bluuebunny/crossref_metadata_2025 huggingface dataset:
Grassland soil organic carbon and the effects of irrigated cropping in Alberta, Canada
Authors: Wang Zhi‐Ping , Li Xiao‐Peng , Pelletier Rick , Chang Scott X. , Bork Edward W.
Published: November 2021

High heterogeneity in the spatial distribution of soil organic carbon (SOC) in grasslands causes uncertainty in estimating its content and storage. In this study, we investigated the spatial distribution of SOC content and storage in the prairies of southern Alberta, Canada, and how it is affected by land use such as irrigated cropping and other environmental conditions such as cattle grazing, slope landscape position and dominant plant species. The mean SOC content was determined to be 11.5 g kg–1 (range: 8.9 to 22.4 g kg–1) in the 0–10 cm layer and 6.8 g kg–1 (range: 4.0 to 13.3 g kg–1) in the 10–30 cm layer; mean SOC storage was 1.59 kg C m–2 (range: 1.23 to 2.78 kg C m–2) in the 0–10 cm layer and 2.07 kg C m–2 (range: 1.21 to 3.62 kg C m–2) in the 10–30 cm layer. The SOC content was significantly affected by slope position in both the 0–10 and 10–30 cm layers, in the following order: bottom >middle > top position. Moreover, SOC storage was higher in sites dominated by shrubs than graminoid/forb communities. Thus, SOC content and storage had distinctly clustered spatial patterns throughout the study area and were significant differences between the 0–10 and 10–30 cm soil layers. Prior land‐use change from arid grassland to irrigated cropland increased SOC content and storage in bulk soils.
Putting humans back in the loop of machine learning in Canadian smart cities
Authors: Zheng Zhibin , Sieber Renee
Published: November 2021

Even as researchers recognize smart cities as sociotechnological assemblages, the attractiveness of artificial intelligence and machine learning (AI/ML) continues to drive cities towards automating urban process and analysis. Rather than arguing whether researchers should automate their analysis, we are interested in identifying where non‐automated, manual judgement calls are made and the analysis is more subjective than presented. We examine topic modelling, an ML method, in an analysis of applications to a pan‐Canadian smart cities grant competition. We document 11 steps in topic modelling from data collection to interpretation. At each step, including the choice of the topic modelling method, some degree of human intervention is required. We draw on human‐centred ML research to argue for a greater recognition of the role of humans‐as‐researchers to preclude further uncritical adoption of AI/ML to research smart cities.
Fluid-Thermal Topology Optimization of Gas Turbine Blade Internal Cooling Ducts
Authors: Ghosh Shinjan , Fernandez Erik , Kapat Jayanta
Published: November 2021

Topology optimization uses a variable permeability approach to manipulate flow geometries. Such a method has been employed in the current work to modify the geometric configuration of internal cooling ducts by manipulating the distribution of material blockage. A modified version of the OpenFOAM solver AdjointShapeOptimizationFOAM has been used to optimize the flow-path of a serpentine channel and high aspect ratio rectangular ducts, with increase in heat transfer and reduction in pressure drop as the objective functions. These duct shapes are typically used as internal cooling channels in gas turbine blades for sustaining the blade material at high inlet temperatures. The serpentine channel shape is initially topologically optimized, the fluid path from which is post-processed and re-simulated in star-ccm+. The end result has an improvement in thermal performance efficiency (η) by 24%. Separation regions are found to be reduced when compared to the original baseline. The second test geometry is a high aspect ratio rectangular duct. Weight factors are assigned to the objective functions in this multi-objective approach, which are varied to obtain a unique shape for each such combination. The addition of mass penalization to the existing objective function results in a complex lattice-like structure, which is a different outcome in geometry and shape when compared to the case without any additional penalization. The thermal performance efficiency of this shape is found to be higher by at-least 18% when compared to the computational fluid dynamics results of a few other turbulator shapes from the literature.
Electrical Performances of Package Layout for High Speed Networking and Cloud Computing Application
Authors: Zhuang Ming-Han , Shih Teny , Lai David , Wang Yu-Po
Published: November 2021

In the present generation, internet with instant data access brings up the demands of high speed Ethernet. Development of 400G Ethernet is currently underway. There are two common coding schemes: non-return-to-zero (NRZ) and pulse-amplitude modulation 4-Level (PAM4). Because NRZ needs signaling in higher Nyquist frequency, which results in higher channel dependent loss, PAM4 has become a popular solution.

