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Observation of a rainbow of visible colors in a near infrared cascaded Raman fiber laser and its novel application as a diagnostic tool for length resolved spectral analysis
No full textIn this work, we report and analyse the surprising observation of a rainbow of visible colors, spanning 390nm to 620nm, in silica-based, Near Infrared, continuous-wave, cascaded Raman fiber lasers. The cascaded Raman laser is pumped at 1117nm at around 200W and at full power we obtain -100 W at 1480nm. With increasing pump power at 1117nm, the fiber constituting the Raman laser glows in various hues along its length. From spectroscopic analysis of the emitted visible light, it was identified to be harmonic and sum-frequency components of various locally propagating wavelength components. In addition to third harmonic components, surprisingly, even 2nd harmonic components were observed. Despite being a continuous-wave laser, we expect the phase-matching occurring between the core-propagating NIR light with the cladding-propagating visible wavelengths and the intensity fluctuations characteristic of Raman lasers to have played a major role in generation of visible light. In addition, this surprising generation of visible light provides us a powerful non-contact method to deduce the spectrum of light propagating in the fiber. Using static images of the fiber captured by a standard visible camera such as a DSLR, we demonstrate novel, image-processing based techniques to deduce the wavelength component propagating in the fiber at any given spatial location. This provides a powerful diagnostic tool for both length and power resolved spectral analysis in Raman fiber lasers. This helps accurate prediction of the optimal length of fiber required for complete and efficient conversion to a given Stokes wavelength
75-mm Wingspan Fixed-Wing Nano Air Vehicle With a Novel Aircraft Configuration
No full textThe development of a fixed-wing nano air vehicle that fits inside a cube of 75 mm is described in this paper. A novel aircraft configuration that satisfies the static and dynamic stability and the mission performance requirements is developed. A performance index is formulated to identify a suitable airfoil as there does not exist a single airfoil that achieves the mission required specifications. Eppler-61 is identified as the suitable airfoil since the value of its performance index is maximum among other airfoils selected for the analysis. The static stability of the nano air vehicle is analyzed using the aerodynamic characteristics obtained from the wind tunnel tests. The outcomes of this analysis indicate that the vehicle is statically stable. The analysis also indicates significant aerodynamic cross-coupling between longitudinal and lateral aerodynamic coefficients. The dynamic stability analysis indicates that the nano air vehicle is dynamically stable. Furthermore, the dynamic stability of the vehicle is validated by flight test results
The PGRS Domain of Mycobacterium tuberculosis PE_PGRS Protein Rv0297 Is Involved in Endoplasmic Reticulum Stress-Mediated Apoptosis through Toll-Like Receptor 4
No full textThe genome of Mycobacterium tuberculosis, the causal organism of tuberculosis (TB), encodes a unique protein family known as the PE/PPE/PGRS family, present exclusively in the genus Mycobacterium and nowhere else in the living kingdom, with largely unexplored functions. We describe the functional significance of the PGRS domain of Rv0297, a member of this family. In silico analyses revealed the presence of intrinsically disordered stretches and putative endoplasmic reticulum (ER) localization signals in the PGRS domain of Rv0297 (Rv0297PGRS). The PGRS domain aids in ER localization, which was shown by infecting macrophage cells with M. tuberculosis and by overexpressing the protein by transfection in macrophage cells followed by activation of the unfolded protein response, as evident from increased expression of GRP78/GRP94 and CHOP/ATF4, leading to disruption of intracellular Ca2+ homeostasis and increased nitric oxide (NO) and reactive oxygen species (ROS) production. The consequent activation of the effector caspase-8 resulted in apoptosis of macrophages, which was Toll-like receptor 4 (TLR4) dependent. Administration of recombinant Rv0297PGRS (rRv0297PGRS) also exhibited similar effects. These results implicate a hitherto-unknown role of the PGRS domain of the PE_PGRS protein family in ER stress-mediated cell death through TLR4. Since this protein is already known to be present at later stages of infection in human granulomas it points