US Signals Research Articles

Data-driven Parameterizable Generative Adversarial Networks for Synthetic Data Augmentation of Guided Ultrasonic Wave Sensor Signals

Detecting and characterizing hidden damages in composite materials like Fibre-Metal Laminates (FML) remains a challenge. Guided Ultrasonic Waves (GUW) or X-ray imaging are commonly used to detect these damages, but their interpretation remains limited. Data-driven predictor models can detect damages in structures using GUW time-dependent signals, but the training data lacks variance, quality, and sufficient coverage of the hyper-parameter space. Synthetic data augmentation is often the only solution to create robust and generalized damage predictor models. Synthetic sensor data can be generated using model-based, model-assisted, or model-free methods. However, computed GUW signals show poor reality conformance due to too much constraints and simplifications. Recent developments in Generative Adversarial (Neural) Networks (GAN), commonly driven by a random generation process [1], include deterministic style vectors to generate specific signal data, determining constraints such as damage size, position, transducer positions, material and environmental properties. These new architectures aim to reduce the impact of environmental changes on data-driven damage predictor models by using parameterizable synthetic data generation. We will elaborate these new architectures and discuss the possibilities and challenges of using such GAN models for data generation of US signals in GUW-based SHM applications, as originally proposed in [2]. We will have a focus on low-quality real measuring data used for training and composite materials (e.g., FML) with hidden damages, and show some preliminary results. [1] Karras et al. "A style-based generator architecture for generative adversarial networks." Proceedings of the IEEE/CVF 2019 [2] Virupakshappa et al. "Using Generative Adversarial Networks to Generate Ultrasonic Signals." 2020 IEEE International Ultrasonics Symposium (IUS). IEEE, 2020

Systemic Change and Regional Orders: Asian Responses to a Gulf in Transition

ABSTRACT The Persian Gulf regional security complex is shaped by intense competition between regional states and, since the aftermath of Operation Desert Storm, US military preponderance. US security cooperation with the Gulf Cooperation Council member states has sustained a status quo that has allowed extra-regional countries to advance their interests without making significant contributions to regional stability. An examination of the presence of five Asian countries (China, India, Japan, Singapore and South Korea) in the Gulf suggests that, as the US signals intentions to reduce its security commitments to the region, the perception of hegemonic retreat will influence the regional policies adopted by these Asian countries. A further and related consideration is the ‘great-power competition’ narrative that is driving politics at the systemic level. The US-China bilateral relationship will have a significant impact on extra-regional powers’ approach to the Gulf.

Alliances, signals of support, and military effort

Do alliances allow states to share defense burdens and reduce military spending? Despite expectations that alliances should lead to decreased military spending, the empirical record offers mixed findings. We argue that not all alliances are reliable; thus, only allies that receive signals of reassurance will rely on the external security of allies and subsequently reduce their military spending. Compared to states that do not receive additional signals, these reassured allies will have greater confidence that an ally will come to their aid. As a result, third-party aggressors are deterred and the demand for military spending will decrease. We test this argument with an analysis of US signals of support, alliance commitments, and military spending. We find that American alliances without additional signals of support have a negligible effect on military spending. Yet, we observe that alliances are negatively associated with military spending when signals of support are present. Additional tests indicate that alliance commitments, coupled with strong US signals, are also associated with lower military spending in the rivals of US allies. Our results potentially help explain the mixed evidence in the arms-versus-allies and burden-sharing literatures and further demonstrate that extra-alliance signals play an important role in the practice of International Relations.

