bluuebunny/crossref_metadata_2025 huggingface dataset:
The economic cost of conflict: Evidence from South Sudan
Authors: Mawejje Joseph , McSharry Patrick
Published: June 2021

This study estimates the output loss in South Sudan as a result of the double shock of the protracted post‐independence conflict and macroeconomic crisis. Using the synthetic control method for comparative studies, the analysis suggests that the cumulative loss in the growth rate of real per‐capita gross domestic product (GDP) was 69.63% (or a yearly average of 15.65%) over the period 2012–2018. This resulted in an accumulated loss in the real per‐capita GDP of US$7,070 (yearly average of US$1,010) and an accumulated loss in the aggregate GDP of US$81.1 billion (yearly average of US$11.6 billion) over the same period. Consequently, South Sudan's real per‐capita GDP in 2018 was just a third of what it would have been in the absence of conflict. Moreover, we find that exports and investment were the main channels through which the economy was adversely impacted by the conflict. These results are robust to several placebo and robustness tests. Implications for future research are discussed.
Academic parenthood: Navigating structure and culture in an elite occupation
Authors: Minnotte Krista Lynn
Published: June 2021

Many contemporary workers struggle to manage paid work and family responsibilities, leading scholars to explore mechanisms contributing to conflict between these two domains. Such examinations often center on pinpointing specific factors that explain variation in work‐family conflict, but these studies have less to say about how some occupational contexts create overwhelming demands for workers. In this article, I advocate for an approach that details the cultural and structural components of specific occupations. Building on scholarship about demanding jobs, I use academic parenthood as an illustrative case to demonstrate how certain occupational contexts are organized in ways that introduce challenges for caregiving. I then analyze how culture and structure jointly influence family‐friendly policies in the university setting, along with comparative experiences across discipline, gender, and race/ethnicity. Next, I describe how academic parents in the face of constraints, make choices, show agency, and demonstrate resistance. I conclude by identifying promising areas for future research.
Finite Element Simulation Technique for Evaluation of Opening Stresses Under High Plasticity
Authors: Rashid Ans Al , Imran Ramsha , Arif Zia Ullah , Khalid Muhammad Yasir
Published: June 2021

The crack closure phenomenon is important to study as it estimates the fatigue life of the components. It becomes even more complex under low-cycle fatigue (LCF) since under LCF high amount of plasticity is induced within the material near notches or defects. As a result, the assumptions used by the linear elastic fracture mechanics (LEFM) approach become invalid. However, several experimental techniques are reported on the topic, the utilization of numerical tools can provide substantial cost and time-saving. In this study, the authors present a finite element simulation technique to evaluate the opening stress levels for two structural steels (25CrMo4 and 30NiCrMoV12) under low-cycle fatigue conditions. The LCF experimental results were used to obtain kinematic hardening parameters through the Chaboche model. The finite element analysis (FEA) model was designed and validated, following the fatigue crack propagation simulation under high plasticity conditions using abaqus. Crack opening displacement versus stress data were exported from abaqus, and 1.5% offset method was employed to define opening stress levels. Numerical simulation results were compared with the experimental results obtained earlier through the digital image correlation (DIC) technique. To conclude, FEA could be a valuable tool to predict crack closure phenomena and, ultimately, the fatigue life of components. However, analysis of opening stresses using crystal plasticity models or extended finite element method (XFEM) tools should be explored for a better approximation in future studies.
Robust Passivity-Based Control Scheme for 1.26 KW Proton Exchange Membrane Fuel Cell Under Temperature and Load Variations
Authors: Zaidi Abdelaziz , Charaabi Asma , Barambones Oscar , Zanzouri Nadia
Published: June 2021

The model-based system engineering (MBSE) is based on simplified mathematical models that reflect the dynamic behavior of the systems. These are most of the time nonlinear and need control schemes taking in consideration of exogenous perturbations. The main contribution of this article is the design of a robust passivity-based sliding mode control scheme for a 1.26 KW proton exchange membrane fuel cell (PEMFC). The uncertainties considered in this article are temperature and load variation. The fuel cell (FC) reference current is adapted in a linear transformation by introducing a temperature sensor. This information is present in most of commercial PEMFC and not used in the closed-loop system. Moreover, the proposed approach cancels the errors caused by the average approach modeling and the observer (the part, which replaces current sensor). Robustness against load variation is assured via a proportional integral compensation of the incremental value of load resistance. The performance of the controller and the effectiveness of our approach is shown through the simulation with matlab-simulink software.
Implications of Buckingham’s Pi Theorem to the Study of Similitude in Discrete Structures: Introduction of the RFN, μN, and SN Dimensionless Numbers and the Concept of Structural Speed
Authors: Rosakis Ares J. , Andrade José E. , Gabuchian Vahe , Harmon John M. , Conte Joel P. , Restrepo José I. , Rodriguez Andrés , Nema Arpit , Pedretti Andrea R.
Published: June 2021

