements goes to infinity. We derive a mean-field limit approximating the locally coupled FHN network with low noise intensities. Further, we apply mean-field approach to the globally coupled FHN network. We compare the results of the mean-field and network frameworks for coherence resonance and find a good agreement in the globally coupled case, where the correspondence between the two approaches is sufficiently good to capture the emergence of anticoherence resonance. Finally, we study the effects of the coupling strength and noise intensity on coherence resonance for both the network and the mean-field model.Comment: 31 pages, 11 figure