50175 research outputs found
Sort by
Switching behavior of bulk, fast ion conducting, vitreous AgI-Ag2O-MoO3 solids with inert electrode
No full textDeveloping efficient, fast performing and thermally stable Silver iodide-based fast ion conducting solids are of great interest for resistive switching applications, but still remain a challenge. Metallization in bulk, behavior of threshold voltage profile over composition, and corrosion reactions are few of the challenges. In this work, the switching behavior of bulk, fast ion conducting, vitreous (AgI)(x)-(Ag2O)(25)-(MoO3)(75-)(x), for 60 <= x <= 40 solids, has been investigated in order to understand the switching mechanism with the inert electrodes. By using inert electrodes, the switching becomes irreversible, memory type. The switching mechanism is the electrochemical metallization process. The inert electrodes restrain ionic mass transfer but exhibit low barrier to electron transfer allowing the cathodic metallization reaction to reach Nernst equilibrium faster. Cations involved in this process transport through the free volume within the solid structure and follows Mott-Gurney model for electric field-driven thermally activated ion hopping conductivity model. This model along with the thermal stability profile provides a narrow region within composition with better switching performance based on swiftness to reach threshold voltage and less power loss. Traces of anionic contribution to metallization are absent. Moreover, anodic oxidation involves reactions that cause bubble formation and corrosion
Effective theories for quantum spin clusters: Geometric phases and state selection by singularity
No full textMagnetic systems with frustration often have large classical degeneracy. We show that their low-energy physics can be understood as dynamics within the space of classical ground states. We demonstrate this mapping in a family of quantum spin clusters where every pair of spins is connected by an XY antiferromagnetic bond. The dimer with two spin-S spins provides the simplest example-it maps to a quantum particle on a ring (S-1). The trimer is more complex, equivalent to a particle that lives on two disjoint rings (S-1 circle times Z(2)). It has an additional subtlety for half-integer S values, wherein both rings must be threaded by pi fluxes to obtain a satisfactory mapping. This is a consequence of the geometric phase incurred by spins. For both the dimer and the trimer, the validity of the effective theory can be seen from a path-integral-based derivation. This approach cannot be extended to the quadrumer which has a nonmanifold ground-state space, consisting of three tori that touch pairwise along lines. In order to understand the dynamics of a particle in this space, we develop a tight-binding model with this connectivity. Remarkably, this successfully reproduces the low-energy spectrum of the quadrumer. For half-integer spins, a geometric phase emerges which can be mapped to two pi-flux tubes that reside in the space between the tori. The nonmanifold character of the space leads to a remarkable effect-the dynamics at low energies is not ergodic as the particle is localized around singular lines of the ground-state space. The low-energy spectrum consists of an extensive number of bound states formed around singularities. Physically, this manifests as an order-by-disorder-like preference for collinear ground states. However, unlike order-by-disorder, this ``order by singularity'' persists even in the classical limit. We discuss consequences for field theoretic studies of magnets
Mouse embryonic stem cell-derived cardiomyocytes cease to beat following exposure to monochromatic light: association with increased ROS and loss of calcium transients
No full textWe earlier established the mouse embryonic stem (ES) cell ``GS-2'' line expressing enhanced green fluorescent protein (EGFP) and have been routinely using it to understand the molecular regulation of differentiation into cardiomyocytes. During such studies, we made a serendipitous discovery that functional cardiomyocytes derived from ES cells stopped beating when exposed to blue light. We observed a gradual cessation of contractility within a few minutes, regardless of wavelength (nm) ranges tested: blue (similar to 420-495), green (similar to 510-575), and red (similar to 600-700), with green light manifesting the strongest impact. Following shifting of cultures back into the incubator (darkness), cardiac clusters regained beatings within a few hours. The observed light-induced contractility-inhibition effect was intrinsic to cardiomyocytes and not due to interference from other cell types. Also, this was not influenced by any physicochemical parameters or intracellular EGFP expression. Interestingly, the light-induced cardiomyocyte contractility inhibition was accompanied by increased intracellular reactive oxygen species (ROS), which could be abolished in the presence of N-acetylcysteine (ROS quencher). Besides, the increased intracar-diomyocyte ROS levels were incidental to the inhibition of calcium transients and suppression of mitochondrial activity, both being essential for sarcomere function. To the best of our knowledge, ours is the first report to demonstrate the monochromatic light-mediated inhibition of contractions of cardiomyocytes with no apparent loss of cell viability and contractility. Our findings have implications in cardiac cell biology context in terms of 1) mechanistic insights into light impact on cardiomyocyte contraction. 2) potential use in laser beam-guided (cardiac) microsurgery, photo-optics-dependent medical diagnostics, 3) transient cessation of hearts during coronary artery bypass grafting, and 4) functional preservation of hearts for transplantation
