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Stress fluctuations in transient active networks
No full textInspired by experiments on dynamic extensile gels of biofilaments and motors, we propose a model of a network of linear springs with kinetics consisting of growth at a prescribed rate, death after a lifetime drawn from a distribution, and birth at a randomly chosen node. The model captures features such as the build-up of self-stress, that are not easily incorporated into hydrodynamic theories. We study the model numerically and show that our observations can largely be understood through a stochastic effective-medium model. The resulting dynamically extending force-dipole network displays many features of yielded plastic solids, and offers a way to incorporate strongly non-affine effects into theories of active solids. A rather distinctive form for the stress distribution, and a Herschel-Bulkley dependence of stress on activity, are our major predictions
Swell-Shrink-Consolidation Behavior of Rubber-Reinforced Expansive Soils
No full textThis study examines the effects of two types of recycled tire rubber of fine and coarse categories on the swell-shrink-consolidation behavior of a highly expansive soil mixture. Each of the two rubber choices were incorporated into the soil at four different content levels (i.e., rubber to dry soil mass ratio) of 5, 10, 20, and 30 %. The experimental program consisted of consistency limits, compaction, swell consolidation, swell-shrink, and unconfined compression tests. Improvement in the swell-shrink-consolidation capacity was in favor of higher rubber contents; however, when excessively included, it raised strength concerns. The swell-shrink-consolidation properties were also rubber size-dependent, meaning that the rubber of coarser sizes often outperformed finer rubber. In terms of strength, however, the two rubber types promoted similar results with marginal differences. The results of the unconfined compression tests were cross checked with the swell-shrink-consolidation properties to arrive at the optimum stabilization scenarios. A maximum rubber inclusion of 10 %, preferably the rubber of coarser category, proved to satisfy the stabilization objectives (i.e., decrease in the swell-shrink-consolidation capacity as well as maintain or improve the strength) and thus was deemed as the optimum choice. Where context changes and the strength and stiffness are not a primary concern, higher rubber inclusions of up to 20 % may also be considered acceptable
Role of longitudinal reinforcement on the behavior of under reinforced concrete beams subjected to fatigue loading
No full textIn this work, the role of steel reinforcement in under reinforced concrete beams when subjected to flexural fatigue loading is studied using the acoustic emission (AE) technique. Three-point bend notched beams of three different sizes and with varying reinforcement ratios are subjected to step-wise increasing variable amplitude fatigue loading. The crack mouth opening displacement (CMOD) and AE parameters are analyzed to study the evolution of damage, load carrying and failure mechanisms in under reinforced concrete beams. It is concluded that the presence of reinforcement substantially increases the fatigue life. Further, the CMOD could be used as a criterion for failure in reinforced concrete beams under fatigue loading
Tavorite LiFePO4OH hydroxyphosphate as an anode for aqueous lithium-ion batteries
No full textIn pursuit to find stable economic anode for aqueous lithium-ion batteries, tavorite structured LiFePO4OH hydroxyphosphate has been investigated in aqueous battery for the first time. First, the target compound is tested with organic electrolyte, giving the highest reported discharge capacity of 140 mAh g(-1) with an Fe3+/Fe2+ redox potential of 2.6 V with excellent reversibility. LiFePO4OH is found to work as a promising anode in aqueous electrolyte with capacity similar to 153 mAh g(-1) (at 0.42 V vs. Ag/AgCl) with good cycling stability. An all-phosphate LiFePO4 vertical bar LiFePO4OH aqueous full cell has been fabricated having the first cycle capacity of 120 mAh g(-1) (energy density similar to 97 Wh kg(-1)). Tavorite LiFePO4OH forms an economic potential anode for aqueous Li-ion batteries
Reactive template synthesis of Li1.2Mn0.54Ni0.13Co0.13O2 nanorod cathode for Li-ion batteries: Influence of temperature over structural and electrochemical properties
No full textCommon preparation methods of manganese-based Li-rich layered oxides include co-precipitation, combustion, spray pyrolysis, and molten salt synthesis. Herein, we present a facile new reactivetemplating route to prepare manganese-based lithium-rich Li1.2Mn0.54Ni0.13Co0.13O2 using beta-MnO2 nanorod, which plays a dual role as reactive template as well as Mn-source. Rietveld refinement and electron diffraction patterns confirm the formation of phase pure, highly crystalline Li1.2Mn0.54Ni0.13Co0.13O2 with two integrated layered components of 0.5(Li2MnO3).(0.5)(LiMn1/3Ni1/3Co1/3O2). Electron microscopy studies reveal the formation of anisotropic rod-like crystals of 0.8-1.0 mm in length and similar to 200 nm in thickness. The Li1.2Mn0.54Ni0.13Co0.13O2 nanorod as cathode for Li-ion battery, delivers an impressive reversible capacity of 223 mAh.g(-1) at 0.1C rate after 150 cycles and 161 mAh.g(-1) at 1 C rate after 300 cycles. Rapid structural transition from layered to spinel-like phase at high temperature (55 degrees C) leads to gradual decay in discharge capacity upon cycling, whereas low Li-ion diffusivity, cell resistance, and high viscosity hampers the performance at low temperature (5 degrees C). Impedance spectroscopy along with (dis) charge differential plots corroborate that activation of Li2MnO3 and Li-ion de(intercalation) into the MnO2 phase is very facile at high temperature (55 degrees C), which leads to high specific capacity, high coulombic efficiency, and high-power capability
Efficacy of black carbon aerosols: the role of shortwave cloud feedback