Motivated by the need to evaluate the seismic response of large-capacity gravity energy storage systems (potential energy batteries) such as the proposed frictional Multiblock Tower Structures (MTS) recently discussed by Andrade et al. (2021, “Seismic Performance Assessment of Multiblock Tower Structures As Gravity Energy Storage Systems,” ASME J. Appl. Mech., Submitted), we apply Buckingham’s Pi theorem (Buckingham, E., 1914, “On Physically Similar Systems; Illustrations of the Use of Dimensional Equations,” Phys. Rev., 4, pp. 345–376) to identify the most general forms of dimensionless numbers and dynamic similitude laws appropriate for scaling discontinuous multiblock structural systems involving general restoring forces resisting inertial loading. We begin by introducing the dimensionless “mu-number” (μN) appropriate for both gravitational and frictional restoring forces and then generalize by introducing the “arbitrary restoring force number” (RFN). RFN is subsequently employed to study similitude in various types of discontinuous or discrete systems featuring frictional, gravitational, cohesive, elastic, and mixed restoring forces acting at the block interfaces. In the process, we explore the additional consequences of inter and intra-block elasticity on scaling. We also formulate a model describing the mechanism of structural signal transmission for the case of rigid MTS featuring inter-block restoring forces composed of elastic springs and interfacial friction, introducing the concept of “structural speed.” Finally, we validate our results by demonstrating that dynamic time-histories of field quantities and structural speeds between MTS models at various scales are governed by our proposed similitude laws, thus demonstrating the consistency of our approach.
Application of Nonlinear Krylov Solvers for Conjugate Heat Transfer Simulations of Electrical Battery Packs
Authors: Sukheswalla Parvez , Raju Mandhapati , Wang Chu , Attal Nitesh , Srivastava Kislaya
Published: June 2021

Krylov-based methods are an attractive alternative to traditional fixed-point iterative schemes, being much more robust and accurate when solving elliptic equations (e.g., the energy equation in the solid domain). This study assesses the performance of a Krylov-based accelerator, when used for conjugate heat transfer (CHT) simulations of an electrical battery pack. The nonlinear nature of CHT simulations (due to spatial and temporal changes in boundary conditions) necessitates the use of the non-inear form of the Krylov-based accelerator (termed NKA), which utilizes the generalized minimized residual (GMRES) method, and works by accelerating an existing fixed-point iteration scheme. NKA is used while performing steady-state CHT simulations of an air-cooled lithium-ion battery pack, specifically to help accelerate the solution of the solid domain energy equation. The effect of using either isotropic or anisotropic thermal conductivity within the cylindrical lithium-ion battery cells is also evaluated. Results obtained using the NKA accelerator are compared, in terms of accuracy and speed, with those obtained from a traditional nonlinear fixed-point iterative scheme based on successive over-relaxation (SOR). The NKA accelerator is found to perform quite well for the problem at hand, providing results with the specified accuracy, while also being between 5 and 20 times faster than SOR (while solving the solid energy equation). The robust nature of NKA also leads to better global heat balance within the battery pack at all times during the simulation. These observations hold for both the isotropic and anisotropic thermal conductivity conditions. Overall, computational cost reductions of 30–40% are observed when using NKA for the battery pack simulations. Although the performance of NKA is demonstrated for a battery cooling application, NKA performs quite well in other applications also.
Characterization of Transient Wall Heat Load for a Low NOx Lean Premixed Swirl Stabilized Can Combustor Under Reacting Conditions
Authors: Ramakrishnan Kishore Ranganath , Ahmed Shoaib , Ekkad Srinath V.
Published: June 2021

As stringent emissions controls are being placed on gas turbines, modern combustor design optimization is contingent on the accurate characterization of the combustor flame side heat loads. Power generation turbines are increasingly moving toward natural gas, biogas, and syngas, whose composition is highly dependent on the sourcing location. With fuel flexible nozzles, it is important to understand the heat load from various gas mixtures to optimize the cooling design to make sure the liner is not under/over cooled for some mixtures as this has a larger effect on NOx/CO emissions. In addition to knowing the heat load distribution, it is important to understand the peak heat load under start/stop transient conditions which tend to be much higher than steady-state/cruise altitude heat loads. The present work focuses on the experimental measurement of the transient heat load along a can combustor under reacting conditions for a swirl-stabilized premixed methane–air flame. Tests were carried out under various equivalence ratios, Reynolds numbers, and pilot fuel flowrate. An infrared camera was used to measure the inner and outer wall temperatures of the liner to calculate the liner heat load. Particle image velocimetry (PIV) was employed to visualize the flowfield for various reacting conditions studied in this work. Based on the heat transfer study, a detailed report of transient heat load along the length of the liner wall has been presented here. Initial start transient heat load on the liner wall is ∼10–40% more than the steady-state heat load.
A Hybrid Antenna in Package Solution Using FOWLP Technology
Authors: Zhang Xuesong , Wang Qian , Wang Bo , Wang Gang , Gu Xin , Chen Yu , Tan Lin , Zhou Shengjuan , Cai Jian
Published: June 2021

Widespread millimeter wave applications have promoted rapid development of system in package (SiP) and antenna in package (AiP). Most AiP structures take the form of flip chip onto antenna substrate, where signal interconnect losses are introduced by solder bumps. The integration may be unavailable for chips with fine pad pitches. Fan-out wafer level package (FOWLP) with antenna patterning on redistributed layers (RDL) is another method for millimeter wave AiP. In this project, a hybrid integration AiP structure is developed. The microwave monolithic integrated circuit (MMIC) chip and antenna unit are integrated with chip-first FOWLP process. Multilayer organic substrate with fine pitch RDL interconnections meets the requirements of wideband antenna design. Modified coplanar waveguide is adopted to feed 2 × 2 aperture array formed on RDL layer. Package warpage is measured using Shadow Moire techniques. The antenna forms an aperture-coupled stacked patch array with bandwidth 25% and gain 8.5dBi for 60 GHz digital communication system. The proposed approach is a convenient hybrid integration solution adopting FOWLP process for millimeter wave AiP systems.
Thermal Performance Intensification of Car Radiator Using SiO2/Water and ZnO/Water Nanofluids
Authors: Maghrabie Hussein M. , Mousa Hamouda M.
Published: June 2021

