50175 research outputs found
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Sessile nanofluid droplet can act like a crane
No full textInteractive droplet systems form the backbone for emerging avenues in droplet based technologies like cell sorting, inkjet printing and digital microfluidics, to name a few. These and their associated fields have gained significant importance in the recent times. Here, we report one such phenomenon wherein a naturally evaporating nanocolloidal sessile droplet interacts with a porous silica gel bead to mimic a macro scale mechanical crane assembly. Precisely, we show a sequence of events displayed by the particle laden aqueous droplet (nanoparticles of silica at different loading rates placed on a hydrophobic substrate) when brought in contact with a meso-porous silica gel bead. First, preferential self-assembly along droplet-bead interface is followed by formation of an adhesive bond. The phenomenon continues until the evaporating droplet naturally lifts the bead. The kinematics of the lift mechanism can be represented by a simple four bar linkage. This work provides insights into interactions between droplets and freely placed porous objects across multiple spatio-temporal scales. Present study should not just motivate researchers to design interactive droplet based systems but also use the same to perform engineering tasks like the crane action. (C) 2017 Elsevier Inc. All rights reserved
Thymic Atrophy: Experimental Studies and Therapeutic Interventions
No full textThe thymus is essential for T cell development and maturation. It is extremely sensitive to atrophy, wherein loss in cellularity of the thymus and/or disruption of the thymic architecture occur. This may lead to lower naive T cell output and limited TCR diversity. Thymic atrophy is often associated with ageing. What is less appreciated is that proper functioning of the thymus is critical for reduction in morbidity and mortality associated with various clinical conditions including infections and transplantation. Therefore, therapeutic interventions which possess thymopoietic potential and lower thymic atrophy are required. These treatments enhance thymic output, which is a vital factor in generating favourable outcomes in clinical conditions. In this review, experimental studies on thymic atrophy in rodents and clinical cases where the thymus atrophies are discussed. In addition, mechanisms leading to thymic atrophy during ageing as well as during various stress conditions are reviewed. Therapies such as zinc supplementation, IL7 administration, leptin treatment, keratinocyte growth factor administration and sex steroid ablation during thymic atrophy involving experiments in animals and various clinical scenarios are reviewed. Interventions that have been used across different scenarios to reduce the extent of thymic atrophy and enhance its output are discussed. This review aims to speculate on the roles of combination therapies, which by acting additively or synergistically may further alleviate thymic atrophy and boost its function, thereby strengthening cellular T cell responses
Stochastic growth of cloud droplets by collisions during settling
No full textIn the last stage of droplet growth in clouds which leads to drizzle formation, larger droplets begin to settle under gravity and collide and coalesce with smaller droplets in their path. In this article, we shall deal with the simplified problem of a large drop settling amidst a population of identical smaller droplets. We present an expression for the probability that a given large drop suffers a given number of collisions, for a general statistically homogeneous distribution of droplets. We hope that our approach will serve as a valuable tool in dealing with droplet distribution in real clouds, which has been found to deviate from the idealized Poisson distribution due to mechanisms such as inertial clustering
Process mediated polymorphism, crystallographic texture and structure-property correlation in crystalline/amorphous blends
No full textSpecific interactions between the blend components (especially in crystalline/amorphous blends) induce miscibility under certain conditions However, depending on the processing history and the composition, the crystalline component crystallizes in different polymorphs. Herein, the effects of the amorphous content and various processing conditions on the phase transformation and the resulting texture were systematically assessed in blends of polyvinylidene fluoride and poly(methyl methacrylate). To this end, various blends were prepared by melt mixing and were subjected to different processing conditions like rolling, poling, and rolling followed by poling. To assess the different polymorphs of the crystalline component (polyvinylidene fluoride) on account of the processing history, spectroscopic, X-ray diffraction, thermal, mechanical and segmental transitions were systematically investigated and an attempt was made to correlate the observations with the resulting texture in the blends. The crystallographic texture was evaluated using X-ray diffraction and the mechanical properties as a result of the texture were studied by dynamic mechanical analyzer. The spectroscopic techniques revealed predominantly a phase in as-pressed samples, irrespective of the amorphous content However, interestingly, after rolling, the blends showed predominantly beta phase. More interestingly, the highest beta phase content (>95%) was obtained for blends that were rich in the crystalline phase which were deformed up to a strain of 80%. It was observed that higher the strain, lower the relaxation leading to stronger texture and facilitated the formation of beta polymorph. This phase transformation after rolling was accompanied by an increase in the degree of crystallinity and storage modulus. The dielectric response revealed that the samples that were initially rolled followed by poled showed maximum dielectric constant and low dielectric loss as compared to the rolled or compression molded samples. This study evidently demonstrates that various processing conditions and the content of the amorphous phase significantly influenced alpha to beta transition, crystallographic texture and mechanical properties and the dielectric response of the blends. Moreover, the mechanical relaxations suggest that relaxations originating from crystalline defects shifts to higher temperatures upon rolling correlating well with the observations that were made using calorimetric transitions. (c) 2018 Elsevier Ltd. All rights reserved