to the possibility of it being employed by M. tuberculosis for its dissemination via an apoptotic mechanism. IMPORTANCE Apoptosis is generally thought to be a defense mechanism in protecting the host against Mycobacterium tuberculosis in early stages of infection. However, apoptosis during later stages in lung granulomas may favor the bacterium in disseminating the disease. ER stress has been found to induce apoptosis in TB granulomas, in zones where apoptotic macrophages accumulate in mice and humans. In this study, we report ER stress-mediated apoptosis of host cells by the Rv0297-encoded PE_PGRS5 protein of M. tuberculosis exceptionally present in the pathogenic Mycobacterium genus. The PGRS domain of Rv0297 aids the protein in localizing to the ER and induces the unfolded protein response followed by apoptosis of macrophages. The effect of the Rv0297PGRS domain was found to be TLR4 dependent. This study presents novel insights on the strategies employed by M. tuberculosis to disseminate the disease
Search for a charged Higgs boson decaying to charm and bottom quarks in proton-proton collisions at root s=8TeV
No full textA search for charged Higgs boson decaying to a charm and a bottom quark pair production in which one top quark decays to a charged Higgs boson and a bottom quark and the other decays to a charged lepton, a neutrino, and a bottom quark. Charged Higgs boson decays to are searched for, resulting in a final state containing at least four jets, a charged lepton (muon or electron), and missing transverse momentum. A kinematic fit is performed to identify the pair of jets least likely to be the bottom quarks originating from direct top quark decays and the invariant mass of this pair is used as the final observable in the search. No evidence for the presence of a charged Higgs boson is observed and upper limits at 95% confidence level of 0.8-0.5% are set on the branching fraction B(t H(+)b), assuming B(H+ = 1.0 and B(t H(+)b) + B(t Wb) = 1.0, for the charged Higgs boson mass range 90-150 GeV
A Hybrid Deep Learning Model to Predict Business Closure from Reviews and User Attributes Using Sentiment Aligned Topic Model
No full textBusiness closure is a very good indicator for success or failure of a business. This will help investors and banks as to whether to invest or lend to a particular business for future growth and benefits. Traditional machine learning techniques require extensive manual feature engineering and still do not perform satisfactorily due to significant class imbalance problem and little difference in the attributes for open and closed businesses. We have used historical data besides taking care of the class imbalance problem. Transfer learning also has been used to tackle the issue of having small categorical dalasets. A hybrid deep learning model has been proposed to predict whether a business would be shut down within a specific period of time. Sentiment Aligned Topic Model (SATM) is used to extract aspect-wise sentiment scores from user reviews. Our results show a marked improvement over traditional machine learning techniques. It also shows how the aspect-wise sentiment scores corresponding to each business, computed using SATM, help to give better results
Nature of the charge carriers in LaAlO3-SrTiO(3 )oxide heterostructures probed using hard X-ray photoelectron spectroscopy
No full textproper investigation of the valence band electronic structure is the essential first step towards understanding the intriguing co-existence of several exotic electronic phases like ferromagnetism and superconductivity, in LaAlO3-SrTiO3 heterostructures. In order to comprehend the electronic structure across the LaAlO3-SrTiO3 oxide interface, a detailed valence band investigation has been carried out using variable energy hard X-ray photoelectron spectroscopy and signatures of both low-energy coherent and high-energy features have been observed in the valence band spectra. Our combined experimental and theoretical study suggests that the charge carriers at the interface are weakly correlated and the high-energy feature does not arise from the lower Hubbard band. Instead, this high-energy feature is attributed to in-gap states induced by oxygen vacancies and possible polaron formation. Copyright (C) EPLA, 201
Perturb and Observe with Momentum Term applied to Current Referenced Boost Converter for PV Interface
