Recording from two neurons: second order stimulus reconstruction from spike trains and population coding

We study the reconstruction of visual stimuli from spike trains, recording simultaneously from the two H1 neurons located in the lobula plate of the fly Chrysomya megacephala. The fly views two types of stimuli, corresponding to rotational and translational displacements. If the reconstructed stimulus is to be represented by a Volterra series and correlations between spikes are to be taken into account, first order expansions are insufficient and we have to go to second order, at least. In this case higher order correlation functions have to be manipulated, whose size may become prohibitively large. We therefore develop a Gaussian-like representation for fourth order correlation functions, which works exceedingly well in the case of the fly. The reconstructions using this Gaussian-like representation are very similar to the reconstructions using the experimental correlation functions. The overall contribution to rotational stimulus reconstruction of the second order kernels - measured by a chi-squared averaged over the whole experiment - is only about 8% of the first order contribution. Yet if we introduce an instant-dependent chi-square to measure the contribution of second order kernels at special events, we observe an up to 100% improvement. As may be expected, for translational stimuli the reconstructions are rather poor. The Gaussian-like representation could be a valuable aid in population coding with large number of neurons

Locating the Source of Diffusion in Large-Scale Networks

How can we localize the source of diffusion in a complex network? Due to the tremendous size of many real networks--such as the Internet or the human social graph--it is usually infeasible to observe the state of all nodes in a network. We show that it is fundamentally possible to estimate the location of the source from measurements collected by sparsely-placed observers. We present a strategy that is optimal for arbitrary trees, achieving maximum probability of correct localization. We describe efficient implementations with complexity O(N^{\alpha}), where \alpha=1 for arbitrary trees, and \alpha=3 for arbitrary graphs. In the context of several case studies, we determine how localization accuracy is affected by various system parameters, including the structure of the network, the density of observers, and the number of observed cascades.Comment: To appear in Physical Review Letters. Includes pre-print of main paper, and supplementary materia

Identificação do processo de disseminação da informação na Embrapa: o uso do Google Docs.

Neste trabalho, apresenta-se o uso do Googledocs, especificamente como um survey, aplicado aos profissionais da informação da Empresa Brasileira de Pesquisa Agropecuária (Embrapa). Foi criado um questionário eletrônico composto de 14 questões com o objetivo de conhecer o processo de comunicação de novos materiais adquiridos pelas 40 bibliotecas existentes na empresa, as quais são coordenadas pelo Sistema Embrapa de Bibliotecas (SEB), o questionário eletrônico foi enviado a todos os bibliotecários responsáveis pelas bibliotecas do Sistema

Evidence for entanglement at high temperatures in an engineered molecular magnet

The molecular compound [Fe$_{2}$($\mu_{2}$-oxo)(C$_{3}$H$_{4}$N$_{2}$)$_{6}$(C$_{2}$O$_{4}$)$_{2}$] was designed and synthesized for the first time and its structure was determined using single-crystal X-ray diffraction. The magnetic susceptibility of this compound was measured from 2 to 300 K. The analysis of the susceptibility data using protocols developed for other spin singlet ground-state systems indicates that the quantum entanglement would remain at temperatures up to 732 K, significantly above the highest entanglement temperature reported to date. The large gap between the ground state and the first-excited state (282 K) suggests that the spin system may be somewhat immune to decohering mechanisms. Our measurements strongly suggest that molecular magnets are promising candidate platforms for quantum information processing

Development of an applicattion to improve traceability and food safety management

