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A study of Barkhausen avalanche statistics through the critical disorder in a ferromagnetic thin film: Experimental investigation and theoretical modeling
No full textIt is well known from theoretical models that a ferromagnetic system should undergo a disorder induced phase transition in its magnetization reversal mode at a critical disorder level R-C, below which, the reversal is characterized by the appearance of the so-called spanning avalanche. The critical regime above R-C is characterized by power-law distributed avalanche sizes and durations, whose exponents determine the universality class to which the magnetic system belongs. The most commonly studied among these is the size-exponent tau, which most theoretical models estimate to be in the range 1.3-1.5. However, experimental determinations of this exponent fall in a much wider interval, between 0.98 and 1.8, well outside the domain of the models. This discrepancy, which is far more common for 2D systems, has not been effectively addressed for more than a decade. In this article, we have determined experimentally the size-exponent `tau' in 2D Permalloy(Ni80Fe20) thin films by measuring Barkhausen noise through the disorder-induced transition using planar Hall effect. This was compared with our simulations of the random field Ising model, an established nucleation model, with a modification that better represented the experimental condition. Our findings indicated that large `tau'-values would arise in samples with very low disorder levels well outside the critical regime, where the statistics were non-universal. In such samples, our measured `tau' increased monotonically with temperature, which indicated a decrease in the effective disorder with temperature according to the nucleation models. This temperature dependence could be understood in the light of an extended Neel-Brown model which we had studied earlier, that had predicted a decrease in the width of switching field distribution with increasing temperature. In this context, we also used micromagnetic simulations, which helped to understand the dependence of coercivity on disorder, a property not predicted correctly by the Ising model
Neurogenesis-on-Chip: Electric field modulated transdifferentiation of human mesenchymal stem cell and mouse muscle precursor cell coculture
No full textA number of bioengineering strategies, using biophysical stimulation, are being explored to guide the human mesenchymal stem cells (hMScs) into different lineages. In this context, we have limited understanding on the transdifferentiation of matured cells to another functional-cell type, when grown with stem cells, in a constrained cellular microenvironment under biophysical stimulation. While addressing such aspects, the present work reports the influence of the electric field (EF) stimulation on the phenotypic and functionality modulation of the coculture of murine myoblasts (C2C12) with hMScs hMSc:C2C12 = 1:10] in a custom designed polymethylmethacrylate (PMMA) based microfluidic device with in-built metal electrodes. The quantitative and qualitative analysis of the immunofluorescence study confirms that the cocultured cells in the conditioned medium with astrocytic feed, exhibit differentiation towards neural-committed cells under biophysical stimulation in the range of the endogenous physiological electric field strength (8 +/- 0.06 mV/mm). The control experiments using similar culture protocols revealed that while C2C12 monoculture exhibited myotube-like fused structures, the hMScs exhibited the neurosphere-like clusters with SOX2, nestin, beta III-tubulin expression. The electrophysiological study indicates the significant role of intercellular calcium signalling among the differentiated cells towards transdifferentiation. Furthermore, the depolarization induced calcium influx strongly supports neural-like behaviour for the electric field stimulated cells in coculture. The intriguing results are explained in terms of the paracrine signalling among the transdifferentiated cells in the electric field stimulated cellular microenvironment. In summary, the present study establishes the potential for neurogenesis on-chip for the coculture of hMSc and C2C12 cells under tailored electric field stimulation, in vitro
Improved Accuracy, Modeling, and Stability Analysis of Power-Hardware-in-Loop Simulation With Open-Loop Inverter as Power Amplifier
No full textThe accuracy of a power-hardware-in-loop (PHIL) simulation is influenced by factors such as dynamics of the power amplifier (PA) and discretization of the real-time simulated part of the system. An open-loop voltage-source inverter (VSI) without an output filter is demonstrated to be a good choice for power amplification in terms of cost, size, design effort, bandwidth, and accuracy when the load on the PA is significantly inductive. An open-loop-VSI-based PA is shown to be accurate in emulating a synchronous generator, including the fast transients in the excitation control system. The discretization effects of the real-time simulator are captured effectively by the discrete-time (DT) modeling approach proposed in this paper. The DT model is shown to replicate fast transients in the PHIL simulation better than the existing continuous-time-based model. Stability of the PHIL simulation of a benchmark circuit is analyzed using the proposed DT modeling approach. The stability analysis is validated through simulations and experiments. The stability limits derived based on the proposed analysis are capable of suggesting maximum and minimum values of certain circuit parameters, as required for stability