In this paper, we use 85 Ohm differential signal to explore a way to improve performance in the aspects of insertion loss, return loss and crosstalk for 112Gbps PAM4 application. A 12 layer substrate with low-loss dielectric of ABF-GL102 is used for the study. We scan the gap size of via pad which contributes the impedance discontinuity thus impacts signal integrity. Die bump and BGA pin assignments are the other two key factors in cause of crosstalk.
Damage of Flexible Electronic Line Under Mechanical and Electrical Stress Loading
Authors: Horiuchi Ryota , Sasagawa Kazuhiko , Fujisaki Kazuhiro
Published: November 2021

Flexible printed circuits (FPCs) are widely used in electronic devices such as movable part line or wearable sensor. Inkjet printing is attracting attention because it can draw electric lines of any shape without a photo mask. The mechanical characteristics such as flexibility or durability of electric lines have been evaluated by bending and tensile tests. Moreover, the reliability characteristics of metal particle ink lines under electric current loading have been recently evaluated. However, the electronic line has not been evaluated under both the mechanical stress due to bending deformation and the electrical stress due to electric current. According to scaling down of electric devices, the current density and Joule heat in interconnect line increase and electromigration (EM) damage becomes a serious problem. EM is a transportation phenomenon of metallic atoms caused by electron wind under high-density electric current. Reducing EM damage is extremely important to enhance device reliability. In this study, high-density current loading tests of flexible electronic line were conducted under bending deformation of the substrate in order to investigate the effect of mechanical stress on the EM damage of the electronic line.

As the results of current loading tests, the specimens with bending deformation became open circuits in shorter time than that without bending deformation. Therefore, it is considered that the bending deformation is affected on the electric reliability characteristic of the flexible electronic lines reflecting EM damage.
A Review on the Current Industrial Uses and the Future Outlook of Battery Thermal Management Systems for Electric Vehicles
Authors: Choi Nicholas , Quach Nhi V. , Won Yoonjin
Published: November 2021

Due to the high-power efficiency of lithium-ion batteries, there is an increased interest in integrating batteries into vehicles to create a more sustainable transportation method. However, batteries require thermal management systems to maintain heat generation within ranges lower than 40 kJ and operation temperatures between 25°C and 40°C. When exposed to extremely high or low temperatures, the battery efficiency decreases, and adverse consequences may occur. To combat this, research is conducted to explore various options to create thermofluidic systems that utilize fluids to regulate the battery pack’s temperatures. Developments in cooling systems have commonly used air as the cooling fluid, but research in recent years is innovating towards liquids to encourage a higher heat dissipation rate.

This paper introduces battery thermal management system applications, current technologies and challenges, and innovations for improving existing models. The current technologies discussed involve manufactured systems based on air- and liquid-cooling for cylindrical and prismatic battery cells. We provide information on new engineered fluids for improvements in fluid properties. In addition to this, new directions related to manufacturing techniques or materials are highlighted to showcase potential changes to current systems to integrate complicated cooling channels in a three-dimensional design. This paper thereby aims to summarize the holistic view showing the direction of the field and possible techniques for battery thermal management.
Novel Air-Cooled Thermosyphon Cooling System for Desktop Computers
Authors: Cataldo Filippo , Amalfi Raffaele L. , Marcinichen Jackson B. , Thome John R.
Published: November 2021

The trade-off between efficient cooling and low power consumption is a goal that has always been very desirable in electronics cooling, especially nowadays that power densities of processing units are increasing. Conventional cooling solutions do not have the necessary cooling capacities for these power densities or require significant power consumption. In this study, a novel air-cooled thermosyphon cooling system for desktop computers is presented and experimentally tested. The thermosyphon comprises a vertical micro-channel cold plate as the evaporator and a horizontal air-cooled multiport coil as the condenser. The thermosyphon has a total height of 12 cm and operates with a fan speed of 1700 RPM. The working fluid selected for the thermosyphon loop is R1234ze(E), chosen for its advantageous thermophysical properties and nearly zero-GWP (Global Warming Potential). The test results presented in this paper aim to analyze thermosyphon’s thermal and hydraulic performance by studying the trends of thermal resistance and mass flow rate as a function of different operating conditions. The maximum heat rejection under safe conditions is 250 W, corresponding to a heat flux of about 18 W/cm2.
Flow and Thermal Resistance Network Modeling of Finned Heat Sinks With Bypass Mounted in Rectangular Enclosure
Authors: Fukada Masaya , Fukue Takashi , Sugimoto Yasuhiro , Hatakeyama Tomoyuki , Ishizuka Masaru
Published: November 2021

This study describes a thermal design method of forced convection cooling in high-density packaging electronic equipment for upstream design processes by flow and thermal resistance network analysis. Forced convection cooling by combining fans and heat sinks is the most standard strategy for dissipating heat from electronic equipment. In recent years, the thermal design of electronic equipment becomes more critical, and fast thermal design is required due to the rapid development of final products. We have been developing the flow and thermal resistance network analysis as the quick thermal design method for electronic equipment. However, an accurate prediction of forced convection cooling performance by finned heat sinks mounted in high-density packaging electronic equipment is generally tricky. Some bypasses, which are clearances between the heat sinks and enclosure walls or other components, exist around the heat sinks. Therefore, a flow rate distribution between the heat sink fins and the bypasses should be predicted. Many researchers have investigated hydrodynamic characteristics and heat transfer characteristics of finned heat sinks. However, many previous studies have been conducted on the finned heat sink performance when there are no bypasses. In order to achieve an optimum design of the finned heat sinks in the upstream configuration regardless of the heat sink dimensions, a systematic database of hydrodynamic characteristics and heat transfer characteristics of the finned heat sinks with bypasses should be investigated.

