[en] This work presents an elastoplastic damage model for argillite in unsaturated conditions. A short resume of experimental investigations is presented in the first part. The results obtained show an important plastic deformation coupled with damage induced by initiation and growth of microcracks. Influences of water content on the mechanical behaviour are also investigated. Based on experimental data and micro-mechanical considerations, a general constitutive model is proposed for the poro-mechanical behavior of argillite in unsaturated conditions. The time dependent creep has also been incorporated in they model. The performance of the model is examined by comparing numerical simulation with experimental data in various load paths under saturated and unsaturated conditions. Finally, the model is applied to hydro-mechanical coupling study of the REP experiment and thermo-hydro-mechanical coupling study of the HE-D experiment. A good agreement is obtained between experimental data and numerical predictions. It has been shown that the proposed model describe correctly the main features of the mechanical behaviour of unsaturated rocks. (author)

[en] Aim: To evaluate the feasibility of a 100 kVp tube voltage combined with an iterative reconstruction algorithm in retrospective electrocardiogram (ECG)-gated thoracoabdominal aortic CT angiography (CTA). Materials and methods: Ninety-eight patients who underwent clinically indicated thoracoabdominal aortic CTA were randomly assigned to two groups: group A (n = 50) were scanned to 120 kVp and group B (n = 48) to 100 kVp. The body mass index of all included patients was <25 kg/m"2. Group A scans were reconstructed with a standard filtered back projection (FBP) algorithm, and group B scans with FBP, iDose, and non-tagged algorithms. Data comparison between groups was performed using t-test and analysis of variance. Results: Compared with group A, the iDose algorithm in group B yielded a higher contrast-to-noise ratio (CNR; 48.1 ± 10.1, p < 0.05), a higher signal-to-noise ratio (SNR; 13.8 ± 5.4, p < 0.05), and a lower standard deviation (SD; 30.3 ± 6.9, p < 0.05). The subjective score of iDose reconstructions from group B was significantly lower than that of FBP reconstruction from group A (p < 0.05). In group B, the non-tagged algorithm resulted in a higher CNR and a higher SNR, but a higher SD and a higher subjective score than did the iDose algorithm. The average effective dose for group B was 35.8% lower than that for group A. Conclusion: A combination of a 100 kVp tube voltage and the iDose algorithm can help to improve image quality and reduce radiation dose in retrospective ECG-gated thoracoabdominal aortic CTA. - Highlights: • 256-slice spiral CT facilitates the retrospective ECG-gated CTA of the whole aorta. • Retrospective ECG-gating displays dynamic information about aorta and branches. • 100 kVp can be used for aortic CTA to reduce radiation dose. • iDose algorithm can improve the image quality with a low radiation dose. • Non-tagged reconstruction cannot be used for a one-stop examination of the aorta

[en] X-ray absorption fine structure (XAFS) is used to characterize the mineralogy of the iron(III)-arsenate(V) precipitates produced during the raffinate (aqueous effluent) neutralization process at the McClean Lake uranium mill in northern Saskatchewan, Canada. To facilitate the structural characterization of the precipitated solids derived from the neutralized raffinate, a set of reference compounds were synthesized and analyzed. The reference compounds include crystalline scorodite, poorly-crystalline scorodite, iron(III)-arsenate co-precipitates obtained under different pH conditions, and arsenate-adsorbed on goethite. The poorly-crystalline scorodite (prepared at pH 4 with Fe/As = 1) has similar As local structure as that of crystalline scorodite. Both As and Fe K-edge XAFS of poorly-crystalline scorodite yield consistent results on As-Fe (or Fe-As) shell. From As K-edge analysis the As-Fe shell has an inter-atomic distance of 3.33 ± 0.02 A and coordination number of 3.2; while from Fe K-edge analysis the Fe-As distance and coordination number are 3.31 ± 0.02 A and 3.8, respectively. These are in contrast with the typical arsenate adsorption on bidentate binuclear sites on goethite surfaces, where the As-Fe distance is 3.26 ± 0.03 A and coordination number is close to 2. A similar local structure identified in the poorly-crystalline scorodite is also found in co-precipitation solids (Fe(III)/As(V) = 3) when precipitated at the same pH (pH = 4): As-Fe distance 3.30 ± 0.03 A and coordination number 3.9; while at pH = 8 the co-precipitate has As-Fe distance of 3.27 ± 0.03 A and coordination number about 2, resembling more closely the adsorption case. The As local structure in the two neutralized raffinate solid series (precipitated at pH values up to 7) closely resembles that in the poorly-crystalline scorodite. All of the raffinate solids have the same As-Fe inter-atomic distance as that in the poorly-crystalline scorodite, and a systematic decrease in the As-Fe coordination is observed when pH is progressively increased; the basic poorly-crystalline scorodite structural feature remains in the raffinate solid up to pH 7.