Recent progress in nanotechnology has led to a revolution in the automotive cooling system. In the present work, enhancement of car radiator thermal performance was investigated using different nanofluids namely SiO2/water and ZnO/water nanofluids as cooling mediums. The present study mainly aims to investigate the impact of 5 wt% from SiO2 and ZnO nanoparticles (NPs) dispersed in water based on car radiator heat transfer with spherical and hexagonal morphology, respectively. The experiments were performed in two working conditions of the nanofluids, i.e., coolant temperature and volume flowrate; moreover, the present results were compared with the previous studies. The experimental working conditions were set at coolant inlet temperature (tc,i) ranged from 45 to 80 °C and the coolant volume flowrate (V˙) varied from 3.5 to 6.5 liter/min. The experimental results show that the hexagonal ZnO/water nanofluid was superior toward enhancement of car radiator thermal performance comparing to that of SiO2 NPs. In addition, at 6.5 liter/min and 45 °C, the improvements of car radiator effectiveness due to using SiO2 and ZnO based water nanofluids and compared with that for the based water are 13.9% and 16%, respectively. The present study used the multiple regression analysis (MRA), and hence empirical correlations are suggested to estimate the overall heat transfer coefficient (U) for all coolants as functions of volume flowrate (V˙) and the coolant inlet temperature (tc,i) with a maximum STDEV of ±1.85%.
Developing certification procedures for quiet supersonic aircraft using shaped sonic boom predictions through atmospheric turbulence
Authors: Loubeau Alexandra , Doebler William , Wilson Sara R. , Ballard Kathryn , Coen Peter G. , Naka Yusuke , Sparrow Victor W. , Kapcsos Joshua , Page Juliet A. , Downs Robert S. , Lemaire Stéphane , Liu Sandy R.
Published: June 2021

New sonic boom noise certification procedures for quiet supersonic aircraft are in development under the International Civil Aviation Organization for a proposed standard that could enable supersonic overland flight. Although these low-boom aircraft do not exist yet, the procedures can be developed and evaluated using existing empirical and simulation datasets. While prior analyses used N-wave datasets to exercise various proposed procedures, these evaluations were limited because the effects of atmospheric turbulence on N-waves do not necessarily generalize to shaped sonic booms. The analysis is therefore extended to include shaped sonic boom predictions through several atmospheric turbulence conditions, such as different atmospheric boundary layer heights, using three different numerical methods. Six noise metrics (PL, ASEL, BSEL, DSEL, ESEL, and ISBAP) are calculated for the ground waveform predictions and compared to metrics for predictions performed under quiescent standard day conditions. Methods for validating prediction tools or correcting for the atmospheric effects are discussed, and ideas for robust methods for implementation in certification procedures are proposed.
An overview of participation in NASA’s CarpetDIEM campaign
Authors: Gee Kent L. , Durrant J T. , Anderson Mark C. , Mathews Logan T. , Rasband Reese D. , Novakovich Daniel J. , Loubeau Alexandra , Doebler William
Published: June 2021

This talk summarizes Brigham Young University’s (BYU) participation in NASA’s 2019 sonic boom data collection campaign in California, USA. Dubbed “Carpet Determination In Entirety Measurement” (CarpetDIEM) Phase I, the program was designed to measure conventional cruise booms across a widespread time-synchronous array, at the site where initial acoustical testing of the X-59 low-boom supersonic aircraft is planned. BYU deployed a total of 11 portable data acquisition systems across 10 nautical miles and tested a variety of microphone and data acquisition configurations. This talk describes both technical and logistical lessons learned at CarpetDIEM Phase I that can help with future X-59 test design including acquisition hardware comparison and evidence of turbulence. [Work supported by NASA Langley Research Center through the National Institute of Aerospace.]
Enhancing the temporal fine structure with the temporal limits encoder for cochlear implants: Effects on pitch ranking
Authors: Zhou Huali , Yu Guangzheng , Meng Qinglin
Published: June 2021

Pitch perception remains a challenge for cochlear-implant (CI) users. Temporal periodicity, as the main cue for pitch, could not be finely encoded by current CI strategies that transmit envelopes only and discard the temporal fine structure (TFS). Moreover, temporal electric pitch percept saturates at a few hundred hertz, which is controversial and has been studied using various psychophysical and physiological methods. The temporal-limits-encoder (TLE) was proposed to enhance TFS representation by frequency-downshifting the high-frequency band-limited signals to a low-frequency temporal-pitch-limits range of CIs. In this work, eleven Nucleus CI subjects were recruited in a pitch ranking task using a CCiMobile processor. The original stimuli were five-harmonics complex tones. Fundamental-frequency difference limens (F0DLs) at two reference F0s 250 and 313 Hz (i.e., center and upper cross-over frequencies of the most apical electrode) were tested using three TLE versions with different modulator lower limits 100, 200, and 300 Hz respectively and a standard advanced-combinational-encoder (ACE) strategy. Results showed that TLE had a comparable performance with ACE at 250-Hz reference F0, but could outperform ACE at 313-Hz reference F0. These indicate that the TLE strategy has the potential to improve pitch ranking in CIs, which implies an enhancement of TFS representation with TLE.
Broadband, frequency-independent acoustic metasurfaces through inverse design
Authors: Shen Chen , Dong Hao-Wen , Zhao Sheng-Dong , Wang Yue-Sheng , Cheng Li
Published: June 2021