No full textThe Photovoltaic (PV) current follows the same direction as the perturbed duty cycle for a DC-DC converter interfaced PV system. Hence current referenced control is well suited for Maximum Power Point Tracking (MPPT). A small signal model for a Boost converter with PV is developed, which gives the input current to duty cycle control signal transfer function in order to design the controller. In addition to the inner current control loop, an MPPT control loop is added to track the Maximum Power Point (MPP). The standard Perturb and Observe (P&O) Algorithm has an inherent trade-off between dynamic performance during rapidly changing irradiation conditions and oscillations about the MPP. To overcome this problem a Momentum term is introduced in the perturbation of the reference control signal in order to accelerate tracking and to reduce oscillations. The Momentum term which is a scaled version of the previous perturbation can be easily implemented in the existing P&O algorithms, with only slight modification and almost no change in computational effort
Sound transmission through a finite perforated panel set in a rigid baffle: A fully coupled analysis
No full textSound transmission through a fluid-loaded finite perforated panel set in an infinite unperforated rigid baffle is considered. Using a fully coupled formulation in the 2-D wavenumber domain, the transmitted pressure due to an incident plane wave is obtained. The change in the panel resonances caused by the perforations is accounted for. The formulation also takes into account the self-and inter-modal coupling coefficients arising due to the fluid-loading effect. The derivation is almost entirely analytical with numerical computations done at the very end. Transmission loss (TL) curves are plotted for various cases and the physics is discussed. Along the way an uncoupled calculation is also done for the sake of comparison. The results are mainly for a light medium like air. For a light medium, in general, the perforate impedance is lower than the panel impedance. Thus, most of the transmission happens through the perforations. The panel velocity contribution is insignificant and hence the uncoupled calculation is adequate. In general, the absolute perforate impedance increases with increasing frequency. So does the TL. At low frequencies, because the resistive component of the hole impedance increases, the absolute perforate impedance rises. Thus, the TL curves rise at the lower frequencies. This effect is prominent for sub-millimeter hole radii, i.e., for micro-perforations. An important issue with the TL values for perforated panels is that they sometimes acquire negative values at low frequencies. This apparent anomaly is resolved by showing that at low frequencies there is an additional power component that flows from the baffle region onto the panel. Upon inclusion of this additional term, the TL values remain positive at all frequencies. (C) 2017 Elsevier Ltd. All rights reserved
Training-Free, Single-Image Super-Resolution Using a Dynamic Convolutional Network
No full textThe typical approach for solving the problem of single-image super-resolution (SR) is to learn a nonlinear mapping between the low-resolution (LR) and high-resolution (HR) representations of images in a training set. Training-based approaches can be tuned to give high accuracy on a given class of images, but they call for retraining if the HR -> LR generative model deviates or if the test images belong to a different class, which limits their applicability. On the other hand, we propose a solution that does not require a training dataset. Our method relies on constructing a dynamic convolutional network (DCN) to learn the relation between the consecutive scales of Gaussian and Laplacian pyramids. The relation is in turn used to predict the detail at a finer scale, thus leading to SR. Comparisons with state-of-the-art techniques on standard datasets show that the proposed DCN approach results in about 0.8 and 0.3 dB gain in peak signal-to-noise ratio for 2x and 3x SR, respectively. The structural similarity index is on par with the competing techniques
Ulvan-chitosan polyelectrolyte complexes as matrices for enzyme induced biomimetic mineralization
No full textPolyelectrolyte complexes (PEC) of chitosan and ulvan were fabricated to study alkaline phosphatase ( ALP) mediated formation of apatitic minerals. Scaffolds of the PEC were subjected to ALP and successful mineral formation was studied using SEM, Raman and XRD techniques. Investigation of the morphology via SEM shows globular structures of the deposited minerals, which promoted cell attachment, proliferation and extracellular matrix formation. The PEC and their successful calcium phosphate based mineralization offers a greener route of scaffold fabrication towards developing resorbable materials for tissue engineering