Showing papers by "Indian Institute of Technology Bombay published in 2017"
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TL;DR: In this paper, the authors used the observed time delay of $(+1.74\pm 0.05)\,{\rm{s}}$ between GRB 170817A and GW170817 to constrain the difference between the speed of gravity and speed of light to be between $-3
Abstract: On 2017 August 17, the gravitational-wave event GW170817 was observed by the Advanced LIGO and Virgo detectors, and the gamma-ray burst (GRB) GRB 170817A was observed independently by the Fermi Gamma-ray Burst Monitor, and the Anti-Coincidence Shield for the Spectrometer for the International Gamma-Ray Astrophysics Laboratory. The probability of the near-simultaneous temporal and spatial observation of GRB 170817A and GW170817 occurring by chance is $5.0\times {10}^{-8}$. We therefore confirm binary neutron star mergers as a progenitor of short GRBs. The association of GW170817 and GRB 170817A provides new insight into fundamental physics and the origin of short GRBs. We use the observed time delay of $(+1.74\pm 0.05)\,{\rm{s}}$ between GRB 170817A and GW170817 to: (i) constrain the difference between the speed of gravity and the speed of light to be between $-3\times {10}^{-15}$ and $+7\times {10}^{-16}$ times the speed of light, (ii) place new bounds on the violation of Lorentz invariance, (iii) present a new test of the equivalence principle by constraining the Shapiro delay between gravitational and electromagnetic radiation. We also use the time delay to constrain the size and bulk Lorentz factor of the region emitting the gamma-rays. GRB 170817A is the closest short GRB with a known distance, but is between 2 and 6 orders of magnitude less energetic than other bursts with measured redshift. A new generation of gamma-ray detectors, and subthreshold searches in existing detectors, will be essential to detect similar short bursts at greater distances. Finally, we predict a joint detection rate for the Fermi Gamma-ray Burst Monitor and the Advanced LIGO and Virgo detectors of 0.1–1.4 per year during the 2018–2019 observing run and 0.3–1.7 per year at design sensitivity.
2,633 citations
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TL;DR: In this article, a GW signal from the merger of two stellar-mass black holes was observed by the two Advanced Laser Interferometer Gravitational-Wave Observatory detectors with a network signal-to-noise ratio of 13.5%.
Abstract: On 2017 June 8 at 02:01:16.49 UTC, a gravitational-wave (GW) signal from the merger of two stellar-mass black holes was observed by the two Advanced Laser Interferometer Gravitational-Wave Observatory detectors with a network signal-to-noise ratio of 13. This system is the lightest black hole binary so far observed, with component masses of ${12}_{-2}^{+7}\,{M}_{\odot }$ and ${7}_{-2}^{+2}\,{M}_{\odot }$ (90% credible intervals). These lie in the range of measured black hole masses in low-mass X-ray binaries, thus allowing us to compare black holes detected through GWs with electromagnetic observations. The source's luminosity distance is ${340}_{-140}^{+140}\,\mathrm{Mpc}$, corresponding to redshift ${0.07}_{-0.03}^{+0.03}$. We verify that the signal waveform is consistent with the predictions of general relativity.
1,268 citations
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University of South Carolina1, Los Alamos National Laboratory2, Moscow State University3, Delhi Technological University4, University of Paris5, University of California, Davis6, Indian Institute of Technology (BHU) Varanasi7, University of Moratuwa8, University of Illinois at Urbana–Champaign9, California Polytechnic State University10, Sandia National Laboratories11, Max Planck Society12, Indian Institute of Technology Kharagpur13, French Institute for Research in Computer Science and Automation14, University of New Mexico15, Charles University in Prague16, Birla Institute of Technology and Science17, Indian Institute of Technology Bombay18, University of West Bohemia19
TL;DR: The architecture of SymPy is presented, a description of its features, and a discussion of select domain specific submodules are discussed, to become the standard symbolic library for the scientific Python ecosystem.
Abstract: SymPy is an open source computer algebra system written in pure Python. It is built with a focus on extensibility and ease of use, through both interactive and programmatic applications. These characteristics have led SymPy to become a popular symbolic library for the scientific Python ecosystem. This paper presents the architecture of SymPy, a description of its features, and a discussion of select submodules. The supplementary material provide additional examples and further outline details of the architecture and features of SymPy.