PION FORM FACTOR AND LOW-ENERGY HADRONIC CONTRIBUTION TO MUON g-2 BY ANALYTIC EXTRAPOLATION: CONSISTENCY AND SENSITIVITY TESTS
No full textThe largest error in the theoretical determination of the muon anomalous magnetic moment is due to the low-energy hadronic vacuum polarization, which cannot be calculated by perturbative QCD and requires nonperturbative techniques. Recently, an accurate determination of the low-energy two-pion contribution to muon g - 2 has been obtained by a parametrization-free analytic continuation of the pion vector form factor from other kinematical regions. In this work we compare the results of the analytic continuation with direct determinations at low momenta from experiment and lattice QCD. We also explore the sensitivity of the method to the timelike data on the modulus of the form factor used as input, by extending the input region to energies up to 0.76 GeV
Heterogeneous Sensor Data Analysis Using Efficient Adaptive Artificial Neural Network on FPGA Based Edge Gateway
No full textWe propose a FPGA based design that performs real-time power-efficient analysis of heterogeneous sensor data using adaptive ANN on edge gateway of smart military wearables. In this work, four independent ANN classifiers are developed with optimum topologies. Out of which human activity, BP and toxic gas classifier are multiclass and ECG classifier is binary. These classifiers are later integrated into a single adaptive ANN hardware with a select line( s) that switches the hardware architecture as per the sensor type. Five versions of adaptive ANN with different precisions have been synthesized into IP cores. These IP cores are implemented and tested on Xilinx Artix-7 FPGA using Microblaze test system and LabVIEW based sensor simulators. The hardware analysis shows that the adaptive ANN even with 8-bit precision is the most efficient IP core in terms of hardware resource utilization and power consumption without compromising much on classification accuracy. This IP core requires only 31 microseconds for classification by consuming only 12 milliwatts of power. The proposed adaptive ANN design saves 61% to 97% of different FPGA resources and 44% of power as compared with the independent implementations. In addition, 96.87% to 98.75% of data throughput reduction is achieved by this edge gateway
A modular paper-and-plastic device for tuberculosis nucleic acid amplification testing in limited-resource settings
No full textWe present a prototype for conducting rapid, inexpensive and point-of-care-compatible nucleic acid amplification tests (NAATs) for tuberculosis (TB). The fluorescent isothermal paper-and-plastic NAAT (FLIPP-NAAT) uses paper-based loop mediated isothermal amplification (LAMP) for DNA detection. The cost of materials required to build a 12-test-zone device is 0.43. An inexpensive imaging platform enables filter-free fluorescence detection of amplified DNA using a cell-phone camera. FLIPP-NAAT can be operated by an untrained user and only requires a regular laboratory incubator as ancillary equipment. All reagents can be dry-stored in the device, facilitating storage and transportation without cold chains. The device design is modular and the assay demonstrated high specificity to Mycobacterium tuberculosis (Mtb), analytical sensitivity of the order of 10 copies of Mtb gDNA, and tolerance to complex samples. The clinical sensitivity and specificity of sputum-based FLIPP NAAT tests were 100% (zero false negatives) and 68.75% (five false positives), respectively (N = 30), using Xpert MTB/RIF assay as the reference standard. FLIPP-NAAT has the potential to provide affordable and accessible molecular diagnostics for TB in low- and middle-income countries, when used in conjunction with an appropriate sample preparation technique. Although demonstrated for the detection of TB, FLIPP-NAAT is a platform technology for amplification of any nucleic acid sequence
Multisite Daily Streamflow Simulation With Time Irreversibility
