bluuebunny/crossref_metadata_2025 huggingface dataset:
Adjuvant therapy for cutaneous melanoma: a systematic review and network meta‐analysis of new therapies
Authors: Longo C. , Pampena R. , Lallas A. , Kyrgidis A. , Stratigos A. , Peris K. , Garbe C. , Pellacani G.
Published: November 2019

New drugs have been recently approved as adjuvant therapies for melanoma. In this Bayesian network meta‐analysis, we aimed to assess the best therapeutic option in terms of recurrence‐free survival (RFS), overall survival (OS) and adverse events (AEs). PubMed, Embase, Cochrane library and the American Society of Clinical Oncology databases were searched from inception until 20 August 2018. We estimated adjusted hazard ratios (HRs) for RFS and OS and relative odds ratios (ORs) for AEs and surface under the cumulative ranking (SUCRA) probabilities were calculated. A number of 872 records were identified, and six were finally included in the meta‐analysis. A total of 4244 patients in six studies were randomized. The following therapies were considered in the selected studies: combined dabrafenib and trametinib, vemurafenib, nivolumab, ipilimumab and pembrolizumab. Nivolumab demonstrated the highest probability (75.1%) of being the best in term of RFS, followed by dabrafenib+trametinib, pembrolizumab, ipilimumab and vemurafenib; however, OS was not estimable. Concerning AEs, pembrolizumab and nivolumab showed the highest probability to be less associated with any and 3–4 grade AEs (83.1% and 64.4%, respectively). In conclusion, all new drugs are highly effective in adjuvant setting, and the best choice is dependent of patient's context.
Optimizing the measurement of comorbidity for a South Australian colorectal cancer population using administrative data
Authors: Pule Lettie , Buckley Elizabeth , Niyonsenga Theo , Roder David
Published: November 2019

Rationale and objectives

In epidemiological research, it is essential to account for the confounding effects of factors such as age, stage, and comorbidity for accurate prediction of cancer outcomes. There are several internationally developed and commonly used comorbidity indices. However, none are regarded as the gold‐standard method. This study will assess and compare the predictive validity of established indices for use in a South Australian (SA) colorectal cancer (CRC) population against a local index. Furthermore, the prognostic influence of comorbidity on survival is investigated.

Methods

A population‐based study of patients diagnosed with CRC from 2003 to 2012 and linked to in‐hospital data to retrieve comorbidity information was conducted. The predictive performance of established indices, Charlson comorbidity index (CCI), National Cancer Institute comorbidity index (NCI), Elixhauser comorbidity index (ECI), and C3 index was evaluated using the Fine and Gray competing risk regression and reported using measures of calibration and discrimination, area under the curve (AUC), and Brier score. Furthermore, to identify the optimal index, a local CRC comorbidity index (CRCCI) was also developed and its performance compared with the established indices.

Results

Comorbidity models adjusted for age, sex, and stage showed that all indices were good predictors of mortality as measured by the AUC (CCI: 0.738, NCI: 0.742, ECI: 0.733, C3: 0.739). CRCCI had similar mortality prediction as established indices (CRCCI: 0.747). There was a significant increase in cumulative risk of noncancer and CRC‐specific mortality with increase in comorbidity scores. The two most prevalent comorbidities were hypertension and diabetes.

Conclusions

The existing indices are still valid for adjusting for comorbidity and accurately predicting mortality in an SA CRC population. Internationally developed indices are preferred when policymakers and researchers wish to compare local study results with those of studies (national and international) that have used these indices. Comorbidity is a predictor of mortality and should be considered when assessing CRC survival.
Identification and characterisation of tumour necrosis factor receptor (TNFR) associated factor 3 from Nile tilapia, Oreochromis niloticus
Authors: Han Xue‐qing , Gao Fengying , Lu Maixin , Liu Zhi‐gang , Wang Miao , Ke Xiao‐li , Gao Yan‐xia
Published: November 2019

In this study, we cloned the complementary (c)DNA sequences of tumour necrosis factor receptor (TNFR)‐associated factor 3 (traf3) in Nile tilapia, Oreochromis niloticus. The expression patterns of the traf3 gene were investigated and preliminary functional analyses were performed. In healthy fish, traf3 transcript was broadly expressed in all examined tissues, with the highest expression level in the blood and the lowest in the liver. The traf3 gene reached its highest expression at 8 days post‐fertilisation (dpf) during embryonic development. Moreover, we found that expression of traf3 was clearly altered following stimulation with Streptococcus agalactiae in vivo and that traf3 could be induced by lipopolysaccharides (LPS), Poly I: C and S. agalactiae WC1535 in Nile tilapia macrophages. Overexpression in 293T cells showed that Traf3 protein was mainly distributed in the cytoplasm and could significantly increase nuclear factor kappa‐light‐chain‐enhancer of activated B cells (NF‐κB) activation. Taken together, these results implied that traf3 could play important roles in the immune response to pathogen invasion.
Labor Regimes and Free Trade in North America: From the North American Free Trade Agreement to the United States–Mexico–Canada Agreement
Authors: Campos Ortiz Francisco E.
Published: November 2019

