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Articles 31 - 60 of 4365

Full-Text Articles in Physics

Fatigue-Resistant High-Performance Elastocaloric Materials Via Additive Manufacturing, Huilong Hou, Emrah Simsek, Tao Ma, Nathan S. Johnson, Suxin Qian, Cheikh Cissé, Drew Stasak, Naila Al Hasan, Lin Zhou, Yunho Hwang, Reinhard Radermacher, Valery I. Levitas, Matthew J. Kramer, Mohsen Asle Zaeem, Aaron P. Stebner, Ryan T. Ott, Jun Cui, Ichiro Takeuchi Aug 2019

Fatigue-Resistant High-Performance Elastocaloric Materials Via Additive Manufacturing, Huilong Hou, Emrah Simsek, Tao Ma, Nathan S. Johnson, Suxin Qian, Cheikh Cissé, Drew Stasak, Naila Al Hasan, Lin Zhou, Yunho Hwang, Reinhard Radermacher, Valery I. Levitas, Matthew J. Kramer, Mohsen Asle Zaeem, Aaron P. Stebner, Ryan T. Ott, Jun Cui, Ichiro Takeuchi

Valery I. Levitas

Elastocaloric cooling, which exploits the latent heat released and absorbed as stress-induced phase transformations are reversibly cycled in shape memory alloys, has recently emerged as a frontrunner in non-vapor-compression cooling technologies. The intrinsically high thermodynamic efficiency of elastocaloric materials is limited only by work hysteresis. Here, we report on creating high-performance low-hysteresis elastocaloric cooling materials via additive manufacturing of Titanium-Nickel (Ti-Ni) alloys. Contrary to established knowledge of the physical metallurgy of Ti-Ni alloys, intermetallic phases are found to be beneficial to elastocaloric performances when they are combined with the binary Ti-Ni compound in nanocomposite configurations. The resulting microstructure gives rise ...


Self-Consistent Two-Gap Description Of Mgb2 Superconductor, Hyunsoo Kim, Kyuil Cho, Makariy A. Tanatar, Valentin Taufour, Stella K. Kim, Sergey L. Bud’Ko, Paul C. Canfield, Vladimir G. Kogan, Ruslan Prozorov Aug 2019

Self-Consistent Two-Gap Description Of Mgb2 Superconductor, Hyunsoo Kim, Kyuil Cho, Makariy A. Tanatar, Valentin Taufour, Stella K. Kim, Sergey L. Bud’Ko, Paul C. Canfield, Vladimir G. Kogan, Ruslan Prozorov

Paul C. Canfield

A self-consistent two-gap γ -model is used to quantitatively describe several thermodynamic properties of MgB 2 superconductor. The superconducting coupling matrix, νij , was obtained from the fitting of the superfluid density in the entire superconducting temperature range. Using this input, temperature-dependent superconducting gaps, specific heat, and upper critical fields were calculated with no adjustable parameters and compared with the experimental data as well as with the first-principles calculations. The observed agreement between fit and data shows that γ -model provides adequate quantitative description of the two-gap superconductivity in MgB 2 and may serve as a relatively simple and versatile self-consistent ...


Composition-Dependent Stability Of The Medium-Range Order Responsible For Metallic Glass Formation, Feng Zhang, Min Ji, Xiao-Wei Fang, Yang Sun, Cai-Zhuang Wang, Mikhail I. Mendelev, Matthew J. Kramer, Ralph E. Napolitano, Kai-Ming Ho Aug 2019

Composition-Dependent Stability Of The Medium-Range Order Responsible For Metallic Glass Formation, Feng Zhang, Min Ji, Xiao-Wei Fang, Yang Sun, Cai-Zhuang Wang, Mikhail I. Mendelev, Matthew J. Kramer, Ralph E. Napolitano, Kai-Ming Ho

Ralph E. Napolitano

The competition between the characteristic medium-range order corresponding to amorphous alloys and that in ordered crystalline phases is central to phase selection and morphology evolution under various processing conditions. We examine the stability of a model glass system, Cu–Zr, by comparing the energetics of various medium-range structural motifs over a wide range of compositions using first-principles calculations. We focus specifically on motifs that represent possible building blocks for competing glassy and crystalline phases, and we employ a genetic algorithm to efficiently identify the energetically favored decorations of each motif for specific compositions. Our results show that a Bergman-type motif ...


