Thermo-hydro-mechanical responses of the host rock in the context of geological nuclear waste disposal

Deep geological disposal facility has been considered as the most appropriated solution for the safe longterm management of high-level radioactive waste (HLW). Geologic disposal solution consists of isolating the radioactive waste from the biosphere. Argillaceous rock has been selected in several countries as host formation due to its favorable properties to isolate radionuclides and chemical contaminants (very low permeability, stable, high retention capacity, self-sealing, etc). Clays in their natural state is usually saturated. Disposal of the exothermic waste packages in the repository leads to an increase in temperature within the host rock, which induces the pore pressure build-up due to the difference in thermal expansion coefficients of the pore water and the solid skeleton. The excess pore pressure generally leads to a decrease in the effective stress and can provoke thermally hydraulic fracturing or shear failure. Therefore, understanding the thermo-hydro-mechanical (THM) responses of the saturated host rock due to the heat generated form waste packages is a key issue to assess the feasibility of the repository. This paper aims at presenting coupled THM constitutive equations for a saturated porous medium and its finite element (FEM) discretization and solution. The solution is validated against analytical solution and other numerical results from a benchmark within an international project. FEM program is then used to describe the THM behavior of the host rock around a HLW repository (i.e. near field responses). Sensitivity analysis were performed to evaluate effect of material anisotropy and hydraulic condition on the micro-tunnel wall

Hierarchically structured LaFeO3 with hollow core and porous shell as efficient sensing material for ethanol detection

Hollow LaFeO3 (LFO-HS) was synthesized by a facile hydrothermal method with the use of cetyltrimethylammonium bromide. Its structural, morphological, microstructural and textual characterizations were performed using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption-desorption analysis. The gas-sensing performance of LFO-HS sensor was studied towards different gases, including ammonia (NH3), ethanol (C2H5OH), acetone (CH3COCH3), and liquefied petroleum gas (LPG). The LFO-HS sensor exhibited p-type gas sensing behavior and enhanced sensing performance towards ethanol gas as compared with bulk LaFeO3 sensor. A rapid, high, and stable response was seen at 300 °C. Meanwhile, a linear response and low limit of detection (1 ppb) to ethanol was observed. After the investigation on sensitivity to different reducing gases, our results revealed that the LFO-HS sensor exhibited good selectivity to ethanol and suggested it being a promising sensor candidate for future practical use in trace ethanol detection

Perceptions of wood-processing industries on FLEGT implementation: Insights from Vietnam

This paper analyses timber and wood processing companies' views on opportunities and challenges for FLEGT implementation in Vietnam based on a literature review, online surveys with 56 timber and wood processing companies, in-depth interviews with 26 stakeholders from different institutions, and a consultation workshop involving 94 participants. Our paper shows that FLEGT has received increasing attention and political support from the Government of Vietnam, which has issued new policies on sustainable forest management, forest certification and financial incentives to enable timber and wood processing companies to participate in FLEGT. The active presence of civil society organizations has helped improve forest governance, which is a key aspect of FLEGT. Perceiving FLEGT as a global market trend able to generate higher profits, timber and wood processing companies see opportunities to benefit from this timber trading initiative, and are therefore more willing to comply with FLEGT requirements. However, these companies also highlight challenges to implementing FLEGT on the ground, including unclear and inconsistent policies, weak monitoring and evaluation, high transaction costs, companies' limited access to information, unclear tenure and erratic land-use planning, and the weak capacity of household and small-scale enterprises. Effective implementation of FLEGT requires regulatory changes, improved law enforcement and translation of policies on the ground, enhanced information exchange between stakeholders, and addressing underlying problems relating to land tenure and forest governance

Slaughterhouse Pigs Are a Major Reservoir of Streptococcus suis Serotype 2 Capable of Causing Human Infection in Southern Vietnam

Streptococcus suis is a pathogen of major economic significance to the swine industry and is increasingly recognized as an emerging zoonotic agent in Asia. In Vietnam, S. suis is the leading cause of bacterial meningitis in adult humans. Zoonotic transmission is most frequently associated with serotype 2 strains and occupational exposure to pigs or consumption of infected pork. To gain insight into the role of pigs for human consumption as a reservoir for zoonotic infection in southern Vietnam, we determined the prevalence and diversity of S. suis carriage in healthy slaughterhouse pigs. Nasopharyngeal tonsils were sampled from pigs at slaughterhouses serving six provinces in southern Vietnam and Ho Chi Minh City area from September 2006 to November 2007. Samples were screened by bacterial culture. Isolates of S. suis were serotyped and characterized by multi locus sequence typing (MLST) and pulse field gel electrophoresis (PFGE). Antibiotic susceptibility profiles and associated genetic resistance determinants, and the presence of putative virulence factors were determined. 41% (222/542) of pigs carried S. suis of one or multiple serotypes. 8% (45/542) carried S. suis serotype 2 which was the most common serotype found (45/317 strains, 14%). 80% of serotype 2 strains belonged to the MLST clonal complex 1, which was previously associated with meningitis cases in Vietnam and outbreaks of severe disease in China in 1998 and 2005. These strains clustered with representative strains isolated from patients with meningitis in PFGE analysis, and showed similar antimicrobial resistance and virulence factor profiles. Slaughterhouse pigs are a major reservoir of S. suis serotype 2 capable of causing human infection in southern Vietnam. Strict hygiene at processing facilities, and health education programs addressing food safety and proper handling of pork should be encourage