Exploring the origin of ice-filled craters in the north polar region of Mars

We investigate the origins of enigmatic ice-filled craters in the north polar region of Mars. We test several explanations for their origin, namely: (1) as polar cap remnants (2) accumulation independently of the polar cap, and (3) upwelling of subsurface water, analogous to either aufice or pingo formation on Earth. Each of these hypotheses has a significant impact on our understanding of Mars’ recent geological and climatic history and the behaviour of water and water ice at high latitudes. We used several lines of evidence to assess the most likely formation mechanism. We first performed a crater survey based on THEMIS visual data and MOLA elevation data to identify any craters that had domal central lumps which were different from normal central peaks. From this survey we identified 17 craters for further study. These include Louth, Korolev, Dokka and other unnamed craters. Using data from orbiting spectrometers; OMEGA on ESA’s Mars Express and CRISM on NASA’s Mars Reconnaissance Orbiter; we verified that the composition of the exposed central domes was predominantly water ice. We found the domes fell into three groups: (1) those completely covered by dunes, (2) those partially covered by dunes and (3) those with no dunes. We investigated the morphology and the relative position of the domes using MOLA elevation data. We found that the domes are always asymmetrically placed within the craters. However, this asymmetry could not easily be linked to wind directions as revealed by dune slip-faces [2]. The domes often have a moat-like structure and in some cases do not cover the entire crater floor, e.g. Louth Crater. From image data, we identified six craters which possessed internal stratigraphy, in the form of regularly spaced layers, and of these we have inspected three in detail. We found that the layers possess both strong sinuosity and high angle unconformities. We interpret the internal stratigraphy as representing a sequence of regular cyclic accumulations, which produced the layers, followed by asymmetric ablation and subsequent resumption of accumulation, to produce the unconformities. Hence, the present-day shape of the domes indicates that they are in a phase of ablation.We attribute the colour contrasts between layers to different levels of dust, or particulate content. This could form a source for the dunes, which are often located on the summits of these domes. We find that this sequence is best explained by a model of atmospheric condensation. Our measurements of internal layer spacing and observations of layer stratigraphy argues that these deposits are not linked directly to a former, more extensive polar cap

Restoration of variable density film soundtracks

Full text available at http://www.eurasip.org/Proceedings/Eusipco/Eusipco2009/contents/papers/1569192297.pdfInternational audienceThe restoration of motion picture films has been an active research field for many years. The restoration of the soundtrack however has mainly been performed at the audio domain in spite of the fast that it is recorded as a continuous image on the film stock. In this paper, we propose a new restoration method for variable density soundtracks. The method first detects and corrects accurately the azimuth deviation. A robust thresholding technique based on the minimization of the total variation is then performed to remove the remaining faults. Restoration results are very promising and testify to the efficiency of our method

Tumor Volume Distributions Based on Weibull Distributions of Maximum Tumor Diameters

(1) Background: The distribution of tumor volumes is important for various aspects of cancer research. Unfortunately, tumor volume is rarely documented in tumor registries; usually only maximum tumor diameter is. This paper presents a method to derive tumor volume distributions from tumor diameter distributions. (2) Methods: The hypothesis is made that tumor maximum diameters d are Weibull distributed, and tumor volume is proportional to dk, where k is a parameter from the Weibull distribution of d. The assumption is tested by using a test dataset of 176 segmented tumor volumes and comparing the k obtained by fitting the Weibull distribution of d and from a direct fit of the volumes. Finally, tumor volume distributions are calculated from the maximum diameters of the SEER database for breast, NSCLC and liver. (3) Results: For the test dataset, the k values obtained from the two separate methods were found to be k = 2.14 ± 0.36 (from Weibull distribution of d) and 2.21 ± 0.25 (from tumor volume). The tumor diameter data from the SEER database were fitted to a Weibull distribution, and the resulting parameters were used to calculate the corresponding exponential tumor volume distributions with an average volume obtained from the diameter fit. (4) Conclusions: The agreement of the fitted k using independent data supports the presented methodology to obtain tumor volume distributions. The method can be used to obtain tumor volume distributions when only maximum tumor diameters are available

Transnational studies twenty years later: a story of encounters and dis-encounters

This article supports the argument that the researches on transnationalism and cultural studies had moments of confrontation and that, in these discussions, they influenced each other positively. I will try to expose this relationship from my own anthropological experience. The work concludes with a concern about the way in which the emergence of transnational actors is forming part of a new hegemonic formula for the functioning of political economy. Therefore, I will argue that the discussion in the researches on transnationalism and on the cultural studies should help to build a critical theory of the current moment, for which I propose five lines of work.Neste artigo se sustenta o argumento de que as pesquisas sobre o transnacionalismo e os estudos culturais tiveram momentos de confrontação e que, nestas discussões, se influenciaram mutuamente de maneira positiva. Tratarei de expor esta relação desde minha própria experiência vinculada à antropologia. O trabalho conclui com uma preocupação sobre a maneira como o surgimento de atores transnacionais está formando parte de uma nova fórmula hegemônica de funcionamento da economia e da política. Por isto, defenderei a importância de que a discussão nas pesquisas sobre o transnacionalismo e nos estudos culturais ajude na construção de uma teoria crítica do momento atual, para o qual proponho cinco linhas de trabalho