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Unconventional energy transfer from narrow to broad luminescent wide band gap materials
No full textHere, we demonstrate an unconventional energy transfer with narrow band gap CdTe/PbS quantum dots as donors and broad luminescent wide-band-gap oxide materials as acceptors. As a result, the luminescence of wide band gap materials increases and the enhancement factor follows a linear process for photon conversion as in the case of Forster resonance energy transfer. In addition, the strong anti-reflection effect enabling efficient light harvesting, broad spectral overlapping and strong coupling between quantum dots and oxides are the key processes for the unconventional energy transfer. An enhancement of around similar to 5500% is observed for GeO2/PbS quantum dots which is higher than that reported for the conventional energy transfer process. The findings demonstrate unconventional energy transfer which enables a greater understanding and rational engineering of light harvesting devices and quantum light sources
``Rinse, Repeat'': An Efficient and Reusable SERS and Catalytic Platform Fabricated by Controlled Deposition of Silver Nanoparticles on Cellulose Paper
No full textGrafting metal nanoparticles (NPs) on flexible platforms is being increasingly attempted to advance their usage in the field of catalysis, sensing, energy storage, etc. However, anchoring NPs on substrates is nontrivial as it involves surface modification of the NPs and/or the substrate, which makes the whole process tedious. Here, we extend the classical ``silver-mirror'' reaction to unmodified filter paper achieving a controllable deposition of Ag NPs. The Ag NPs/filter paper thus obtained was employed as an enhanced Raman scattering (SERS) substrate achieving detection limits down to picomolar (10(-12) M) and nanomolar (10(-9) M) concentrations for rhodamine 6G and rhodamine B, with an enhancement factor (EF) of 1.42 X 10(10) and 0.659 X 10(6), respectively. To check its usage for practical applications, the substrate was extended to detect trace amounts of illicit dyes used on common vegetables and contaminants in rain, pond, and tap water with excellent reproducibility. Moreover, the as-prepared Ag paper can be directly employed for 4-nitrophenol reduction, which can be completely reduced to 4-aminophenol (4-AP) in a single step within seconds. The substrate can be reused several times over without any noticeable change in its catalytic activity. Finally, we studied the chemical transformation of 4-nitrophenol to 4-aminophenol by studying the concomitant spectral response, thereby integrating catalysis and SERS on a single substrate. This method thus provides a facile avenue to low-cost paper-based functional substrates for multimodal applications
Application of 1D and 2D hydrodynamic modeling to study glacial lake outburst flood (GLOF) and its impact on a hydropower station in Central Himalaya
No full textThe existence of numerous lakes in the higher reaches of the Himalaya makes it a potential natural hazard as it imposes a risk of glacial lake outburst flood (GLOF), which can cause great loss of life and infrastructure in the downstream regions. Hydrodynamic modeling of a natural earth-dam failure and hydraulic routing of the breach hydrograph allow us to characterize the flow behavior of a potential flood along a given flow channel. In the present study, the flow hydraulics of a potential GLOF generated due to the moraine failure of the Satopanth lake located in the Alaknanda basin is analyzed using one-dimensional and two-dimensional hydrodynamic computations. Field measurements and mapping were carried out at the lake site and along the valley using high-resolution DGPS points. The parameters of Manning's roughness coefficient and terrain elevation were derived using satellite-based raster, the accuracy of which is verified using field data. The volume of the lake is calculated using area-based scaling method. Unsteady flood routing of the dam-break outflow hydrograph is performed along the flow channel to compute hydraulic parameters of peak discharge, water depth, flow velocity, inundation and stream power at a hydropower dam site located 28km downstream of the lake. Assuming the potential GLOF event occurs contemporaneously with a 100-year return period flood, unsteady hydraulic routing of the combined flood discharge is performed to evaluate its impact on the hydropower dam. The potential GLOF resulted in a peak discharge of2600 m(3)s(-1) at the dam site which arrived 38min after the initiation of the moraine-failure event. The temporal characteristics of the flood wave analyzed using 2D unsteady simulations revealed maximum inundation depth and flow velocity of 7.12m and 7.6ms(-1), respectively, at the dam site. Assuming that the control gates of the dam remain closed, water depth increases at a rate of 4.5m per minute and overflows the dam approximately 4min after the flood wave arrival
Towards multiscale modeling of the CD8(+) T cell response to viral infections
