451 research outputs found
Fuzzy Logic Based DSR Trust Estimation Routing Protocol for MANET Using Evolutionary Algorithms
In MANET attaining consistent routing is a main problem due to several reasons such as lack of static infrastructure, exposed transmission medium, energetic network topology and restricted battery power. These features also create the scheme of direction-finding protocols in MANETs become even more interesting. In this work, a Trust centered routing protocol is suggested, since trust plays a vital role in computing path in mobile ad hoc networks (MANETs). Estimating and computing trust encourages cooperation in mobile ad hoc networks (MANETs). Various present grade systems suddenly estimate the trust by considering any one of the parameters such as energy of node, number of hops and mobility. Estimating trust is an Energetic multi objective optimization problem (EMOPs) typically including many contradictory goals such as lifetime of node, lifetime of link and buffer occupancy proportion which change over time. To solve this multi objective problem, a hybrid Harmony Search Combined with Genetic algorithm and Cuckoo search is used along with reactive method Dynamic Source routing protocol to provide the mobile hosts to find out and sustain routes between the origin node (SN) to the target node (TN). In this work, the performance of the direction-finding practice is assessed using throughput, end to end delay, and load on the network and route detection period
A three-dimensional open-framework tin(II) phosphate exhibiting reversible dehydration and ion-exchange properties
A three-dimensional open-framework tin(II) phosphate, prepared hydrothermally with 1,3-diaminopentane as the template, is shown to exhibit reversible dehydration and ion-exchange properties
Synthesis of agarose-metal/semiconductor nanoparticles having superior bacteriocidal activity and their simple conversion to metal-carbon composites
Agarose, a naturally occurring biopolymer is used for the stabilization of metal, semiconductor nanoparticles. Ag and Cu nanoparticles stabilized in agarose matrix show excellent antibacterial activity against E. coli bacteria. The well dispersed metal nanoparticles within the agarose composite films can be readily converted to carbon-metal composites of catalytic importance
Water-solubilized aminoclay–metal nanoparticle composites and their novel properties
Nanoparticles of metals such as Au, Ag, Pd and Pt embedded in exfoliated sheets of aminoclays of the type R8Si8Mg6O16(OH)4, where R=CH2CH2NH2 are entirely water soluble. These sheets of the composite come to the organic-aqueous interface on addition of alkane thiols to the aqueous layer
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Crystal Structure Analysis of a Putative Oxidoreductase From Klebsiella Pneumoniae
Klebsiella pneumoniae, a gram-negative enteric bacterium, is found in nosocomial infections which are acquired during hospital stays for about 10% of hospital patients in the United States. The crystal structure of a putative oxidoreductase from K. pneumoniae has been determined. The structural information of this K. pneumoniae protein was used to understand its function. Crystals of the putative oxidoreductase enzyme were obtained by the sitting drop vapor diffusion method using Polyethylene glycol (PEG) 3350, Bis-Tris buffer, pH 5.5 as precipitant. These crystals were used to collect X-ray data at beam line X12C of the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory (BNL). The crystal structure was determined using the SHELX program and refi ned with CNS 1.1. This protein, which is involved in the catalysis of an oxidation-reduction (redox) reaction, has an alpha/beta structure. It utilizes nicotinamide adenine dinucleotide phosphate (NADP) or nicotine adenine dinucleotide (NAD) to perform its function. This structure could be used to determine the active and co-factor binding sites of the protein, information that could help pharmaceutical companies in drug design and in determining the protein’s relationship to disease treatment such as that for pneumonia and other related pathologies
Pulsed Feedback Defers Cellular Differentiation
Environmental signals induce diverse cellular differentiation programs. In certain systems, cells defer differentiation for extended time periods after the signal appears, proliferating through multiple rounds of cell division before committing to a new fate. How can cells set a deferral time much longer than the cell cycle? Here we study Bacillus subtilis cells that respond to sudden nutrient limitation with multiple rounds of growth and division before differentiating into spores. A well-characterized genetic circuit controls the concentration and phosphorylation of the master regulator Spo0A, which rises to a critical concentration to initiate sporulation. However, it remains unclear how this circuit enables cells to defer sporulation for multiple cell cycles. Using quantitative time-lapse fluorescence microscopy of Spo0A dynamics in individual cells, we observed pulses of Spo0A phosphorylation at a characteristic cell cycle phase. Pulse amplitudes grew systematically and cell-autonomously over multiple cell cycles leading up to sporulation. This pulse growth required a key positive feedback loop involving the sporulation kinases, without which the deferral of sporulation became ultrasensitive to kinase expression. Thus, deferral is controlled by a pulsed positive feedback loop in which kinase expression is activated by pulses of Spo0A phosphorylation. This pulsed positive feedback architecture provides a more robust mechanism for setting deferral times than constitutive kinase expression. Finally, using mathematical modeling, we show how pulsing and time delays together enable “polyphasic” positive feedback, in which different parts of a feedback loop are active at different times. Polyphasic feedback can enable more accurate tuning of long deferral times. Together, these results suggest that Bacillus subtilis uses a pulsed positive feedback loop to implement a “timer” that operates over timescales much longer than a cell cycle
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