A Computational Study Of Diffusion In A Glass-Forming Metallic Liquid, T. Wang, F. Zhang, L. Yang, X. W. Fang, S. H. Zhou, Matthew J. Kramer, Cai-Zhuang Wang, Kai-Ming Ho, Ralph E. Napolitano Aug 2019

A Computational Study Of Diffusion In A Glass-Forming Metallic Liquid, T. Wang, F. Zhang, L. Yang, X. W. Fang, S. H. Zhou, Matthew J. Kramer, Cai-Zhuang Wang, Kai-Ming Ho, Ralph E. Napolitano

Ralph E. Napolitano

Liquid phase diffusion plays a critical role in phase transformations (e.g. glass transformation and devitrification) observed in marginal glass forming systems such as Al-Sm. Controlling transformation pathways in such cases requires a comprehensive description of diffusivity, including the associated composition and temperature dependencies. In the computational study reported here, we examine atomic diffusion in Al-Sm liquids using ab initio molecular dynamics (AIMD) and determine the diffusivities of Al and Sm for selected alloy compositions. Non-Arrhenius diffusion behavior is observed in the undercooled liquids with an enhanced local structural ordering. Through assessment of our AIMD result, we construct a general ...


On Classification Approaches For Crystallographic Symmetries Of Noisy 2d Periodic Patterns, Peter Moeck Aug 2019

On Classification Approaches For Crystallographic Symmetries Of Noisy 2d Periodic Patterns, Peter Moeck

Peter Moeck

The existing types of classification approaches for the crystallographic symmetries of patterns that are more or less periodic in two dimensions (2D) are reviewed. Their relative performance is evaluated in a qualitative manner. Pseudo-symmetries of different kinds are discussed as they present severe challenges to most classification approaches when noise levels are moderate to high. The author’s information theory based approaches utilize digital images and geometric Akaike Information Criteria. They perform well in the presence of pseudo-symmetries and turn out to be the only ones that allow for fully objective (completely researcher independent) and generalized noise level dependent classifications ...


3d Systems' Technology Overview And New Applications In Manufacturing, Engineering, Science, And Education, Trevor Snyder, Mike Andrews, Mark M. Weislogel, Peter Moeck, Jennifer Stone-Sundberg, Derek Birkes, Madeline Paige Hoffert, Adam Lindeman, Jeff Morrill, Ondrej Fercak, Sasha Friedman, Jeff Gunderson, Anh Ha, Jack Mccollister, Yongkang Chen, John T. Geile, Andrew Paul Wollman, Babek Attari, Nathan Botnen, Vasant Vuppuluri, Jennifer Shim, Werner Kaminsky, Dustin Adams, John Graft Aug 2019

3d Systems' Technology Overview And New Applications In Manufacturing, Engineering, Science, And Education, Trevor Snyder, Mike Andrews, Mark M. Weislogel, Peter Moeck, Jennifer Stone-Sundberg, Derek Birkes, Madeline Paige Hoffert, Adam Lindeman, Jeff Morrill, Ondrej Fercak, Sasha Friedman, Jeff Gunderson, Anh Ha, Jack Mccollister, Yongkang Chen, John T. Geile, Andrew Paul Wollman, Babek Attari, Nathan Botnen, Vasant Vuppuluri, Jennifer Shim, Werner Kaminsky, Dustin Adams, John Graft

Mark M. Weislogel

Since the inception of 3D printing, an evolutionary process has taken place in which specific user and customer needs have crossed paths with the capabilities of a growing number of machines to create value-added businesses. Even today, over 30 years later, the growth of 3D printing and its utilization for the good of society is often limited by the various users' understanding of the technology for their specific needs. This article presents an overview of current 3D printing technologies and shows numerous examples from a multitude of fields from manufacturing to education.