1,126 citations
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California Institute of Technology1, Tel Aviv University2, Goddard Space Flight Center3, University of Maryland, College Park4, University of Wisconsin–Milwaukee5, Stockholm University6, Princeton University7, Liverpool John Moores University8, National Central University9, Hebrew University of Jerusalem10, Australian Research Council11, University of Sydney12, Indian Institute of Astrophysics13, Indian Institute of Science14, Commonwealth Scientific and Industrial Research Organisation15, University of Colorado Boulder16, Columbia University17, University of Washington18, Indian Institute of Technology Bombay19, Inter-University Centre for Astronomy and Astrophysics20, University of California, Berkeley21, Lawrence Berkeley National Laboratory22, George Washington University23, Texas Tech University24, University College London25, University of Leicester26, Space Telescope Science Institute27, National Radio Astronomy Observatory28, University of Portsmouth29, University of Southampton30, Radboud University Nijmegen31, Tokyo Institute of Technology32, Max Planck Society33, Northwestern University34, Adler Planetarium35, University of Oxford36, Weizmann Institute of Science37, Institute for the Physics and Mathematics of the Universe38, San Diego State University39, University of California, Merced40
TL;DR: It is demonstrated that merging neutron stars are a long-sought production site forging heavy elements by r-process nucleosynthesis, which is dissimilar to classical short gamma-ray bursts with ultrarelativistic jets.
Abstract: Merging neutron stars offer an excellent laboratory for simultaneously studying strong-field gravity and matter in extreme environments. We establish the physical association of an electromagnetic counterpart (EM170817) with gravitational waves (GW170817) detected from merging neutron stars. By synthesizing a panchromatic data set, we demonstrate that merging neutron stars are a long-sought production site forging heavy elements by r-process nucleosynthesis. The weak gamma rays seen in EM170817 are dissimilar to classical short gamma-ray bursts with ultrarelativistic jets. Instead, we suggest that breakout of a wide-angle, mildly relativistic cocoon engulfing the jet explains the low-luminosity gamma rays, the high-luminosity ultraviolet-optical-infrared, and the delayed radio and x-ray emission. We posit that all neutron star mergers may lead to a wide-angle cocoon breakout, sometimes accompanied by a successful jet and sometimes by a choked jet.
579 citations
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Czech Technical University in Prague1, Academy of Sciences of the Czech Republic2, Panjab University, Chandigarh3, CERN4, Polytechnic University of Turin5, Indian Institute of Technology Bombay6, Variable Energy Cyclotron Centre7, University of Bergen8, Korea Institute of Science and Technology Information9, Yale University10, University of Santiago de Compostela11, Bergen University College12, National Autonomous University of Mexico13, California Polytechnic State University14, Sejong University15, Sewanee: The University of the South16, State University of Campinas17, Kurchatov Institute18, University of Birmingham19, CINVESTAV20
TL;DR: In this article, the authors present the first observation of strangeness enhancement in high-multiplicity proton-proton collisions, showing that the integrated yields of strange and multi-strange particles relative to pions increases significantly with the event charged-particle multiplicity.
Abstract: At sufficiently high temperature and energy density, nuclear matter undergoes a transition to a phase in which quarks and gluons are not confined: the quark-gluon plasma (QGP). Such an exotic state of strongly interacting quantum chromodynamics matter is produced in the laboratory in heavy nuclei high-energy collisions, where an enhanced production of strange hadrons is observed. Strangeness enhancement, originally proposed as a signature of QGP formation in nuclear collisions, is more pronounced for multi-strange baryons. Several effects typical of heavy-ion phenomenology have been observed in high-multiplicity proton-proton (pp) collisions, but the enhanced production of multi-strange particles has not been reported so far. Here we present the first observation of strangeness enhancement in high-multiplicity proton-proton collisions. We find that the integrated yields of strange and multi-strange particles, relative to pions, increases significantly with the event charged-particle multiplicity. The measurements are in remarkable agreement with the p-Pb collision results, indicating that the phenomenon is related to the final system created in the collision. In high-multiplicity events strangeness production reaches values similar to those observed in Pb-Pb collisions, where a QGP is formed.
500 citations
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California Institute of Technology1, Texas Tech University2, University of Oxford3, York University4, Princeton University5, Tel Aviv University6, University of Wisconsin–Milwaukee7, National Radio Astronomy Observatory8, Australian Research Council9, University of Sydney10, Commonwealth Scientific and Industrial Research Organisation11, Indian Institute of Technology Bombay12, Tata Institute of Fundamental Research13, United States Naval Research Laboratory14, Hebrew University of Jerusalem15, First Green Bank16, Radboud University Nijmegen17, Inter-University Centre for Astronomy and Astrophysics18, Goddard Space Flight Center19
TL;DR: In this paper, the authors reported the detection of a counterpart radio source that appears 16 days after the GW170817 binary neutron star merger event, allowing them to diagnose the energetics and environment of the merger.
