Light interception principally drives the understory response to boxelder invasion in riparian forests

Since several decades, American boxelder (Acer negundo) is replacing white willow (Salix alba) riparian forests along southern European rivers. This study aims to evaluate the consequences of boxelder invasion on understory community in riparian areas. We determined the understory species richness, composition and biomass in boxelder and white willow stands located in three riparian forests, representative of three rivers with distinct hydrological regimes. We investigated correlation of these variables to soil moisture and particle size, main soil nutrient stocks, potential nitrification and denitrification, tree canopy cover and photosynthetic active radiation (PAR) at the ground level. A greenhouse experiment was then conducted to identify the causal factors responsible for changes in the understory. The effect of soil type, PAR level and water level on the growth and the biomass production of Urtica dioica were examined. A lower plant species richness and biomass, and a modification of community composition were observed for boxelder understory in all sites, regardless of their environmental characteristics. The strongest modification that follows boxelder invasion was the decline in U. dioica, the dominant species of the white willow forest understory. These differences were mainly correlated with a lower incident PAR under boxelder canopy. The greenhouse experiment identified PAR level as the main factor responsible for the changes in U. dioica stem number and biomass. Our results indicate that adult boxelder acts as an ecosystem engineer that decreases light availability. The opportunistic invasion by boxelder leads to important understory changes, which could alter riparian ecosystem functioning

Magnetic resonance imaging (MRI) contrast agents for tumor diagnosis

10.1260/2040-2295.4.1.23Journal of Healthcare Engineering4123-4

A comprehensive overview of radioguided surgery using gamma detection probe technology

The concept of radioguided surgery, which was first developed some 60 years ago, involves the use of a radiation detection probe system for the intraoperative detection of radionuclides. The use of gamma detection probe technology in radioguided surgery has tremendously expanded and has evolved into what is now considered an established discipline within the practice of surgery, revolutionizing the surgical management of many malignancies, including breast cancer, melanoma, and colorectal cancer, as well as the surgical management of parathyroid disease. The impact of radioguided surgery on the surgical management of cancer patients includes providing vital and real-time information to the surgeon regarding the location and extent of disease, as well as regarding the assessment of surgical resection margins. Additionally, it has allowed the surgeon to minimize the surgical invasiveness of many diagnostic and therapeutic procedures, while still maintaining maximum benefit to the cancer patient. In the current review, we have attempted to comprehensively evaluate the history, technical aspects, and clinical applications of radioguided surgery using gamma detection probe technology

The influence of fish farming intensification on taxonomic richness and biomass density of macrophyte-dwelling invertebrates in French fishponds

Fishponds are man-made ecosystems where fish farming may strongly interfere with biodiversity. Intensified practices could be suspected to have a negative impact on animal and plant communities. We investigated the hypothesis that, in French fishponds, taxonomic richness and biomass density of macrophyte-dwelling macro-invertebrates could be influenced by fish stock density and pond fertilization. With a sample of 95 water bodies from three of the most important fishpond regions, studied in 2000, 2001 or 2002, we compared a series of models in which macrophyte cover (in three classes), emergent shore vegetation (in % of pond area) and invertebrate biomass in pond sediment were also considered. Among explanatory variables, macrophyte and helophyte abundance were included in the best models explaining variation in invertebrate taxonomic richness and in biomass density. Taxonomic richness was lower when abundance of both macrophytes and emergent shore vegetation was low (<10% and  <7.5%, respectively). Biomass density was higher when macrophyte cover was ≥ 10% provided that emergent vegetation was abundant (≥ 7.5%). We conclude that fish farming intensification in French fishponds may affect aquatic invertebrate communities, mainly through its impact on the development of aquatic vegetation

Singularities of tensile behavior of advanced austenitic steels obtained by different cold processes