Surveillance and Cyber Operations

This chapter examines the extent to and the basis on which human rights treaties apply extraterritorially to state surveillance and cyber operations. Consider only the following examples: (1) The targeted surveillance of a specific individual outside a state’s territory – as, for instance, with the operations allegedly conducted by the authorities of Saudi Arabia against Saudi dissidents abroad, one of which ultimately led to the plot to assassinate the journalist Jamal Khashoggi, or against the CEO of Amazon, Jeff Bezos, apparently in a rather crude attempt to blackmail him. (2) Mass surveillance or bulk collection programmes, such as those run by the US and UK signals intelligence agencies, that syphon the content of electronic communications of millions of people outside the state’s territory, or the metadata about these communications, in order to create searchable datasets in which persons of particular interest, e.g. suspected terrorists, can then be found. (3) Cyber operations that exfiltrate data on Covid-19 vaccine research, potentially affecting the development of vaccines that could save many thousands of lives. (4) Cyber operations that destroy or manipulate such data. (5) Cyber operations against hospitals or against critical infrastructure, which directly endanger many lives. (6) Cyber operations against media outlets, which disrupt their activities and inhibit their freedom of expression. (7) Online misinformation operations for various purposes, for example to manipulate the outcome of an election or to destroy public trust in state institutions during the pandemic. Common to all of these scenarios is that through entirely digital means states can violate a host of different human rights, from the rights to privacy and the freedom of expression, to the right to life and the right to health, of persons located outside their territories.The chapter will first proceed to briefly outline how the traditional models of extraterritorial application, the spatial and the personal, would apply to surveillance and cyber operations, examining a few old cases in which the issue was raised, if never properly resolved. It will then look at recent developments that are particularly important in the surveillance and cyber context, even if some of them are not directly apposite: a judgment of the UK Investigatory Powers Tribunal, the advisory opinion of the Inter-American Court of Human Rights on the environment and human rights, the Human Rights Committee’s General Comment No. 36 on the right to life, and the judgment of the Federal Constitutional Court of Germany on the applicability of the German Basic Law to surveillance operations abroad. The chapter will then finally offer some concluding thoughts on the direction towards which the legal position is likely to evolve, and should evolve, regarding the applicability of human rights law to extraterritorial surveillance and cyber operations.

Optimization of microbubble side-scattering signal analysis for efficient cavitation dosimetry

In this study microbubble (MB) cavitation signal analysis was performed in both pressure and exposure duration domains of the acoustic field with the aim to optimize current cavitation dosimetry model by the application of signal processing. The discrete wavelet transform is applied to denoise the non-stationary US signals. For the development of universal cavitation dosimetry model and unification of cavitation dosimetry protocols, we have defined the optimal frequency range to be associated with the highest values of differential inertial cavitation dose (ICD). At our experimental conditions, it was evaluated to be 1.5–1.8 MHz, as ICD, quantified in this frequency band, is clearly distinguished from ICD of other frequency ranges. The explicitly high RMS values, obtained in 1.5–1.8 MHz frequency range, not only allow to track MB dynamics with the highest accuracy but also perform sonoporation optimization in exposure duration scale by RMS decrease to the background level. For sonoporation temporal dosimetry we have introduced “MB survival time” - the estimate, based on system output characteristics and directly related to sonoporation outcome. The rate of “MB survival time” has high correlation (R = 0.85, p < 0.05) with pre-existing index, ICD, and therefore, implies a possibility to be used for dosimetric applications for US-mediated drug and gene delivery. The rate of “MB survival time” is a time-dependent measure, which implies universal result reproducibility, as it is possible to relate absolute values of time-dependent indexes to particular in vitro/in vivo bioeffects.

Artificial taste avoidance memory induced by coactivation of NMDA and β-adrenergic receptors in the amygdala

The association between a taste and gastric malaise allows animals to avoid the ingestion of potentially toxic food. This association has been termed conditioned taste aversion (CTA) and relies on the activity of key brain structures such as the amygdala and the insular cortex.The establishment of this gustatory-avoidance memory is related to glutamatergic and noradrenergic activity within the amygdala during two crucial events: gastric malaise (unconditioned stimulus, US) and the post-acquisition spontaneous activity related to the association of both stimuli. To understand the functional implications of these neurochemical changes on avoidance memory formation, we assessed the effects of pharmacological stimulation of β-adrenergic and glutamatergic NMDA receptors through the administration of a mixture of L-homocysteic acid and isoproterenol into the amygdala after saccharin exposure on specific times to emulate the US and post-acquisition local signals that would be occurring naturally under CTA training. Our results show that activation of NMDA and β-adrenergic receptors generated a long-term avoidance response to saccharin, like a naturally induced rejection with LiCl. Moreover, the behavioral outcome was accompanied by changes in glutamate, norepinephrine and dopamine levels within the insular cortex, analogous to those displayed during memory retrieval of taste aversion memory. Therefore, we suggest that taste avoidance memory can be induced artificially through the emulation of specific amygdalar neurochemical signals, promoting changes in the amygdala-insular cortex circuit enabling memory establishment.