[en] Epitaxial SrBi₂Nb₂O₉ thin films have been grown on (110) SrTiO₃ substrates by pulsed laser deposition. Four-circle x-ray diffraction and transmission electron microscopy reveal nearly phase pure epitaxial films with the c axis of the films at 45^o with respect to the substrate normal. Electrical characterization is presented for films grown on epitaxial SrRuO₃ electrodes. The low-field relative permittivity was 235, the remanent polarization was 11.4 μC/cm², and the dielectric loss was 3.0% for 0.3-μm-thick films. From the remanent polarization and an understanding of the epitaxial geometry, a lower bound of 22.8 μC/cm² was determined for the spontaneous polarization of SrBi₂Nb₂O₉

[en] Some new results on magnetic dipole (M1) transitions in heavy quarkonium from nonrelativistic effective field theories of QCD are briefly reported. This model-independent approach not only facilitates a systematic and lucid way to investigate relativistic corrections, it also clarifies some inconsistent treatment in previous potential model approach. The impact of our formalism on J/ψ→η_cγ is discussed

[en] The Pi-ta gene in rice has been used to prevent the rice blast disease worldwide for several decades. In the US, Pi-ta was introgressed from a landrace indica variety, Tetep, into several tropical japonica cultivars including Katy. Pi-ta is predicted to encode a cytoplasmic receptor that directly binds to the elicitor produced by the pathogen avirulence gene AVR-Pita for initiating resistance. Katy, expressing resistance conditioned by Pi-ta, Pi-ta2, and Pi-ks to the races of M. oryzae, IB1, IB45, IB49, IB54, IC17, IH1, IE1, and IG1, was treated with mutagens, fast neutrons and ethyl methyl sulfate (EMS). Six mutants with enhanced resistance or susceptibility were identified by screening M2 seedlings derived from 15,000 M1 plants. Among them, M562, induced by EMS, is a lesion mimic mutant (named as LMM1) that produces spontaneous hypersensitive cell death. This rapid cell death was quickly induced using detached leaves at and near the site of inoculation by the virulent race IE1k and more slowly induced when inoculated with the avirulent isolate IB49. Similar hypersensitive cell death was observed after detached leaves were inoculated with the fungus Rhizoctonia solani, the causal agent of rice sheath blight disease. Hypersensitive cell death is known to be a form of the defense response. Thus, we suggest that LMM1 has enhanced resistance to both rice blast and sheath blight pathogens. Although the Pi-ta gene in rice provides resistance to the races, IB1, IB45, IB49, IC17, IH1, IE1, IB54, and IG1, the mutant M2354 was observed to be susceptible to all races except IB54 although there was no change in the Pi-ta DNA sequence. Expression of Pi-ta in M2354 was also similar to that of the parent examined by qRT-PCR. Thus, mutations in M2354 likely occurred at a new locus named as Ptr(t). Another four lines were determined to be near isogenic lines at a 9 megabase genomic region spanning the Pi-ta locus of Katy. Progress on characterizing these six genetic stocks is presented. (author)

[en] Document available in extended abstract form only. The clay formation provides the geological background to many industrial and engineering applications. Especially in recent years, these types of material have been largely studied because they can be considered as potential host geological barrier for the underground storage of high level radioactive wastes. In view of this, several underground laboratories have been constructed in different countries. For instance: the Meuse/Haute Marne underground research laboratory (France), excavated in Callovo-Oxfordian argillite; the Mont Terri underground rock laboratory (Switzerland), constructed in Opalinus clay; the HADES Underground Research Laboratory (Belgium), located in Boom clay; the AECL underground research laboratory (Canada), achieved in the Lac du Bonnet granite batholith. The research realised in the underground laboratories allows us to obtain extensive experimental measurements and helps us to get a good understanding of the generalised behaviour of theses clays when subjected to complex solicitations (thermal, hydraulic, mechanical and chemical). In the underground storage, the experimental investigation and numerical prediction show that coupled hydro-mechanical processes will occur in the geological barrier for a very long time due to excavation/ ventilation and subsequence backfilling/sealing. In the excavation and exploitation stage, the unloading of host rock creates an EDZ zone and induces an increase local of permeability by several orders of magnitude around the galleries. Moreover, additional damage may be induced by the desaturation/re-saturation processes during ventilation/backfilling phase. On the other hand, the behaviour of clay formation is affected also by the presence of water and the pore pressure evolution. It is necessary to achieve a good understanding of the coupled hydro-mechanical behaviour to of clay formation for the designer of an underground storage. This paper focus on the hydro-mechanical response of Callovo-Oxfordian argillite, a stiff, layered Mesozoic clay, located at 500 m depth in Eastern France. Thanks to its low permeability, significant retardation properties for solute transport, high mechanical strength and self-healing capacity when fracture, the Callovo-Oxfordian argillite is studied as potential geological barrier for radioactive wastes and an underground research laboratory, called M/HM URL is under construction.Various experimental studies have been performed to study the different aspects of rock behaviour. Meanwhile, different constitutive model have been proposed for this material. Among recently proposed models for argillites, the contributions Zhou et al. (2008) and Jia et al. (2009) are of direct interest to this paper. Zhou et al. (2008) have proposed a unified approach for modelling of elastic-plastic and viscoplastic behaviour coupled with induced damage in Callovo-Oxfordian argillite. Both instantaneous and differ plastic deformations are described within the unique constitutive model. Material damage induced by microcrack is coupled with plastic deformation. Jia et al. (2009) have developed a constitutive model, where the plastic deformation was considered as the principal mechanism, to consider coupling between plastic deformations and damage and evolution of mechanical properties with water content. In addition, a special attention is paid on the residual state of rocks after peak strength and the shrinkage/swelling deformation during the desaturation/re-saturation processes. However, the influence of water content on the elastic proprieties and the long term mechanical behaviour of argillite are not dealt with in these models. These two phenomena will be studied in this paper. Firstly, a synthesis of experimental study on the poro-mechanical behavior of argillites is presented. Special attention is given to the influence of water content on the long term mechanical aspects of the clay behaviour. In the second part, after a brief the coupled elastoplastic damage model proposed by Jia et al. (2009), the time-dependant behaviour of argillite is incorporated in the previous model by using the unified approach. The influence of water content on the long term mechanical behaviour of argillite under different water contents is taken into account in the framework of partially saturated porous media. The proposed model is validated by simulation of a series of creep tests with different water content. Finally, the experiment performed on the hollow cylindrical sample is simulated and analyzed. The evolutions of deformations generated and mass of sample is goodly predicted by the simulations. The numerical results help us get a good understanding of the drying/wetting impact on the poro-mechanical behaviour of argillite. (authors)