This article provides a comparative assessment of the labor provisions in the United States–Mexico–Canada Agreement (USMCA) and the North American Free Trade Agreement. It also evaluates new labor‐related requirements incorporated in the rules of origin (ROO) rather than the labor chapter of the newer treaty. The ROO in the USMCA determine a labor value content requirement for passenger vehicles and light and heavy trucks. No previous free trade agreement mandates that a fraction of a product be made by workers earning a specific minimum wage to qualify for duty‐free access. The new clause has raised concerns about its enforceability, which this article explores. Private compliance initiatives are presented as a means to strengthen compliance with the new labor regime without disrupting existing regional production networks.
Colonic neuronal loss and delayed motility induced by high‐fat diet occur independently of changes in the major groups of microbiota in Swiss mice
Authors: Beraldi Evandro José , Borges Stephanie Carvalho , de Almeida Fernanda Losi Alves , dos Santos Andrey , Saad Mario José Abdalla , Buttow Nilza Cristina
Published: November 2019

Background

Obesity has been linked to gastrointestinal disorders, and the loss of myenteric neurons in the intestine caused by high‐fat diets (HFD) has been attributed to changes in microbiota and lipotoxicity. We investigated whether the prebiotic inulin modulates bacterial populations and alleviates neuronal loss in mice fed HFD.

Methods

Swiss mice were fed purified rodent diet or HFD (59% kcal fat), or both diets supplemented with inulin for 17 weeks. Intestinal motility was assessed and a metagenome analysis of the colonic microbiota was performed. The gene expression of inflammatory markers was evaluated, and immunofluorescence was performed for different types of myenteric neurons and glial cells in the distal colon.

Key Results

The HFD caused obesity and delayed colonic motility. The loss of myenteric neurons and glial cells in obese mice affected all of the studied neuronal populations, including neurons positive for myosin‐V, neuronal nitric oxide synthase, vasoactive intestinal peptide, and calretinin. Although obese mice supplemented with inulin exhibited improvements in colonic motility, neuronal, and glial cell loss persisted. The HFD did not altered the expression levels of inflammatory cytokines in the intestine or the prevalence of the major groups in microbiota, but inulin increased the proportion of the genus Akkermansia in the obese mice.

Conclusions and Inferences

In Swiss mice, the HFD‐induced neuronal loss but did not change the major groups in microbiota. This suggests that, despite the increase in the beneficial bacteria, other factors that are directly linked to excess dietary lipid intake affect the enteric nervous system.
Financial Condition and Internal Control Deficiencies: Evidence From New York Counties
Authors: Kim Youngsung , Matkin David S. T.
Published: November 2019

In recent years, significant attention has been given to measuring the financial condition of local governments, predicting when those governments will experience fiscal distress, and understanding how public managers navigate financial shortfalls. Researchers have given less focus, however, to understanding how financial condition affects other financial management practices—such as the administrative systems used to ensure financial accountability. This study uses a 19‐year panel of county‐level data from New York State to examine whether financial condition affects the likelihood of internal control deficiencies. The findings indicate that the incidence and severity of internal control deficiencies increase as financial condition deteriorates.
Maybe not so independent after all: The possibility, prevalence, and consequences of violating the independence assumptions in psychometric meta‐analysis
Authors: Yuan Zhenyu , Morgeson Frederick P. , LeBreton James M.
Published: November 2019

Psychometric meta‐analysis assumes that moderators are unrelated to study artifacts (e.g., criterion reliability), and that study artifacts are independent of true validities. Meeting these assumptions is important for researchers seeking to accurately partition the variance in effect sizes due to study artifacts from the variance due to meaningful moderators. Despite the critical role of these assumptions, we know very little about their tenability. To address this basic gap in the literature, we conducted three studies to determine if there are potential violations of the independence assumptions (Study 1), the prevalence of such violations (Study 2), and the consequences of violating the independence assumptions via a series of Monte Carlo simulations (Study 3). We found that violations of the independence assumptions are not only plausible but also routinely detected across a wide array of topics. Simulation results indicate that violating the independence assumptions can result in biases under certain circumstances, which are further accentuated due to the lack of stability in the estimators. We offer suggestions for the future use of psychometric meta‐analysis and discuss the implications for research focused on refining psychometric meta‐analysis.
Application of photogrammetry to generate quantitative geobody data in ephemeral fluvial systems
Authors: Priddy Charlotte L. , Pringle Jamie K. , Clarke Stuart M. , Pettigrew Ross P.
Published: November 2019

Outcrop studies are often used as analogues to subsurface sedimentary reservoirs, with photogrammetry representing a useful technique to obtain quantitative geometrical data of sedimentary architectures. Digital photogrammetric techniques were used to study fluvial sediments of the Lower Jurassic Kayenta Formation of the western USA. Model‐extracted statistics for channel and sheetflood elements, relevant to reservoir modelling, were compared with 1D and 2D datasets from the same outcrops. Results suggest that the 1D/2D data significantly underestimated element dimensions and ranges in ephemeral fluvial systems. Consequently, this study demonstrates the value of photogrammetric techniques for obtaining statistically relevant and more accurate reservoir modelling input data from outcrops.
Optimal Pricing Model of Digital Music: Subscription, Ownership or Mixed?
Authors: Li Shengli , Luo Qiuyue , Qiu Liangfei , Bandyopadhyay Subhajyoti
Published: November 2019