The recent development of acoustic metasurfaces has broadened the capabilities of wave engineering devices with a compact profile. However, the application of acoustic metasurfaces in many scenarios has been limited by their bandwidths. In this work, we report the realization of broadband acoustic metasurfaces that deliver frequency-independent functionalities. Three examples are demonstrated, namely beam steering, focusing and acoustic levitation with fixed refraction angle, constant focal depth and stable levitation. This is achieved by analyzing the requirement of each functionality and engineering the dispersion of the unit cells. The architecture of the unit cells is obtained through inverse design and each unit cell displays a unique dispersive response outlined by the theoretical requirements. The designed metasurface is experimentally verified and we demonstrate a fractional bandwidth of around 100% for all three functionalities. We also attempt to reveal the mechanism for such broadband by characterizing the behavior of representative unit cells.
Deep embedded clustering of coral reef bioacoustics
Authors: Reeves Ozanich Emma , Thode Aaron M. , Gerstoft Peter , Freeman Lauren A. , Freeman Simon E.
Published: June 2021

Deep clustering was applied to unlabeled, automatically detected signals in a coral reef soundscape to distinguish fish pulse calls from segments of whale song. Deep embedded clustering (DEC) learned latent features of the signals and formed clusters using fixed-length power spectrograms of the signals. Handpicked spectral and temporal features were also extracted and clustered with Gaussian mixture models (GMM) and conventional clustering. DEC, GMM, and conventional clustering were tested on simulated datasets of fish pulse calls and whale song units with randomized bandwidth, duration, and SNR. Both GMM and DEC achieved high accuracy and identified clusters with fish calls, whale song units, and simultaneous fish calls and whale song units. Conventional clustering methods K-means and hierarchical agglomerative clustering had low accuracy in scenarios with unequally sized clusters or multiple signals. Experimentally detected fish pulse calls and whale song units recorded near Hawaii in February–March 2020 were clustered with DEC, GMM, and conventional clustering. DEC demonstrated the highest accuracy on a small, manually labeled dataset and successfully separated clusters of fish calls and whale song units. GMM achieved high recall for detecting whale song units but accuracy. Both GMM and DEC overpredicted the number of whale song unit signals.
Improved Siamese Network for motion tracking in ultrasound images
Authors: Bharadwaj Skanda , Almekkawy Mohamed
Published: June 2021

In recent years, the use of Convolutional Neural Networks in medical imaging applications has been increasing drastically. Siamese Networks are among the top architectures that are being borrowed for motion tracking. In this work, we propose an improved Siamese network for robust and accurate landmark tracking in ultrasound image sequences. Despite the staggering efficacy of Siamese networks, the inherent assumptions in the original architecture lead to certain limitations. The assumption of the constant position model and not incorporating any motion model remain unaddressed. In our proposed model, we employ a reference template update module to resolve the assumption of the constant position model and incorporate a Linear Kalman Filter to address the issue of the missing motion model. The proposed model was evaluated for robustness on the training set of the Liver Ultrasound Tracking (CLUST) 2D data set. The robustness of the architecture was evaluated by inducing synthetic occlusions around the landmark. The performance was then compared to the original architecture. Experiments proved that the proposed model outperformed the original model by a significant margin.
Focused ultrasound mediated intranasal delivery
Authors: Ye Dezhuang
Published: June 2021

This presentation will introduce that focused ultrasound combined with intranasal delivery can achieve locally enhanced delivery of anti-programmed cell death-ligand 1 antibody to an intracranial murine glioma model.
Histotripsy combined with catheter-directed thrombolytics for clot disintegration in vitro
Authors: Hendley Samuel A. , Bhargava Aarushi , Paul Jonathan D. , Bader Kenneth B.
Published: June 2021

Histotripsy is a focused ultrasound therapy under development as an adjuvant to lytic therapy for the treatment of deep vein thrombosis. In this study, we investigate the mechanisms of clot disintegration (e.g., hemolysis and thrombolysis) under the action of histotripsy and catheter-directed thrombolytics, and demonstrate that this combination significantly reduces the threshold lytic dose required for effective thrombolysis.
Histotripsy bubble dynamics in an anisotropic tissue-mimicking phantom
Authors: Elliott Jacob C. , Simon Julianna , Arguelles Andrea
Published: June 2021

Collagenous, anisotropic tissue such as tendon has proven resistant to fractionation by histotripsy, prompting the need to better understand and quantify bubble dynamics in anisotropic tissue. The elastic moduli in each axial direction were measured for collagen, fibrin, and polyacrylamide hydrogels prior to applying histotripsy; high-speed photography and cavitation emission data were used to evaluate bubble size and collapse strength. [Work supported by NIH R21EB027886.]
Analysis and perception of a viscoelastic, frequency-dependent Finite-Difference Time Domain damping model of a drum
Authors: Pauli Theresa , Bader Rolf
Published: June 2021