Pictionary-Style Word Guessing on Hand-Drawn Object Sketches: Dataset, Analysis and Deep Network Models
No full textThe ability of intelligent agents to play games in human-like fashion is popularly considered a benchmark of progress in Artificial Intelligence. In our work, we introduce the first computational model aimed at Pictionary, the popular word-guessing social game. We first introduce Sketch-QA, a guessing task. Styled after Pictionary, Sketch-QA uses incrementally accumulated sketch stroke sequences as visual data. Sketch-QA involves asking a fixed question (''What object is being drawn?'') and gathering open-ended guess-words from human guessers. We analyze the resulting dataset and present many interesting findings therein. To mimic Pictionary-style guessing, we propose a deep neural model which generates guess-words in response to temporally evolving human-drawn object sketches. Our model even makes human-like mistakes while guessing, thus amplifying the human mimicry factor. We evaluate our model on the large-scale guess-word dataset generated via Sketch-QA task and compare with various baselines. We also conduct a Visual Turing Test to obtain human impressions of the guess-words generated by humans and our model. Experimental results demonstrate the promise of our approach for Pictionary and similarly themed games
Crystal structure, DNA crosslinking and photo-induced cytotoxicity of oxovanadium(IV) conjugates of boron-dipyrromethene
No full textCis-dichloro-oxovanadium(IV) complexes VO(L-1/L-2)Cl-2], where L-1 is N-(4-(5,5-difluoro-1,3,7,9-tetramethyl-5H-4(sic)(4),5(sic)(4)-dipyrrolo 1, 2-c:2',1'-f] 1,3, 2]diazaborinin-10-yl)benzyl)-1-(pyridin-2-yl)-N-(pyridin-2-ylmethyl) methanamine in 1 and L-2 is N-(4-(5,5-difluoro-2,8-dliodo-1,3,7,9-tetramethyl-5H-4(sic)(4),5(sic)(4) -dipyrrolo1,2-c:2',1'-f]1,3,2]diazaborinin-10-yl)benzyl)-1-(pyridi n-2-yl)-N-(pyridin-2-ylmethyl)methanamine in 2) having 4,4-di-fluoro-4-bora-3a,4a-diaza-s-indacene as boron-dipyrromethene (BODIPY) appended dipicolylamine bases were prepared, characterized and their photocytotoxicity studied. X-ray crystal structure of 1 showed distorted octahedral geometry with a (VON3Cl2)-O-IV core having Cl-V-Cl angle of 91.93(4)degrees. The complexes showed variable solution conductivity properties. They were non-electrolytes in dry DMF at 25 degrees C but showed 1:1 electrolytic behavior in an aqueous medium due to dissociation of one chloride ligand as evidenced from the mass spectral study. Complexes 1 and 2 showed absorption bands at 500 and 535 nm, respectively. The calf thymus DNA melting study revealed their interaction through DNA crosslinking on exposure to light which was further confirmed from the alkaline agarose gel electrophoresis using plasmid supercoiled pUC19 DNA. Complex 2 showed disruption of the mitochondrial membrane potential in the JC-1 (1,1',3,3'-tetraethyl-5,5',6,6'-tetrachloroimidacarbocyanine iodide) assay. The complexes were photocytotoxic in visible light (400-700 nm, power: 10 J cm(-2)) in cervical cancer HeLa and breast cancer MCF-7 cells. Complex 2 having a photoactive diiodo-boron-dipyrromethene moiety gave a singlet oxygen quantum yield (Phi(Delta)) value of similar to 0.6. It showed singlet oxygen mediated apoptotic photodynamic therapy activity with remarkably low IC50 (half maximal inhibitory concentration) value of similar to 0.15 mu M. The cis-disposition of chlorides gave a cis-divacant 4-coordinate intermediate structure from the density functional theory (DFT) study thus mimicking the DNA crosslinking property of cisplatin
Natural tripeptide capped pH-sensitive gold nanoparticles for efficacious doxorubicin delivery both: In vitro and in vivo
No full textNanobiotechnology has been gaining ever-increasing interest for the successful implementation of chemotherapy based treatment of cancer. Gold nanoparticles (AuNPs) capped with a natural pH-responsive short tripeptide (Lys-Phe-Gly or KFG) sequence are presented herein for significant intracellular delivery of an anti-cancer drug, doxorubicin (DOX). A particularly increased apoptotic response has been observed for DOX treatments mediated by KFG-AuNPs when compared with drug alone treatments in various cell lines (BT-474, HeLa, HEK 293 T and U251). Furthermore, KFG-AuNP mediated DOX treatment significantly decreases cell proliferation and tumor growth in a BT-474 cell xenograft model in nude mice. In addition, KFG-AuNPs demonstrate efficacious drug delivery in DOX-resistant HeLa cells (HeLa-DOXR).