This paper discusses the development of function models of pressure drop, flow rate distribution, and heat transfer of the finned heat sinks with the bypasses for the resistance network analysis through experiments and CFD analysis. Several types of finned heat sinks with 40 mm in width and 80 mm in length were prepared, and these were mounted in a rectangular enclosure with 45 mm in width and height. First, the pressure drop characteristic around the heat sink was investigated. In addition, the flow rate distribution between the heat sink and the bypass was evaluated separately.

A flow branching coefficient was developed to predict the flow rate distribution around the heat sink combined with the pressure drop coefficient. Using the developed flow branching coefficient, the flow and thermal resistance network model around the finned heat sink was developed. The results from the proposed resistance network model showed good agreement with those from the experiment.
Efficient Thermal Analysis of Lab-Grown Diamond Heat Spreaders
Authors: Yuan Zihao , Zhang Tao , Van Duren Jeroen , Coskun Ayse K.
Published: November 2021

Lab-grown diamond heat spreaders are becoming attractive solutions compared to traditional copper heat spreaders due to their high thermal conductivity, the ability to directly bond them on silicon, and allow for an ultra-thin silicon layer. Researchers have developed various thermal models and prototypes of lab-grown diamond heat spreaders to evaluate their cooling performance and heat spreading ability. The majority of existing thermal models are built using finite-element method (FEM) based simulators such as COMSOL and ANSYS. However, such commercial simulators are computationally expensive and lead to long solution times along with large memory requirements. These limitations make commercial simulators unsuitable for evaluating numerous design alternatives or runtime scenarios for real-world high-performance processors. Because of this modeling challenge, none of the existing works have evaluated the thermal behavior of lab-grown diamond heat spreaders on real-world high-performance processors running realistic application benchmarks. Recently, we have developed a parallel compact thermal simulator, PACT, that is able to carry out fast and accurate steady-state and transient thermal simulations and can be extended to support emerging integration and cooling technologies. In this paper, we use PACT to evaluate the steady-state and transient cooling performance of lab-grown diamond heat spreaders against traditional copper heat spreaders on various real-world high-performance processors (e.g., Intel i7 6950X, IBM Power9, and PicoSoC). By using PACT with architectural performance and power simulators such as Sniper and McPAT, we are able to run transient simulations with realistic benchmarks. Simulation results show that lab-grown diamond heat spreaders achieve maximum temperature and thermal gradient reductions of up to 26.73 °C and 13.75 °C when compared to traditional copper heat spreaders, respectively. The maximum steady-state and transient simulation times of PACT for the real-world high-performance chips and realistic applications used in our experiments are 259 s and 22 min, respectively.
Performance and Durability Validation of Voltage Blocking Technologies to Enable Direct Cooled High-Voltage, High-Power Modules
Authors: Iradukunda Ange-Christian , Huitink David , Gebrael Tarek , Miljkovic Nenad
Published: November 2021

Power densification and rising module heat losses cannot be managed by traditional “external-to-case” cooling solutions. This is especially pronounced in high voltage systems, where intervening layers of insulating material between the power devices and cooling solution need to be sufficiently thick to provide adequate voltage isolation. As operating voltages increase, the required thicknesses for these insulating layers become so large that they limit the ability to extract the heat. A direct cooling approach that addresses voltage separation issues represents a unique opportunity to deliver coolant to the hottest regions, while opening up the opportunity for increased scaling of power electronics modules. However technical concerns about long-term performance of coolants and their voltage isolation characteristics coupled with integration challenges impede adoption. Here, the reliability and performance of voltage blocking strategies, namely dielectric fluids and dielectric surface coatings, are examined to advance the feasibility of a direct cooling approach for improved thermal management of high-voltage, high-power module. The breakdown voltage of the dielectric fluid is characterized through relevant temperatures, flow, and electric fields with the ultimate goal of developing design rules for direct integrated cooling schemes. The development and electrical characterization of conformal dielectric surface coatings to provide further protection of the electronics is also undertaken. Results showed the ability for layers of Parylene C to maintain their insulating capacity when subject to E-fields as high as 33.5V/μm.
Ultra-High-Density Interconnect Enabled by Hybrid Bonding for Heterogeneous Integration: Interfacial Characteristics
Authors: Lu Mei-Chien
Published: November 2021

Hybrid bonding has been explored for more than a decade and implemented recently in high volume production at wafer-to-wafer level for image sensor applications to enable high performance chip-stacking architectures with ultra-high-density chip-to-chip interconnect. The feasibility of sub-micron hybrid bond pitch leading to ultra-high-density chip-to-chip interconnect has been demonstrated due to the elimination of solder bridging issues from microbump method. Hybrid bonding has also been actively considered for logic and memory chip-stacking, chiplets, and heterogeneous integration in general but encountering additional challenges for bonding at die-to-wafer or die-to-die level. Overlay precision, throughput, wafer dicing are among the main causes. Widening the process margin against overlay error by designing innovative hybrid bonding pad structure is highly desirable. This work proposes a method to evaluate these hybrid bonding pad structure designs and to assess the potential performance metrics by analyzing interfacial characteristics at design phase. The bonding areas and ratios of copper-copper, copper-dielectric, and dielectric-dielectric are the proposed key parameters. The correlation between bonding area ratios and overlay errors can provide insights on the sensitivity to process margins. Nonetheless, the impact of copper recess or protrusion associated with bonding area ratios are also highlighted. The proposed method is demonstrated by examining and analyzing the hybrid bonding pad structure design concepts from a few cases reported in literatures as examples. Concerns are identified for elaboration in future designs and optimizations.
Thermal Performance of Modular Microconvective Heat Sinks for Multi-Die Processor Assemblies
Authors: May Chris , Mizerak Jordan , Earley David , Malouin Bernard
Published: November 2021