Black Movement Formation: Race, Class, Gender, Capitalist Globalization, and White Nationalism Today

Abstract The arc of the Black Freedom struggle in the US signals the early twenty-first century as a period of high contention, resistance, and possibility. It is also rife with contradictions. The radicalism which informs Black liberation struggle today is complex, disparate, and signals the need to rearticulate social transformation given Black resistance in the era of new nationalism. The struggle is theorized in this analysis in the context of racial capitalism, changing organizational forms, state violence, and nonlinear, disparate contentions around the police. Understanding white supremacist nationalism in the US today is core to this discussion. Ultimately, Black lives in this new movement moment struggle for a broad and notable shift, which places gender, gender nonconforming, and sexuality at the center of the resistance and our understanding.

Modeling wave propagation through the skull for ultrasonic transcranial Doppler

One problem associated with transcranial Doppler ultrasound (TCD) is the relatively low energy penetrating inside the brain through the skull, seriously limiting the image quality. This may be due to the impedance mismatch at the bone interface and to the bone frequency dependent attenuation. The objective of this paper is to model ultrasonic wave propagation through the skull. To do so, an analytical model was developed based on the estimation of the transmission coefficients inside the brain, leading to frequency dependent overall transmission coefficient for a given skin and bone thickness. Moreover, a finite element model was developed taking into account absorption phenomena. Both methods were validated experimentally by comparing the numerical and analytical results with results obtained from a phantom mimicking the skull having an attenuation coefficient equal to 30 dB/cm at 2.25 MHz and a thickness of 4.4 mm. A 2 mm layer of water mimicked the skin. The difference between the maximum amplitude of normalized received US signals obtained analytically and experimentally was 1%. The average relative difference between them was 0.3%. Thus, a working model is designed which can predict the energy inside the brain. Furthermore, the results show that impedance mismatch plays a major role in transmission loss rather than frequency dependent attenuation

SAT0053 Persistence of Subclinical Joint Activity in Rheumatoid Arthritis Joints

BackgroundUltrasound (US) assessment was shown to be a sensitive tool for the evaluation of joint activity in patients with rheumatoid arthritis (RA). Synovial effusion and synovial hypertrophy can be evaluated...

SAT0223 The Diagnostic Utility of Fluorescence Optical Imaging in Evaluating Synovitis of the Hands and Wrists

BackgroundThe timely identification of synovial inflammation is critical for early diagnosis & treatment of rheumatoid arthritis & other inflammatory arthritides. Fluorescence Optical Imaging (FOI, “Rheumascan”), a novel imaging modality, uses...

Deterrence in the Gulf War

A recently published collection of captured Iraqi records offers an opportunity to better understand Saddam Hussein's perception of US and Israeli deterrence signals, affording innovative insights into the reasons behind Iraq's restraint from using weapons of mass destruction against Israeli targets during the 1991 Gulf War. This article tests a wide range of suggested hypotheses, and suggests that US and Israeli deterrence played only a minimal role in dissuading Iraqi use of WMD. The article concludes with some thoughts on the practical implications, particularly on the effectiveness of a “no-first-use” nuclear policy.

Supporter of stability or agent of agitation? The effect of US foreign policy on coups in Latin America, 1960—99

This article takes a two-step approach to improving our understanding of how US foreign policy signals affect the likelihood of coups in Latin America. First, a large body of qualitative literature has developed a ‘conventional wisdom’ on this subject, suggesting that pressure from the USA plays a key role in stabilizing favored leaders and destabilizing unfavored leaders. Meanwhile, quantitative scholarship analyzing coups focuses almost exclusively on intrastate factors. The first step brings these two bodies of work together by providing quantitative evidence that hostile US signals increase the likelihood of coups, while supportive signals have a stabilizing effect. The second step moves beyond the conventional wisdom by (1) reconsidering theoretical assumptions within the conventional argument and (2) identifying anomalies within the preliminary empirical analyses. These efforts reveal several factors that are likely to impact how coup plotters respond to US signals. Among these factors, empirical analyses indicate that US signals are particularly important when economic dependence on the USA increases, during the middle of a US president’s term in office, when they have moderate levels of consistency, and when they specifically mention the military. Overall, the first stage of this article provides a robust confirmation of the conventional wisdom, while the second stage moves the literature down a path that is largely unexplored by previous work.