Tuning Phase-Stability And Short-Range Order Through Ai-Doping In (Cocrfemn)100-Xaix High Entropy Alloys, Prashant Singh, Amalraj Marshal, Andrei V. Smirnov, Aayush Sharma, Ganesh Balasubramanian, K. G. Pradeep, Duane D. Johnson Aug 2019

Tuning Phase-Stability And Short-Range Order Through Ai-Doping In (Cocrfemn)100-Xaix High Entropy Alloys, Prashant Singh, Amalraj Marshal, Andrei V. Smirnov, Aayush Sharma, Ganesh Balasubramanian, K. G. Pradeep, Duane D. Johnson

Ganesh Balasubramanian

For (CoCrFeMn)100−xAlx high-entropy alloys, we investigate the phase evolution with increasing Al content (0≤x≤20 at.%). From first-principles theory, aluminum doping drives the alloy structurally from fcc to bcc separated by a narrow two-phase region (fcc+bcc), which is well supported by our experiments. Using KKR-CPA electronic-structure calculations, we highlight the effect of Al doping on the formation enthalpy (alloy stability) and electronic dispersion of (CoCrFeMn)100−xAlx alloys. As chemical short-range order indicates the nascent local order, and entropy changes, as well as expected low-temperature ordering behavior, we use KKR-CPA-based thermodynamic linear response to predict the ...


Dependence Of The Absolute Value Of The Penetration Depth In (Ba1–X Kx) Fe2 As2 On Doping, Avior Almoalem, Alon Yagil, Kyuil Cho, Serafim Teknowijoyo, Makariy A. Tanatar, Ruslan Prozorov, Yong Liu, Thomas A. Lograsso, Ophir M. Auslaender Aug 2019

Dependence Of The Absolute Value Of The Penetration Depth In (Ba1–X Kx) Fe2 As2 On Doping, Avior Almoalem, Alon Yagil, Kyuil Cho, Serafim Teknowijoyo, Makariy A. Tanatar, Ruslan Prozorov, Yong Liu, Thomas A. Lograsso, Ophir M. Auslaender

Thomas A. Lograsso

We report magnetic force microscopy (MFM) measurements on the iron-based superconductor Ba1−xKxFe2As2. By measuring locally the Meissner repulsion with the magnetic MFM tip, we determine the absolute value of the in-plane magnetic penetration depth (λab) in underdoped, optimally doped, and overdoped samples. The results suggest an abrupt increase of λab as doping is increased from xopt, which is potentially related to the presence of a quantum critical point. The response of superconducting vortices to magnetic forces exerted by the MFM tip for x=0.19 and 0.58 is compatible with previously observed structural symmetries at those doping levels.


Non-Fermi-Liquid Behaviors Associated With A Magnetic Quantum-Critical Point In Sr(Co{1-X}Ni{X})2as2 Single Crystals, Nediadath S. Sangeetha, Lin-Lin Wang, Andrei V. Smirnov, Volodymyr Smetana, A.-V. Mudring, Duane D. Johnson, Makariy A. Tanatar, Ruslan Prozorov, David C. Johnston Jul 2019

Non-Fermi-Liquid Behaviors Associated With A Magnetic Quantum-Critical Point In Sr(Co{1-X}Ni{X})2as2 Single Crystals, Nediadath S. Sangeetha, Lin-Lin Wang, Andrei V. Smirnov, Volodymyr Smetana, A.-V. Mudring, Duane D. Johnson, Makariy A. Tanatar, Ruslan Prozorov, David C. Johnston

Duane D. Johnson

Electron-doped Sr(Co{1-x}Ni{x})2As2 single crystals with compositions x = 0 to 0.9 were grown out of self-flux and SrNi2As2 single crystals out of Bi flux. The crystals were characterized using single-crystal x-ray diffraction (XRD), magnetic susceptibility chi(H,T), isothermal magnetization M(H,T), heat capacity Cp(H,T), and electrical resistivity ho(H,T) measurements versus applied magnetic field H and temperature T. The chi(T) data show that the crystals exhibit an antiferromagnetic (AFM) ground state almost immediately upon Ni doping on the Co site. Ab-initio electronic-structure calculations for x = 0 and x = 0 ...