Food safety has become an important food quality attribute within the last decade. Facing recent food scandals taken up by the media, consumers are more and more concerned about and interested in the provenance and authenticity of their food. Both food industry and authorities need to be able to trace back and to authenticate food products and raw materials used for food production to comply with legislation and to meet the food safety and food quality requirements as well as the increasing consumer demand. Therefore, food companies are faced with the problem of defining and implementing a series of procedures, controls and measures. Moreover, it is necessary to define an application method which is both rigorous and economically sustainable in order to guarantee the safe production of food and to be able to trace it along the food chain. The application was designed to manage traceability as well as to help in the quality control and production improvement, using an user-friendly interface. This application was developed in Visual Basic over an SQL database and its main features are: to register quality control parameters of raw materials, in-course products and final products; to manage reception, production and expedition orders; to analyse production costs, productivity, raw materials and products’ consumptions; to define and print labels containing lot information and other relevant data; to trace products during the food chain (from raw materials to final client). All these informations are accessible either from pre-defined reports either exported to intranet based on Internet Explorer or other browser. Usually the process to assure traceability, specially in food products (due to the large number of ingredients involved in a single formulation) is very time-consuming, involves lots of paperwork and consequently a large number of resources are expended in this laborious task. This application can minimize efforts involved in traceability and managing food quality and safety systems.Fundação para a Ciência e a Tecnologia (FCT)

The use of TIC’s as a managing tool for traceability in the food industry

Food safety has become an important food quality attribute. Both food industry and authorities need to be able to trace back and to authenticate food products and raw materials used for food production to comply with legislation and to meet the food safety and food quality requirements. PaniGest is a user-friendly computer package designed to manage traceability and help in the quality control and production improvement. This application was developed in Visual Basic language over an SQL database and its main features are: to register quality control parameters of raw materials, in-course products and final products; to manage reception, production and expedition orders; to analyse production costs, productivity, raw materials and products’ consumptions; to trace products during the food chain. It runs on a personal computer over Windows 95/98 or Windows 2000/XP operating system. The program also uses common Internet Browsers to make information available to users.Fundação para a Ciência e a Tecnologia (FCT)

Evidence for a Variable Ultrafast Outflow in the Newly Discovered Ultraluminous Pulsar NGC 300 ULX-1

Ultraluminous pulsars are a definite proof that persistent super-Eddington accretion occurs in nature. They support the scenario according to which most Ultraluminous X-ray Sources (ULXs) are super-Eddington accretors of stellar mass rather than sub-Eddington intermediate mass black holes. An important prediction of theories of supercritical accretion is the existence of powerful outflows of moderately ionized gas at mildly relativistic speeds. In practice, the spectral resolution of X-ray gratings such as RGS onboard XMM-Newton is required to resolve their observational signatures in ULXs. Using RGS, outflows have been discovered in the spectra of 3 ULXs (none of which are currently known to be pulsars). Most recently, the fourth ultraluminous pulsar was discovered in NGC 300. Here we report detection of an ultrafast outflow (UFO) in the X-ray spectrum of the object, with a significance of more than 3{\sigma}, during one of the two simultaneous observations of the source by XMM-Newton and NuSTAR in December 2016. The outflow has a projected velocity of 65000 km/s (0.22c) and a high ionisation factor with a log value of 3.9. This is the first direct evidence for a UFO in a neutron star ULX and also the first time that this its evidence in a ULX spectrum is seen in both soft and hard X-ray data simultaneously. We find no evidence of the UFO during the other observation of the object, which could be explained by either clumpy nature of the absorber or a slight change in our viewing angle of the accretion flow.Comment: 10 pages, 4 figures. Accepted to MNRA

Testing the Relation Between the Local and Cosmic Star Formation Histories

Recently, there has been great progress toward observationally determining the mean star formation history of the universe. When accurately known, the cosmic star formation rate could provide much information about Galactic evolution, if the Milky Way's star formation rate is representative of the average cosmic star formation history. A simple hypothesis is that our local star formation rate is proportional to the cosmic mean. In addition, to specify a star formation history, one must also adopt an initial mass function (IMF); typically it is assumed that the IMF is a smooth function which is constant in time. We show how to test directly the compatibility of all these assumptions, by making use of the local (solar neighborhood) star formation record encoded in the present-day stellar mass function. Present data suggests that at least one of the following is false: (1) the local IMF is constant in time; (2) the local IMF is a smooth (unimodal) function; and/or (3) star formation in the Galactic disk was representative of the cosmic mean. We briefly discuss how to determine which of these assumptions fail, and improvements in observations which will sharpen this test.Comment: 14 pages in LaTeX (uses aaspp4.sty). 5 postscript figures. To appear in the Astrophysical Journa