Traditionally, consumers purchase physical music (often in the form of CDs or cassettes) from local retailers. With the development of Internet technology, the market share of digital music has grown rapidly in recent years. Unlike physical music, digital music is provided by several emerging digital music providers through the Internet to consumers. Pricing models of digital music are also drastically different from those of physical music. In this study, we identify three common schemes for selling digital music: ownership, subscription and mixed pricing models. Under the ownership model, consumers purchase and download their preferred songs and enjoy music using their local devices. Under the subscription model, music is provided through an online streaming service. The mixed pricing model is a combination of the previous two. Our paper explores and compares the three pricing models. Through a stylized model, we find that several factors, including the advertisement revenue rate and consumers’ reservation value for the music service, have crucial effects on the comparison of the three pricing models.
Set‐theoretic Multimethod Research: The Role of Test Corridors and Conjunctions for Case Selection
Authors: Schneider Carsten Q. , Rohlfing Ingo
Published: November 2019

Set‐theoretic multimethod research (SMMR) using Qualitative Comparative Analysis (QCA) formalizes the choice of cases based on a truth table analysis. We make three recommendations for improving SMMR. First, current standards can lead to faulty case selection if causal inference on a conjunction is the goal. Case selection needs to take into account that the non‐members of a conjunction might be empirically diverse and that only selected types of non‐members are ideal for causal inference. Second, we formally show that cases with similar fuzzy‐set memberships in a term and the outcome are the superior choice for process tracing. They minimize the expected membership in the mechanism and make it most difficult to pass a hypothesis test. Third, we propose formulas that comply with all SMMR principles and identify the best pairs of cases for analysis. We illustrate our arguments with a study of the effectiveness of sanctions against authoritarian regimes.
The House in Time: In Search of a Just Image
Authors: Carter Rebecca Louise
Published: November 2019

This essay considers the photographic encounter in Black New Orleans, focusing on a news image of a fire that destroyed several homes in the wake of Hurricane Katrina. I trace the circulation of this image, first published in Time, examining the devastation it documents as well as the race and class stereotypes it perpetuates. I simultaneously follow the homeowners as they renegotiate the photograph, asserting their true identity and position. Inspired by Roland Barthes and the search for a “just” image, the essay explores the possibilities of the photographic encounter for the reclamation of Black being and dwelling.
Nurse‐Led Tele‐Coaching on Modifiable Cardiovascular Risk Factors in People with Type 2 Diabetes Mellitus: A Systematic Review and Meta‐Analysis
Authors: Yu‐Mei Chen Delphine , Wu Xi Vivien , Chan Ee Yuee , Goh Yong Shian
Published: November 2019

Background

Tele‐coaching has been used by nurses as one of the accessible and sustainable interventions for individuals with type 2 diabetes mellitus. However, evidence has been lacking to demonstrate its effectiveness in mitigating the related cardiovascular risk factors.

Aims

To systematically evaluate the effectiveness of nurse‐led tele‐coaching on the modifiable cardiovascular risk factors (glycated hemoglobin, blood pressure, & lipid levels) among individuals with type 2 diabetes mellitus.

Methods

A systematic search of eight databases (Cochrane Library, PubMed, Embase, Cumulative Index to Nursing and Allied Health Literature, Scopus, PsycINFO, Web of Science, & ProQuest Dissertations and Theses) was conducted for randomized controlled trials of nurse‐led tele‐coaching for individuals with type 2 diabetes mellitus published in English up to October 30, 2018. A meta‐analysis was conducted for the primary outcomes of the studies.

Results

Twelve randomized controlled trials were selected that included 3,030 participants. Results from the meta‐analysis revealed statistically significant reductions for not only glycated hemoglobin (pooled mean difference = −1.23, 95% CI: −1.63 to −0.8, I2 = 0%, p < .00) but also systolic blood pressure (SBP; pooled mean difference = −2.22, 95% CI: −3.95 to −0.49, I2 = 0%, p < .01); such findings are supportive of the use of nurse‐led tele‐coaching on the primary outcome.

Linking Evidence to Action

Results from the meta‐analyses have shown that nurse‐led tele‐coaching is an effective and accessible intervention that could improve the glycemic control and SBP among individuals with type 2 diabetes mellitus.
Early postoperative mobilization in patients undergoing abdominal surgery: a best practice implementation project
Authors: Hu Yan , McArthur Alexa , Yu Zhenghong
Published: November 2019

Objectives:

The aim of this project was to improve early postoperative mobilization in patients undergoing abdominal surgery according to best practice.

Introduction:

Early mobilization is a crucial element of postoperative care; however, there are challenges implementing early mobilization protocols in daily practice. This project used the evidence to improve awareness and practice of early mobilization in patients undergoing abdominal surgery.