This study investigates the influence of viscoelastic damping parameters in a Viscoelastic Finite Difference Time Domain (FDTD) model on the sound of a drum head. Due to the strong nonlinearity between the complex, frequency-dependent Young’s modulus as a model input parameter and resulting damping frequencies and damping strength, this relation can no longer be analyzed analytically. One reference and eight altered membranes are constructed. Integrating the sound into minor third bands, nonlinear mode couplings due to viscoelasticity are found, relating to the real part of the Young’s modulus as well as to the Laplace-Transform parameter of the FDTD model. Furthermore, the perception of the sounds was investigated. The results are compared to the physical observation, showing variations in brightness and pitch. Hereby, the perception can be described as proportional to the physical analysis, as long as the variation of the Laplace parameter in one or more damped frequencies does not lead to a huge difference in the sounds decay time, which seems to distract the attention from other acoustical characteristics.
Material properties at extreme pressures and temperatures using ultrasound
Authors: Sturtevant Blake , Moss Eric , Velisavljevic Nenad , Hrubiak Rostislav , Kenney-Benson Curtis , Kono Yoshio
Published: June 2021

Accurate knowledge of material properties at extreme pressures and temperatures is very valuable in the fields of planetary science and condensed matter physics, as well as in mechanical and structural engineering applications. Sound speeds and elastic moduli are particularly important properties since they can be used to refine equation of state and strength models. One way to determine the temperature and pressure dependence of sound speeds and elastic moduli is to use the ultrasonic pulse-echo technique on a sample compressed in a hydraulic press, often in situ at a synchrotron X-ray source. X-ray radiography is used to determine the physical dimensions of the sample during compression which is needed for sound speed determination. Additionally, X-ray diffraction is used to determine the sample’s density, which is used to determine the elastic moduli. This talk will present the technique and some results of such measurements using the Paris-Edinburgh hydraulic press at the High Pressure Collaborative Access Team (HPCAT) sector of the Advanced Photon Source.
Engineering the electromechanical response of piezoelectric transducers: Some challenging applications
Authors: Chillara Vamshi K.
Published: June 2021

Piezoelectric transducers are widely used for ultrasonic applications both as actuators to excite and as sensors to receive vibration/wave response. The electromechanical characteristics of the piezoelectric transducers dictate their choice for specific applications. These can be tuned in several ways ranging from modifying the geometry and material properties of the element to changing the excitation electrode pattern and the boundary conditions of the vibrating piezoelectric element. This talk discusses two different ways to achieve such tuning for single-element piezoelectric transducers and their corresponding applications. The first application is to achieve a low-frequency collimated beam using lateral stiffening of a piezoelectric disc vibrating in its radial resonance. The resonance and vibration characteristics of such a disc are presented and the ultrasonic wave propagation from such a laterally stiffened disc in fluids is discussed. The second application uses tailored polarization profiles for piezoelectric elements to enhance/suppress specific resonant modes in an otherwise homogeneous element. The fundamental theory for such behavior is presented and some applications of such polarization-tuned piezoelectric elements are discussed.
In situ resonant ultrasound spectroscopy for neutron scattering
Authors: Torres James , Fanelli Victor , Shinohara Yuya , May Andrew , Ruiz-Rodriguez Mariano , Hermann Raphael
Published: June 2021

Resonant ultrasound spectroscopy (RUS) is an efficient nondestructive technique to study the elastic properties of solid materials. In principle, the full elastic tensor can be determined for regularly shaped solids (e.g., sphere, cuboid, cylinder). Here, we report our progress in developing RUS probes for in situ neutron scattering at beamlines of the Spallation Neutron Source at Oak Ridge National Laboratory. A low-temperature (2–300 K) probe has been assembled and tested at the NOMAD and SEQUOIA beamlines to assess the probe’s neutronics, data acquisition system, and compatibility with the existing sample environment. Our discussion will include how the probe and data acquisition system operate as well as results for two measurements: bulk metallic glass (La65Cu20Al10Co5) and bismuth-antimony (Bi0.89Sb0.11 [1]). Assembly of a high-temperature (300–875 K) probe is currently underway and both probes are scheduled to be available to users by late-2021. Our aim is to provide users with live monitoring of an intrinsic variable at the neutron scattering beamlines, in addition to existing controls, to monitor the state of their samples and make informed decisions in real time. The probe developments are accompanied by developments of data acquisition and analysis software. 1. D. Vu et al., arXiv: 1906.02248 [cond-mat.mtrl-sci] (2019).
Correcting microphone response mismatch for improved intensity measurements at infrasonic frequencies
Authors: Irarrazabal Francisco J. , Gee Kent L. , Sommerfeldt Scott D. , Cook Mylan R.
Published: June 2021

Sound intensity measurements using multimicrophone probes at infrasonic frequencies are challenging mainly because the mismatch between microphone responses can be larger than the acoustic differences. Correcting microphone response mismatch via relative calibration requires an infrasound source that can provide good signal-to-noise ratios and sufficiently long averaging times. This paper describes the use of a moving vehicle as an infrasound source to obtain the necessary transfer functions between 12.7 mm diameter, type-1 microphones. The calibration approach is validated and an improved infrasound and low-audio range intensity measurement capability is demonstrated using hot-air balloon burners.
Sound manipulation through multi-scattering, gradient-based optimization, deep learning and reinforcement learning
Authors: Amirkulova Feruza
Published: June 2021