As processors continually seek greater computational output, the traditional single die processor configuration is giving way to emerging multi-die processor assemblies. As a result, dies of varying powers are spatially distributed in processor packages, causing local areas of high heat density and non-uniform temperature patterns. If not properly addressed, local hot spots may limit the total device operating power, increase leakage current to lower processor efficiency, and accelerate thermal induced semiconductor deterioration to reduce device lifetime.

In this article, a modular microconvective heat sink (M2HS) is developed as a high effectiveness, high flexibility cooling solution for multi-die assemblies. Microconvective cooling, featuring optimized single-phase impingement cooling and effluent fluid flow control, provides high power density heat removal from localized heat flux zones on semiconductor dies. An AMD Threadripper 3960X is chosen as a multi-die test vehicle for the M2HS to test thermal performance in a liquid cooled experimental flow loop. Experimental results in overclocked thermal stress tests are presented, achieving power draws of up to 75% higher than the nominal processor TDP. Further, compared to a recommended product pairing of the CPU serving as a baseline heat sink, the M2HS showed a 51% improvement in CPU power draw performance. When operating at nominal, non-overclocked conditions, reduced temperature operation of the CPU using M2HS solutions resulted in a CPU efficiency increase of up to 10% compared to the baseline heat sink, providing opportunities for reduced PUE in large scale data centers. The study concludes that the M2HS shows promise as a high effectiveness, implementation-friendly cooling solution for emerging multi-die processor assemblies.
Prognostics and RUL Estimations of SAC305, SAC105 and SnAg Solders Under Temperature and Vibration Using Long Short-Term Memory (LSTM) Deep Learning
Authors: Lall Pradeep , Thomas Tony , Blecker Ken
Published: November 2021

Prognostics and Remaining Useful Life (RUL) estimations of complex systems are essential to operational safety, increased efficiency, and help to schedule maintenance proactively. Modeling the remaining useful life of a system with many complexities is possible with the rapid development in the field of deep learning as a computational technique for failure prediction. Deep learning can adapt to multivariate parameters complex and nonlinear behavior, which is difficult using traditional time-series models for forecasting and prediction purposes. In this paper, a deep learning approach based on Long Short-Term Memory (LSTM) network is used to predict the remaining useful life of the PCB at different conditions of temperature and vibration. This technique can identify the different underlying patterns in the time series that can predict the RUL. This study involves feature vector identification and RUL estimations for SAC305, SAC105, and Tin Lead solder PCBs under different vibration levels and temperature conditions. The acceleration levels of vibration are fixed at 5g and 10g, while the temperature levels are 55°C and 100°C. The test board is a multilayer FR4 configuration with JEDEC standard dimensions consists of twelve packages arranged in a rectangular pattern. Strain signals are acquired from the backside of the PCB at symmetric locations to identify the failure of all the packages during vibration. The strain signals are resistance values that are acquired simultaneously during the experiment until the failure of most of the packages on the board. The feature vectors are identified from statistical analysis on the strain signals frequency and instantaneous frequency components. The principal component analysis is used as a data reduction technique to identify the different patterns produced from the four strain signals with failures of the packages during vibration. LSTM deep learning method is used to model the RUL of the packages at different individual operating conditions of vibration for all three solder materials involved in this study. A combined model for RUL prediction for a material that can take care of the changes in the operating conditions is also modeled for each material.
Repeatability and Extended Time Stability Study of an Additively Printed Strain Gauge Under Different Load Conditions
Authors: Lall Pradeep , Narangaparambil Jinesh , Thomas Tony , Schulze Kyle
Published: November 2021

Printed electronics has found new applications in wearable electronics owing to the opportunities for integration, and the ability of sustaining folding, flexing and twisting. Continuous monitoring necessitates the production of sensors, which include temperature, humidity, sweat, and strain sensors. In this paper, a process study was performed on the FR4 board while taking into account multiple printing parameters for the direct-write system. The process parameters include ink pressure, print speed, and stand-off height, as well as their effect on the trace profile and print consistency using white light interferometry analysis. The printed traces have also been studied for different sintering conditions while keeping the FR4 board’s temperature limit in mind. The paper also discusses the effect of sintering conditions on mechanical and electrical properties, specifically shear load to failure and resistivity. The data from this was then used to print strain gauges and compared them to commercially available strain gauges. By reporting the gauge factor, the printed strain gauge has been standardized. The conductive ink’s strain sensing capabilities will be studied under tensile cyclic loading (3-point bending) at various strain rates and maximum strains. Long-term performance testing will be carried out using cyclic tensile loads.
Observations of high-frequency acoustic attenuation due to bubble entrainment at estuarine fronts
Authors: Bassett Christopher , Lavery Andone C.
Published: November 2021