Methods:

This study utilized clinical audit strategies under the JBI Practical Application of Clinical Evidence System (JBI PACES) module. An audit-feedback cycle was used from April 2018 to August 2018. The baseline audit was conducted using 18 nurses and 30 patients in a general surgery ward. The Getting Research into Practice audit and feedback tool was used to identify barriers, strategies, resources and outcomes. After implementing evidence-based strategies, a follow-up was conducted using the same number of samples and audit criteria. We analyzed the compliance with best practice and its impact on length of hospitalization, postoperative physical activities, gastrointestinal function and complications.

Results:

After implementing best-practice strategies, the compliance rate of the six criteria improved as follows: criterion 1 from 0% to 100% (P = 0.000), criterion 2 from 87% to 100% (χ2 = 4.29, P = 0.038), criterion 3 from 60% to 70% (χ2 = 6.67, P = 0.010), criterion 4 from 7% to 79% (χ2 = 52.55, P = 0.000), criterion 5 from 40% to 70% (χ2 = 35.00, P = 0.000), and criterion 6 from 0% to 100% (P = 0.000). The differences in the length of hospitalization and physical activities between the pre-implementation and post-implementation were statistically significant (all P < 0.05). The rate of postoperative complications did not show a significant difference because of low occurrence.

Conclusions:

The results indicate that evidence-based practice is an effective method for enhancing early recovery in patients undergoing abdominal surgery through promoting early mobilization. Sustaining best practice should continue through further follow-up audits.
Bistatic echo discrimination in the bottlenose dolphin (Tursiops truncatus)
Authors: Christman Katie , Ram Danielle , Coffinger Sean P. , Mulsow Jason , Finneran James J. , Houser Dorian S.
Published: November 2019

Prior research suggests that dolphins can echo-discriminate targets by eavesdropping on conspecific echolocation or by listening to the pulse-echo sequence of an electronic sonar system. To evaluate dolphins as bistatic receivers/classifiers, a three-year old, male bottlenose dolphin was trained to produce a conditioned phonic response upon hearing a “target” echo (n = 1) in a stream of “distractor” echoes (n = 7). Echoes, which were generated by insonification of variable shapes constructed of 1/8-inch thick stainless steel, were highly similar. Echoes were presented sequentially and grouped into “packets” of the same echo; three to nine packets of distractor echoes were randomly presented prior to presentation of the target echo packet. A 30-ms inter-echo interval was implemented and packet durations were randomized between 1.8 and 2.7 s. Echo amplitudes were first equalized with regard to their peak-peak pressures, then roved (±3 dB) to eliminate amplitude cues. The dolphin’s discrimination threshold was determined through an adaptive staircase procedure and defined as the echo level (calculated as the ratio of echo energy to the nominal within-band noise spectral density) corresponding to 50% correct discrimination. The dolphin’s threshold of discrimination was determined to be ∼1 dB, which was similar to a prior report on dolphin passive echo discrimination.
Relationship between biosonar click emissions, age, and hearing bandwidth in bottlenose dolphins, Tursiops truncatus
Authors: Strahan Madelyn , Finneran James J. , Mulsow Jason , Houser Dorian S.
Published: November 2019

Previous studies have reported changes in biosonar emissions in a few odontocete subjects as audible frequency range is reduced with increasing age (i.e., presbycusis). For example, some animals have been observed to lower the dominant frequencies of their biosonar clicks to better match their reduced audible frequency range. In the present study, relationships between age, biosonar click emissions, auditory evoked potentials, and hearing bandwidth were studied in 10 bottlenose dolphins (Tursiops truncatus) of various ages and hearing capabilities. Underwater hearing thresholds were estimated by measuring steady-state auditory evoked potentials to sinusoidal amplitude modulated tones at frequencies from 20 to 160 kHz. Input-output functions were generated at each tested frequency and used to calculate frequency-specific thresholds and the upper cut-off frequency of hearing for each subject. Click emissions were measured during a physical target aspect change detection task at a fixed range of 10 m. Relationships between hearing thresholds and the acoustic parameters of biosonar signals will be presented and compared to previous experiments with fewer subjects. [Work supported by the Office of Naval Research.]
Auditory brainstem responses to stimulus offset in the bottlenose dolphin (Tursiops truncatus)
Authors: Finneran James J. , Jones Ryan A. , Mulsow Jason , Burkard Robert F.
Published: November 2019

The auditory brainstem response (ABR) is typically associated with the onset of a sound stimulus; however, ABRs can also be produced at sound offset. Here, ABRs in response to stimulus offset were examined in normal hearing (NH) and hearing impaired (HI) bottlenose dolphins. Tests were conducted in San Diego Bay, with the dolphin positioned underwater in front of a piezoelectric sound projector. Scalp activity was amplified (94 dB) and filtered (300–3000 Hz) before synchronous, weighted averaging and digitization. Each ABR was the averaged response to 512 stimuli; two ABRs were obtained for each stimulus condition. Stimuli included spectrally pink noisebursts (bandwidth: 20–160 kHz) and tonebursts (40-kHz; 113-kHz for the NH dolphins only). Stimulus level, risetime, and duration were systematically manipulated across experimental trials. Regardless of onset/offset envelope (cosine or linear), large amplitude offset responses were observed to 40-kHz tonebusts presented at higher levels with faster rise times for the NH but not the HI animals. One interpretation of these findings is that the offset response may be arising from more basal regions of the cochlea than the onset response. [Work supported by US Navy Living Marine Resources Program.]
Effects of jawphone position and stimulus frequency on the auditory brainstem response in bottlenose dolphins (Tursiops truncatus)
Authors: Mulsow Jason , Burkard Robert F. , Accomando Alyssa W. , Finneran James J.
Published: November 2019

