Effects of linear and exponential heterogeneity on the dynamic response of a moving load in an irregular isotropic half-space: a comparative study

Heterogeneity, being a trivial feature inside the earth or in a geostructure, makes a strong basis for its consideration in the study of geomechanics. Inclusion of the concept of heterogeneity along with irregularity in the medium brings a novelty to the existing literature related to the study of the moving load. The present study investigates the effects of linear and exponential heterogeneity on the dynamic response due to a normal load moving with constant velocity on a rough irregular heterogeneous isotropic half-space in a comparative approach. Expressions for both normal and shear stresses for either case of heterogeneity have been established in closed form. Substantial effects of the affecting parameters such as depth, irregularity factor, maximum depth of irregularity, frictional coefficient, linear heterogeneity parameter and exponential heterogeneity parameter on normal and shear stresses for both the cases of heterogeneity have been observed. Numerical computation has been carried out and the effects of said parameters have been meticulously examined by means of graphs. Moreover, different cases of heterogeneity and homogeneity along with various types of irregularity namely rectangular, parabolic and no irregularity are compared which serve as a focal theme of the study.     

Influence of varying nitrogen levels on lipid accumulation in <Emphasis Type="Italic">Chlorella</Emphasis> sp.

Microalgal lipids can be enhanced through varying nitrogen (N) content, and limited supply of nitrogen source seems to be valuable approach for increased lipid accumulation in microalgae. In this study, Chlorella sp. IM-02 was observed under fluorescence microscope for increased number of lipid bodies under nitrogen scarcity. Fourier transform infrared spectroscopy was used to determine spectral changes due to varying lipid content under nitrogen-starved (N₀, without sodium nitrate), nitrogen-limited (N_0.1, N_0.25, N_0.5 and N_1.0 representing 0.1, 0.25, 0.5 and 1.0 g/L of sodium nitrate, respectively) and nitrogen-sufficient (N_1.5, i.e., 1.5 g/L sodium nitrate) setting. Chlorophyll content was also monitored under these conditions as growth indicator. Various biochemical components viz. total carbohydrates, total proteins and total lipids were also estimated under varying nitrogen levels spectrophotometrically. On fourth day itself, maximum lipid productivity was observed in case of N_0.5, which is having one-third of nitrogen concentration present in original growth media, BG-11. This concludes N_0.5 as suitable nitrogen provision for better production of lipids in Chlorella sp. IM-02 without much compromising the biomass production as both growth and lipid quantity are key parameters affecting the lipid productivity of any microalgal strain.     

Diversity of marine and brackish water nitrite-oxidizing consortia developed for activating nitrifying bioreactors in aquaculture

Nitrite is a well-known toxicant in aquaculture, produced as intermediate in nitrification. Two nitrite-oxidizing bacterial consortia, one from marine environment and the other from brackish water, were developed by enrichment technique at National Centre for Aquatic Animal Health, for removal of nitrite from recirculating aquaculture systems. In the present study, bacterial diversity of the consortia was assessed based on 16S ribosomal RNA and the functional gene analysis. Clone libraries of 16S ribosomal RNA gene and nitrite oxidoreductase A gene were constructed, and amplified ribosomal DNA restriction analysis was carried out to cluster the clones. Dendrograms generated through molecular characterization showed 29 and 27 clusters in marine and brackish water consortia, respectively. Phylogenetic analyses of representative clones from each cluster depicted profound diversity in the consortia consisting autotrophic nitrifiers belonging to Proteobacteria, anaerobic ammonia oxidizers, Actinobacteria, Bacteroidetes and heterotrophic denitrifiers. Functional gene analysis corroborated with the presence of specific nitrite oxidizers. Quantitative polymerase chain reaction showed the abundance of nitrite oxidizers in the order of 1.51 ± 0.38 × 10⁹/g and 4.88 ± 0.42 × 10⁷/g in marine and brackish water consortia, respectively. Diversity indices and pattern of distribution of organisms within the consortia were analyzed using Geneious, VITCOMIC, Mega 5 and Primer software. The marine nitrite-oxidizing consortium showed higher Shannon–Wiener diversity and mean population diversity than brackish water consortium, suggesting that the former was having more diverse flora and higher potential to be used as startup cultures for activating nitrifying bioreactors subsequent to acclimatization to the required salinity.     

Geomorphic characteristics of a bedrock river inferred from drainage quantification,longitudinal profile,knickzone identification and concavity analysis: a DEM-based study

An examination of river channels has ability to provide substantial information regarding the geomorphic characteristics, control of lithology, tectonic uplift and geomorphic evolution during the geological past of an area. In this paper, a detailed study of geomorphic and structural investigation has been carried out for Pravara basin, Maharashtra, with the help of 90-m resolution SRTM DEM and geospatial techniques. Drainage network analysis performed in this paper demonstrates the general geomorphic characteristics, while the analysis of longitudinal profile synthesises lithological control over Pravara basin. Pravara is a 6th order drainage basin, encompassing an area of 2637 km². Bifurcation ratio reveals low to moderate structural control. Due to the hard rock lithology, the drainage density and stream frequency are low, and it indicates higher permeability in the sub-surface layers. The shape parameters denote that Pravara is highly elongated and it is easier to control floods in this basin. Relief parameters show very steep slope and higher vulnerability to the slope failure in some areas. Upstream of Pravara river has shown that series of breaks and knickzones indicate active erosion and acute lithological control on the channel. Major breaks are observed only in the main channel whereas in two major tributaries, no such breaks found, instead these tributaries are characterised by several knickzones which indicate regional variation in the lithological physiognomies. Different lithological stages on knickpoint and channel incision substantiate rejuvenation of Pravara river in several phases during geological past. The geospatial methodology carried out in this study can be pragmatic elsewhere around this world to recognise the geomorphic appearances and lithological control of a drainage basin.