Two Time-Scale Stochastic Approximation with Controlled Markov Noise and Off-Policy Temporal-Difference Learning
No full textWe present for the first time an asymptotic convergence analysis of two time-scale stochastic approximation driven by ``controlled'' Markov noise. In particular, the faster and slower recursions have nonadditive controlled Markov noise components in addition to martingale difference noise. We analyze the asymptotic behavior of our framework by relating it to limiting differential inclusions in both time scales that are defined in terms of the ergodic occupation measures associated with the controlled Markov processes. Finally, we present a solution to the off-policy convergence problem for temporal-difference learning with linear function approximation, using our results
A Cu(II) mediated approach for colorimetric detection of aqueous fluoride in ppm level with a Schiff base receptor
No full textInspired by the importance of fluoride detection in aqueous environment, a new methodology is demonstrated by employing the synergistic reaction of fluoride and Cu(ii) salts with a designed Schiff base receptor. The cooperative ion binding behaviour of the ligand SR involves the reduction of Cu(ii) centre to Cu(i) in the presence of fluoride. In chloroform solution, the sensor shows equivalent reversible colorimetric change from amber yellow to red irrespective of the order of the addition of copper and fluoride. However, the change is equivalent but reversibility cannot not be attained in DMSO. The ion binding event can be easily recycled by adding EDTA and the resulting reversible colorimetric change mimics AND and a combinatorial logic gate. The mechanism of interaction is thoroughly analyzed by the UV-Vis, H-1 NMR, F-19 NMR, ESR spectroscopy and cyclic voltammetry techniques, which is further supported by DFT calculations. The methodology is applied in the detection of fluoride in real life samples such as ground water and toothpaste extract. The method successfully detects fluoride at concentrations as low as 5 ppm
A highly selective Fe@ZnO modified disposable screen printed electrode based non-enzymatic glucose sensor (SPE/Fe@ZnO)
No full textHerein, we report a non-enzymatic glucose sensor screen printed electrode based on iron doped zinc oxide (Fe@ZnO) nanoparticles. The Fe@ZnO nanoparticles were synthesized by a simple stirring method at room temperature and the obtained Fe@ZnO nanoparticles were characterized by using XRD and SEM. These Fe@ZnO nanoparticles were drop casted to modify the surface area of screen printed electrode (Fe@ZnO/SPE) for the electro-oxidation of glucose using cyclic voltammetry for glucose sensor. Our obtained results demonstrate that this simply prepared Fe@ZnO/SPE is promising candidate for electro-oxidation of glucose. The obtained results show a remarkable good limit of detection of 030 M. (C) 2017 Elsevier B.V. All rights reserved
Influence of Fe substitution on structural and electrical properties of Gd orthochromite ceramics
No full textStructural and dielectric properties of GdCr1-xFexO3 perovskite ceramic nanoparticles prepared by sol-gel auto-combustion method are presented. The structural investigations of these samples confirmed the single-phase orthorhombic symmetry with Pbnm space group. Lattice parameters and unit cell volume were calculated and found to increase with an increase in Fe concentration. The estimated average grain size from SEM is found to be 80 nm and increased with an increase in Fe content. Impedance spectroscopy has been employed to investigate the frequency (1 Hz-1MHz), temperature (RT-500 degrees C) and composition dependent impedance, dielectric and conductivity of compounds. All these materials are found to be semiconducting in nature. All the materials except x = 1 showed colossal dielectric constant (epsilon' > 10(3)) at room temperature. Both electrical conductivity and dielectric constant were found to be maximum for x = 0.4 sample. (C) 2017 Elsevier B.V. All rights reserved
Performance of MIMO Modulation Schemes With Imaging Receivers in Visible Light Communication
No full textIn multiple-input multiple-output (MIMO) indoor visible light communication (VLC) systems, the elements of the channel matrix can be highly correlated which is a cause for degraded bit error performance. Imaging receiver techniques can resolve the spatial correlation in VLC channels because of the increased spatial resolution possible in imaging receivers. In this paper, we investigate the performance of MIMO modulation schemes using imaging receivers that employ an imaging lens above the receiving plane to focus the energy from the transmitting LEDs onto the receiving plane. Hemispherical lens and fish-eye lens for imaging are considered in the study. The MIMO modulation schemes considered include spatial multiplexing, generalized spatial modulation, quad-LED complex modulation, and dual-LED complex modulation. Analytical and simulation results show that imaging receivers can provide significant performance gains compared to nonimaging receivers. We analytically capture the high SNR performance of the modulation schemes with nonimaging and imaging receivers by computing the normalized minimum distance of the received signal set. Simulation results validate the analytical results. Using this distance measure, we study the spatial distribution of the best performing modulation scheme with nonimaging and imaging receivers
Curvature Constrained Cubic Spline Impact Angle Guidance for Intercepting Stationary Targets
No full textIn this paper, a cubic spline guidance law is proposed for intercepting a stationary target at a desired impact angle in surface-to-surface engagement scenarios. An inverse method is used, which represents the altitude as a cubic polynomial of the downrange. The paper addresses many shortcomings of earlier work in this area. In particular, an explicit guidance expression is derived, which makes the guidance law effective and accurate in the presence of disturbances and uncertainties. It is also shown that the guidance command can be obtained using a single cubic spline polynomial even for impact angles greater than and equal to pi/2, While resulting in substantial improvement in terms of lateral acceleration and length of the trajectory. The paper also obtains an analytically derived capture region. The proposed guidance law is conceptually simple, independent of time-to-go, computationally inexpensive, and does not need linearization