Abstract: Gravitational waves have been detected from a binary neutron star merger event, GW170817. The detection of electromagnetic radiation from the same source has shown that the merger occurred in the outskirts of the galaxy NGC 4993, at a distance of 40 megaparsecs from Earth. We report the detection of a counterpart radio source that appears 16 days after the event, allowing us to diagnose the energetics and environment of the merger. The observed radio emission can be explained by either a collimated ultrarelativistic jet, viewed off-axis, or a cocoon of mildly relativistic ejecta. Within 100 days of the merger, the radio light curves will enable observers to distinguish between these models, and the angular velocity and geometry of the debris will be directly measurable by very long baseline interferometry.
465 citations
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TL;DR: A novel neural network architecture for encoding and synthesis of 3D shapes, particularly their structures, is introduced and it is demonstrated that without supervision, the network learns meaningful structural hierarchies adhering to perceptual grouping principles, produces compact codes which enable applications such as shape classification and partial matching, and supports shape synthesis and interpolation with significant variations in topology and geometry.
Abstract: We introduce a novel neural network architecture for encoding and synthesis of 3D shapes, particularly their structures. Our key insight is that 3D shapes are effectively characterized by their hierarchical organization of parts, which reflects fundamental intra-shape relationships such as adjacency and symmetry. We develop a recursive neural net (RvNN) based autoencoder to map a flat, unlabeled, arbitrary part layout to a compact code. The code effectively captures hierarchical structures of man-made 3D objects of varying structural complexities despite being fixed-dimensional: an associated decoder maps a code back to a full hierarchy. The learned bidirectional mapping is further tuned using an adversarial setup to yield a generative model of plausible structures, from which novel structures can be sampled. Finally, our structure synthesis framework is augmented by a second trained module that produces fine-grained part geometry, conditioned on global and local structural context, leading to a full generative pipeline for 3D shapes. We demonstrate that without supervision, our network learns meaningful structural hierarchies adhering to perceptual grouping principles, produces compact codes which enable applications such as shape classification and partial matching, and supports shape synthesis and interpolation with significant variations in topology and geometry.
403 citations
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California Institute of Technology1, Tel Aviv University2, University of Maryland, College Park3, Goddard Space Flight Center4, University of Wisconsin–Milwaukee5, Stockholm University6, Princeton University7, Liverpool John Moores University8, National Central University9, Hebrew University of Jerusalem10, Australian Research Council11, University of Sydney12, Indian Institute of Astrophysics13, Indian Institute of Science14, Commonwealth Scientific and Industrial Research Organisation15, University of Colorado Boulder16, Columbia University17, University of Washington18, Indian Institute of Technology Bombay19, Inter-University Centre for Astronomy and Astrophysics20, Lawrence Berkeley National Laboratory21, University of California, Berkeley22, George Washington University23, Texas Tech University24, University College London25, University of Leicester26, Space Telescope Science Institute27, National Radio Astronomy Observatory28, University of Portsmouth29, University of Southampton30, Radboud University Nijmegen31, Tokyo Institute of Technology32, Max Planck Society33, Northwestern University34, Adler Planetarium35, University of Oxford36, Weizmann Institute of Science37, San Diego State University38, Institute for the Physics and Mathematics of the Universe39, University of California, Merced40
TL;DR: In this paper, the authors established the physical association of an electromagnetic counterpart EM170817 to gravitational waves (GW 170817) detected from merging neutron stars by synthesizing a panchromatic dataset.
Abstract: Merging neutron stars offer an exquisite laboratory for simultaneously studying strong-field gravity and matter in extreme environments. We establish the physical association of an electromagnetic counterpart EM170817 to gravitational waves (GW170817) detected from merging neutron stars. By synthesizing a panchromatic dataset, we demonstrate that merging neutron stars are a long-sought production site forging heavy elements by r-process nucleosynthesis. The weak gamma-rays seen in EM170817 are dissimilar to classical short gamma-ray bursts with ultra-relativistic jets. Instead, we suggest that breakout of a wide-angle, mildly-relativistic cocoon engulfing the jet elegantly explains the low-luminosity gamma-rays, the high-luminosity ultraviolet-optical-infrared and the delayed radio/X-ray emission. We posit that all merging neutron stars may lead to a wide-angle cocoon breakout; sometimes accompanied by a successful jet and sometimes a choked jet.
403 citations
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TL;DR: Against the backdrop of a declining monsoon, the number of extreme rain events is on the rise over central India, driven by an increasing variability of the low-level monsoon westerlies over the Arabian Sea.
