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Accurate modeling of doubly fed induction generator based wind farms in load flow analysis
No full textThis paper presents an iterative approach for incorporating doubly fed induction generator (DFIG) based variable speed wind farms in steady state studies such as load flow analysis. The proposed approach is based on an accurate steady state equivalent circuit of a DFIG. In the proposed approach, the power flow model of a node with DFIG is determined based on the reference to reactive power control loop of rotor side converter. In addition, the proposed approach takes into consideration various limits associated with the DFIG. Case studies on sample 6-bus system and 418-bus equivalent system of Indian southern grid are presented to validate the proposed approach. (c) 2017 Elsevier B.V. All rights reserved
Sustainable Growth and Lipid Production from Chlorella pyrenoidosa Using N-Doped Carbon Nanosheets: Unravelling the Role of Graphitic Nitrogen
No full textThe advent of novel carbonaceous nanomaterials (CMs) associated with microalgae paved an alternate way for the bioeconomic production of biofuels as well as high value added compounds. Herein, we for the first time, present a holistic approach for sustainable biomass and lipid production from Chlorella pyrenoidosa, wherein CMs, namely N-doped carbon nanosheets (CNS) and N-doped graphene nanosheets (NGS) were used as one of the algal growth supporting factors. Doping carbon nanomaterials with nitrogen can effectively tune its electronic structure and other intrinsic properties for efficient photocatalysis. The utilization of CNS and NGS in this process lead to rapid, environment friendly, and facile assimilation of biomass and lipids for the development of nutraceuticals, pharmaceuticals, and other bioenergy associated applications. Employing a suite of characterization methods, the intrinsic structural and morphological properties of CMs were revealed. Compared with control, the lipid content obtained in the presence of undoped carbonized carbon materials (CCM), CNS, and NGS were found to be around 1.5-,2-, and 6-fold higher, respectively, at similar growth conditions. We, therefore, envisage that graphitic nitrogen rich NGS plays a pivotal role in enhancing the lipid production from algae. This finding, therefore, exhibits a promising potential to bring about a paradigm shift in the field of bioenergy frameworks
Structure, folding and stability of a minimal homologue from Anemonia sulcata of the sea anemone potassium channel blocker ShK
No full textPeptide toxins elaborated by sea anemones target various ion-channel sub-types. Recent transcriptomic studies of sea anemones have identified several novel candidate peptides, some of which have cysteine frameworks identical to those of previously reported sequences. One such peptide is AsK132958, which was identified in a transcriptomic study of Anemonia sulcata and has a cysteine framework similar to that of ShK from Stichodactyla helianthus, but is six amino acid residues shorter. We have determined the solution structure of this novel peptide using NMR spectroscopy. The disulfide connectivities and structural scaffold of AsK132958 are very similar to those of ShK but the structure is more constrained. Toxicity assays were performed using grass shrimp (Palaemonetes sp) and Artemia nauplii, and patch-clamp electrophysiology assays were performed to assess the activity of AsK132958 against a range of voltage-gated potassium (K-V) channels. AsK132958 showed no activity against grass shrimp, Artemia nauplii, or any of the K-V channels tested, owing partly to the absence of a functional Lys-Tyr dyad. Three AsK132958 analogues, each containing a Tyr in the vicinity of Lys19, were therefore generated in an effort to restore binding, but none showed activity against any of K-V channels tested. However, AsK132958 and its analogues are less susceptible to proteolysis than that of ShK. Our structure suggests that Lys19, which might be expected to occupy the pore of the channel, is not sufficiently accessible for binding, and therefore that AsK132958 must have a distinct functional role that does not involve K-V channels
SNR based secure communication via untrusted amplify-and-forward relay nodes using artificial noise