[en] This paper reports the design, analysis and experimental characterisation of a piezoelectric MEMS cantilever vibration energy harvester, the enhancement of its power output by adding various values of end mass, as well as assessing the responsiveness towards white noise. Devices are fabricated using a 0.5 μm AlN on 10 μm doped Si process. Cantilevers with 5 mm length and 2 mm width were tested at either unloaded condition (MC0: f_n 577 Hz) or subjected to estimated end masses of 2 mg (MC2: f_n 129 Hz) and 5 mg (MC5: f_n 80 Hz). While MC0 was able to tolerate a higher drive acceleration prior to saturation (7 g with 0.7 μW), MC5 exhibited higher peak power attainable at a lower input vibration (2.56 μW at 3 ms"−"2). MC5 was also subjected to band-limited (10 Hz to 2 kHz) white noise vibration, where the power response was only a fraction of its resonant counterpart for the same input: peak instantaneous power >1 μW was only attainable beyond 2 g of white noise, whereas single frequency resonant response only required 2.5 ms"−"2. Both the first resonant response and the band-limited white noise response were also compared to a numerical model, showing close agreements

[en] In the realm of MEMS piezoelectric vibration energy harvesters, cantilever-based designs are by far the most popular. Despite being deceptively simple, the active piezoelectric area near the clamped end is able to accumulate maximum strain-generated-electrical-charge, while the free end is able to accommodate a proof mass without compromising the effective area of the piezoelectric generator since it experiences minimal strain anyway. While other contending designs do exist, this paper investigates five micro-cantilever (MC) topologies, namely: a plain MC, a tapered MC, a lined MC, a holed MC and a coupled MC, in order to assess their relative performance as an energy harvester. Although a classical straight and plain MC offers the largest active piezoelectric area, alternative MC designs can potentially offer higher average mechanical strain distribution for a given mechanical loading. Numerical simulation and experimental comparison of these 5 MCs (0.5 μ AlN on 10 μm Si) with the same practical dimensions of 500 μm and 2000 μm, suggest a cantilever with a coupled subsidiary cantilever yield the best power performance, closely followed by the classical plain topology

[en] The mechanical amplification effect of parametric resonance has the potential to outperform direct resonance by over an order of magnitude in terms of power output. However, the excitation must first overcome the damping-dependent initiation threshold amplitude prior to accessing this more profitable region. In addition to activating the principal (1st order) parametric resonance at twice the natural frequency ω₀, higher orders of parametric resonance may be accessed when the excitation frequency is in the vicinity of 2ω₀/n for integer n. Together with the passive design approaches previously developed to reduce the initiation threshold to access the principal parametric resonance, vacuum packaging (< 10 torr) is employed to further reduce the threshold and unveil the higher orders. A vacuum packaged MEMS electrostatic harvester (0.278 mm³) exhibited 4 and 5 parametric resonance peaks at room pressure and vacuum respectively when scanned up to 10 g. At 5.1 ms⁻², a peak power output of 20.8 nW and 166 nW is recorded for direct and principal parametric resonance respectively at atmospheric pressure; while a peak power output of 60.9 nW and 324 nW is observed for the respective resonant peaks in vacuum. Additionally, unlike direct resonance, the operational frequency bandwidth of parametric resonance broadens with lower damping