Suction-cups with embedded acoustic transmitters (“jawphones”) can be used to deliver sound to odontocetes while out of water. When used for electrophysiological hearing tests, both jawphone and recording electrode location are important considerations. This study examined bottlenose dolphin auditory brainstem response (ABR) patterns across jawphone and electrode location. Stimuli were tonebursts with center frequencies of 28–160 kHz. When recorded using an electrode immediately behind the blowhole, ABR peak amplitudes were generally highest when the jawphone was placed on the middle of the mandible and lowest when placed near the tip of the rostrum. However, responses were comparable between the middle and posterior mandible when recorded with an electrode near the auditory meatus. These patterns were consistent across frequency, suggesting that ABRs recorded at the blowhole likely contain more binaural contributions than those recorded at the meatus. While blowhole electrode placements with a jawphone on the middle of the mandible provide the highest signal-to-noise ratios, they may not provide ear-specific information at suprathreshold stimulus levels, which could lead to confusion regarding the optimal location for transmitting sound to the ear. [Funded by US Fleet Forces Command.]
A real-time acoustic drifter for active and passive sonar applications
Authors: Turgut Altan , Schindall Jeffrey
Published: November 2019

A low-cost, long-duration acoustic drifter has been developed to measure directional ambient noise and man-made acoustic signals in both shallow and deep oceans. Traditional acoustic and oceanographic measurements are typically performed by deploying fixed moorings that would limit retrieving the data only after the recovery. With the advancements in low-power CPUs and satellite telemetry, real-time oceanographic and acoustic measurements are possible with in-buoy data reduction and satellite transmission of processed data. A Raspberry Pi computer with a 16-channel data acquisition board is used for both active and passive sonar applications, including directional ambient measurements, seabed characterization, and ocean acoustic tomography. A specific version of the acoustic drifter was built for on-ice deployments in the Arctic as an ice-tethered acoustic buoy. Several examples of its applications from recent sea-going experiments are given. Successful deployments and instant data analysis would indicate a practical alternative to more traditional acoustic and oceanographic measurement techniques by providing a real-time monitoring capability. [Work supported by the ONR.]
Targeted ultrasound enhanced drug delivery to foam cell spheroids
Authors: Thomas Reju G. , Su Xiaoqian , Vizetto-Duarte Catarina , Muktabar Aristo , Ng Kee W. , Kwan James J.
Published: November 2019

Atherosclerosis is a chronic vascular disorder marked by the accumulation of foam cells in the intimal space of the artery. Foam cells are macrophages that reside in the arterial wall after internalizing excessive cholesterol. Though many strategies to remove cholesterol from foam cells have been put forward, delivering these agents at the site of the lesion remains a challenge. Here, we investigated the ability of our previously reported multi-cavity poly-co-lactic-co-glycolic acid microparticles (mc-PLGA MPs) to penetrate into a model for early stage atherosclerosis, a 3D foam cell spheroid, and deliver hydroxyl beta cyclodextrin (HBCD) and sirolimus. HBCD is a polysaccharide that solubilizes cholesterol and promotes cholesterol efflux from foam cells. First, the drug release capability of mcPLGA MPs was tested using DAPI dye as a model drug. Sustained release of DAPI from mcPLGA MPs was observed in foam cell nuclei three days after implantation. We found that DAPI released from mcPLGA MPs distributed evenly throughout the spheroid even though mcPLGA MPs were implanted predominantly at the periphery. FITC conjugated HBCD was co-administered with sirolimus loaded mc-PLGA MPs and was also found to be implanted only under ultrasound exposure. Foam cell viability and the inflammatory response of the ultrasound treatment were also monitored across a week. In conclusion, this study shows the possibility of atherosclerosis treatment with targeted ultrasound enhanced drug delivery.
Cavitation response from multi-cavity and porous PLGA microparticles
Authors: Su Xiaoqian , Thomas Reju G. , Kwan James J.
Published: November 2019

Solid cavitation agents have become an emerging technology for both diagnostic and therapeutic ultrasound applications. The key trait amongst the many formulations of solid cavitation agents is the ability to trap gas either within pores or cavities throughout the particle. Recently, we have reported on the development of a degradable multi-cavity PLGA microparticle for ultrasound-enhanced drug delivery. The cavitation signal from these particles suggested the presence of both inertial and non-inertial cavitation. Here, we conducted a deeper analysis on the cavitation signal from both these multi-cavity PLGA microparticles as well as highly porous PLGA microparticles. We investigated their acoustic response to a spherically focused ultrasound transducer at various pressure amplitudes and frequencies. The power spectral density curves from the received acoustic signals, as measured by a passive cavitation detector, were obtained and analyzed for harmonic and broadband content. Ultrasound contrast enhancement using a conventional ultrasound imaging system of both porous and multi-cavity particles was also investigated. These results provide further insights into the design and acoustic response of solid polymeric cavitation agents for diagnostic and therapeutic applications.
Acoustic streaming near a sharp edge
Authors: Thompson Charles , Chandra Kavitha , Joasil Arielle , Kamal Sarah
Published: November 2019