No full textA two-phase beamforming solution for secure communication using untrusted relay nodes is presented. To thwart eavesdropping attempts of participant relay nodes, we deliberately introduce artificial noise in the source message. We observe that for certain scenarios, the source node prefers to allocate its full power to the message signal and, therefore, in the absence of artificial noise, such transmissions will be vulnerable to eavesdropping. Therefore, we provide a signal-to-noise ratio (SNR) based framework for secure communication. We intend to bring down the SNR at each of the untrusted relay nodes below a certain predefined threshold; whereas, using beamforming, we want to boost the SNR at the destination. With this motive, we evaluate the optimal scaling vector for the beamforming phase, which not only nullifies the artificial noise transmitted initially, but also maximizes the SNR at the destination. We discuss both the total and individual power constraint scenarios and provide an analytical optimal solution and an iterative algorithm, respectively
Electrochemical nonenzymatic sensing of glucose using advanced nanomaterials
No full textAn overview (with 376 refs.) is given here on the current state of methods for electrochemical sensing of glucose based on the use of advanced nanomaterials. An introduction into the field covers aspects of enzyme based sensing versus nonenzymatic sensing using nanomaterials. The next chapter cover the most commonly used nanomaterials for use in such sensors, with sections on uses of noble metals, transition metals, metal oxides, metal hydroxides, and metal sulfides, on bimetallic nanoparticles and alloys, and on other composites. A further section treats electrodes based on the use of carbon nanomaterials (with subsections on carbon nanotubes, on graphene, graphene oxide and carbon dots, and on other carbonaceous nanomaterials. The mechanisms for electro-catalysis are also discussed, and several Tables are given where the performance of sensors is being compared. Finally, the review addresses merits and limitations (such as the frequent need for working in strongly etching alkaline solutions and the need for diluting samples because sensors often have analytical ranges that are far below the glucose levels found in blood). We also address market/technology gaps in comparison to commercially available enzymatic sensors
Satellite-based estimates of surface water dynamics in the Congo River Basin
No full textIn the Congo River Basin (CRB), due to the lack of contemporary in situ observations, there is a limited understanding of the large-scale variability of its present-day hydrologic components and their link with climate. In this context, remote sensing observations provide a unique opportunity to better characterize those dynamics. Analyzing the Global Inundation Extent Multi-Satellite (GIEMS) time series, we first show that surface water extent (SWE) exhibits marked seasonal patterns, well distributed along the major rivers and their tributaries, and with two annual maxima located: i) in the lakes region of the Lwalaba sub-basin and ii) in the ``Cuvette Centrale'', including Tumba and Mai-Ndombe Lakes. At an interannual time scale, we show that SWE variability is influenced by ENSO and the Indian Ocean dipole events. We then estimate water level maps and surface water storage (SWS) in floodplains, lakes, rivers and wetlands of the CRB, over the period 2003-2007, using a multi satellite approach, which combines the GIEMS dataset with the water level measurements derived from the ENVISAT altimeter heights. The mean annual variation in SWS in the CRB is 81 +/- 24 km(3) and contributes to 19 +/- 5% of the annual variations of GRACE-derived terrestrial water storage (33 +/- 7% in the Middle Congo). It represents also similar to 6 +/- 2% of the annual water volume that flows from the Congo River into the Atlantic Ocean
c-Abl-TWIST1 Epigenetically Dysregulate Inflammatory Responses during Mycobacterial Infection by Co-Regulating Bone Morphogenesis Protein and miR27a
No full textMycobacteria propelled modulation of host responses is of considerable interest in the face of emerging drug resistance. Although it is known that Abl tyrosine kinases affect entry and persistence of mycobacteria, mechanisms that couple c-Abl to proximal signaling pathways during immunity are poorly understood. Loss-of-function of c-Abl through Imatinib, in a mouse model of tuberculosis or RNA interference, identified bone morphogenesis protein (BMP) signaling as its cellular target. We demonstrate that c-Abl promotes mycobacterial survival through epigenetic modification brought about by KAT5-TWIST1 at Bmp loci. c-Abl-BMP signaling deregulated iNOS, aggravating the inflammatory balance. Interestingly, BMP signaling was observed to have far-reaching effects on host immunity, as it attenuated TLR3 pathway by engaging miR27a. Significantly, these events were largely mediated via WhiB3 and DosR/S/T but not SecA signaling pathway of mycobacteria. Our findings suggest molecular mechanisms of host pathways hijacked by mycobacteria and expand our understanding of c-Abl inhibitors in potentiating innate immune responses