Single Pair Of Weyl Fermions In The Half-Metallic Semimetal Eucd2as2, Lin-Lin Wang, Na Hyun Jo, Brinda Kuthanazhi, Yun Wu, Robert J. Mcqueeney, Adam Kaminski, Paul C. Canfield Jul 2019

Single Pair Of Weyl Fermions In The Half-Metallic Semimetal Eucd2as2, Lin-Lin Wang, Na Hyun Jo, Brinda Kuthanazhi, Yun Wu, Robert J. Mcqueeney, Adam Kaminski, Paul C. Canfield

Paul C. Canfield

Materials with the ideal case of a single pair of Weyl points (WPs) are highly desirable for elucidating the unique properties of Weyl fermions. EuC d 2 A s 2 is an antiferromagnetic topological insulator or Dirac semimetal depending on the different magnetic configurations. Using first-principles band-structure calculations, we show that inducing ferromagnetism in EuC d 2 A s 2 can generate a single pair of WPs from splitting the single pair of antiferromagnetic Dirac points due to its half-metallic nature. Analysis with a low-energy effective Hamiltonian shows that a single pair of WPs is obtained in EuC d 2 ...


Interplay Between Superconductivity And Itinerant Magnetism In Underdoped Ba1−Xkxfe2as2 (X = 0.2) Probed By The Response To Controlled Point-Like Disorder, Ruslan Prozorov, Marcin Kończykowski, Makariy A. Tanatar, Hai-Hu Wen, Rafael M. Fernandes, Paul C. Canfield Jul 2019

Interplay Between Superconductivity And Itinerant Magnetism In Underdoped Ba1−Xkxfe2as2 (X = 0.2) Probed By The Response To Controlled Point-Like Disorder, Ruslan Prozorov, Marcin Kończykowski, Makariy A. Tanatar, Hai-Hu Wen, Rafael M. Fernandes, Paul C. Canfield

Paul C. Canfield

The response of superconductors to controlled introduction of point-like disorder is an important tool to probe their microscopic electronic collective behavior. In the case of iron-based superconductors, magnetic fluctuations presumably play an important role in inducing high-temperature superconductivity. In some cases, these two seemingly incompatible orders coexist microscopically. Therefore, understanding how this unique coexistence state is affected by disorder can provide important information about the microscopic mechanisms involved. In one of the most studied pnictide family, hole-doped Ba1−xKxFe2As2 (BaK122), this coexistence occurs over a wide range of doping levels, 0.16 ≲ x ≲ 0.25. We used ...


Transverse Localization Of Transmission Eigenchannels, Hasan Yılmaz, Chia Wei Hsu, Alexey Yamilov, Hui Cao Jul 2019

Transverse Localization Of Transmission Eigenchannels, Hasan Yılmaz, Chia Wei Hsu, Alexey Yamilov, Hui Cao

Alexey Yamilov

Transmission eigenchannels are building blocks of coherent wave transport in diffusive media, and selective excitation of individual eigenchannels can lead to diverse transport behaviour. An essential yet poorly understood property is the transverse spatial profile of each eigenchannel, which is relevant for the associated energy density and critical for coupling light into and out of it. Here, we discover that the transmission eigenchannels of a disordered slab possess exponentially localized incident and outgoing profiles, even in the diffusive regime far from Anderson localization. Such transverse localization arises from a combination of reciprocity, local coupling of spatial modes and non-local correlations ...


Few-Body Dynamics Underlying Postcollision Effects In The Ionization Of H₂ By 75-Kev Proton Impact, M. Dhital, S. Bastola, A. Silvus, Don H. Madison, Michael Schulz Jul 2019

Few-Body Dynamics Underlying Postcollision Effects In The Ionization Of H₂ By 75-Kev Proton Impact, M. Dhital, S. Bastola, A. Silvus, Don H. Madison, Michael Schulz

Michael Schulz

We have measured fully differential cross sections (FDCS) for ionization in 75-keVp+H2 collisions for ejected electron speeds close to the projectile speed. The data were analyzed in dependence on both the electron emission angle and the projectile scattering angle. Pronounced postcollisional effects between the projectile and the ejected electrons were observed. Significant differences between experiment and theory and between two conceptually very similar theoretical models were found. This shows that in the region of electron-projectile velocity-matching the FDCS is very sensitive to the details of the underlying few-body dynamics.