This talk discusses recent advances and current challenges encountered during the application of gradient-based optimization, deep learning, reinforcement learning, and generative modeling in an inverse design of acoustic metamaterials. We first summarize and group existing approaches in the inverse design of metamaterials then discuss current algorithmic limitations and open challenges to preview possible future developments in metamaterial design. Specifically, broadband sound focusing, cloaking, steering, localization, and diffusion are the focus of this talk. The objective (loss) functions are evaluated by means of multiple scattering theory, and analytical gradients are evaluated with respect to a design vector, i.e., the positions of each scatterer. Our observations show that the development of hybrid models improves the performance of these algorithms. Specifically, the performance of deep reinforcement learning and gradient-based optimization as well as generative network models are enhanced when gradients of target functions are supplied to the model. In reinforcement learning models, the agent receives a reward proportional to the negative of the target function. The performance of the double-deep Q-learning network (DDQN) and the deep deterministic policy gradient (DDPG) algorithms were improved when gradients were supplied to the reward function. Numerical examples are presented for planar configurations of cylindrical scatterers.
Geoacoustic inversion of modal dispersion on the New England Mud Patch. II: Hybrid parameterization for gradient estimation
Authors: Dosso Stan , Bonnel Julien , Knobles David P. , Wilson Preston S.
Published: June 2021

This paper applies Bayesian geoacoustic inversion with a hybrid seabed model parameterization to modal-dispersion data from the New England Mud Patch to attempt to estimate gradient structure in the upper mud layer. The hybrid seabed parameterization is based on an upper layer with a general representation of gradients based on Bernstein-polynomial basis functions, above an unknown number of discrete (uniform) layers formulated trans-dimensionally. The dataset, collected during the 2017 Seabed Characterization Experiment (SBCEX17), involves high-order modes (up to mode 21) extracted via warping time-frequency analysis from recordings of a combustive sound source on a vertical hydrophone array. The inversion results are compared to those from a trans-dimensional inversion of the same data with no gradient layer, and to results from other acoustic data sets collected in the region as well as to nearby core measurements.
The impact of the “Anthropause” on the communication and acoustic habitat of Southeast Alaskan humpback whales
Authors: Fournet Michelle E. , Matthews Leanna P. , Gabriele Christine
Published: June 2021

The COVID-19 pandemic caused profound changes in global human behavior, including substantial decreases in marine transportation, a pervasive ocean noise source. The human tragedy of the pandemic provides an unprecedented opportunity to investigate how humpback whales communicate in the absence of chronic noise common to their acoustic habitats. The Alaskan tourism industry was impacted particularly strongly; Southeast Alaska experienced a near complete absence cruise ships during the 2020 tourism season (May—September). In summer 2019 and 2020, we deployed a SoundTrap hydrophone in Glacier Bay National Park to document vessel-generated ambient noise and vocal characteristics of humpback whales (Megaptera novaeangliae) which have been studied in this region since the 1980’s. In the absence of cruise ships, underwater noise from vessels was significantly lower in Glacier Bay compared to 2019. Median daily noise levels (dBRMS 100–1500 Hz) were three times quieter during 2020 than in 2019. Preliminary analyses of humpback whale calling behavior show an increased number of call types in 2020 compared to the same period in 2019. Documenting humpback whale communication in quiet conditions can help illuminate impacts of chronic vessel noise and aid the development of measures to reduce human impacts in this and other marine protected areas.
Physical Literacy for Children Labeled With Autism Spectrum Disorder: Mothers’ Experiences of Ableism, Exclusion, and Trauma
Authors: Pushkarenko Kyle , Causgrove Dunn Janice , Goodwin Donna L.
Published: June 2021

Countering the declining physical activity patterns of children labeled with autism spectrum disorder (ASD) has gained considerable research attention given its impact on health and quality of life. The purpose of this study was to explore how parents of children labeled with ASD understand the concept of physical literacy, based on their children’s participation in community-based physical activity programs. Using interpretive phenomenological analysis, six mothers of children labeled with ASD participated in one-on-one semistructured interviews. The conceptual framework of ecological systems theory supported the rationale for the study purpose, provided structure for the interview guide, and offered a reflexive context for interpretation. Four themes were generated from the thematic analysis: From embodied movement to normative skill expectations, Be flexible, not rigid, Systematic exclusion, and Valuable? . . . Absolutely! Despite experiences of marginalization, exclusion, and trauma within physical activity programs, mothers valued physical literacy development for their children given the positive outcomes of increasing family connections, engagement with peers, and enhanced wellness.
Molecular cloning of pheR in Escherichia coli K-12
Authors: Gowrishankar J , Pittard J
Published: June 2021

The regulator gene pheR, which in Escherichia coli controls the expression of pheA, the structural gene for chorismate mutase P-prephenate dehydratase, was cloned on to multicopy plasmids directly from the E. coli chromosome; this was achieved with the aid of the tetracycline resistance transposon, Tn10, that had been inserted very close to the pheR gene. Subsequently, pheR was subcloned on a 1.1-kilobase-pair fragment on the plasmid vector pBR322; its position on the plasmid was localized by the method of gamma delta-mediated transpositional inactivation. The pheR gene product was identified in maxicells and found to be a protein of subunit molecular weight 19,000, suggesting that the coding segment of the gene is about 500 nucleotide pairs long.
Analysis of lambda insertions in the fucose utilization region of Escherichia coli K-12: use of lambda fuc and lambda argA transducing bacteriophages to partially order the fucose utilization genes
Authors: Skjold A C , Ezekiel D H
Published: June 2021