Estimation of the climate change impact on a catchment water balance using an ensemble of GCMs
No full textThis work evaluates the impact of climate change on the water balance of a catchment in India. Rainfall and hydro-meteorological variables for current (20C3M scenario, 1981-2000) and two future time periods: mid of the 21st century (2046-2065) and end of the century (2081-2100) are simulated using Modified Markov Model-Kernel Density Estimation (MMM-KDE) and k-nearest neighbor downscaling models. Climate projections from an ensemble of 5 GCMs (MPI-ECHAM5, BCCR-BCM2.0, CSIRO-mk3.5, IPSL-CM4, and MRI-CGCM2) are used in this study. Hydrologic simulations for the current as well as future climate scenarios are carried out using Soil and Water Assessment Tool (SWAT) integrated with ArcGIS (ArcSWAT v.2009). The results show marginal reduction in runoff ratio, annual streamflow and groundwater recharge towards the end of the century. Increased temperature and evapotranspiration project an increase in the irrigation demand towards the end of the century. Rainfall projections for the future shows marginal increase in the annual average rainfall. Short and moderate wet spells are projected to decrease, whereas short and moderate dry spells are projected to increase in the future. Projected reduction in streamflow and groundwater recharge along with the increase in irrigation demand is likely to aggravate the water stress in the region under the future scenario. (C) 2017 Elsevier B.V. All rights reserved
Sustained drag reduction and thermo-hydraulic performance enhancement in textured hydrophobic microchannels
No full textDrag reduction obtained on flow over textured hydrophobic surfaces has been ascribed to the presence of entrapped air within the surface micro-texture. To sustain the drag reduction, it is important that the entrapped air be maintained on the surface. However, the entrapped air bubbles tend to shrink with time and finally disappear, causing the drag reduction also to reduce and eventually vanish. Recent research shows that by controlling the absolute pressure of water, it is possible to sustain the entrapped air bubbles on the surface and hence the drag reduction for extended periods of time. In this paper, we explore the possibility of sustaining the entrapped air by varying the absolute temperature of water in the vicinity of the textured surface. For this, the textured surface is externally heated and the evolution in the size of trapped air bubbles with time is observed. Simultaneous pressure and temperature measurements are made along with the visualization, to study the concomitant effects on drag and heat transfer. We find that, varying the absolute temperature influences the trapped air bubble dynamics appreciably, which in turn affects the measured pressure drop across the channel. By varying the external heat input, it was found that the trapped air bubbles can be maintained on the surface for prolonged periods of time, at an optimum size suitable for drag reduction, such that sustained and maximized drag reduction can be achieved. The presence of trapped air bubbles is found to inhibit the heat transfer across the surface. However, when the pressure drop reduction achieved due to the presence of air bubbles is significant enough, the combined thermo-hydraulic performance is found to be enhanced. The results, not only provides important inputs towards achieving sustained drag reduction from textured hydrophobic surfaces, but also ascertains the feasibility of using such surfaces in micro-scale heat transfer applications. (C) 2017 Elsevier Ltd. All rights reserved
Universal RCFT correlators from the holomorphic bootstrap
No full textWe elaborate and extend the method of Wronskian differential equations for conformal blocks to compute four-point correlation functions on the plane for classes of primary fields in rational (and possibly more general) conformal field theories. This approach leads to universal differential equations for families of CFT's and provides a very simple re-derivation of the BPZ results for the degenerate fields phi(1,2) and phi(2,1) in the c < 1 minimal models. We apply this technique to compute correlators for the WZW models corresponding to the Deligne-Cvitanovic exceptional series of Lie algebras. The application turns out to be subtle in certain cases where there are multiple decoupled primaries. The power of this approach is demonstrated by applying it to compute four-point functions for the Baby Monster CFT, which does not belong to any minimal series