Annual Variation of Water Quality in Aquaculture Ponds for Apostichopus japonicus

By measuring water temperature,salinity,pH,dissolved oxygen,nitrite and ammonia nitrogen,the annual variation regularity of water quality in the aquaculture ponds for sea cucumbers Apostichopus japonicus in Dalian were studied.Results showed that the physicochemical indicators kept changing in the year,and the various ranges of water temperature,salinity,pH,dissolved oxygen,nitrite,and ammonia nitrogen were 6.38-27.27℃,29.20‰-33.78‰,7.86-8.38,5.19-13.36 mg/L,0.0037-0.0090 mg/L and 0.0171-0.0908 mg/L,respectively.Analysis indicated that there was an extremely significant negative correlation between water temperature and dissolved oxygen(P<0.01),an extremely significant positive correlation between water temperature and ammonia nitrogen(P<0.01),a significant negative correlation between salinity and nitrite(P<0.05),a significant negative correlation between dissolved oxygen and nitrite(P<0.05),and an extremely significant negative correlation between dissolved oxygen and ammonia nitrogen(P<0.01)in the aquaculture ponds for sea cucumber in Dalian.Research showed that the water quality of aquaculture ponds kept fluctuating all the time during the tested period,there were complicated and close relationships among physicochemical indicators,and a slight variation of external factors would bring consecutive reactions to different indicators in the water quality of aquaculture ponds.A reference for the production and management of sea cucumbers could be provided from the results.

Revealing the atomistic deformation mechanisms of face-centered cubic nanocrystalline metals with atomic-scale mechanical microscopy: A review

Nanocrystalline metals have many functional and structural applications due to their excellent mechanical properties compared to their coarse-grained counterparts. The atomic-scale understanding of the deformation mechanisms of nanocrystalline metals is important for designing new materials, novel structures and applications. The review presents recent developments in the methods and techniques for in situ deformation mechanism investigations on face-centered-cubic nanocrystalline metals. In the first part,we will briefly introduce some important techniques that have been used for investigating the deformation behaviors of nanomaterials. Then, the size effects and the plasticity behaviors in nanocrystalline metals are discussed as a basis for comparison with the plasticity in bulk materials. In the last part, we show the atomic-scale and time-resolved dynamic deformation processes of nanocrystalline metals using our in-lab developed deformation device.