The Role Of Multiple Electron Capture In The X-Ray Emission Process Following Charge Exchange Collisions With Neutral Targets, Sebastian Otranto, N. D. Cariatore, Ronald E. Olson Jul 2019

The Role Of Multiple Electron Capture In The X-Ray Emission Process Following Charge Exchange Collisions With Neutral Targets, Sebastian Otranto, N. D. Cariatore, Ronald E. Olson

Ronald E. Olson

In this work we theoretically study photonic spectra that follow charge exchange processes between highly charged ions and neutral argon and CO targets. The range of collision energies studied is 5 eV/amu-10 keV/amu, covering typical EBIT-traps and Solar Wind energies. Our studies are based on multiple electrons schemes within the classical trajectory Monte Carlo method. Electrons are sorted with the sequential binding energies for the target under consideration. The role played by the multiple electron capture process for the different collision systems under consideration is explicitly analyzed and its contribution separated as arising from double radiative decay and ...


Low Energy Electron And Positron Impact Differential Cross Sections For The Ionization Of Water Molecules In The Coplanar And Perpendicular Kinematics, P. Singh, G. Purohit, C. Champion, D. Sebilleau, Don H. Madison Jul 2019

Low Energy Electron And Positron Impact Differential Cross Sections For The Ionization Of Water Molecules In The Coplanar And Perpendicular Kinematics, P. Singh, G. Purohit, C. Champion, D. Sebilleau, Don H. Madison

Don H. Madison

We report here triply differential cross sections (TDCSs) for 81 eV electron and positron-impact ionization of the combined (1b1 + 3a1 ) orbitals of the water molecule by using the second-order distorted wave Born approximation (DWBA2) for ejection electron and positron energies of 5 eV and 10 eV and different momentum transfer conditions. The electron-impact TDCS will be compared with the experimental data measured by Ren et al. [Phys. Rev. A 95, 022701 (2017)] and with the molecular 3-body distorted wave (M3DW) approximation results in the scattering plane as well as the perpendicular plane. The DWBA2 results are in better ...


Triple Differential Cross Sections For Electron-Impact Ionization Of Methane At Intermediate Energy, Esam Ali, Carlos Granados, Ahmad Sakaamini, Don H. Madison Jul 2019

Triple Differential Cross Sections For Electron-Impact Ionization Of Methane At Intermediate Energy, Esam Ali, Carlos Granados, Ahmad Sakaamini, Don H. Madison

Don H. Madison

We report an experimental and theoretical investigation of electron-impact single ionization of the highest occupied molecular orbital 1t2 and the next highest occupied molecular orbital 2a1 states of CH4 at an incident electron energy of 250 eV. Triple differential cross sections measured in two different laboratories were compared with results calculated within the molecular 3-body distorted wave and generalized Sturmian function theoretical models. For ionization of the 1t2 state, the binary peak was observed to have a single maximum near the momentum transfer direction that evolved into a double peak for increasing projectile scattering angles, as ...


Few-Body Dynamics Underlying Postcollision Effects In The Ionization Of H₂ By 75-Kev Proton Impact, M. Dhital, S. Bastola, A. Silvus, Don H. Madison, Michael Schulz Jul 2019

Few-Body Dynamics Underlying Postcollision Effects In The Ionization Of H₂ By 75-Kev Proton Impact, M. Dhital, S. Bastola, A. Silvus, Don H. Madison, Michael Schulz

Don H. Madison

We have measured fully differential cross sections (FDCS) for ionization in 75-keVp+H2 collisions for ejected electron speeds close to the projectile speed. The data were analyzed in dependence on both the electron emission angle and the projectile scattering angle. Pronounced postcollisional effects between the projectile and the ejected electrons were observed. Significant differences between experiment and theory and between two conceptually very similar theoretical models were found. This shows that in the region of electron-projectile velocity-matching the FDCS is very sensitive to the details of the underlying few-body dynamics.


Modelling And Evaluation Of Electrical Resonance Eddy Current For Submillimeter Defect Detection, Yew San Hor, Vinod K. Sivaraja, Yu Zhong, Bui V. Phuong, Christopher Lane Jul 2019

Modelling And Evaluation Of Electrical Resonance Eddy Current For Submillimeter Defect Detection, Yew San Hor, Vinod K. Sivaraja, Yu Zhong, Bui V. Phuong, Christopher Lane

Yew San Hor

Eddy current (EC) inspection is used extensively in non-destructive testing (NDT) to detect surface-breaking defects of engineering components. However, the sensitivity of conventional eddy current inspection has plateaued in recent years. The ability to detect submillimetre defects before it becomes critical would allow engineering components to remain in-service safely for longer. Typically, it is required that higher frequency EC is employed to achieve a suitable sensitivity for detection of such submillimetre defects. However, that would lead to significant electromagnetic noise affecting the sensitivity of the inspection. To overcome this issue, the electrical-resonance based eddy current method has been proposed, where ...