Frontal boundary features with strong gradients in water properties and velocity are common features in coastal environments where fresh discharge meets ambient ocean waters. Convergence at these fronts results in two features that support the entrainment of bubbles. First, horizontal velocity gradients causes surface waves to steepen and break at these boundaries. Second, localized downwelling can further entrain and transport these bubbles. In experiments using broadband echosounders (45–420 kHz) at the Connecticut River ebb plume front and James River tidal intrusion front, bubble entrainment was observed to cause frequency-dependent excess attenuation. Seabed backscattering near fronts is used as a baseline, whereas a decrease in observed backscattering from the seabed under bubble plumes was attributed to excess attenuation due to bubble concentrations. Despite observing significant (>10 dB in some cases) excess attenuation in lower-frequency channels, we hypothesize that these fronts are unlikely to significantly affect propagation in the horizontal at these frequencies and that factors, such as refraction and three-dimension structure, are more operationally significant. [This work was funded by ONR.]
Observations of 11 to 12.5 kHz sea ice pulse reflections around 50–55 deg grazing angle in the Beaufort Sea from summer 2016 to summer 2017
Authors: Kucukosmanoglu Murat , Colosi John A. , Miller Christopher W. , Worcester Peter F. , Dzieciuch Matthew A. , Olson Derek , Richards Edward
Published: November 2021

Beaufort Sea ice has acoustic characteristics that change across time and space. This research aims to quantify sea ice scattering statistics with the goal of using them to predict physical ice characteristics. Over the time between summer 2016 and summer 2017, ice and ocean surface scattering in the 11–12.5 kHz frequency range between grazing angles 50 deg and 55 deg was studied using the navigation systems for a seven mooring 150-km radius acoustic array. Surface scattering has five primary epochs: open water (OW), early ice formation (IF) occurring for a few weeks, ice solidification (IS) occurring again for a few weeks, ice thickening (IT) occurring for about six months, and eventually, ice melting (IM) occurring for 1.5 to 2 months. Important changes in acoustic scattering behavior occurs between these epochs, here expressed in terms of the moments of reflected intensity, intensity probability density function, and pulse time spread. The eras of most considerable change in the observables belong to transition epochs of IF, IS, and IM. These results are interpreted physically and qualitatively in terms of the notions of partially and fully saturated wave fields, an incoherent Kirchhoff-like approximation for the rough surface, and a thin elastic layer reflection coefficient model.
Carbocyanine dye-patterned microbubbles as ultrasound-modulated fluorescent contrast agents
Authors: Schutt Ibsen Carolyn , Benchimol Michael , Hsu Mark , Esener Sadik
Published: November 2021

Combining fluorescence and acoustic techniques enables the characterization of biochemical environments with optical sensors while utilizing the penetration depth and spatial resolution of focused ultrasound. Localized light generation within a small tissue volume can yield spatially resolved chemical information useful for delineating tissue pathology such as cancerous lesions. Our work develops fluorescent microbubble contrast agents that generate light in the focal zone of an ultrasound beam through modulation of their fluorescence intensity. Microbubbles were designed with a self-quenching lipophilic dye patterned within the lipid layer, enabling the dye molecules to quench and dequench with the ultrasound-driven particle size oscillations. Distinct dye patterns were generated on the microbubble surfaces and investigated for their ultrasound-driven fluorescence response. By amplifying the microbubble fluorescence intensity modulations using a lock-in amplifier, the optical signal from these locally activated particles was detected within an optically scattering environment and at significant depth. We additionally observed that these microbubbles also displayed harmonic oscillations of fluorescence intensity beyond the ultrasound driving frequency which could be used to further improve the signal-to-noise ratio for detection. This technique could enable sensitive optical imaging with ultrasound-scale millimeter-level spatial resolution, providing a valuable tool to address the challenge of optical imaging in deep tissue.
A novel microbubble platform for cancer immunotherapy
Authors: Khorsandi Sina , Li Xuefeng , Wang Yifan , Mattrey Robert , Jiang Wen , Lux Jacques
Published: November 2021

