Paleomagnetism, rock magnetism and geochemical aspects of early Cretaceous basalts of the Paraná Magmatic Province, from Misiones, Argentina

The basalts of the Posadas Formation were extruded during the huge continental volcanism that affected the Parana Basin in the Lower Cretaceous. We have carried out a paleomagnetic and rock-magnetic study on samples collected along a basalt outcrop section in Misiones, Argentina and determined that rocks classified as tholeiitic basalts and andesi-basalts are characterized by a low to intermediate content of Ti. Paleomagnetic and rockmagnetic studies suggest that the main magnetic mineral is low-Ti titanomagnetite of superparamagnetic (SP) to single-domain (SD) sizes, and very low amounts of multi-domain (MD) particles. The stable magnetic remanence enabled us to define characteristic remanent magnetizations (ChRMs) with a maximum angular deviation (MAD)<5◦ in most cases; and in all the cases, a MAD <10◦. The sequence has registered at least two polarity reversions, starting from a normal polarity at the base. The calculated virtual geomagnetic poles (VGPs) present an elongated distribution similar to other distributions of VGPs published for the Parana Magmatic Province. The elongated distribution of the VGPs could be a real feature of the geomagnetic field at a time of frequent changes of polarityThe basalts of the Posadas Formation were extruded during the huge continental volcanism that affected the Paran´a Basin in the Lower Cretaceous. We have carried out a paleomagnetic and rock-magnetic study on samplescollected along a basalt outcrop section in Misiones, Argentina and determined that rocks classified as tholeiitic basalts and andesi-basalts are characterized by a low to intermediate content of Ti. Paleomagnetic and rockmagneticstudies suggest that the main magnetic mineral is low-Ti titanomagnetite of superparamagnetic (SP) tosingle-domain (SD) sizes, and very low amounts of multi-domain (MD) particles. The stable magnetic remanence enabled us to define characteristic remanent magnetizations (ChRMs) with a maximum angular deviation (MAD)in most cases. The starting from a normal polarity at the base. The calculated virtual geomagnetic poles (VGPs) present an elongated distribution similar to other distributions of VGPs published for the Paran´a Magmatic Province. The elongated distribution of the VGPs could be a real feature of the geomagnetic field at a time of frequent changes of polarity. The sequence has registered at least two polarity reversions, starting from a normal polarity at the base. The calculated virtual geomagnetic poles (VGPs) present an elongateddistribution similar to other distributions of VGPs published for the Paran´a Magmatic Province. The elongated distribution of the VGPs could be a real feature of the geomagnetic field at a time of frequent changes of polarity.Fil: Orgeira, Maria Julia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Mena, Mabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Lagorio, Silvia Leonor. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; Argentin

Rileggere Primo Levi ad ora incerta

Il libro di poesia Ad ora incerta di Primo Levi, pubblicato nel 1984, continua ad essere ancora oggi un capolavoro isolato dentro della sua opera. La poesia è stata per Primo Levi un vero e proprio bisogno, annche se la sua vita è stata dedicata alla scienza più che alla letteratura e dominata da una memoria ineluttabile. Ho aggiunto alla riflessione e commenti sulla poesia di Levi il ricordo di alcuni dei momenti della nostra amicizia.The book of poetry Ad ora incerta (At un uncertain hour) by Primo Levi, published in 1984, still remains an isolated highpoint in his works. His poetry was an authentic necessity to him even though his life was devoted to science more than to literature and dominated by un unavoidable memory. I have added an account of some of the moments from our friendship to my thoughts and comments on his poetic work

Crossover from weak to strong disorder regime in the duration of epidemics

We study the Susceptible-Infected-Recovered model in complex networks, considering that not all individuals in the population interact in the same way between them. This heterogeneity between contacts is modeled by a continuous disorder. In our model the disorder represents the contact time or the closeness between individuals. We find that the duration time of an epidemic has a crossover with the system size, from a power law regime to a logarithmic regime depending on the transmissibility related to the strength of the disorder. Using percolation theory, we find that the duration of the epidemic scales as the average length of the branches of the infection. Our theoretical findings, supported by simulations, explains the crossover between the two regimes

Understanding critical factors in gender recognition

Gender classification is a task of paramount importance in face recognition research, and it is potentially useful in a large set of applications. In this paper we investigate the gender classification problem by an extended empirical analysis on the Face Recognition Grand Challenge version 2.0 dataset (FRGC2.0). We propose challenging experimental protocols over the dimensions of FRGC2.0 – i.e., subject, face expression, race, controlled or uncontrolled environment. We evaluate our protocols with respect to several classification algorithms, and processing different types of features, like Gabor and LBP. Our results show that gender classification is independent from factors like the race of the subject, face expressions, and variations of controlled illumination conditions. We also report that Gabor features seem to be more robust than LBPs in the case of uncontrolled environment