No full textThe CD8(+) T cell response is critical to the control of viral infections. Yet, defining the CD8(+) T cell response to viral infections quantitatively has been a challenge. Following antigen recognition, which triggers an intracellular signaling cascade, CD8(+) T cells can differentiate into effector cells, which proliferate rapidly and destroy infected cells. When the infection is cleared, they leave behind memory cells for quick recall following a second challenge. If the infection persists, the cells may become exhausted, retaining minimal control of the infection while preventing severe immunopathology. These activation, proliferation and differentiation processes as well as the mounting of the effector response are intrinsically multiscale and collective phenomena. Remarkable experimental advances in the recent years, especially at the single cell level, have enabled a quantitative characterization of several underlying processes. Simultaneously, sophisticated mathematical models have begun to be constructed that describe these multiscale phenomena, bringing us closer to a comprehensive description of the CD8(+) T cell response to viral infections. Here, we review the advances made and summarize the challenges and opportunities ahead
Neuron-Astrocyte Liaison to Maintain Lipid Metabolism of Brain
No full textNeuron-astrocyte crosstalk is a tightly regulated process that is essential for overall proper functioning of the brain. Maria S. Ioannou et al. (Cell, 2019) revealed a novel and compelling function of neuronastrocyte crosstalk that explains how neurons cope with their accumulating toxic lipid particles under various scenarios
Parameterized dichotomy of choosing committees based on approval votes in the presence of outliers
No full textApproval voting provides an opportunity for the agents to make a comment about every candidate, without incurring the overhead of determining a full ranking on the entire set of candidates. This makes approval voting a natural choice for many practical applications. In this work, we focus on the use of approval voting for selecting a committee in scenarios where we can have few outrageous voters whom we call outliers. More specifically, we study the computational complexity of the committee selection problem for commonly used approval-based voting rules in the presence of outliers. Our first result shows that outliers render the committee selection problem intractable for approval, net approval, and minisum approval voting rules. We next study the parameterized complexity of this problem with five natural parameters, namely the target score, the size of the committee (and its dual parameter namely the number of candidates outside the committee); and the number of outliers (and its dual parameter namely the number of non-outliers). Our main contribution in this paper is dichotomous results, which establish the parameterized complexity of the problem of selecting a committee under approval, net approval, and minisum approval voting rules for all subsets of the above five parameters considered here (by showing either FPT or W1]-hardness for all subsets of parameters)
Bridging micro-to-macro scale damage in UD-FRP laminates under tensile loading
No full textA unified numerical framework for progressive damage analysis of a unidirectional fiber reinforced plastic (UD-FRP) laminate has been developed by explicitly accounting for damage progression at the micro-level. At the micro-level, a three dimensional repeating unit cell (3D-RUC) comprised of polymer matrix with fibers and interfaces has been modeled allowing for plasticity based matrix damage, maximum stress based fiber failure, and a cohesive traction-separation criterion for interface failure. Coupling of macro- and micro-levels has been accomplished using non-linear homogenization. In other words, the homogenized stress-strain curve obtained at the micro-level is utilized to predict the constitutive behavior at the macro-level. Typical material characterization tests have been conducted to estimate constituent behavior. Predictions from the current analysis are found to match well with the response of UD-FRP plates of different fiber orientations with a central hole under tensile loading
Enantioselective Direct Vinylogous Allylic Alkylation of 4-Methylquinolones under Iridium Catalysis
No full textThe first enantioselective vinylogous allylic alkylation of 4-methylquinolones has been developed. This iridium-catalyzed reaction introduces an allyl group at the gamma-position of 4-methyl-2-quinolones with exclusive branched selectivity and an excellent level of enantioselectivity. This in turn allows for the enantioselective synthesis of gamma-allylquinolines and related nitrogenous heterocycles. This is the first application of 4-methylquinolones in an enantioselective transformation
Biconservative Submanifolds in S-n x R and H-n x R
No full textIn this paper we study biconservative submanifolds in S-n x R and H-n x R with parallel mean curvature vector field and codimesion 2. We obtain some sufficient and necessary conditions for such submanifolds to be conservative. In particular, we obtain a complete classification of 3-dimensional biconservative submanifolds in S-4 x R and H-4 x R with nonzero parallel mean curvature vector field. We also get some results for biharmonic submanifolds in S-n x R and H-n x R
A note on the deformed Hermitian Yang-Mills PDE
No full textWe prove a priori estimates for a generalised Monge-Ampere PDE with `non-constant coefficients' thus improving a result of Sun in the Kahler case. We apply this result to the deformed Hermitian Yang-Mills (dHYM) equation of Jacob-Yau to obtain an existence result and a priori estimates for some ranges of the phase angle assuming the existence of a subsolution. We then generalise a theorem of Collins-Szekelyhidi on toric varieties and use it to address a conjecture of Collins-Jacob-Yau