Abstract: Socioeconomic challenges continue to mount for half a billion residents of central India because of a decline in the total rainfall and a concurrent rise in the magnitude and frequency of extreme rainfall events. Alongside a weakening monsoon circulation, the locally available moisture and the frequency of moisture-laden depressions from the Bay of Bengal have also declined. Here we show that despite these negative trends, there is a threefold increase in widespread extreme rain events over central India during 1950–2015. The rise in these events is due to an increasing variability of the low-level monsoon westerlies over the Arabian Sea, driving surges of moisture supply, leading to extreme rainfall episodes across the entire central subcontinent. The homogeneity of these severe weather events and their association with the ocean temperatures underscores the potential predictability of these events by two-to-three weeks, which offers hope in mitigating their catastrophic impact on life, agriculture and property. Against the backdrop of a declining monsoon, the number of extreme rain events is on the rise over central India. Here the authors identify a threefold increase in widespread extreme rains over the region during 1950–2015, driven by an increasing variability of the low-level westerlies over the Arabian Sea.
362 citations
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01 Jul 2017TL;DR: This paper introduces a deep architecture for segmenting 3D objects into their labeled semantic parts that significantly outperforms the existing state-of-the-art methods in the currently largest segmentation benchmark (ShapeNet).
Abstract: This paper introduces a deep architecture for segmenting 3D objects into their labeled semantic parts. Our architecture combines image-based Fully Convolutional Networks (FCNs) and surface-based Conditional Random Fields (CRFs) to yield coherent segmentations of 3D shapes. The image-based FCNs are used for efficient view-based reasoning about 3D object parts. Through a special projection layer, FCN outputs are effectively aggregated across multiple views and scales, then are projected onto the 3D object surfaces. Finally, a surface-based CRF combines the projected outputs with geometric consistency cues to yield coherent segmentations. The whole architecture (multi-view FCNs and CRF) is trained end-to-end. Our approach significantly outperforms the existing state-of-the-art methods in the currently largest segmentation benchmark (ShapeNet). Finally, we demonstrate promising segmentation results on noisy 3D shapes acquired from consumer-grade depth cameras.
357 citations
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TL;DR: Automatic sarcasm detection is the task of predicting sarcasm in text as mentioned in this paper, which is a crucial step to sentiment analysis, considering prevalence and challenges of sarcasm of sentiment-bearing text.
Abstract: Automatic sarcasm detection is the task of predicting sarcasm in text. This is a crucial step to sentiment analysis, considering prevalence and challenges of sarcasm in sentiment-bearing text. Beginning with an approach that used speech-based features, automatic sarcasm detection has witnessed great interest from the sentiment analysis community. This article is a compilation of past work in automatic sarcasm detection. We observe three milestones in the research so far: semi-supervised pattern extraction to identify implicit sentiment, use of hashtag-based supervision, and incorporation of context beyond target text. In this article, we describe datasets, approaches, trends, and issues in sarcasm detection. We also discuss representative performance values, describe shared tasks, and provide pointers to future work, as given in prior works. In terms of resources to understand the state-of-the-art, the survey presents several useful illustrations—most prominently, a table that summarizes past papers along different dimensions such as the types of features, annotation techniques, and datasets used.
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TL;DR: This work provides an upper bound to the achievable quantum advantage when the interaction order is restricted; i.e., at most k batteries are interacting, which constitutes a fundamental limit on the advantage offered by quantum technologies over their classical counterparts.
Abstract: Can collective quantum effects make a difference in a meaningful thermodynamic operation? Focusing on energy storage and batteries, we demonstrate that quantum mechanics can lead to an enhancement in the amount of work deposited per unit time, i.e., the charging power, when N batteries are charged collectively. We first derive analytic upper bounds for the collective quantum advantage in charging power for two choices of constraints on the charging Hamiltonian. We then demonstrate that even in the absence of quantum entanglement this advantage can be extensive. For our main result, we provide an upper bound to the achievable quantum advantage when the interaction order is restricted; i.e., at most k batteries are interacting. This constitutes a fundamental limit on the advantage offered by quantum technologies over their classical counterparts.
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TL;DR: In this paper, the important features of triphenylamine (TPA) based organic hole transport materials (HTMs) in accordance with their structural diversities are discussed from their evolution to recent advancements.
Abstract: In this review article, the important features (optical, thermal and electrochemical) of triphenylamine (TPA) based organic hole transport materials (HTMs) in accordance with their structural diversities are discussed from their evolution to recent advancements. The literature here covers past and ongoing work mostly relevant to HTMs used in DSSCs and PSCs. Besides the good optical properties and high hole mobility, the stability of the amorphous state of the HTM layer is a crucial factor in the commercialization of PSCs. The stability of the amorphous glassy state of HTMs is defined by an important physical parameter, i.e., the glass transition temperature (Tg) which is discussed on the basis of the molecular structure of HTMs.
