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Analyzing Large-Scale Hydrologic Processes Using GRACE and Hydrometeorological Datasets
No full textWater demand in India is growing due to its increasing population, economic growth and urbanization. Consequently, knowledge of interdependencies of large-scale hydrometeorological processes is crucial for efficient water resources management. Estimates of Groundwater (GW) derived from Terrestrial Water Storage (TWS) data provided by Gravity Recovery and Climate Experiment (GRACE) satellite mission along with various other satellite observations and model estimates now facilitates such investigations. In an attempt which is first of its kind in India, this study proposes Independent Component Analysis (ICA) based spatiotemporal analysis of Precipitation (P), Evapotranspiration (ET), Surface Soil Moisture (SSM), Root Zone Soil Moisture (RZSM), TWS and GW to understand such interdependencies at intra- and interannual time scales. Results indicate that 84-99% of the total variability is explained by the first 6 ICs of all the variables, analyzed for a period 2002-2014. The Indian Summer Monsoon Rainfall (ISMR) is the causative-factor of the first component describing 61 82% of the total variability. The phase difference between all seasonal components of P and that of RZSM and ET is a month whereas it is 2 months between the seasonal components of P and that of SSM, TWS and GW. ET is observed to be largely dependent on RZSM while GW appears as the major component of TWS. GW and TWS trends of opposite nature were observed in northern and southern part of India caused by inter-annual rainfall variability. These findings when incorporated in modelling frameworks would improve forecasts resulting in better water management
Collaborative Learning of Stochastic Bandits Over a Social Network
No full textWe consider a collaborative online learning paradigm, wherein a group of agents connected through a social network are engaged in learning a stochastic multi-armed bandit problem. Each time an agent takes an action, the corresponding reward is instantaneously observed by the agent, as well as its neighbors in the social network. We perform a regret analysis of various policies in this collaborative learning setting. A key finding of this paper is that natural extensions of widely studied single agent learning policies to the network setting need not perform well in terms of regret. In particular, we identify a class of non-altruistic and individually consistent policies and argue by deriving regret lower bounds that they are liable to suffer a large regret in the networked setting. We also show that the learning performance can be substantially improved if the agents exploit the structure of the network and develop a simple learning algorithm based on dominating sets of the network. Specifically, we first consider a star network, which is a common motif in hierarchical social networks and show analytically that the hub agent can be used as an information sink to expedite learning and improve the overall regret. We also derive network-wide regret bounds for the algorithm applied to general networks. We conduct numerical experiments on a variety of networks to corroborate our analytical results
Influence of thermal annealing on optical and structural properties change in Bi-doped Ge30Se70 thin films
No full textThe effect of annealing on the structural and optical properties of thermally evaporated Ge30Se70 and Ge30Se60Bi10 thin films is reported in this paper. The prepared films were thermally annealed at 250 degrees C to optimize the optical properties which can be used for the optical device fabrication. X-ray diffraction study revealed no structural transformation whereas the surface morphology changed as observed from scanning electron microscopy. The optical properties of the deposited and annealed films have been investigated by using a UV-VIS-NIR spectrophotometer in the wavelength range of 400-1100 nm. The optical band gap of the Ge30Se70 annealed film is found to be increased while the energy gap of the Bi-doped annealed Ge30Se60Bi10 thin film decreased which is explained by the chemical disorderness, defect states and density of localized states in the mobility gap. The Tauc parameter and Urbach energy which measure the degree of disorder changed with the annealing process. The transmittivity increases and the absorption power decreases in the Ge30Se70 annealed film, whereas the reverse effect is noticed for the annealed Ge30Se60Bi10 thin film. The irreversible nature of this change can be useful for optical recording purposes
AMP-activated protein kinase promotes epithelial-mesenchymal transition in cancer cells through Twist1 upregulation
No full textThe developmental programme of epithelial-mesenchymal transition (EMT), involving loss of epithelial and acquisition of mesenchymal properties, plays an important role in the invasion-metastasis cascade of cancer cells. In the present study, we show that activation of AMP-activated protein kinase (AMPK) using A769662 led to a concomitant induction of EMT in multiple cancer cell types, as observed by enhanced expression of mesenchymal markers, decrease in epithelial markers, and increase in migration and invasion. In contrast, inhibition or depletion of AMPK led to a reversal of EMT. Importantly, AMPK activity was found to be necessary for the induction of EMT by physiological cues such as hypoxia and TGF beta treatment. Furthermore, AMPK activation increased the expression and nuclear localization of Twist1, an EMT transcription factor. Depletion of Twist1 impaired AMPK-induced EMT phenotypes, suggesting that AMPK might mediate its effects on EMT, at least in part, through Twist1 upregulation. Inhibition or depletion of AMPK also attenuated metastasis. Thus, our data underscore a central role for AMPK in the induction of EMT and in metastasis, suggesting that strategies targeting AMPK might provide novel approaches to curb cancer spread
Substrate-induced domain movement in a bifunctional protein, DcpA, regulates cyclic di-GMP turnover: Functional implications of a highly conserved motif