International audienceWork-hardened titanium stabilized austenitic steels have been chosen as cladding material for ASTRID (Advanced Sodium Technological Reactor for Industrial Demonstration). The cold-worked level and the stabilization by titanium allow delaying the beginning of the swelling under irradiation and make 15Cr-15Ni steel suitable for use up to 110 dpa at least which is the required target for ASTRID first core. Several fabrication routes involving three cold processes (i.e. drawing, pilgering or swaging) are conducted to produce 15Cr-15Ni cladding tubes. This study investigates the effects of processing paths using various heat treatments and amount of cold work (from 17% to 37%) on the final microstructure and the tensile properties. The microstructure is characterized by examinations in the optical and electron microscopes. Tensile tests are carried out on both longitudinal and circumferential directions by means of respectively tile and ring tensile specimens for temperatures between 20°C and 700°C. The stress-strain curves show strong temperature dependencies of strength and ductility. Both yield strength and ultimate tensile strength decrease linearly from 600-800 MPa below to 450-550 MPa as test temperature increases from 20°C to 700°C. But, on contrary to most metals, the effect of temperature on ductility is not monotonous, with uniform elongation decreasing between 20°C and 200°C, increasing up to 500-600°C and finally decreasing above 600°C (see Figure 1). Very low uniform elongation is thus measured in both directions at 200°C. For the same cold worked state, no effect of the different processes could be highlighted. However, the higher the amount of cold work ( ~ 37%), the higher the yield strength and the ultimate strength and the lower the uniform elongation. In the circumferential direction, the levels of strength are slightly higher and the uniform elongations are weaker than those measured in the longitudinal direction, suggesting a low degree of anisotropy. Figure 1: Uniform elongations measured as a function of the temperature and comparison with an interpolated law proposed for 20-25% cold worked 15Cr-15Ni titanium stabilized stee

Comprehension des mecanismes de deformation de tubes de gaine en acier austenitique 15-15Ti AIM1

International audienceLes reacteurs nucleaires de IVeme Generation sont en phase de developpement dans de nombreux pays. Ils doivent repondre a de nouvelles exigences en matiere de surete, d'efficacite energetique, et de recyclage du combustible nucleaire.La France, par l'intermediaire du CEA, etudie de nouveaux concepts de reacteurs a neutrons rapides refroidis au sodium (RNR-Na), pour lesquels les tubes de gaine des assemblages combustibles seront en acier 15-15Ti AIM1 (Austenitic Improved Material 1).Il s'agit d'un acier inoxydable austenitique avance stabilise au titane, dont la composition est optimisee en elements mineurs (rapport Ti/C, Si, P) pour ameliorer sa resistance au gonflement. Cet acier presente une singularite de comportement plastique, visible en traction une chute importante des allongements homogene et total entre 20 et 200°C. Cette singularite, presente a l'etat hypertrempe, s'accentue a l'etat ecroui correspondant a l'etat metallurgique d'utilisation des tubes de gaine. Le but de cette etude est de determiner les mecanismes de deformation impliques dans cette evolution de comportement.La demarche suivie repose sur une approche multi-echelle basee sur la realisation d'essais de traction dont certains sont couples a des examens au MEB/MET in-situ. Des examens au MEB-EBSD permettent une etude microstructurale globale a l'echelle de plusieurs grains, completee par des observations au MET plus locales au sein d'un grain. L'analyse des cartographies EBSD, apres deformation en traction ex-situ, montrent une evolution des mecanismes de deformation entre 20 et 200°C A 20°C, on met en evidence du glissement, du stockage des dislocations et du maclage mecanique alors qu'a 200°C, le maclage mecanique n'est plus present. Plus precisement, pour les essais realises en traction MEB in-situ a 20°C, on observe que le maclage mecanique s'active uniquement a partir d'une contrainte critique d'activation dont la valeur se situe en dessous de Rm (Rm ~ 580 MPa). Les essais de traction couples a des observations au MET in-situ a 20°C mettent en evidence le role de la dissociation des dislocations parfaites dans la formation des macles mecaniques.En conclusion, le maclage mecanique present a 20°C permet une consolidation importante. Cette consolidation retarde la localisation de la deformation et explique l'allongement plus important obtenu a 20°C par rapport a 200°C

Comprehension des mecanismes de deformation de tubes de gaine en acier austenitique 15-15Ti AIM1