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California Institute of Technology1, Texas Tech University2, University of Oxford3, York University4, Princeton University5, Tel Aviv University6, University of Wisconsin–Milwaukee7, National Radio Astronomy Observatory8, Australian Research Council9, University of Sydney10, Commonwealth Scientific and Industrial Research Organisation11, Indian Institute of Technology Bombay12, Tata Institute of Fundamental Research13, United States Naval Research Laboratory14, Hebrew University of Jerusalem15, First Green Bank16, Radboud University Nijmegen17, Inter-University Centre for Astronomy and Astrophysics18, Goddard Space Flight Center19
TL;DR: Radio observations constrain the energy and geometry of relativistic material ejected from a binary neutron star merger, and the detection of a counterpart radio source that appears 16 days after the event is reported, allowing us to diagnose the energetics and environment of the merger.
Abstract: Gravitational waves have been detected from a binary neutron star merger event, GW170817. The detection of electromagnetic radiation from the same source has shown that the merger occurred in the outskirts of the galaxy NGC 4993, at a distance of 40 megaparsecs from Earth. We report the detection of a counterpart radio source that appears 16 days after the event, allowing us to diagnose the energetics and environment of the merger. The observed radio emission can be explained by either a collimated ultra-relativistic jet viewed off-axis, or a cocoon of mildly relativistic ejecta. Within 100 days of the merger, the radio light curves will distinguish between these models and very long baseline interferometry will have the capability to directly measure the angular velocity and geometry of the debris.
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TL;DR: This Review provides an overview on the most recent progress in the field of C-C bond formation involving decarboxylation as a key step involving carboxylic acid.
Abstract: C−C bond forming reactions incarnate the core of organic synthesis because of their fundamental applications to molecular diversity and complexity. In recent years, use of carboxylic acid as one of the coupling partners in place of conventional organometallic reagents has seen an upsurge due to its potency to generate similar organometallic intermediates after decarboxylation. This Review provides an overview on the most recent progress in the field of C−C bond formation involving decarboxylation as a key step. Different important developments, which are not included in earlier Reviews in this area, have been summarized with representative examples and discussions on their reaction mechanisms.
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TL;DR: In this article, a digital twin of the laser-based directed energy deposition additive manufacturing (DED) process is proposed to provide accurate predictions of the spatial and temporal variations of metallurgical parameters that affect the structure and properties of components.
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TL;DR: The results suggest that future climate warming will lead to substantial increases in heat-related mortality, particularly in developing low-latitude countries, such as India, where heat waves will become more frequent and populations are especially vulnerable to these extreme temperatures.
Abstract: Rising global temperatures are causing increases in the frequency and severity of extreme climatic events, such as floods, droughts, and heat waves. We analyze changes in summer temperatures, the frequency, severity, and duration of heat waves, and heat-related mortality in India between 1960 and 2009 using data from the India Meteorological Department. Mean temperatures across India have risen by more than 0.5°C over this period, with statistically significant increases in heat waves. Using a novel probabilistic model, we further show that the increase in summer mean temperatures in India over this period corresponds to a 146% increase in the probability of heat-related mortality events of more than 100 people. In turn, our results suggest that future climate warming will lead to substantial increases in heat-related mortality, particularly in developing low-latitude countries, such as India, where heat waves will become more frequent and populations are especially vulnerable to these extreme temperatures. Our findings indicate that even moderate increases in mean temperatures may cause great increases in heat-related mortality and support the efforts of governments and international organizations to build up the resilience of these vulnerable regions to more severe heat waves.
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TL;DR: In this paper, the authors presented a search for GWs from the remnant of the binary neutron star merger GW170817 using data from Advanced LIGO and Advanced Virgo.
Abstract: The first observation of a binary neutron star (NS) coalescence by the Advanced LIGO and Advanced Virgo gravitational-wave (GW) detectors offers an unprecedented opportunity to study matter under the most extreme conditions. After such a merger, a compact remnant is left over whose nature depends primarily on the masses of the inspiraling objects and on the equation of state of nuclear matter. This could be either a black hole (BH) or an NS, with the latter being either long-lived or too massive for stability implying delayed collapse to a BH. Here, we present a search for GWs from the remnant of the binary NS merger GW170817 using data from Advanced LIGO and Advanced Virgo. We search for short- (lesssim1 s) and intermediate-duration (lesssim500 s) signals, which include GW emission from a hypermassive NS or supramassive NS, respectively. We find no signal from the post-merger remnant. Our derived strain upper limits are more than an order of magnitude larger than those predicted by most models. For short signals, our best upper limit on the root sum square of the GW strain emitted from 1–4 kHz is ${h}_{\mathrm{rss}}^{50 \% }=2.1\times {10}^{-22}\,{\mathrm{Hz}}^{-1/2}$ at 50% detection efficiency. For intermediate-duration signals, our best upper limit at 50% detection efficiency is ${h}_{\mathrm{rss}}^{50 \% }=8.4\times {10}^{-22}\,{\mathrm{Hz}}^{-1/2}$ for a millisecond magnetar model, and ${h}_{\mathrm{rss}}^{50 \% }=5.9\times {10}^{-22}\,{\mathrm{Hz}}^{-1/2}$ for a bar-mode model. These results indicate that post-merger emission from a similar event may be detectable when advanced detectors reach design sensitivity or with next-generation detectors.