Escherichia coli K-12 strains have deletions for the normal lambda integration site were lysogenized with bacteriophage lambda at a site within the L-fucose utilization system (fuc). The frequency of lambda integration at this site is approximately 2 X 10(-8) to 5 X 10(-7). Studies of the lytic properties of these strains indicated very infrequent cell lysis with a relatively low phage burst size. Transductional ability of the phage lysates was found to be normal, comparable to that found in conventional low-frequency transducing lysates. Two major classes of transducing phage were found. One carried the markers argA and fucA (a fucose utilization gene of unknown function previously referred to as fuc-1) and the gene for D-arabinose utilization (dar+). The other carried only fucC, the gene specifying L-fuculose-1-phosphate aldolase. A minor class of phage was found that carried fucA, but not argA or dar+. Upon consideration of the transductional nature of these phage classes, we are proposing that the gene order for the L-fucose utilization system is dar, fucA, (lambda), fucC.
Comparison of kinetics of active tetracycline uptake and active tetracycline efflux in sensitive and plasmid RP4-containing Pseudomonas putida
Authors: Hedstrom R C , Crider B P , Eagon R G
Published: June 2021

Membrane vesicles prepared from tetracycline-sensitive cells of Pseudomonas putida took up tetracycline by an active transport system with an apparent Km of 2.5 mM and a Vmax of 50 nmol min-1 mg protein-1. In contrast, resistance determinant RP4-containing P. putida had an active high-affinity efflux system for tetracycline with a Km of 2.0 to 3.54 microM and a Vmax of 0.15 nmol min-1 mg protein-1. Thus, the efflux system of tetracycline-resistant P. putida(RP4) had an average of 1,000-fold greater affinity for tetracycline than the influx system of tetracycline-sensitive cells. From these results, it is clear that a major mechanism of tetracycline resistance in RP4-containing P. putida is an active tetracycline efflux mechanism. There was also evidence for a second tetracycline efflux system with low affinity for tetracycline n P. putida(RP4). This efflux system had a Km of 0.25 mM and a Vmax of 1.45 nmol min-1 protein-1. Whether this low-affinity efflux system was also present in tetracycline-sensitive P. putida could not be discerned from these experiments.
Induction and control of the autolytic system of Escherichia coli
Authors: Leduc M , Kasra R , van Heijenoort J
Published: June 2021

Various methods of inducing autolysis of Escherichia coli cells were investigated, some being described here for the first time. For the autolysis of growing cells only induction methods interfering with the biosynthesis of peptidoglycan were taken into consideration, whereas with harvested cells autolysis was induced by rapid osmotic or EDTA shock treatments. The highest rates of autolysis were observed after induction by moenomycin, EDTA, or cephaloridine. The different autolyses examined shared certain common properties. In particular, regardless of the induction method used, more or less extensive peptidoglycan degradation was observed, and 10(-2) M Mg2+ efficiently inhibited the autolytic process. However, for other properties a distinction was made between methods used for growing cells and those used for harvested cells. Autolysis of growing cells required RNA, protein, and fatty acid synthesis. No such requirements were observed with shock-induced autolysis performed with harvested cells. Thus, the effects of Mg2+, rifampicin, chloramphenicol, and cerulenin clearly suggest that distinct factors are involved in the control of the autolytic system of E. Coli. Uncoupling agents such as sodium azide, 2,4-dinitrophenol, and carbonyl-cyanide-m-chlorophenyl hydrazone used at their usual inhibiting concentration had no effect on the cephaloridine or shock-induced autolysis.
Absence of DNA in peroxisomes of Candida tropicalis
Authors: Kamiryo T , Abe M , Okazaki K , Kato S , Shimamoto N
Published: June 2021

Yeast peroxisomes were purified to near homogeneity from cells of Candida tropicalis grown on oleic acid for the purpose of examining the possible presence of DNA in this organelle. The purification procedure includes the effective conversion of cells to spheroplasts with Zymolyase and sodium sulfite and the separation of the organelles at extremely low ionic strength. The mitochondrial contamination was less than 1%, based on several criteria, and the yield of peroxisomes was about 40%. The purified peroxisomal fraction contained a very small amount of DNA, which yielded restriction fragments indistinguishable from those of mitochondrial DNA. The absence of DNA in peroxisomes was also supported by cesium chloride density gradient centrifugation of the organelles lysed with a detergent, staining of the organelles with a fluorescent dye specific to DNA, and labeling of the DNA with [3H]adenine.
Molecular cloning and regulation of expression of the genes for initiation factor 3 and two aminoacyl-tRNA synthetases
Authors: Elseviers D , Gallagher P , Hoffman A , Weinberg B , Schwartz I
Published: June 2021