Properties Of The Binary Neutron Star Merger Gw170817, B. P. Abbott, R. Abbott, T. D. Abbott, Marco Cavaglia Jul 2019

Properties Of The Binary Neutron Star Merger Gw170817, B. P. Abbott, R. Abbott, T. D. Abbott, Marco Cavaglia

Marco Cavaglia

On August 17, 2017, the Advanced LIGO and Advanced Virgo gravitational-wave detectors observed a low-mass compact binary inspiral. The initial sky localization of the source of the gravitational-wave signal, GW170817, allowed electromagnetic observatories to identify NGC 4993 as the host galaxy. In this work, we improve initial estimates of the binary's properties, including component masses, spins, and tidal parameters, using the known source location, improved modeling, and recalibrated Virgo data. We extend the range of gravitational-wave frequencies considered down to 23 Hz, compared to 30 Hz in the initial analysis. We also compare results inferred using several signal models ...


Tests Of General Relativity With Gw170817, B. P. Abbott, R. Abbott, T. D. Abbott, Marco Cavaglia Jul 2019

Tests Of General Relativity With Gw170817, B. P. Abbott, R. Abbott, T. D. Abbott, Marco Cavaglia

Marco Cavaglia

The recent discovery by Advanced LIGO and Advanced Virgo of a gravitational wave signal from a binary neutron star inspiral has enabled tests of general relativity (GR) with this new type of source. This source, for the first time, permits tests of strong-field dynamics of compact binaries in the presence of matter. In this Letter, we place constraints on the dipole radiation and possible deviations from GR in the post-Newtonian coefficients that govern the inspiral regime. Bounds on modified dispersion of gravitational waves are obtained; in combination with information from the observed electromagnetic counterpart we can also constrain effects due ...


Search For Multimessenger Sources Of Gravitational Waves And High-Energy Neutrinos With Advanced Ligo During Its First Observing Run, Antares, And Icecube, A. Albert, M. André, M. Anghinolfi, Marco Cavaglia Jul 2019

Search For Multimessenger Sources Of Gravitational Waves And High-Energy Neutrinos With Advanced Ligo During Its First Observing Run, Antares, And Icecube, A. Albert, M. André, M. Anghinolfi, Marco Cavaglia

Marco Cavaglia

Astrophysical sources of gravitational waves, such as binary neutron star and black hole mergers or core-collapse supernovae, can drive relativistic outflows, giving rise to non-thermal high-energy emission. High-energy neutrinos are signatures of such outflows. The detection of gravitational waves and high-energy neutrinos from common sources could help establish the connection between the dynamics of the progenitor and the properties of the outflow. We searched for associated emission of gravitational waves and high-energy neutrinos from astrophysical transients with minimal assumptions using data from Advanced LIGO from its first observing run O1, and data from the Antares and IceCube neutrino observatories from ...


Constraining The P-Mode-G-Mode Tidal Instability With Gw170817, B. P. Abbott, R. Abbott, T. D. Abbott, Marco Cavaglia Jul 2019

Constraining The P-Mode-G-Mode Tidal Instability With Gw170817, B. P. Abbott, R. Abbott, T. D. Abbott, Marco Cavaglia

Marco Cavaglia

We analyze the impact of a proposed tidal instability coupling p modes and g modes within neutron stars on GW170817. This nonresonant instability transfers energy from the orbit of the binary to internal modes of the stars, accelerating the gravitational-wave driven inspiral. We model the impact of this instability on the phasing of the gravitational wave signal using three parameters per star: An overall amplitude, a saturation frequency, and a spectral index. Incorporating these additional parameters, we compute the Bayes factor (ln Bpg!pg) comparing our p-g model to a standard one. We find that the observed signal is ...


