A new population of very high energy gamma-ray sources in the Milky Way     

Aharonian F  Akhperjanian AG  Aye KM  Bazer-Bachi AR  Beilicke M  Benbow W  Berge D  Berghaus P  Bernlöhr K  Boisson C  Bolz O  Borgmeier C  Braun I  Breitling F  Brown AM  Gordo JB  Chadwick PM  Chounet LM  Cornils R  Costamante L  Degrange B  Djannati-Ataï A  Drury LO  Dubus G  Ergin T  Espigat P  Feinstein F  Fleury P  Fontaine G  Funk S  Gallant YA  Giebels B  Gillessen S  Goret P  Hadjichristidis C  Hauser M  Heinzelmann G  Henri G  Hermann G  Hinton JA  Hofmann W  Holleran M  Horns D  de Jager OC  Jung I  Khélifi B  Komin N 《Science (New York, N.Y.)》2005,307(5717):1938-1942

Very high energy gamma-rays probe the long-standing mystery of the origin of cosmic rays. Produced in the interactions of accelerated particles in astrophysical objects, they can be used to image cosmic particle accelerators. A first sensitive survey of the inner part of the Milky Way with the High Energy Stereoscopic System (HESS) reveals a population of eight previously unknown firmly detected sources of very high energy gamma-rays. At least two have no known radio or x-ray counterpart and may be representative of a new class of "dark" nucleonic cosmic ray sources.  相似文献   

Morphometric evaluation of changes in the digestive tract of rainbow trout (Oncorhynchus mykiss) due to fish meal replacement with soy protein concentrate     

Anne-Marie Escaffre  Muriel Mambrini 《Aquaculture (Amsterdam, Netherlands)》2007,273(1):127-138

Effects of the complete replacement of fish meal (FM) by soy protein concentrate (SPC) in high-energy diets (23 MJ kg^− 1 gross energy) on intestinal and liver histology were investigated in rainbow trout (Oncorhynchus mykiss). We developed a novel morphometric method to quantify the changes at the macro- and micromorphology level. Fish were acclimatized to the diet for 90 d and were then fed 1.0 g kg BW^− 1 d^− 1 once per day for 14 d before 10 fish per diet were randomly sampled, 6 h after their last meal. Fold height, epithelium length, stroma proportion of the proximal and distal intestines were not affected by the diet. No significant diet effect was detected on the features of the valve in the distal intestine. Fold height was linked to epithelium length in the proximal and distal intestines and this relationship was not modified by FM replacement. Enterocyte height and width were lower in SPC-fed fish in the distal intestine, but in the proximal intestine their morphology was not affected by the diet. There was no diet effect on the number of cells infiltered between the enterocytes in the proximal and distal intestines. The enterocyte nucleus was closer to the apex in the proximal and distal intestines in SPC-fed fish, but the features of the nucleus were not affected by the diet. The mean hepatocyte volume was on an average 36% lower in SPC-fed fish and was positively correlated to the hepatosomatic index for fish fed this diet only. In conclusion, SPC used in the present study did not either cause inflammatory reaction of the gut nor affected the epithelium surface. We suggest that the modifications due to SPC are linked to variations in the metabolic status of the enterocyte.  相似文献   

Spatial variability of the functional stability of microbial respiration process: a microcosm study using tropical forest soil     

Nathalie Fromin  Benjamin Porte  Robert Lensi  Jér?me Hamelin  Anne-Marie Domenach  Bruno Buatois  Jean-Christophe Roggy 《Journal of Soils and Sediments》2012,12(7):1030-1039

Purpose

Understanding the ability of ecosystem processes to resist to and to recover from disturbances is critical to sustainable land use. However, the spatial variability of the stability has rarely been addressed. Here, we investigated the functional stability of a soil microbial process for 24 soils collected from adjacent locations from a 0.3?ha tropical rainforest plot in Paracou, French Guiana.

Materials and methods

The 24 locations were characterized regarding soil chemical and biological (microbial diversity) parameters and forest structure. The corresponding soils were submitted to an experimental transient heat disturbance during a microcosm experiment. The response of the respiration process was followed using substrate-induced respiration (SIR).

Results and discussion

The response of soil SIR to heat disturbance varied widely between samples. The variability of the SIR response increased just after the disturbance, and a global rather homogeneous decrease in SIR rates was observed 15 and 30?days after. The stability of SIR in response to heat disturbance could not be related to either the genetic or the metabolic diversity of the microbial community. The initial level of SIR before the disturbance was the soil variable that best correlated with the impact of the disturbance: the soil locations with the highest initial SIR rates were the most affected 15 and 30?days after the heat disturbance.

Conclusions

Such a heterogeneous response suggests that the response of soil processes to a disturbance will be difficult to assess from only local-scale analyses and highlights the need for spatial explicitness in understanding biogeochemical processes.  相似文献   

Marine polysaccharides: a source of bioactive molecules for cell therapy and tissue engineering     

Senni K  Pereira J  Gueniche F  Delbarre-Ladrat C  Sinquin C  Ratiskol J  Godeau G  Fischer AM  Helley D  Colliec-Jouault S 《Marine drugs》2011,9(9):1664-1681

The therapeutic potential of natural bioactive compounds such as polysaccharides, especially glycosaminoglycans, is now well documented, and this activity combined with natural biodiversity will allow the development of a new generation of therapeutics. Advances in our understanding of the biosynthesis, structure and function of complex glycans from mammalian origin have shown the crucial role of this class of molecules to modulate disease processes and the importance of a deeper knowledge of structure-activity relationships. Marine environment offers a tremendous biodiversity and original polysaccharides have been discovered presenting a great chemical diversity that is largely species specific. The study of the biological properties of the polysaccharides from marine eukaryotes and marine prokaryotes revealed that the polysaccharides from the marine environment could provide a valid alternative to traditional polysaccharides such as glycosaminoglycans. Marine polysaccharides present a real potential for natural product drug discovery and for the delivery of new marine derived products for therapeutic applications.  相似文献