A 22-kilobase fragment of the Escherichia coli chromosome which contains the genes for translation initiation factor 3, phenylalanyl-tRNA synthetase, and threonyl-tRNA synthetase was cloned into plasmid pACYC184. The hybrid plasmid (designated pID1) complements a temperature-sensitive pheS lesion in E. coli NP37. pID1-transformed NP37 overproduce initiation factor 3 and phenylalanyl-tRNA synthetase. Gene expression from pID1 was studied in vitro in a coupled transcription-translation system and in minicells. The results suggest that the genes for initiation factor 3 and phenylalanyl- and threonyl-tRNA synthetase are regulated by different mechanisms.
Requirement for Carbon Dioxide for Nonsymbiotic Expression of
Rhizobium japonicum
Nitrogenase Activity
Authors: Aguilar O. Mario , Favelukes Gabriel
Published: June 2021

The expression and maintenance of nitrogenase (C
2
H
2
) activity in growing, microaerobic liquid cultures of
Rhizobium japonicum
3I1b110 was found to be stringently dependent on the sustained supply of CO
2
. This requirement for CO
2
appeared to exceed the basal requirement for growth and was not related to effects on pH.
Identification of an Insertion Sequence in the Chromosome ofPseudomonas aeruginosaPAO
Authors: Nash J. H. E. , Krishnapillai V.
Published: June 2021

An insertion sequence, IS22, inPseudomonas aeruginosaPAO was identified by its genetic properties. It occurred as a single copy in the chromosome, as shown by Southern hybridization. A restriction map of it was constructed.
Cytochrome c3 from the sulfate-reducing anaerobe Desulfovibrio africanus Benghazi: antigenic properties
Authors: Singleton R , Denis J , Campbell L L
Published: June 2021

Antisera were prepared against cytochromes c3 from Desulfovibrio africanus, D. vulgaris, and D. salexigens. Cross-reactions were observed between antisera to D. vulgaris and D. africanus cytochromes and heterologous cytochromes c3. A weak cross-reaction with antisera against both D. vulgaris and D. africanus cytochromes and the acid form of the D. salexigens cytochrome was seen; the basic form did not react.
O6-methylguanine-DNA methyltransferase in wild-type and ada mutants of Escherichia coli
Authors: Mitra S , Pal B C , Foote R S
Published: June 2021

O(6)-Methylguanine-DNA methyltransferase is induced in Escherichia coli during growth in low levels of N-methyl-N'-nitro-N-nitrosoguanidine. We have developed a sensitive assay for quantitating low levels of this activity with a synthetic DNA substrate containing 3H-labeled O(6)-methylguanine as the only modified base. Although both wild-type and adaptation-deficient (ada) mutants of E. coli contained low but comparable numbers (from 13 to 60) of the enzyme molecules per cell, adaptation treatment caused a significant increase of the enzyme in the wild type but not in the ada mutants, suggesting that the ada mutation is in a regulatory locus and not in the structural gene for the methyltransferase.
Application of hybrid plasmids carrying glycolysis genes to ATP production by Escherichia coli
Authors: Shimosaka M , Fukuda Y , Murata K , Kimura A
Published: June 2021

The closely linked structural genes of phosphofructokinase (pfkA) and triosephosphate isomerase (tpi) of Escherichia coli were separately cloned onto plasmid pBR322. By gene dosage effects, transformed cells of E. coli C600 with these pBR322 hybrid plasmids showed 7- and 16-fold increases in the specific activities of phosphofructokinase and triosephosphate isomerase, respectively, over the specific activities in C600. Dried preparations of E. coli cells dosed with these genes showed appreciably high ATP-regenerating activity.
Effect of detergents on membrane-associated glucan synthetase from Paracoccidioides brasiliensis
Authors: San-Blas G , San-Blas F
Published: June 2021

Yeast and mycelial particulate preparations of Paracoccidioides brasiliensis were subjected to the action of several detergents in an attempt to solubilize the glucan synthetase present in these preparations. This was achieved more successfully in the yeast membranes than in the mycelial ones. The enzymatic activity was greatly stimulated in the insoluble fractions upon treatment with some of the detergents used. The results suggest that the yeast and mycelial phases of P. brasiliensis may differ in the structures of their membranes and also in the characteristics of their glucan synthetases.
Control of nitrogenase in a photosynthetic autotrophic bacterium, Ectothiorhodospira sp
Authors: Bognar A , Desrosiers L , Libman M , Newman E B
Published: June 2021

An Ectothiorhodospira species fixed nitrogen when grown as an autotroph in completely inorganic medium by using a variety of electron donors. The organism also used organic carbon sources; however, this required induction of synthesis of various enzymes, whereas the enzymes needed for autotrophic growth were synthesized constitutively. Nitrogenase induction and function were inhibited by ammonium chloride. Nitrogenase activity was dependent on light and inhibited by oxygen.
An amber mutation in the gene encoding the beta' subunit of Escherichia coli RNA polymerase
Authors: Ridley S P , Oeschger M P
Published: June 2021

An Escherichia coli strain carrying an amber mutation (UAG) in rpoC, the gene encoding the beta prime subunit of RNA polymerase, was isolated after mutagenesis with nitrosoguanidine. The mutation was moved into an unmutagenized strain carrying the supD43,74 allele, which encodes a temperature-sensitive su1 amber suppressor, and sue alleles, which enhance the efficiency of the suppressor. In this background, beta prime is not synthesized at high temperature. Suppression of the mutation by the non-temperature-sensitive amber suppressor su1+ yields a protein which is functional at all temperatures examined (30, 37, and 42 degrees C).