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TL;DR: In this article, a modulation-doped two-dimensional electron gas (2DEG) at the β-(Al 0.2Ga 0.8)2O3/Ga2O 3 heterojunction by silicon delta doping was confirmed using capacitance voltage measurements.
Abstract: Modulation-doped heterostructures are a key enabler for realizing high mobility and better scaling properties for high performance transistors. We report the realization of a modulation-doped two-dimensional electron gas (2DEG) at the β-(Al0.2Ga0.8)2O3/Ga2O3 heterojunction by silicon delta doping. The formation of a 2DEG was confirmed using capacitance voltage measurements. A modulation-doped 2DEG channel was used to realize a modulation-doped field-effect transistor. The demonstration of modulation doping in the β-(Al0.2Ga0.8)2O3/Ga2O3 material system could enable heterojunction devices for high performance electronics.
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TL;DR: Recent advances in the construction and utilization of novel anodes for microbial fuel cells are reviewed, highlighting some of the critical roles and functions of anodes in MFCs, strategies available for improving surface areas of anode areas, dominant performance of stainless-steel based anode materials, and the emerging benefits of inclusion of nanomaterials.
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TL;DR: In this paper, the mass of the dynamical ejecta can be estimated without a direct electromagnetic observation of the kilonova, using GW measurements and a phenomenological model calibrated to numerical simulations of mergers with dynamical ejecteda.
Abstract: The source of the gravitational-wave (GW) signal GW170817, very likely a binary neutron star merger, was also
observed electromagnetically, providing the first multi-messenger observations of this type. The two-week-long
electromagnetic (EM) counterpart had a signature indicative of an r-process-induced optical transient known as a
kilonova. This Letter examines how the mass of the dynamical ejecta can be estimated without a direct
electromagnetic observation of the kilonova, using GW measurements and a phenomenological model calibrated to
numerical simulations of mergers with dynamical ejecta. Specifically, we apply the model to the binary masses
inferred from the GW measurements, and use the resulting mass of the dynamical ejecta to estimate its contribution
(without the effects of wind ejecta) to the corresponding kilonova light curves from various models. The
distributions of dynamical ejecta mass range between = - - - M M ej 10 10
3 2 for various equations of state,
assuming that the neutron stars are rotating slowly. In addition, we use our estimates of the dynamical ejecta mass
and the neutron star merger rates inferred from GW170817 to constrain the contribution of events like this to the
r-process element abundance in the Galaxy when ejecta mass from post-merger winds is neglected. We find that if
10% of the matter dynamically ejected from binary neutron star (BNS) mergers is converted to r-process
elements, GW170817-like BNS mergers could fully account for the amount of r-process material observed in the
Milky Way.
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TL;DR: In this paper, multicomponent rare earth oxide (REO) nanocrystalline powders containing up to seven equiatomic rare earth elements were successfully synthesized in a single-phase CaF2-type (Fm-3) structure.
Abstract: Multicomponent rare earth oxide (REO) nanocrystalline powders containing up to seven equiatomic rare earth elements were successfully synthesized in a single-phase CaF2-type (Fm-3 m) structure. The addition of more than six elements resulted in the formation of a secondary phase. Annealing at 1000°C for 1 h led to the formation of a single-phase (Ia-3) even in the 7-component system. In the absence of cerium (Ce4+), secondary phases were observed irrespective of the number of cations or the extent of thermal treatment indicating that cerium cations played a crucial role in stabilizing the multicomponent REOs into a phase pure structure.
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TL;DR: In this article, multicomponent entropy stabilised oxides containing four and five metal elements in equiatomic amounts were successfully synthesized in nanocrystalline form by nebulised spray pyrolysis (NSP), flame spray pyrotelysis and reverse co-precipitation (RCP) techniques, demonstrating that entropy stabilisation of these recently discovered materials is independent of the synthesis method.