No full textSynthetic daily streamflow generation requires a critical understanding of the underlying dynamics resulting from the inherent temporal asymmetry (time irreversibility) in the rising and falling limbs of the hydrograph. Most models considering the time irreversibility deal with single-site streamflow simulation. Addressing intersite dependencies is, however, crucial for interconnected stream networks. This study presents a time irreversibility dynamics-based multisite streamflow generating framework to simulate concurrent streamflow sequences at multiple sites in a basin. This framework explicitly takes into account the spatial correlation and time irreversible dynamics of streamflow. To demonstrate the utility and applicability, a few selected streamflow gauging stations in the Godavari River Basin, located in southern India, are considered. The proposed framework shows the ability to adequately generate multisite simulations capturing at-site statistics as well as intersite correlations for the case study. Furthermore, the approach ensures that the simulated flow values are not merely resampled from the historical data, uses the physical features of the hydrograph, and shows variability beyond that observed in the historical sequence. Such a rich variety of streamflow sequences can help water managers to investigate how existing water resources systems on interconnected stream networks will operate in scenarios which have not been observed in the historical record
Modelling Methods for Planning and Operation of Bike-Sharing Systems
No full textBike-sharing systems (BSSs) are emerging as a popular type of shared vehicle platform where users can rent bicycles without having to own and maintain them. BSSs are ideal for short trips and for connecting to public transit systems. Bicycle usage is associated with several unique characteristics which make planning and operation of BSSs very different from car sharing problems and other traditional transportation modelling approaches. In this paper, we summarize existing literature on strategic planning which involves selecting stations, designing bike paths, and figuring out station capacity. Research on operational measures which include day-to-day and within-day repositioning activities are also collated. Additionally, models for understanding demand, pricing and incentives, maintenance, and other technological aspects are reviewed
Li and Na-ion diffusion and intercalation characteristics in vertically aligned TiS2 nanowall network grown using atomic layer deposition
No full textWe present here the study of diffusion and intercalation mechanisms of Li-ion and Na-ion in titanium disulfide (TiS2) films grown by atomic layer deposition (ALD). The layered TiS2 has been explored here due to the interesting differences between the intercalation mechanisms of Li+ and Na+. The ALD grown TiS2 films further facilitate the study as this method provides compact and dense films with no polymer binder and carbon additives. The diffusion and intercalation processes are observed to depend on the ionic size and character of the solid electrolyte interphase. The increased capacity obtained for the present ALD synthesized samples is attributed to the enhanced anchoring ability of the TiS2 films, which comprises of an extended nanowall network. The charge transfer resistance (R-ct) obtained from impedance data correlate well with the lithiation steps observed in the galvanostatic discharge-charge studies. At potentials where lithiation takes place, R-ct value is observed to drop. This direct correlation is however, not observed between the R-ct and sodiation potential. The diffusion coefficients, calculated using GITT and impedance methods, are observed to be independent of the type of Li-salts. However, the variation of diffusion coefficients with the lithiation/sodiation voltages are different. This is attributed to the combined differences in the ionic radii and phase formation. Intercalation-de-intercalation in to TiS2 coated with alumina is also studied here. Coating with alumina results in a stable SEI. However, coating leads to higher R-ct, lower DLi+ and poor capacity retention as a function of cycle number
A comparative study of a class of mean field theories of the glass transition
No full textIn a recently developed microscopic mean field theory, we have shown that the dynamics of a system, when described only in terms of its pair structure, can predict the correct dynamical transition temperature. Further, the theory predicted the difference in dynamics of two systems (the Lennard-Jones and the Weeks-Chandler-Andersen) despite them having quite similar structures. This is in contrast to the Schweizer-Saltzman (SS) formalism which predicted the dynamics of these two systems to be similar. The two theories although similar in spirit have certain differences. Here we present a comparative study of these two formalism to find the origin of the difference in their predictive power. We show that not only the dynamics in the potential energy surface, as described by our earlier study, but also that in the free energy surface, like in the SS theory, can predict the correct dynamical transition temperature. Even an approximate one component version of our theory, similar to the system used in the SS theory, can predict the transition temperature reasonably well. Interestingly, we show here that despite the above mentioned shortcomings the SS theory can actually predict the correct transition temperatures. Thus microscopic mean field theories of this class which express dynamics in terms of the pair structure of the liquid while being unable to predict the actual dynamics of the system are successful in predicting the correct dynamical transition temperature