Time filter

Source Type

Berlin, Germany

Jandard F.,Aix - Marseille University | Fauquet C.,Aix - Marseille University | Dehlinger M.,Aix - Marseille University | Ranguis A.,Aix - Marseille University | And 5 more authors.
Applied Surface Science

In this work we show the feasibility of simultaneous topographic and luminescence mapping with an home-built Shear-Force Microscope under X-ray irradiation with a tabletop microfocused X-ray source (maximum electric power of 30 W). A commercial fluorescent screen, containing europium uranyl compounds, is used as test sample. Simultaneous topography and luminescence maps on the fluorescent screen are first obtained with the apparatus. The two images totally overlap, however the luminescence is not homogeneous on the whole scanned area. Moreover, a photoluminescence spectrum is presented with a good signal-to-noise ratio under X-ray irradiation on a grain of the fluorescent screen and shows peaks in agreement with Europium uranyl compounds. A ZnO/ZnS powder mixture embedded in PMMA is then studied with the same equipment. A 20 μm-wide grain is clearly visible on the topographic image. With the instrument, the grain could be unambiguously identified as containing mainly ZnO. © 2012 Elsevier B.V. All rights reserved. Source

Gunther R.-M.,IFG GmbH | Salzer K.,IFG GmbH
Mechanical Behavior of Salt VII - Proceedings of the 7th Conference on the Mechanical Behavior of Salt

A powerful constitutive model is presented which describes the complex mechanical behavior of rock salt in a good approximation. The model contains a state variable to characterize the effective material hardening which is growing with ongoing creeping. However, hardening is reduced again by recovery and damage. The viscosity of the creep model depends on the hardening state variable so that the three well known creep phases develop. The measured dilatancy is formulated as a function of a special deformation work and the minimum stress. The identification of dilatancy parameters for the constitutive model is shown. Additionally a new concept for the handling of tensile stresses within a creep model and also a term for damage healing are presented. This model has been verified based on the results of numerous strength and creep tests. The capability of the approach will be demonstrated by the back calculation of special laboratory tests and two field applications. Source

Dehlinger M.,Aix - Marseille University | Fauquet C.,Aix - Marseille University | Lavandier S.,Aix - Marseille University | Aumporn O.,Aix - Marseille University | And 4 more authors.
Nanoscale Research Letters

XRF (X-ray fluorescence) is a powerful technique for elemental analysis with a high sensitivity. The resolution is presently limited by the size of the primary excitation X-ray beam. A test-bed for confocal-type XRF has been developed to estimate the ultimate lateral resolution which could be reached in chemical mapping using this technique. A polycapillary lens is used to tightly focus the primary X-ray beam of a low power rhodium X-ray source, while the fluorescence signal is collected by a SDD detector through a cylindrical monocapillary. This system was used to characterize the geometry of the fluorescent zone. Capillary radii ranging from 50 μm down to 5 μm were used to investigate the fluorescence signal maximum level This study allows to estimate the ultimate resolution which could be reached in-lab or on a synchrotron beamline. A new tool combining local XRF and scanning probe microscopy is finally proposed. © 2013 Dehlinger et al. Source

News Article | November 24, 2015
Site: http://motherboard.vice.com/

In December, representatives from more than 190 countries will come together for a high level meeting at the United Nations to determine the future of the internet. But first, a select few are meeting behind closed doors this week to set the agenda. The December meeting is a planned ten year review of policies for global internet deployment laid out at the World Summit on the Information Society (WSIS) in 2005. Delegates will discuss issues such as the digital divide and internet governance, taking into account input from a variety of non-governmental stakeholders. One of those non-government entities is the Internet Society, a nonprofit that promotes internet freedom and accessibility. CEO Kathryn Brown said a lot of issues are on the table this year, and some internet freedom advocates are concerned governments will use the review to push control of the internet into their hands. “We have been working very hard to ensure the governance of the internet remains as it is, which is in the hands of the private sector; with roles and responsibilities of governments when it is called for, but not a centrally-controlled, top-down control,” she said. It’s not clear which countries will be present at the closed doors meetings. There are four main areas to be discussed at the high-level WSIS meeting in December: internet accessibility, human rights and free speech, internet governance, and internet security. Around 60 percent of the world’s population is still not online, most of which is in extremely inaccessible areas. The UN will discuss how to make the internet available to the most difficult-to-reach users and how those services will be administered and governed. Many countries have already made their views public ahead of the WSIS, with countries such as Russia advocating for more extreme government controls over the internet. The country has also said it advocates transferring power over internet domains and IP addresses from US control to an international organization overseen by the UN. The US has already announced it intends to hand control over the Internet Corporation for Assigned Names and Numbers (ICANN) to a “global multi-stakeholder body.” Other countries have called for more transparency and multi stakeholder conversations surrounding internet governance, including the renewal of the Internet Governance Forum (IGF), an annual multi-stakeholder forum established by the UN in 2006 to set internet standards and policies. The IFG’s mandate expires this year. The informal meeting this week has a huge bearing on December’s main event, and will set the tone for how much oversight and control governments have over the internet, especially in the developing world. Brown said she is concerned the recent terror attacks in Paris may be used to push censorship and anti-privacy measures at the forum. “After Paris, there are governments who have always thought they should be in charge and now have a way to argue this that is persuasive to other governments, at least with respect to the security issues,” she said. “Our work is to try to create understanding around cyber security issues, and it is going to take a concerted, collaborative effort around security.” Sally Wentworth, the vice president of global policy development at the Internet Society, said internet security will be a major issue at this meeting, not necessarily because concrete policies will be formed there but because it will shape the global conversation. “They will discuss what is the role of the UN to some degree, but really these are more declaratory statements of how the international community can address cyber security and who should be involved, who is at the table, and how we should deal with issues like mass surveillance,” she said. Declarations made by the UN following meeting like these are often used as framework, especially in developing countries, for internet policy. Brown said that is why the meeting is “hugely important.” The negotiations are set to end this week, but Wentworth said she anticipates they could continue all the way up to the December meetings.

Popp T.,IFG GmbH | Minkley W.,IFG GmbH | Salzer K.,IFG GmbH | Schulze O.,Federal Institute for Geosciences and Natural Resources
Mechanical Behavior of Salt VII - Proceedings of the 7th Conference on the Mechanical Behavior of Salt

Due to their unique isolation capacity, rock salt formations are favored for the long-term storage of radioactive waste. Most relevant for performance assessment is demonstration of integrity of the geological barrier during the various stages of a repository, i.e., construction, operation and in the post-closure phase. In this context, the impacts of disturbance induced by the excavation of the underground facilities and long-term effects during re-compaction of the EDZ are important items. In addition, because the formation of gases by processes occurring in many radioactive waste packages is unavoidable, the impact of increasing gas pressures on the salt integrity has to be assessed, too. The objective of this paper is to review current understanding of the gas transport properties of rock salt in a rock salt environment associated with a radioactive waste repository. This knowledge has been mainly developed by laboratory and field work during the last two decades. Source

Discover hidden collaborations