Abstract: Multicomponent entropy stabilised oxides containing four and five metal elements in equiatomic amounts were successfully synthesised in nanocrystalline form by nebulised spray pyrolysis (NSP), flame spray pyrolysis (FSP) and reverse co-precipitation (RCP) techniques, demonstrating that entropy stabilisation of these recently discovered materials is independent of the synthesis method. Both 4- and 5-cationic systems, (Co,Mg,Ni,Zn)O and (Co,Cu,Mg,Ni,Zn)O, can be stabilised into a single rocksalt structure directly only using NSP, while in FSP and RCP, stabilisation can be achieved after thermal treatment. This result indicates, that in 5-cationic NSP system configurational entropy is high enough to directly stabilise single rocksalt phase at lower temperature, while higher synthesis temperature is required to compensate the lower configurational entropy in 4-cationic system. Retention of single-phase at room temperature indicates sluggish diffusion kinetics, making entropy stabilised phases quenchable.
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TL;DR: In this paper, a combined model-independent and model-dependent analysis was performed to deduce properties of new physics (NP) in b→sμ+μ-decays.
Abstract: The recent measurement of RK* is yet another hint of new physics (NP) and supports the idea that it is present in b→sμ+μ- decays. We perform a combined model-independent and model-dependent analysis in order to deduce properties of this NP. Like others, we find that the NP must obey one of two scenarios: (I) C9μμ(NP)<0 or (II) C9μμ(NP)=-C10μμ(NP)<0. A third scenario, (III) C9μμ(NP)=-C9′μμ(NP), is rejected largely because it predicts RK=1, in disagreement with experiment. The simplest NP models involve the tree-level exchange of a leptoquark (LQ) or a Z′ boson. We show that scenario II can arise in LQ or Z′ models, but scenario I is only possible with a Z′. Fits to Z′ models must take into account the additional constraints from Bs0-B¯s0 mixing and neutrino trident production. Although the LQs must be heavy, O(TeV), we find that the Z′ can be light, e.g., MZ′=10 GeV or 200 MeV.
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TL;DR: In this paper, the authors search for high-energy neutrinos from the binary neutron star merger in the GeV-EeV energy range using the Antares, IceCube, and Pierre Auger Observatories.
Abstract: The Advanced LIGO and Advanced Virgo observatories recently discovered gravitational waves from a binary neutron star inspiral. A short gamma-ray burst (GRB) that followed the merger of this binary was also recorded by the Fermi Gamma-ray Burst Monitor (Fermi-GBM), and the Anti-Coincidence Shield for the Spectrometer for the International Gamma-Ray Astrophysics Laboratory (INTEGRAL), indicating particle acceleration by the source. The precise location of the event was determined by optical detections of emission following the merger. We searched for high-energy neutrinos from the merger in the GeV–EeV energy range using the Antares, IceCube, and Pierre Auger Observatories. No neutrinos directionally coincident with the source were detected within ±500 s around the merger time. Additionally, no MeV neutrino burst signal was detected coincident with the merger. We further carried out an extended search in the direction of the source for high-energy neutrinos within the 14 day period following the merger, but found no evidence of emission. We used these results to probe dissipation mechanisms in relativistic outflows driven by the binary neutron star merger. The non-detection is consistent with model predictions of short GRBs observed at a large off-axis angle.
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TL;DR: An overview of the unique chemistry that cyanobacteria have been co-opted to perform is presented and key lessons learned are highlighted.
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28 Nov 2017TL;DR: X-ray diffraction peak at around 10° and broad D band peak at 1350 cm–1 in Raman spectra confirm the presence of oxygen-rich functional groups on the surface of GOQDs, which show tunable oxygen functional groups, which are confirmed by X-ray photoelectron spectroscopy.
Abstract: In this study, we present the preparation of graphene quantum dots (GQDs) and graphene oxide quantum dots (GOQDs). GQDs/GOQDs are prepared by an easy electrochemical exfoliation method, in which two graphite rods are used as electrodes. The electrolyte used is a combination of citric acid and alkali hydroxide in water. Four types of quantum dots, GQD1–GQD4, are prepared by varying alkali hydroxide concentration in the electrolyte, while keeping the citric acid concentration fixed. Variation of alkali hydroxide concentration in the electrolyte results in the production of GOQDs. Balanced reaction of citric acid and alkali hydroxide results in the production of GQDs (GQD3). However, three variations in alkali hydroxide concentration result in GOQDs (GQD1, GQD2, and GQD4). GOQDs show tunable oxygen functional groups, which are confirmed by X-ray photoelectron spectroscopy. GQDs/GOQDs show absorption in the UV region and show excitation-dependent photoluminescence behavior. The obtained average size is 2–3 nm...
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TL;DR: Intumescent fire resistive coatings as mentioned in this paper are a newer type of passive fireproofing coatings usually applied as thin film and forming an insulating char which acts as a barrier between the fire and the structural steel.