This work examines the generation of acoustic streaming near a sharp edge. For an edge having an exterior angle larger than 180 deg, the local fluid velocity at its apex is singular. The implication of this state of affairs and the role it plays in vorticity generation and transport are examined. A theoretical model for the scattering and dissipation will be presented.
Effects of metal 3-D printing processes on acoustic metamaterial elements
Authors: Rohde Charles , Naify Christina J. , Birnbaum Andrew , Guild Matthew D.
Published: November 2019

Acoustic metamaterial properties derive from inherently complex, sub-wavelength geometries which aim to control the propagation of sound and elastic waves. The material properties of the unit cell element, the meta-atom, are important when considering either resonant response, or when the transport medium is a high density fluid, such as water. For water applications, this typically means using metals in the design. Metal additive manufacturing (AM) is a logical approach to achieve the needed design complexity. The most common approach in metal AM is selective laser melting. This approach utilizes a high-power laser beam to locally melt powder into a solid. 3D geometries are built through layer-by-layer melting of material. This approach to fabrication incorporates thermodynamic complexities such as extreme temperature gradients, simultaneous multiple material phases, gradient driven convection, rapid solidification, and occasional void formation. We will outline the complications that arise when using this technology to build one of the simplest acoustic meta-atoms: a thin disk. We show that thermal stresses can thermally warp the geometry, and microstructural heterogeneities can locally change material properties. These effects alter both the AM membrane’s macroscale (resonance) and microscale (crystal structure), significantly impacting the acoustic response. [Work Sponsored by the Office Of Naval Research.]
Three-dimensional printing of tunable stiffness acoustic materials
Authors: Naify Christina J. , Rohde Charles , Ikei Alec , Sieck Caleb F.
Published: November 2019

Three-dimensional printing has opened up a wide range of new avenues in acoustics with the ability to rapid-prototype and to create structures with unusual acoustic properties such as space-coiling and exotic lattices. In most cases, however, the mechanical, and thus acoustic properties of the printed structures are fixed once printed. Recently, specifically within the area of acoustic metamaterials, the field of tunable acoustic structures have gained a large amount of interest for their ability to adapt to a wide range of frequencies. In this work, we explore the intersection of tunable acoustic structures and additive manufacturing by 3-D printing a structure whose acoustic response can be locally, actively tuned via resistive heating in order to decrease the elastic modulus of the material and achieve a more highly damped structure. This phenomena is demonstrated by tuning the acoustic response of membrane structures since many acoustic metamaterial phenomena such as sound insulation, negative density, negative index, supercoupling, acoustic steering, metasurfaces, and demonstration of Willis coupling, utilize membrane structures. Specifically, we present two demonstrations of tunable membranes to achieve non-symmetric acoustic modes in a normal incidence sound tube, and to tune Willis coupling in an extremely subwavelength unit cell. [Work Sponsored by the Office Of Naval Research.]
Utilizing a spark gap generator as an impulsive noise source for scale model experiments investigating novel metamaterial arrays
Authors: Ochi Gordon M. , Swearingen Michelle E. , Kreiger Megan , Dunn Kyle G. , Muhlestein Michael , Vargas Emanuel J. , Punt Douglas A.
Published: November 2019

A spark gap generator is demonstrated as a surrogate blast source for scale model experiments. It provides a portable, repeatable, and safe option for investigating the propagation of impulsive signals through a 3-D printed metamaterial. Key insights into proper design and implementation of the spark gap circuit, relating to the characteristic frequency and peak pressure of the signal created by the spark gap, are given. Properties of the signal, including directivity, duration, and spectral characteristics, are discussed. The ability of the spark gap to replicate features of an explosives related shock wave, such as the rise time and N-wave behavior, is also discussed. Finally, the spark gap generator is used to conduct scale model experiments with novel 3-D printed metamaterial arrays, which are compared to simulated results.
Bayesian optimization of optically transparent multilayer micro-slit panel broadband sound absorbers
Authors: Hoeft Michael , Xiang Ning , Fackler Cameron J.
Published: November 2019

Bayesian analysis is applied to the design and fabrication of multilayer micro-slit panel (MSP) absorbers to increase the manufacturing accuracy of each panel. An iterative inversion is applied to quantify fabrication inaccuracies. Re-manufacturing the panels with compensated MSP parameters improves the accuracy of measured sound absorption coefficients. This study builds on previous research where optically transparent, broadband sound absorption is made possible using a two-tiered Bayesian inference approach. The Bayesian design method automatically determines the most concise number of layers required to achieve a desired sound absorption, simultaneously yielding the MSP parameters for each layer of the resulting composite. This work aims to show that design of an optically transparent sound absorber with a broad frequency range of high absorption can be iteratively optimized using Bayesian inference with a multi-step fabrication process.
Spatial Fourier transform-based localized sound zone generation methods with loudspeaker arrays
Authors: Okamoto Takuma
Published: November 2019