International audienceLes reacteurs nucleaires de IVeme Generation sont en phase de developpement dans de nombreux pays. Ils doivent repondre a de nouvelles exigences en matiere de surete, d'efficacite energetique, et de recyclage du combustible nucleaire.La France, par l'intermediaire du CEA, etudie de nouveaux concepts de reacteurs a neutrons rapides refroidis au sodium (RNR-Na), pour lesquels les tubes de gaine des assemblages combustibles seront en acier 15-15Ti AIM1 (Austenitic Improved Material 1).Il s'agit d'un acier inoxydable austenitique avance stabilise au titane, dont la composition est optimisee en elements mineurs (rapport Ti/C, Si, P) pour ameliorer sa resistance au gonflement. Cet acier presente une singularite de comportement plastique, visible en traction une chute importante des allongements homogene et total entre 20 et 200°C. Cette singularite, presente a l'etat hypertrempe, s'accentue a l'etat ecroui correspondant a l'etat metallurgique d'utilisation des tubes de gaine. Le but de cette etude est de determiner les mecanismes de deformation impliques dans cette evolution de comportement.La demarche suivie repose sur une approche multi-echelle basee sur la realisation d'essais de traction dont certains sont couples a des examens au MEB/MET in-situ. Des examens au MEB-EBSD permettent une etude microstructurale globale a l'echelle de plusieurs grains, completee par des observations au MET plus locales au sein d'un grain. L'analyse des cartographies EBSD, apres deformation en traction ex-situ, montrent une evolution des mecanismes de deformation entre 20 et 200°C A 20°C, on met en evidence du glissement, du stockage des dislocations et du maclage mecanique alors qu'a 200°C, le maclage mecanique n'est plus present. Plus precisement, pour les essais realises en traction MEB in-situ a 20°C, on observe que le maclage mecanique s'active uniquement a partir d'une contrainte critique d'activation dont la valeur se situe en dessous de Rm (Rm ~ 580 MPa). Les essais de traction couples a des observations au MET in-situ a 20°C mettent en evidence le role de la dissociation des dislocations parfaites dans la formation des macles mecaniques.En conclusion, le maclage mecanique present a 20°C permet une consolidation importante. Cette consolidation retarde la localisation de la deformation et explique l'allongement plus important obtenu a 20°C par rapport a 200°C

Discrepancy between antihypertensive effect and angiotensin converting enzyme inhibition by captopril

Captopril, an inhibitor of angiotensin converting enzyme, was administered twice daily to 13 hypertensive patients for a mean period of 9 weeks. Continuous blood pressure control in the ambulatory patients was established with a portable blood pressure recorder. Notwithstanding, in eight patients with normal renal function, plasma converting enzyme was found to resume normal activity before administration of the morning dose of captopril. Only in 5 patients with impaired renal function did some blockade of plasma converting enzyme persist for more than 12 hours. Measured plasma converting enzyme activity seemed to reflect total conversion of angiotensin I, including conversion in the pulmonary vascular bed, since changes in its activity were closely paralled by changes in plasma aldosterone levels. Bradykinin accumulation seems unlikely when converting enzyme and thus, presumably, kininase II has resumed normal activity. Captopril administration does not seem to alter plasma epinephrine or norepinephrine levels. Blood pressure reduction in the face of normal angiotensin converting enzyme activity is probably due to hyporesponsiveness of the arterioles to pressor hormones, which may be due to specific renin-related and/or nonspecific effects of captopril

Lymphoscintigraphy in the sentinel lymph node technique for breast tumor: value of early and late images for the learning curve1

As the performance of early (H+1 to H+4) and late (D1) lymphoscintigraphic images raises organizational problems in outpatient surgery for breast cancer, only early images are generally obtained. The present study evaluated whether two series of images are better than one and defined the advantages of both methodologies. One hundred and eighteen patients with infiltrating breast carcinoma (T(0), T(1) and T(2)) were included in the study: 87 in group A (early and late images) and 31 in group B (only early images). All patients received two peritumoral injections of (99m)Tc-sulfur colloid, 15-18 MBq (group A) and &lt;15 MBq (group B). During the operation, the patent blue bye technique was associated with radioactivity detection. The two groups were comparable for histological type and tumor size and localization. Successful localization of sentinel nodes on early lymphoscintigraphic images was significantly greater for group B. The identification of a sentinel node focus on early lymphoscintigraphy increased by 10% during the study. Sentinel node detection by the isotopic method alone, or the two methods combined, was comparable for both groups. In radioactivity detection, the count rate for sentinel nodes versus background (contralateral breast) was similar for the two groups. During the learning phase, two series of images gave a definite advantage. Subsequently, lymphoscintigraphy performed at +2 h was sufficient (the results for the two groups became indistinguishable