Analysis of Strength Characteristics and Energy Dissipation of Improved-Subgrade Soil of High-Speed Railway above Mined-Out Areas

To reveal the effect of sand content on the mechanical performance and energy dissipation of cement improved subgrade soil, using universal testing machine and SHPB test device, unconfined compressive strength (UCS) and impact compression strength under different impact load (0.2, 0.3, 0.4, and 0.5 MPa) were carried out for the cement improved subgrade soil with different sand content (0%, 5%, 10%, 15%, and 20%). Results show that the dynamic and static stress-strain curves of the cement improved soil have similar variation trend. With the increase of the sand content, the UCS and impact compressive strength of the cement improved soil both increase first, then decrease later, showing the form of a quadratic function. The strength growth rate and the dynamic increase factor (DIF) reach the maximum values when the sand content is 10%, which is 64.7% and 18.6% larger than that of ordinary improved subgrade soil, respectively. In addition, when the sand content increases from 0% to 20%, the specific dissipation energy increases first, and decreases later. Mixing 10% natural sand is the optimal proportion to obtain better energy dissipation capacity of the sand-cement-improved soil

Monitoring long-term ocean health using remote sensing: A case study of the Bay of Bengal

Oceans play a significant role in the global carbon cycle and climate change, and the most importantly it is a reservoir for plenty of protein supply, and at the center of many economic activities. Ocean health is important and can be monitored by observing different parameters, but the main element is the phytoplankton concentration (chlorophyll-a concentration) because it is the indicator of ocean productivity. Many methods can be used to estimate chlorophyll-a (Chl-a) concentration, among them, remote sensing technique is one of the most suitable methods for monitoring the ocean health locally, regionally and globally with very high temporal resolution. In this research, long term ocean health monitoring was carried out at the Bay of Bengal considering three facts i.e. i) very dynamic local weather (monsoon), ii) large number of population in the vicinity of the Bay of Bengal, and iii) the frequent natural calamities (cyclone and flooding) in and around the Bay of Bengal. Data (ten years: from 2001 to 2010) from SeaWiFS and MODIS were used. Monthly Chl-a concentration was estimated from the SeaWiFS data using OC4 algorithm, and the monthly sea surface temperature was obtained from the MODIS sea surface temperature (SST) data. Information about cyclones and floods were obtained from the necessary sources and in-situ Chl-a data was collected from the published research papers for the validation of Chl-a from the OC4 algorithm. Systematic random sampling was used to select 70 locations all over the Bay of Bengal for extracting data from the monthly Chl-a and SST maps. Finally the relationships between different aspects i.e. i) Chl-a and SST, ii) Chl-a and monsoon, iii) Chl-a and cyclones, and iv) Chl-a and floods were investigated monthly, yearly and for long term (i.e 10 years). Results indicate that SST, monsoon, cyclone, and flooding can affect Chl-a concentration but the effect of monsoon, cyclone, and flooding is temporal, and normally reduces over time. However, the effect of SST on Chl-a concentration can't be minimized very quickly although the change of temperature over this period is not very large.Remote Sensing of the Ocean, Sea Ice, Coastal Waters, and Large Water Regions 2013 (24 September 2013, Dresden, Germany

Contrasting ability to take up leucine and thymidine among freshwater bacterial groups: implications for bacterial production measurements

We examined the ability of different freshwater bacterial groups to take up leucine and thymidine in two lakes. Utilization of both substrates by freshwater bacteria was examined at the community level by looking at bulk incorporation rates and at the single-cell level by combining fluorescent in situ hybridization and signal amplification by catalysed reporter deposition with microautoradiography. Our results showed that leucine was taken up by 70–80% of Bacteria-positive cells, whereas only 15–43% of Bacteria-positive cells were able to take up thymidine. When a saturating substrate concentration in combination with a short incubation was used, 80–90% of Betaproteobacteria and 67–79% of Actinobacteria were positive for leucine uptake, whereas thymidine was taken up by < 10% of Betaproteobacteria and by < 1% of the R-BT subgroup that dominated this bacterial group. Bacterial abundance was a good predictor of the relative contribution of bacterial groups to leucine uptake, whereas when thymidine was used Actinobacteria represented the large majority (> 80%) of the cells taking up this substrate. Increasing the substrate concentration to 100 nM did not affect the percentage of R-BT cells taking up leucine (> 90% even at low concentrations), but moderately increased the fraction of thymidine-positive R-BT cells to a maximum of 35% of the hybridized cells. Our results show that even at very high concentrations, thymidine is not taken up by all, otherwise active, bacterial cells