No full textIn eubacteria, cyclic di-GMP (c-di-GMP) signaling is involved in virulence, persistence, motility and generally orchestrates multicellular behavior in bacterial biofilms. Intracellular c-di-GMP levels are maintained by the opposing activities of diguanylate cyclases (DGCs) and cognate phosphodiesterases (PDEs). The c-di-GMP homeostasis in Mycobacterium smegmatis is supported by DcpA, a conserved, bifunctional protein with both DGC and PDE activities. DcpA is a multidomain protein whose GAF-GGDEF-EAL domains are arranged in tandem and are required for these two activities. To gain insight into how interactions among these three domains affect DcpA activity, here we studied its domain dynamics using real-time FRET. We demonstrate that substrate binding in DcpA results in domain movement that prompts a switch from an open to a closed conformation and alters its catalytic activity. We found that a single point mutation in the conserved EAL motif (E384A) results in complete loss of the PDE activity of the EAL domain and in a significant decrease in the DGC activity of the GGDEF domain. Structural analyses revealed multiple hydrophobic and aromatic residues around Cys(579) that are necessary for proper DcpA folding and maintenance of the active conformation. On the basis of these observations and taking into account additional bioinformatics analysis of EAL domain-containing proteins, we identified a critical putatively conserved motif, GCXXXQGF, that plays an important role in c-di-GMP turnover. We conclude that a substrate-induced conformational switch involving movement of a loop containing a conserved motif in the bifunctional diguanylate cyclase-phosphodiesterase DcpA controls c-di-GMP turnover in M. smegmatis
Recent Advances in the Organocatalytic Enantioselective Synthesis of Functionalized -Lactones
No full textThis Focus Review highlights recent developments in the organocatalytic enantioselective synthesis of -lactone derivatives. Owing to the importance of -lactones as a heterocyclic motif that is present in a variety of natural products and biologically active molecules, several catalytic methods have been developed for the synthesis of these compounds in their enantiomerically pure form. Organocatalytic methods that employ N-heterocyclic carbenes (NHCs), cinchona alkaloids, isothioureas, 4-dimethylaminopyridine (DMAP) derivatives, and phosphines have allowed the highly enantioselective synthesis of -lactones from cheap and readily available starting materials. Moreover, the inherent strain in the four-membered ring of -lactones has also been utilized in further synthetic transformations, thus making -lactones a versatile intermediate in organic synthesis
Spatial patterns of long-term vegetation greening and browning are consistent across multiple scales: Implications for monitoring land degradation
No full textUnderstanding spatial-temporal patterns of terrestrial vegetation response to climate change (long-term greening/browning) is important for developing strategies to mitigate degradation. Semiarid rangelands are especially susceptible to degradation, which challenges wildlife conservation and human livelihoods that depend on livestock production. In the cold-arid Trans-Himalayan ecosystem (northern India), temperature is increasing, and it is also becoming progressively wetter. Yet, counter-intuitively, there are widespread concerns over degradation. We evaluated whether greening/browning patterns in long-term satellite-derived vegetation indices (normalized difference vegetation index NDVI]) are consistent across different spatial and temporal scales using 6 datasets: MODIS (250m, 500m, 1km, and 5.5km), SPOT 1km, and GIMMS 8km. Results indicate browning in the spring and greening in late summer. Location of hotspots of degradation (browning) was broadly consistent across spatial scales (10(-2)-10(2)km(2)) and were found in regions with warmer temperature and at higher elevations. Broadly, the spatial/temporal pattern of browning does not coincide strongly with location and timing of human land use via livestock grazing. This geographical and seasonal context indicates that vegetation response may be more strongly related to climate than to human land use (overgrazing). Importantly, the dynamic nature of greening/browning, across space and time, is not captured by composite annual metrics (sum-NDVI, max-NDVI, and mean-NDVI). This reiterates the importance of both intraannual and interannual assessments. Location of hotspots indicates that degradation occurs in a spatially contiguous manner, but these are not stationary and instead shift with seasons. Overall, the results show that evaluating the consistency of greening/browning trends across different spatial/temporal scales is critical for understanding and managing vegetation degradation
Optimal Renormalization and the Extraction of Strange Quark Mass from Semi-leptonic tau-Decay
No full textProgressive damage through interface microcracking in cementitious composites: A micromechanics based approach
No full textA multiscale model in the framework of micromechanics is developed to study the effect of microcracks present at the interface between coarse aggregates and mortar matrix in cementitious composites. The different stages of damage induced by the propagation of microcracks are analyzed at the mesoscale with the aid of solutions based on interface fracture mechanics. Using the solution of the interaction between an edge dislocation and a circular inclusion with an interface crack, the stress intensity factor of a kinked arc crack is derived numerically by the method of distributed dislocations. The macroscopic response under uniaxial tensile loading is seen to be affected considerably by the presence of microcracks. Various factors such as the inclusion size, inclusion volume fraction, initial size of microcrack and elastic properties of the individual phases are found to influence the overall constitutive behaviour of the composite. The findings of the study can be utilized to provide guidelines to tailor the material properties and enhance the performance of such composites. (C) 2018 Elsevier Ltd. All rights reserved