The innate immune sensor cyclic GMP–AMP synthase–stimulator of interferon genes (cGAS-STING) has recently emerged as a potential therapeutic target to boost antitumor immune responses. However, STING is a cytoplasmic protein, and its natural activator cGAMP is a negatively charged dinucleotide that is difficult to deliver intracellularly. We have developed a new platform called Microbubble-assisted UltraSound (US)-guided Immunotherapy of Cancer (MUSIC) to activate STING with spatio-temporal control to treat cancer. MUSIC showed greater STING activation compared to cGAMP alone in vitro. In murine models,MUSIC showed dramatic tumor growth inhibition and increased survival in both syngeneic breast cancer models. The absence of antitumor immune responses in STING-/- mice shows that MUSIC action is STING-dependent. Furthermore, 6/10 MUSIC-treated mice were tumor-free versus 2/10 cGAMP-treated mice. All the rechallenged MUSIC-treated mice remained tumor-free 30 days after rechallenge. MUSIC also resulted in a 7-fold decrease in metastatic burden when compared to cGAMP alone. In summary, MUSIC showed efficient STING activation invitro. In addition, local MUSIC treatment of primary tumors produced systemic antitumor immune responses in vivo as well as anticancer immune memory preventing tumor growth upon rechallenge. We are now exploring the use of nanobubbles for systemic administration. [Work supported by CPRIT Grants RR150010 and RP190233. R.F.M. is a CPRIT Established Investigator.]
The crevice model of cavitation inception
Authors: Crum Lawrence A. , Simon Julianna
Published: November 2021

In Robert Apfel’s Ph.D. dissertation and in subsequent published articles, he demonstrated that if one chose a volume small enough—say a microdroplet—cavitation could not be generated even at elevated temperatures. He expanded the work of Harvey (J. Cell. Comp. Physiol. 24, 23 (1944) who proposed the crevice model of cavitation nucleation. Recently, Lu demonstrated that the phenomenon of twinkling was due to the presence of trapped bubbles on solid concretions (Lu, et al., U. S. Med. Biol. 39, 1026 (2013). Subsequently, Simon demonstrated that twinkling occurred in humans (Simon, et al., U. S. Med. and Biol. 46, 1802 (2020). In this presentation, the crevice model will be reviewed and asserted that it is the principal model for inception of cavitation in mammalian tissue.
Ultrafast dynamics of acoustic vaporization and payload release of phase-shift emulsions
Authors: Aliabouzar Mitra , Kripfgans Oliver D. , Estrada Jon B. , Fowlkes J. Brian , Fabiilli Mario L.
Published: November 2021

Acoustic droplet vaporization (ADV) is the phase-transitioning of perfluorocarbon emulsions via focused ultrasound. ADV has been utilized in many biomedical applications. For drug delivery and tissue regeneration, we developed composite hydrogel scaffolds, termed acoustically responsive scaffolds (ARSs), which here contained fluorescently labeled monodispersed emulsions (Ø: 12.3 ± 0.8 μm). Using ultra-high speed microscopy, we investigated the dynamics of ADV (2.5 MHz, P-: 6 MPa, pulse length: 6μs) in ARSs containing emulsions with perfluoropentane, perfluorohexane, and perfluorooctane. Vaporization and growth dynamics were studied in micro- to millisecond time scales at frame rates up to 10 Mfps. During ADV, the generated bubbles expanded 4.8-, 2.8-, and 2-fold greater than the initial diameter of the perfluoropentane, perfluorohexane, and perfluorooctane emulsions, respectively. Stable bubbles formed from ADV in perfluoropentane and perfluorohexane, though growth rates post-ADV were significantly different. Bubbles recondensed within perfluorooctane emulsions, which exhibited a 20% decrease in diameter following five repeated ADV events. Stable or transient bubble formation was further compared with classical nucleation theory predictions. Additionally, we compared the release dynamics of fluorescently labeled payloads from the emulsions. The results provide physical insight enabling the modulation of bubble dynamics with ADV and hence release kinetics, which can be used for therapeutic applications.
Ultrasonic intra-body communication using semi-guided waves through human body tissues
Authors: Gerguis John O. , Nath Mayukh , Sen Shreyas
Published: November 2021

Body Area Network (BAN) demands a secure and low-power technology. Traditionally, RF signals were used, which suffer from high losses and lack of security. Recently, electro-quasistatic human body communication has emerged, enabling low-power communication, but somewhat susceptible to leakage. Ultrasound is presented as a promising alternative owing to its ability of propagating in water-dominated media, like the human body, besides being safe. Existing studies employ ultrasound devices for powering or communicating across tissues; either through transmitter-receiver aligned configurations (not suitable for non-line-of-sight communication) or using omnidirectional transducers, hence limiting the communication distance to only a few centimeters. This paper presents a theoretical study on confining ultrasound waves inside the human tissues (muscle, fat and skin). Through oblique incidence on the bone/muscle interface, the waves can bypass the bone (highly attenuative tissue) through total internal reflection, and be guided through water-rich body tissues. In addition, the high reflection at the skin/air interface (∼99.9%) confines most of the signal inside the body, ensuring secure communication. Simulations are performed on a simplified cylindrical-shaped human body model at 100 kHz, demonstrating the possibility of transmitting a signal over a distance of ∼1 m with losses <50 dB and leaked signal attenuation of additional >20 dB.
Quantitative contrast-enhanced ultrasound for the evaluation and early detection of hepatocellular carcinoma
Authors: Krolak Connor D. , Clark Alicia , Dighe Manjiri , Averkiou Michalakis A.
Published: November 2021

