Showing papers by "Sanjay Ghosh published in 2015"

Loss-of-function analysis reveals distinct requirements of the translation initiation factors eIF4E, eIF4E-3, eIF4G and eIF4G2 in Drosophila spermatogenesis.

Abstract: In eukaryotes, post-transcriptional regulation of gene expression has a key role in many cellular and developmental processes. Spermatogenesis involves a complex developmental program that includes changes in cell cycle dynamics and dramatic cellular remodeling. Translational control is critical for spermatogenesis in Drosophila as many mRNAs synthesized in the spermatocytes are translated only much later during spermatid differentiation. Testes-specific translation initiation factors eIF4E-3 and eIF4G2 are essential specifically for male fertility. However, details of their roles during different stages of spermatogenesis are unknown, and the role of canonical translation initiation factors in spermatogenesis remains unexplored. In this study, we addressed the functional role of eIF4E-1, eIF4E-3, eIF4G and eIF4G2 in testes development and formation of mature sperm. Using the UAS-Gal4 system and RNA interference, we systematically knocked down these four genes in different stages of germ cell development, and in the somatic cells. Our results show that eIF4E-1 function in early germ cells and the surrounding somatic cells is critical for spermatogenesis. Both eIF4E-1 and eIF4E-3 are required in spermatocytes for chromosome condensation and cytokinesis during the meiotic stages. Interestingly, we find that eIF4G knockdown did not affect male fertility while eIF4G2 has distinct functions during spermatogenesis; it is required in early germ cells for proper meiotic divisions and spermatid elongation while its abrogation in spermatocytes caused meiotic arrest. Double knockdown of eIF4G and eIF4G2 shows that these proteins act redundantly during the early stages of spermatogenesis. Taken together, our analysis reveals spatio-temporal roles of the canonical and testes-specific translation initiation factors in coordinating developmental programs during spermatogenesis.

Automated change detection in satellite images using machine learning algorithms for Delhi, India

Abstract: In remote sensing, change detection is used in land use and cover analysis, forest or vegetation assessment and, flood monitoring. Although manual change detection is an option, the time required for it can be prohibitive. It is also highly subjective depending on the expertise of the analyst. Hence, the need for automated methods for such analysis tasks have emerged and thus gives rise to unsupervised machine learning algorithm. This paper analyzes the effectiveness of the three types of unsupervised Machine learning algorithms (MLAs) for change detection to detect the change in some of the dominant classes in an urban area, such as, vegetation, built-up and water bodies. Landsat 5 TM and Landsat 8 OLI imageries have been selected for a part of New Delhi and its nearby area. In this study, three indices namely Normalized Difference Built-up Index (NDBI), Modified Normalized Difference Water Index (MNDWI) and Modified Soil Adjusted Vegetation Index (MSAVI 2 ) have been generated from the Landsat data. Three algorithms, namely, K-Means, FCM and EM have been used, since these represent three different concepts in machine learning category i.e. partition based, fuzzy and probability based respectively. The same have been implemented in MATLAB for identifying different type of land cover over a period of 1998–2011. Considering both the intra- and inter-cluster distances, silhouette coefficients have been used for evaluation of cluster quality. The change is quantified in terms of percentage that depends upon the outcome of clustering and the number of pixel grouped in each class i.e. urban, vegetation and water.

Relay placement and spectrum sharing strategies for soft and fractional frequency reuse schemes

Abstract: In this paper, we consider the problem of relay placement and resource sharing among the relays and the base station in a cellular network. Specifically, we focus on the problem of deploying half duplex relays in cellular systems employing soft frequency reuse (SFR) and fractional frequency reuse (FFR) schemes. For both SFR and FFR schemes, we propose strategies for relay placement and assigning mobile stations among the relays and the base station. We also propose strategies for allocating the spectrum among the relays and the base station, which are consistent with the frequency planning of SFR and FFR layouts. We study the performance of the proposed techniques using simulations of a cellular network with 19 cells layout. Our results show that the proposed relay-aided schemes achieve significant improvements in terms of both coverage probability and throughput over the conventional cellular system without relays.