Low-Latency Gravitational-Wave Alerts For Multimessenger Astronomy During The Second Advanced Ligo And Virgo Observing Run, B. P. Abbott, R. Abbott, T. D. Abbott, Marco Cavaglia Jul 2019

Low-Latency Gravitational-Wave Alerts For Multimessenger Astronomy During The Second Advanced Ligo And Virgo Observing Run, B. P. Abbott, R. Abbott, T. D. Abbott, Marco Cavaglia

Marco Cavaglia

Advanced LIGO's second observing run (O2), conducted from 2016 November 30 to 2017 August 25, combined with Advanced Virgo's first observations in 2017 August, witnessed the birth of gravitational-wave multimessenger astronomy. The first ever gravitational-wave detection from the coalescence of two neutron stars, GW170817, and its gamma-ray counterpart, GRB 170817A, led to an electromagnetic follow-up of the event at an unprecedented scale. Several teams from across the world searched for EM/neutrino counterparts to GW170817, paving the way for the discovery of optical, X-ray, and radio counterparts. In this article, we describe the online identification of gravitational-wave transients ...


A Fermi Gamma-Ray Burst Monitor Search For Electromagnetic Signals Coincident With Gravitational-Wave Candidates In Advanced Ligo's First Observing Run, E. Burns, A. Goldstein, C. M. Hui, Marco Cavaglia Jul 2019

A Fermi Gamma-Ray Burst Monitor Search For Electromagnetic Signals Coincident With Gravitational-Wave Candidates In Advanced Ligo's First Observing Run, E. Burns, A. Goldstein, C. M. Hui, Marco Cavaglia

Marco Cavaglia

We present a search for prompt gamma-ray counterparts to compact binary coalescence gravitational wave (GW) candidates from Advanced LIGO's first observing run (O1). As demonstrated by the multimessenger observations of GW170817/GRB 170817A, electromagnetic and GW observations provide complementary information about the astrophysical source, and in the case of weaker candidates, may strengthen the case for an astrophysical origin. Here we investigate low-significance GW candidates from the O1 compact binary coalescence searches using the Fermi Gamma-Ray Burst Monitor (GBM), leveraging its all sky and broad energy coverage. Candidates are ranked and compared to background to measure the significance. Those ...


Narrow-Band Search For Gravitational Waves From Known Pulsars Using The Second Ligo Observing Run, B. P. Abbott, R. Abbott, T. D. Abbott, Marco Cavaglia Jul 2019

Narrow-Band Search For Gravitational Waves From Known Pulsars Using The Second Ligo Observing Run, B. P. Abbott, R. Abbott, T. D. Abbott, Marco Cavaglia

Marco Cavaglia

Isolated spinning neutron stars, asymmetric with respect to their rotation axis, are expected to be sources of continuous gravitational waves. The most sensitive searches for these sources are based on accurate matched filtering techniques that assume the continuous wave to be phase locked with the pulsar beamed emission. While matched filtering maximizes the search sensitivity, a significant signal-to-noise ratio loss will happen in the case of a mismatch between the assumed and the true signal phase evolution. Narrow-band algorithms allow for a small mismatch in the frequency and spin-down values of the pulsar while coherently integrating the entire dataset. In ...


All-Sky Search For Long-Duration Gravitational-Wave Transients In The Second Advanced Ligo Observing Run, B. P. Abbott, R. Abbott, T. D. Abbott, Marco Cavaglia Jul 2019

All-Sky Search For Long-Duration Gravitational-Wave Transients In The Second Advanced Ligo Observing Run, B. P. Abbott, R. Abbott, T. D. Abbott, Marco Cavaglia

Marco Cavaglia

We present the results of a search for long-duration gravitational-wave transients in the data from the Advanced LIGO second observation run; we search for gravitational-wave transients of 2-500 s duration in the 24-2048 Hz frequency band with minimal assumptions about signal properties such as waveform morphologies, polarization, sky location or time of occurrence. Signal families covered by these search algorithms include fallback accretion onto neutron stars, broadband chirps from innermost stable circular orbit waves around rotating black holes, eccentric inspiral-merger-ringdown compact binary coalescence waveforms, and other models. The second observation run totals about 118.3 days of coincident data between ...