Hepatocellular carcinoma (HCC) is the most common primary liver malignancy with high mortality mainly due to pre-existing liver disease and delay in diagnosis, limiting treatment options. Currently, the state-of-the-art diagnostic metric for HCC is LiRADS (Liver Imaging Reporting and Data System), a qualitative image assessment based on the bolus transit characteristics of microbubbles that stratifies liver tumors suspected for HCC. However, with contrast-enhanced ultrasound, liver tumor perfusion can be quantifiably characterized to identify abnormal arterial flow after an initial portal venous and hepatic arterial flow reduction in the liver, which are typical features of HCCs. The image intensity in a region of interest (ROI) in the HCC is used to form a time-intensity curve (TIC) of the bolus transit (wash-in/washout). A lognormal curve is fitted to the TIC and parameters related to blood flow in the tumor are extracted. Respiratory gating and motion compensation are applied to the video loops before forming the TIC to remove noise and improve the accuracy of the HCC perfusion measurements. Parametric images of the rise time and peak intensity provide an HCC classification algorithm. Utilizing this approach, we provide an improvement to the LiRADS method for an earlier and more accurate diagnosis of HCC.
Reflecting on universal design for learning in hybrid and in-person acoustics education
Authors: Simeon Katherine , Hilger Allison
Published: November 2021

When transitioning to remote (Spring 2020) and hybrid (2020-21 academic year) learning during the COVID-19 pandemic, educators worked quickly to make lectures, coursework, and assessments accessible remotely. As educators return to in-person instruction, accessibility has become an even more essential and evolving part of effective course design (Kim, 2021). The Universal Design for Learning (UDL) Framework aims to maximize learning for all students through flexibility and choice (CAST, 2018). However, to broaden UDL’s impact, these strategies should be transparent to students (Super et al., 2020). This presentation will discuss the use of exam wrappers for students to reflect on UDL practices and their own learning in an undergraduate acoustics class. Exam wrappers are a reflective exercise where students analyze their study strategies after a summative assessment (Lovett, 2013). We will present how UDL practices were implemented in a Speech Science course. Then, we will review lessons learned from using a custom exam wrapper where students reflect on their study habits after exams that assess their application of anatomy and physiology to speech acoustic output. The exam wrapper also aims to obtain formative feedback on UDL practices. This work can inform strategies for UDL implementation and student reflection in acoustics education.
Strategies for teaching and extracurricular activities during COVID-19 transitions
Authors: Morrison Andrew C.
Published: November 2021

As the COVID-19 pandemic moved through waves of severity, it became necessary to have contingency plans for teaching classes and alternative plans ready for related co-curricular and extra-curricular activities. This presentation will detail how our department handled the COVID-19 pandemic as we transitioned from fully online courses to a hybrid learning model. Also detailed is how the pandemic has affected our co-curricular and extra-curricular activities, many of which have connections to our department's undergraduate research program in acoustics. Strategies employed in the recent semester include online lecture components with on-campus laboratories, at-home portions of lab activities, creative uses of classroom spaces on campus, hybrid meetings, and hybrid colloquium presentions.
Understanding and exploiting acoustic field-microswimmer interactions in acoustofluidic devices
Authors: Meacham J. Mark , Kim Minji , Cui Mingyang , Barnkob Rune
Published: November 2021

Acoustic microfluidic devices offer exquisite control for manipulation of objects sized from tens of nanometers to tens of microns. Our work focuses on applying various acoustofluidic solutions to understand microswimmer behavior and the mechanisms underlying the beating of propulsive cilia/flagella. Ultrasonic trapping in bulk acoustic wave (BAW) and substrate acoustic wave (SAW) fields enables observation of swimming without constraining rotational degrees of freedom and without damaging the cells. Here, we summarize recent studies using biciliate C. reinhardtii algae cells, including three-dimensional body motion, synchronization/asynchronization of cis and trans cilia waveforms, and thermal and fluid-property effects. Acoustofluidic approaches provide unprecedented flexibility as a tool to investigate cell motility. Conversely, acoustic field-microswimmer interactions can also be exploited by applying the C. reinhardtii cells as dynamic probes to assess acoustofluidic device performance. We have previously reported use of these cells to identify optimal resonant frequencies of operation and to qualitatively map the strength of the acoustic field in BAW devices. Here, we extend the method to quantify the acoustic energy density of a straight microchannel operating at the first half-wavelength resonance, achieving agreement within 1 % to a standard method based on passive particle tracking. New applications for SAW devices are also presented.
Transferred energy and acoustic spin density in fluid spherical core-shell scattering scenarios
Authors: Alcaras Jose R. , Martinez Alexandre S.
Published: November 2021

Sound wave scattering, along with radiation force and torque, are constantly in vogue topics for several distinct applications, such as small object manipulations and Acoustofluidics. Specially for scattering scenarios, far-field approximations are often considered for dealing with the sound waves far beyond the scattering objects. However, a more in-depth investigation of near and internal fields during a scattering process may be able to unravel dynamical and mechanical properties of the scattering objects. In this study, we propose a time-averaged study of the transferred energy and acoustic spin density in a fluid spherical core-shell. We derive the expressions for the internal waves in terms of spherical harmonics and obtaining Mie-like coefficients. Using those expressions, we analytically compute the time-averaged acoustic energy transferred by a plane wave. Furthermore, we use very recent results with regards to acoustic spin to bring a discussion about spin density transfer, properly computing the quantity for this scenario. This is a follow-up study for understanding acoustical properties of compressible fluids with different geometries, searching for electromagnetic parallels, such as Fano resonance regimes, that may be applicable for building or characterizing acoustic metamaterials.
Direct observation of capillary waves due to high frequency ultrasound and their relation to atomized droplets
Authors: Connacher William , Zhang Shuai , Orosco Jeremy , Friend James
Published: November 2021