A probabilistic framework for freehand 3D ultrasound reconstruction applied to catheter ablation guidance in the left atrium

The catheter ablation procedure is a minimally invasive surgery used to treat atrial fibrillation. Difficulty visualizing the catheter inside the left atrium anatomy has led to lengthy procedure times and limited success rates. In this paper, we present a set of algorithms for reconstructing 3D ultrasound data of the left atrium in real-time, with an emphasis on automatic tissue classification for improved clarity surrounding regions of interest. Using an intracardiac echo (ICE) ultrasound catheter, we collect 2D-ICE images of a left atrium phantom from multiple configurations and iteratively compound the acquired data into a 3D-ICE volume. We introduce two new methods for compounding overlapping US data-occupancy-likelihood and response-grid compounding-which automatically classify voxels as "occupied" or "clear," and mitigate reconstruction artifacts caused by signal dropout. Finally, we use the results of an ICE-to-CT registration algorithm to devise a response-likelihood weighting scheme, which assigns weights to US signals based on the likelihood that they correspond to tissue-reflections. Our algorithms successfully reconstruct a 3D-ICE volume of the left atrium with voxels classified as "occupied" or "clear," even within difficult-to-image regions like the pulmonary vein openings. We are robust to dropout artifact that plagues a subset of the 2D-ICE images, and our weighting scheme assists in filtering out spurious data attributed to ghost-signals from multi-path reflections. By automatically classifying tissue, our algorithm precludes the need for thresholding, a process that is difficult to automate without subjective input. Our hope is to use this result towards developing 3D ultrasound segmentation algorithms in the future.

In the right place at the right time: US signals intelligence relations with Scandinavia,1945–1960

This paper demonstrates that US–Scandinavian intelligence relations in general, and Signals Intelligence (Sigint) relations in particular, during the period 1945 through 1960 were more extensive and complicated than had previously been believed. Bilateral US intelligence liaison relations with nominally neutral Sweden were of particular importance in the early years of the Cold War given its geographic location adjacent to the northwestern portion of the USSR. Moreover, the importance of Sigint received from the three principal Scandinavian countries covered by this paper (Norway, Denmark, and Sweden) proved to be quite important to the US intelligence community during the early years of the Cold War, when the US Sigint infrastructure was relatively weak and stretched thin by commitments in Asia and elsewhere. This paper covers the quantity, quality, and types of intelligence information provided to the US by each of the Scandinavian nations, demonstrating that the nature of US intelligence relations with these countries changed substantially as time went by.

Molecular signals into the insular cortex and amygdala during aversive gustatory memory formation.

In this paper, we will provide evidence of the putative molecular signals and biochemical events that mediate the formation of long-lasting gustatory memory trace. When an animal drinks a novel taste (the conditioned stimulus; CS) and it is later associated with malaise (unconditioned stimulus; US), the animal will reject it in the next presentation, developing a long-lasting taste aversion, i.e., the taste cue becomes an aversive signal, and this is referred to as conditioning taste aversion. Different evidence indicates that the novel stimulus (taste) induces a rapid and strong cortical acetylcholine activity that decreases when the stimulus becomes familiar after several presentations. Cholinergic activation via muscarinic receptors initiates a series of intracellular events leading to plastic changes that could be related to short- and/or long-term memory gustatory trace. Such plastic changes facilitate the incoming US signals carried out by, in part, the glutamate release induced by the US. Altogether, these events could produce the cellular changes related to the switch from safe to aversive taste memory trace. A proposed working model to explain the biochemical sequence of signals during taste memory formation will be discussed.

Ultrasonic monitoring of setting and hardening of cement mortar—A new device

An almost fully automated device has been developed which is suitable for the continuous monitoring of setting and hardening of cement paste and fresh mortar. Some special features are presented and discussed with respect to the reliable contact of ultrasound transmitter and recorder. The analysis of the US signals employs a modified Hinkley criterion.