This presentation provides spatial Fourier transform-based localized sound zone generation methods with multiple loudspeakers. First, these approaches are compared with conventional acoustic contrast and pressure matching approaches which are based on the least squares (LS) solution. Whereas these LS-based methods are unstable and some regularization schemes are required because the acoustic inverse problem is very ill-conditioned, the proposed spatial Fourier transform-based approaches can directly derive stable driving functions of loudspeakers without regularizations since the propagation and evanescent components of sound fields can be separated and only the propagation components are introduced to the driving functions. Then, spatial Fourier transform-based multiple sound zone generation methods with linear and circular loudspeaker arrays are introduced. In these approaches, the sound pressures on a line or a circle are modeled as rectangular or Hann windows, and the driving functions are analytically derived from the spatial Fourier transform. Additionally, localized sound zone generation approaches with linear, circular, and spherical loudspeaker arrays are introduced. In these approaches, the sound pressures produced by a loudspeaker are cancelled by the linear, circular, and spherical loudspeaker arrays. These driving functions are also derived from the spatial Fourier transform. Challenges and prospects of these approaches are finally described.
Measurement of the directional properties of non-diffuse sound fields in ordinary rooms
Authors: Nolan Mélanie , Nilsson Erling
Published: November 2019

Reverberation time measurements are often inadequate in predicting the acoustical behavior of small ordinary rooms, particularly in spaces with non-uniform placement of absorptive materials (such as classrooms, offices, and clinical rooms). On the other hand, numerical predictions depend strongly on the quality of input data (i.e., absorption and scattering coefficients), which are generally inaccurate due to the lack of reliable experimental methods to measure them. This work investigates how spatially distributed measurements can be used to characterize the spatio-temporal properties of the sound field in non-Sabine spaces, and how this information can supplement traditional methods in tasks related to room acoustical design. In this study, measurements are conducted in a classroom with absorbing ceiling using a programmable robotic arm. It is shown that by expanding the measured sound field into an elementary wave basis, it is possible to reconstruct and extract the spatial distribution of sound pressure and energy flows in the room. Additionally, spatio-temporal post-processing enables to characterize the decay process and to assess the dominant directions of sound propagation, leading to a time-dependent analysis of the properties of the sound field.
Preliminary estimates of year-round acoustic communications potential in the Canada Basin
Authors: Binder Carolyn , Pecknold Sean , Badiey Mohsen
Published: November 2019

Long-range acoustic communication networks, which operate over hundreds of kilometers, are important enablers for persistent surveillance in the Arctic. Acoustic communication must take place over such long ranges due to difficulty in deploying communication nodes in such an inhospitable environment. Signal transmission over long ranges is challenged by distortion caused by refraction and multipath addition, so the propagation medium should be understood in order to optimize node placement and estimate the network performance. The Arctic is a unique acoustic propagation environment due to the presence of an ice-covered surface and oceanographic variability around the shelf breaks. To better understand the current state of Arctic propagation, acoustic signals were transmitted during the year-long Canada Basin Acoustic Propagation Experiment (CANAPE). In this talk, signals from the CANAPE data are used to assess the feasibility of year-round, long-range acoustic communications in the Canada Basin by examining several metrics. These metrics include: the signal-to-noise ratio (SNR) of the received signals, time-spreading of the signals due to multipath arrivals, and signal coherence. This talk will focus on the seasonality of these metrics in order to assess how the performance of acoustic communication systems may be altered by temporal variability of the Arctic acoustic propagation characteristics.
A channel state information updating method based on the first-order Gauss Markov model under time-varying underwater acoustic channel
Authors: Qiao Gang , Liu Lei , Ma Lu
Published: November 2019

Because of the time-varying characteristic and the large propagation delay in underwater acoustic (UWA) channel, adaptive resource allocation in UWA orthogonal frequency-division multiplexing access (OFDMA) system cannot be performed with the assumption of perfect channel state information (CSI) at the transmitter. Therefore, this paper focuses on the imperfect CSI and proposes a CSI updating method to reduce the impact of imperfect CSI on the performance of resource allocation under time-varying UWA channel. First, we analyze the channel estimation error of OFDM system under time-varying UWA channel and define the per-subcarrier channel temporal correlation (PSCTC). Finally, a CSI updating method based on the first-order Gauss-Markov model (GM-CSI) is proposed for optimizing CSI feedback in the UWA channel with large propagation delay, where the channel estimation error and PSCTC factor are considered as two influencing factors in this model. Simulation results show that the GM-CSI can effectively mitigate the effect of time on CSI effectiveness, and the resource allocation by using GM-CSI has higher effective throughput and lower BER than that of imperfect CSI.
Laboratory sound transmission loss testing for steel-framed partitions II: Stud spacing and steel material properties
Authors: Shafer Benjamin
Published: November 2019