Ultrasonic atomization has been studied and used in applications for decades, but a mechanistic understanding of droplet production does not exist at a quantitative level. Early work seemed to indicate that droplet size follows from the driving frequency according to Kelvin's equation. The underlying assumptions in this model do not hold at larger frequencies, and the model relies on a fitting parameter that has not been consistent across experimental studies. Additionally, modern experiments often indicate multi-modal droplet size distributions further complicating the physics. It is difficult to experimentally measure relevant quantities like capillary wavelength because of the time and length scales involved and the fact that the phenomenon occurs at a free liquid surface. We use a high speed digital holographic microscope, the only one of its kind in the world, to image the liquid surface—in full 3D and real time—fast enough to resolve capillary waves generated by 5–50 MHz ultrasound. We extract from this data the spectrum of capillary wavelengths and then compare these to droplet size distributions measured with laser diffraction particle sizing. Both thickness mode and surface acoustic wave lithium niobate transducers are included as well as a range of frequencies in each case. It is shown that droplet size does depend directly on capillary wavelength, but that capillary wavelength is not related to the driving frequency in a simple way.
Enhanced resonant ultrasound spectroscopy for multi-material characterization
Authors: Geimer Paul , Beardslee Luke , Remillieux Marcel , Ulrich Timothy J.
Published: November 2021

Resonant ultrasound spectroscopy (RUS) is a non-destructive technique to describe the elastic tensor of a material through inversion of a sample’s measured resonance frequencies. The original RUS approach is limited to simple geometries as it uses a semi-analytical method to simulate the vibrational response. We modified this approach by combining the finite-element method with genetic algorithm. The new approach is applicable to systems with composite materials, complex geometries, and misaligned material and geometry axes. We present recent work focused on the response of a graphite-TZM composite system. We find composite material properties only vary a few percent from results from single-material RUS. Results from varied geometries and materials suggest further optimizations to enhanced RUS.
Acoustic influence of L1 Spanish on L2 English vowel production
Authors: Conklin Jenna T. , Dmitrieva Olga , Jung Ye-Jee , Zhai Weiyi
Published: November 2021

The strength of influence of the L1 vowel inventory on L2 vowel acquisition is well-documented: learners who identify an L2 phoneme as belonging to an L1 category may fail to establish a distinct category for the new phoneme (Flege, 2002), while those who establish a new category for an L2 vowel may ultimately exhibit more native-like pronunciation (Bohn & Flege, 1992). In learning an L2 with many more vowel categories than the L1, as Spanish-English bilinguals must, speaker-specific category assimilation and discrimination are important contributors to the level of accentedness and intelligibility. This study examines the influence of L1 vowels on L2 production via formants and duration of stressed and unstressed L1 Spanish/L2 English vowels. Ten advanced Spanish-English bilinguals completed a shadowing task in both languages, producing five vowels from each language in various target words. Examined in the aggregate, most vowels remained spectrally distinct along both the F1 and F2 dimensions, with a few categories collapsed across one dimension or the other; unstressed vowels raised in both languages, but raised further in English than Spanish. However, interspeaker differences in the patterns of category assimilation necessitate an individual analysis, highlighting the high level of variation in acquisition across individuals.
Perceptual adaptation to an artificial accent: Phonetic category shift or expansion?
Authors: Melguy Yevgeniy , Johnson Keith
Published: November 2021

Listeners can rapidly adapt to a novel accent. For example, following exposure to a speaker whose /f/ sound is ambiguous between [s] and [f], they categorize more sounds along an [s]-[f] phonetic continuum as /f/. Wetested the adaptation mechanism underlying such changes in category structure — do listeners adjust their phonetic boundary for the target sound (category shift), or simply relax their categorization criteria (category expansion)? We trained listeners on a pronunciation containing ambiguous /θ/ [θ / s] and then tested them on categorizing either [θ]-[s] or [θ]-[f] phonetic continua. If listeners simply shift their /θ/ boundary, we predicted an increase in /θ/ responses for the [θ]-[s] continuum, but not [θ]-[f]. By contrast, if listeners expand the category, we predicted a categorization change in both continua, indicating a general broadening of the /θ/ category in phonetic space. Consistent with the boundary shift hypothesis, we found that listeners tested on the [θ]-[s] continua showed a significant increase in proportion of /θ/ responses versus controls [χ2(1) = 4.80, p < 0.05), while those tested on [θ]-[f] did not [χ2(1) = 1.30, p = 0.25). [Work supported by an NSF GRFP Fellowship to YVM.]