Abstract: Fire is a serious threat to people and the structures they build. There is a continuous development of newer methods and materials to prevent its effects on them. Nowadays, a lot of attention is being paid in the design of public and commercial buildings by incorporating fire safety. Passive fireproofing of high-rise structures has become very important due to the use of steel in load bearing mode and has attracted increased attention after the collapse of the WTC towers. Conventional passive fireproofing materials include concrete covering, gypsum board and cementitious coatings which have a poor aesthetic. Intumescent fire-resistive coatings are a newer type of passive fireproofing coatings usually applied as thin film and they swell many times their original thickness forming an insulating char which acts as a barrier between the fire and the structural steel. It prevents the temperatures of the steel members from reaching a critical value and helps in maintaining the integrity of the structure in fire event. They are the preferred choice for passive fire protection of load bearing steel frame structures of architects and designers as they offer aesthetic appearance, flexibility, speed of application, and ease of inspection and maintenance. The present review covers recent developments in the field of intumescent coatings with a major emphasis on organic intumescent coatings. The role of various ingredients, their interactions in intumescent coatings, effects of various pigments, binders and additives are discussed briefly.
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TL;DR: A new local descriptor for 3D shapes is presented, directly applicable to a wide range of shape analysis problems such as point correspondences, semantic segmentation, affordance prediction, and shape-to-scan matching by a convolutional network trained to embed geometrically and semantically similar points close to one another in descriptor space.
Abstract: We present a new local descriptor for 3D shapes, directly applicable to a wide range of shape analysis problems such as point correspondences, semantic segmentation, affordance prediction, and shape-to-scan matching. The descriptor is produced by a convolutional network that is trained to embed geometrically and semantically similar points close to one another in descriptor space. The network processes surface neighborhoods around points on a shape that are captured at multiple scales by a succession of progressively zoomed-out views, taken from carefully selected camera positions. We leverage two extremely large sources of data to train our network. First, since our network processes rendered views in the form of 2D images, we repurpose architectures pretrained on massive image datasets. Second, we automatically generate a synthetic dense point correspondence dataset by nonrigid alignment of corresponding shape parts in a large collection of segmented 3D models. As a result of these design choices, our network effectively encodes multiscale local context and fine-grained surface detail. Our network can be trained to produce either category-specific descriptors or more generic descriptors by learning from multiple shape categories. Once trained, at test time, the network extracts local descriptors for shapes without requiring any part segmentation as input. Our method can produce effective local descriptors even for shapes whose category is unknown or different from the ones used while training. We demonstrate through several experiments that our learned local descriptors are more discriminative compared to state-of-the-art alternatives and are effective in a variety of shape analysis applications.
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TL;DR: PM2.5 pollution is a pan-India problem, with a regional character, and is not limited to urban areas or megacities, and even under the most active reductions envisioned, the 2050 mean exposure is estimated to be nearly 3 times higher than the WHO Air Quality Guideline.
Abstract: . India is currently experiencing degraded air quality, and future economic development will lead to challenges for air quality management. Scenarios of sectoral emissions of fine particulate matter and its precursors were developed and evaluated for 2015–2050, under specific pathways of diffusion of cleaner and more energy-efficient technologies. The impacts of individual source sectors on PM2.5 concentrations were assessed through systematic simulations of spatially and temporally resolved particulate matter concentrations, using the GEOS-Chem model, followed by population-weighted aggregation to national and state levels. We find that PM2.5 pollution is a pan-India problem, with a regional character, and is not limited to urban areas or megacities. Under present-day emissions, levels in most states exceeded the national PM2.5 annual standard (40 µg m−3). Sources related to human activities were responsible for the largest proportion of the present-day population exposure to PM2.5 in India. About 60 % of India's mean population-weighted PM2.5 concentrations come from anthropogenic source sectors, while the remainder are from other sources, windblown dust and extra-regional sources. Leading contributors are residential biomass combustion, power plant and industrial coal combustion and anthropogenic dust (including coal fly ash, fugitive road dust and waste burning). Transportation, brick production and distributed diesel were other contributors to PM2.5. Future evolution of emissions under regulations set at current levels and promulgated levels caused further deterioration of air quality in 2030 and 2050. Under an ambitious prospective policy scenario, promoting very large shifts away from traditional biomass technologies and coal-based electricity generation, significant reductions in PM2.5 levels are achievable in 2030 and 2050. Effective mitigation of future air pollution in India requires adoption of aggressive prospective regulation, currently not formulated, for a three-pronged switch away from (i) biomass-fuelled traditional technologies, (ii) industrial coal-burning and (iii) open burning of agricultural residue. Future air pollution is dominated by industrial process emissions, reflecting larger expansion in industrial, rather than residential energy demand. However, even under the most active reductions envisioned, the 2050 mean exposure, excluding any impact from windblown mineral dust, is estimated to be nearly 3 times higher than the WHO Air Quality Guideline.