Electronic Structure Of The Topological Superconductor Candidate Au2pb, Yun Wu, Gil Drachuck, Lin-Lin Wang, Duane D. Johnson, Przemyslaw Swatek, Benjamin Schrunk, Daixiang Mou, Lunan Huang, Sergey L. Bud’Ko, Paul C. Canfield, Adam Kaminski Jul 2019

Electronic Structure Of The Topological Superconductor Candidate Au2pb, Yun Wu, Gil Drachuck, Lin-Lin Wang, Duane D. Johnson, Przemyslaw Swatek, Benjamin Schrunk, Daixiang Mou, Lunan Huang, Sergey L. Bud’Ko, Paul C. Canfield, Adam Kaminski

Duane D. Johnson

We use magnetization measurements, high-resolution angle-resolved photoemission spectroscopy (ARPES), and density functional theory (DFT) calculations to study the electronic properties of Au2Pb, a topological superconductor candidate. The magnetization measurements reveal three discontinuities at 40, 51, and 99 K that agree well with reported structural phase transitions. To measure the band structure along desired crystal orientations, we utilized polishing, sputtering, and annealing to obtain clean flat sample surfaces. ARPES measurements of the Au2Pb (111) surface at 110 K shows a shallow hole pocket at the center and flower-petal-like surface states at the corners of the Brillouin zone. These observations match the ...


Mechanisms Of Methane Transport Through Populus Trichocarpa, Ellynne Marie Kutschera, M. A. K. Khalil, Andrew Rice, Todd Rosenstiel Jul 2019

Mechanisms Of Methane Transport Through Populus Trichocarpa, Ellynne Marie Kutschera, M. A. K. Khalil, Andrew Rice, Todd Rosenstiel

M.A.K. Khalil

Although the dynamics of methane (CH4) emission from croplands and wetlands have been fairly well investigated, the contribution of trees to global CH4 emission and the mechanisms of tree transport are relatively unknown. CH4 emissions from the common wetland tree species Populus trichocarpa (black cottonwood) native to the Pacific Northwest were measured under hydroponic conditions in order to separate plant transport mechanisms from the influence of soil processes. Roots were exposed to CH4 enriched water and canopy emissions of CH4 were measured. The average flux for 34 trials (at temperatures ranging from 17 to 25 °C) was 2.8 ± 2 ...


Electronic Structure Of The Topological Superconductor Candidate Au2pb, Yun Wu, Gil Drachuck, Lin-Lin Wang, Duane D. Johnson, Przemyslaw Swatek, Benjamin Schrunk, Daixiang Mou, Lunan Huang, Sergey L. Bud’Ko, Paul C. Canfield, Adam Kaminski Jul 2019

Electronic Structure Of The Topological Superconductor Candidate Au2pb, Yun Wu, Gil Drachuck, Lin-Lin Wang, Duane D. Johnson, Przemyslaw Swatek, Benjamin Schrunk, Daixiang Mou, Lunan Huang, Sergey L. Bud’Ko, Paul C. Canfield, Adam Kaminski

Paul C. Canfield

We use magnetization measurements, high-resolution angle-resolved photoemission spectroscopy (ARPES), and density functional theory (DFT) calculations to study the electronic properties of Au2Pb, a topological superconductor candidate. The magnetization measurements reveal three discontinuities at 40, 51, and 99 K that agree well with reported structural phase transitions. To measure the band structure along desired crystal orientations, we utilized polishing, sputtering, and annealing to obtain clean flat sample surfaces. ARPES measurements of the Au2Pb (111) surface at 110 K shows a shallow hole pocket at the center and flower-petal-like surface states at the corners of the Brillouin zone. These observations match the ...


High-Tc Superconductivity In Cakfe4 As4 In Absence Of Nematic Fluctuations, W.-L. Zhang, William R. Meier, Tai Kong, Paul C. Canfield, G. Blumberg Jul 2019

High-Tc Superconductivity In Cakfe4 As4 In Absence Of Nematic Fluctuations, W.-L. Zhang, William R. Meier, Tai Kong, Paul C. Canfield, G. Blumberg

Paul C. Canfield

We employ polarization-resolved Raman spectroscopy to study the multiband stoichiometric Tc = 35 K superconductor CaKFe4As4. We do not detect Pomeranchuk-like electronic nematic fluctuations which were universally observed in the XY (B2g) symmetry Raman response for most families of the Fe-based superconductors. In the superconducting state we observe, consistent with a nodeless order parameter, a full spectral weight suppression at low energies and the emergence of a composite pair-breaking coherence feature at energies between 12 and 20 meV. We analyze the superconductivity-induced phonon self-energy effects and give an estimation for the electron-phonon coupling constant λΓ=0.0015 which is insufficient ...