No full textUsing idealized climate model simulations, we investigate the effectiveness of black carbon (BC) aerosols in warming the planet relative to CO2 forcing. We find that a 60-fold increase in the BC aerosol mixing ratio from the present-day levels leads to the same equilibrium global mean surface warming (similar to 4.1 K) as for a doubling of atmospheric CO2 concentration. However, the radiative forcing is larger (similar to 5.5 Wm(-2)) in the BC case relative to the doubled CO2 case (similar to 3.8 Wm(-2)) for the same surface warming indicating the efficacy (a metric for measuring the effectiveness) of BC aerosols to be less than CO2. The lower efficacy of BC aerosols is related to the differences in the shortwave (SW) cloud feedback: negative in the BC case but positive in the CO2 case. In the BC case, the negative SW cloud feedback is related to an increase in the tropical low clouds which is associated with a northward shift (similar to 7 degrees) of the Intertropical Convergence Zone (ITCZ). Further, we show that in the BC case fast precipitation suppression offsets the surface temperature mediated precipitation response and causes similar to 8% net decline in the global mean precipitation. Our study suggests that a feedback between the location of ITCZ and the interhemispheric temperature could exist, and the consequent SW cloud feedback could be contributing to the lower efficacy of BC aerosols. Therefore, an improved representation of low clouds in climate models is likely the key to understand the global climate sensitivity to BC aerosols
A New Formula for Predicting Solar Cycles
No full textA new formula for predicting solar cycles based on the current theoretical understanding of the solar cycle from the flux transport dynamo is presented. Two important processes-fluctuations in the Babcock-Leighton (BL) mechanism and variations in the meridional circulation (MC), which are believed to be responsible for irregularities of the solar cycle-are constrained using observational data. We take the polar field near minima of the cycle as a measure of the randomness in the BL process, and the decay rate near the minima as a consequence of the change in MC. We couple these two observationally derived quantities into a single formula to predict the amplitude of the future solar cycle. Our new formula suggests that cycle 25 would be a moderate cycle. Whether this formula for predicting the future solar cycle can be justified theoretically is also discussed using simulations from the flux transport dynamo model
Mycobacterial transcript cleavage factor Gre, exhibits chaperone-like activity
No full textGre factors reactivate stalled elongation complexes by enhancing the intrinsic transcript cleavage activity of RNA polymerase. Previous work by us has shown that unlike in Escherichia coli (E.coli), Mycobacterium tuberculosis Gre factor is essential for its survival. Apart from their role in transcription regulation Gre factors have been implicated in stress response. A recent study has shown the role of E.coli GreA as a cellular chaperone, which inhibits aggregation of substrate proteins under heat stress condition. Moreover it was shown that GreA enables E.coli to survive heat shock and oxidative stress. In the current work, we have characterized the moonlighting chaperone activity and its plausible mechanism in Mycobacterium smegmatis Gre (MsGre) factor. We show here that MsGre prevents heat-induced aggregation of the substrate protein and also protects enzymatic activity. Interestingly Gre factor exists as a dimer in solution and does not undergo heat induced oligomerization. From the 8-anilino-1-naphthalene sulfonate (ANS) binding studies MsGre was shown to expose hydrophobic surface upon heat stress that would allow binding to unfolded or partially folded substrate protein. From Circular Dichroism (CD) studies, we also show that MsGre has a stable secondary structure under thermal stress. We propose that the presence of C-terminal FKBP-like fold in MsGre factor that might contribute to its chaperone-like function
Construction of highly redundant incoherent unit norm tight frames as a union of orthonormal bases
No full textUnit norm tight frames are useful in providing stable reconstruction. Incoherence, restricted isometry property and statistical restricted isometry property of a frame provide performance guarantees of sparse signal recovery algorithms in compressed sensing. Equiangular tight frames, mutually unbiased bases and chirp matrices are well known incoherent unit norm tight frames that exhibit near optimal sparse recovery guarantees. The dimension of frame elements belongs to some particular family of numbers and the number of elements in these frames is in the order of square of the dimension of the underlying space. In the present work, we construct incoherent unit norm tight frames for more general dimensions with higher redundancy than these frames. One of the important features of our construction is that it produces incoherent unit norm tight frames that are a union of orthonormal bases. In addition, the incoherent unit norm tight frames that we construct possess the statistical restricted isometry property and statistical incoherence property. As a result they exhibit near optimal theoretical guarantees in recovering sparse signals obtained from a generic random signal model. Using simulations, we demonstrate the efficacy of the constructed tight frames as good candidates for recovering sparse signals as against partial Fourier matrices and with existing constructions of incoherent unit norm tight frames
The WNT Framework in Shaping Immune Cell Responses During Bacterial Infections
No full textA large proportion of the world is inflicted with health concerns arising from infectious diseases. Moreover, there is a widespread emergence of antibiotic resistance among major infectious agents, partially stemming from their continuous dialog with the host, and their enormous capacity to remodel the latter toward a secure niche. Among the several infection-driven events, moderation of WNT signaling pathway has been identified to be strategically tuned during infections to govern host-pathogen interactions. Primarily known for its role in arbitrating early embryonic developmental events; aberrant activation of the WNT pathway has also been associated with immunological consequences during diverse patho-physiological conditions. Here, we review the different mechanisms by which components of WNT signaling pathways are exploited by discrete bacterial agents for their pathogenesis. Furthermore, recent advances on the cross-talk of WNT with other signaling pathways, the varied modes of WNT-mediated alteration of gene expression, and WNT-dependent post-transcriptional and post-translational regulation of the immune landscape during distinct bacterial infections would be highlighted