There exists a large variation in laboratory sound transmission loss (STL) results and calculated STL-based ratings. Multiple research studies have found that this laboratory variation is consistent over multiple test series and assemblies, but more especially for steel-framed assembly designs. A previous research study presented at the Acoustical Society of America illustrated and quantified the STL difference for various steel mil thicknesses from 15-mil nonstructural to 97-mil structural. This research study is the second phase of this steel-framed STL research study and it investigates stud spacing and steel material- and shape-characteristics. The effect that each of these properties has on the STL of steel-framed partitions will be illustrated and discussed.
Weight loss is good, right?
Authors: Herreman Kevin , Taylor Corey
Published: November 2019

Since the introduction of lightweight drywall there has been concern related to the effect on the sound transmission loss of wall systems built using these products due to the reduced weight. Maintaining drywall strength while reducing weight 20 to 30 percent should improve installation productivity and worker safety on the build site. The process of reducing the weight is likely accomplished by entraining more air pockets into the slurry during manufacturing thus displacing a portion of the gypsum in the board. However, those familiar with the performance of wall systems know that the mass of the wall contributes to the overall sound transmission performance. A reduction in mass, of which the drywall is a significant portion, should reduce the transmission loss of the wall. This paper will highlight test data and modeling from the Owens Corning Acoustic Research Center demonstrating how these losses could be overcome.
Long-range target detection and classification system for environmental monitoring at marine hydrokinetic (MHK) sites
Authors: Acker Timothy W.
Published: November 2019

BioSonics and team members are developing a practical, unobtrusive, robust, and cost-effective long range (200–300 m) active acoustic monitoring system to automatically assess marine life behavior at potential or operational MHK sites. The proposed system includes a Perimeter Detector, that will automatically detect and geolocate targets at ranges of 200–300 m. The system will include a Directed Classifier that will be automatically aimed at a detected target to track the target’s position in three dimensions. This tracking capability allows automated measurement of the target’s behavior (i.e., speed, direction, and tortuosity), a strong indicator of target classification. Acoustic signatures from tracked targets will be analyzed to provide additional target classification information. Low band width, real-time reports will be automatically generated and transmitted to project operators, including target location, depth, behavior, and classification.
Perfluorocarbon nanodroplets versus microbubbles in cavitation-enhanced sonothrombolysis of retracted clots
Authors: Kim Jinwook , DeRuiter Ryan , Durham Philip , Tsuruta James , Goel Leela , Jiang Xiaoning , Xu Zhen , Dayton Paul A.
Published: November 2019

Microbubble-mediated sonothrombolysis has been effective in the treatment of acute clots (<24 h old), where microbubbles provide cavitation nuclei for cavitation-enhanced clot lysis. However, sonothrombolysis has shown very limited efficacy for the treatment of retreated clots (aged >3 days), as retracted clots have denser fibrin network which impedes the permeation of microbubbles. We hypothesize that the phase-change nanodroplets can permeate into retracted clots and improve sonothrombolysis. Phase-change nanodroplets are hundred-nanometer, liquid-filled contrast agents that convert to microbubbles upon excitation by thermal and acoustic energy. Due to their smaller size and higher stability than microbubbles, nanodroplets can provide longer circulation time and improved extravasation into less porous tissues. Here, we compared the thrombolytic effects of lipid shell-decafluorobutane microbubbles and similarly formulated nanodroplets in a flow model that contains a retracted bovine blood clot. Short burst ultrasound (1 MHz, 5.8 MPa, 0.5% duty cycle) was applied in three different therapy scenarios: ultrasound only, ultrasound with microbubbles, ultrasound with nanodroplets (n = 5). We observed internal clot erosion starting inside the clot samples by nanodroplet-mediated ultrasound, whereas the microbubble-mediated case resulted in only surface erosion. The nanodroplet-mediated treatment exhibited an averaged weight loss rate of 3.8 ± 0.1%/min, which was higher than the microbubble-mediated treatment (2.7 ± 0.15%/min).
Response of chemically crosslinked microbubble clusters in an ultrasound field
Authors: Chaudhary Sugandha , Hall Ronald , Juan-Sing Zachary , Sirsi Shashank
Published: November 2019

The purpose of this study is to introduce a new concept of chemically cross-linked microbubble clusters (CCMCs), demonstrate a facile means of their production, and describe how they can potentially be used in biomedical applications. Currently, ultrasound contrast agents (UCAs- also known as "microbubbles") are thought of as single gas bubbles stabilized by a biocompatible shell with sizes ranging from 1–10 μm. By tethering UCAs together into CCMCs, we propose that novel methods of ultrasound-mediated imaging and therapy can be developed through unique inter-bubble interactions in an ultrasound field. One of the major challenges in generating CCMCs is maintaining stability to Ostwald Ripening and coalescence. In this study, we demonstrate that chemically cross-linked microbubble clusters can produce small (<10 μm) quasi-stable complexes that slowly fuse into bubbles with individual gas cores. Furthermore, we demonstrate that this process can be driven with low-intensity ultrasound pulses, enabling a rapid fusion of clusters which could potentially be used to generate novel acoustics. The development of novel microbubble clusters here presents a simple yet robust process for generating novel UCAs with a design that could allow for more versatility in contrast-enhanced ultrasound (CEUS), molecular imaging, and drug delivery applications.