Magnesium chloride impairs physio-biochemical and neurochemical responses in cirrhinusmrigala (Hamilton, 1822) upon short term exposure
No full textThe present investigation was performed to establish the biochemical and physiological impact of Magnesium chloride (MgCl2) on fresh water fish Cirrhinusmrigala. In this direction we have evaluated the biochemical and neurochemical impact of MgCl2 on C. mrigala, a fresh water fish extensively consumed. Biochemical, neurochemical and physiological alterations were analyzed in the present study and LC50 of MgCl2 was found to be 192 ppm, observed for 24h. Further 1/10th of the LC50 concentration of MgCl2 (19.2 ppm) was chosen for short term examination at 96 h. The results demonstrate elevation in levels of serum lactate dehydrogenase (LDH), aspartate transaminase (AST) and alanine transaminase (ALT) levels compared to control groups. Studies revealed variations in oxidative stress markers with significant reduction in the serum super oxide dismutase (SOD) and catalase (CAT) levels, and increase in malondialdehyde (MDA). The study showed an increase in brain glutamate levels reflecting possible brain tissue damage. The above study highlights the potential biochemical impact of MgCl2 on fresh water fish
Broadband optical single sideband generation using an ultra high shape-factor self coupled ring resonator
No full textIn this study, we realize an integrated generation of optical Single SideBand with Carrier (SSB+C) signal for microwave photonics applications. It has been achieved using a Micro Ring Modulator (MRM) combined with a cavity based wavelength selective filter. MRM, when applied with an RF input, results in a Double SideBand with Carrier (DSB+C) signal where one sideband is suppressed by applying this signal to the filter. The filter has been created using a single resonance-split self-coupled cavity with an extremely high shape factor of 0.69. The sideband suppression ratio between DSB+C and SSB+C ranges from 16 dB to 55 dB for a frequency range of 4 GHz to 20 GHz. Tunable suppression ratio of 21 dB has been achieved at a fixed frequency of 15 GHz. Dynamic range performance of the generated signal has been evaluated at a noise floor of -156 dBm. The dynamic range remains stable in the range of 1 GHz - 5 GHz at � 80 dB.Hz2�3
An improved tunnel field-effect transistor with an L-shaped gate and channel
No full textAn improved tunnel field-effect transistor with an L-shaped gate and channel (LLTFET) is proposed herein. The new structure shows an increased ON-current without any change in the overall area in comparison with state-of-the-art structures. The L-shaped gate extends into the substrate and overlaps with part of the source. An N+ pocket located just below the gate facilities tunneling in both the horizontal and vertical directions, which results in the increased ON-current. Three different models are proposed herein to increase the ON-current with the added advantage of simplified fabrication steps. For one of the proposed models, the ON-current is improved by 63 while the OFF-current is reduced to 12.5 compared with an L-shaped gate TFET (LGTFET) described in literature. An optimum model is also proposed, achieving a subthreshold swing of 21.2Â mV/decade at 0.05Vgs. The simulations are performed using Silvaco ATLAS with the nonlocal band to band tunneling (BTBT) model
On the Convergence of a Bayesian Algorithm for Joint Dictionary Learning and Sparse Recovery
No full textDictionary learning (DL) is a well-researched problem, where the goal is to learn a dictionary from a finite set of noisy training signals, such that the training data admits a sparse representation over the dictionary. While several solutions are available in the literature, relatively little is known about their convergence and optimality properties. In this paper, we make progress on this problem by analyzing a Bayesian algorithm for DL. Specifically, we cast the DL problem into the sparse Bayesian learning (SBL) framework by imposing a hierarchical Gaussian prior on the sparse vectors. This allows us to simultaneously learn the dictionary as well as the parameters of the prior on the sparse vectors using the expectation-maximization algorithm. The dictionary update step turns out to be a non-convex optimization problem, and we present two solutions, namely, an alternating minimization (AM) procedure and an Armijo line search (ALS) method. We analytically show that the ALS procedure is globally convergent, and establish the stability of the solution by characterizing its limit points. Further, we prove the convergence and stability of the overall DL-SBL algorithm, and show that the minima of the cost function of the overall algorithm are achieved at sparse solutions. As a concrete example, we consider the application of the SBL-based DL algorithm to image denoising, and demonstrate the efficacy of the algorithm relative to existing DL algorithms