On the use of SIFT features for face authentication

Several pattern recognition and classification techniques have been applied to the biometrics domain. Among them, an interesting technique is the Scale Invariant Feature Transform (SIFT), originally devised for object recognition. Even if SIFT features have emerged as a very powerful image descriptors, their employment in face analysis context has never been systematically investigated. This paper investigates the application of the SIFT approach in the context of face authentication. In order to determine the real potential and applicability of the method, different matching schemes are proposed and tested using the BANCA database and protocol, showing promising results

Reviewing the relevance of fluorescence in biological systems

Fluorescence is emitted by diverse living organisms. The analysis and interpretation of these signals may give information about their physiological state, ways of communication among species and presence of specific chemicals. In this manuscript we review the state of the art in the research on the fluorescence emitted by plant leaves, fruits, flowers, avian, butterflies, beetles, dragonflies, millipedes, cockroaches, bees, spiders, scorpions and sea organisms and discuss its relevance in nature.Fil: Lagorio, María Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de Los Materiales, Medioambiente y Energía; ArgentinaFil: Cordon, Gabriela Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas A la Agricultura; ArgentinaFil: Iriel, Analia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Unidad Ejecutora de Investigaciones En Produccion Animal; Argentin

Update on women in physics in Argentina

Data collected 10 years ago in Argentina concluded that women in physics were underrepresented in many instances and that a “crystal ceiling” was firmly in place. We have collected updated data for several indicators and compared them with those obtained 10 years ago. Although there is not a clear conclusion to be drawn from this comparison, we try to explain the results within the framework of the changes in scientific policies in Argentina.Fil: Brudny, Vera Leonor. Universidad de Buenos Aires. Departamento de Ciencias Exactas; ArgentinaFil: Lagorio, Cecilia. Universidad Nacional de Mar del Plata; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigaciones Físicas de Mar del Plata; ArgentinaFil: Frechero, Marisa Alejandra. Universidad Nacional del Sur. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto de Química del Sur; ArgentinaFil: Tamarit, Francisco. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto de Física "Enrique Gaviola"; Argentin

Quarantine generated phase transition in epidemic spreading

We study the critical effect of quarantine on the propagation of epidemics on an adaptive network of social contacts. For this purpose, we analyze the susceptible-infected-recovered (SIR) model in the presence of quarantine, where susceptible individuals protect themselves by disconnecting their links to infected neighbors with probability w, and reconnecting them to other susceptible individuals chosen at random. Starting from a single infected individual, we show by an analytical approach and simulations that there is a phase transition at a critical rewiring (quarantine) threshold w_c separating a phase (w<w_c) where the disease reaches a large fraction of the population, from a phase (w >= w_c) where the disease does not spread out. We find that in our model the topology of the network strongly affects the size of the propagation, and that w_c increases with the mean degree and heterogeneity of the network. We also find that w_c is reduced if we perform a preferential rewiring, in which the rewiring probability is proportional to the degree of infected nodes.Comment: 13 pages, 6 figure

A very low power and low signal 5 bit 50 M samples/s double sampling pipelined ADC for Monolithic Active Pixel Sensors in high energy physics and biomedical imaging applications

International audienc

A low power and low signal 5-bit 25MS/s pipelined ADC for monolithic active pixel sensors

For CMOS monolithic active pixels sensor readout, we developed a 5 bit low power analog to digital converter using a pipelined architecture. A non-resetting sample and hold stage is included to amplify the signal by a factor of 4. Due to the very low level of the incoming signal, this first stage compensates both the amplifier offset effect and the input common mode voltage dispersion. The converter consists of three 1.5 bit sub-ADC and a 2 bit flash. We present the results of a prototype, made of eight ADC channels. The maximum sampling rate is 25MS/s. The total DC power consumption is 1.7mW/channel on a 3.3V supply voltage recommended for the process. But at a reduced 2.5V supply, it consumes only 1.3mW. The size of each ADC channel layout is only 43μm*1.43mm. This corresponds to the pitch of two pixel columns each one would be 20μm wide. The full analog part of the converter can be quickly switched to a standby idle mode in less than 1μs; thus reducing the power dissipation to a ratio better than 1/1000. This fast shutdown is very important for the ILC vertex detector as the total DC power dissipation becomes directly proportional to the low beam duty cycle