Persistent Echo Research Articles

Historical Criminology as a Methodological Approach to the Study of Crime Problems

The principle of historicism as a basic methodological requirement of dialectics has not received an independent theoretical interpretation in domestic criminology. Historical criminology can be considered its emanation in modern English-language criminology, which has established itself in recent decades as an authoritative methodological approach to the study of crime and related problems. Based on several authoritative publications, primarily the monograph “Historical Criminology” by D. Churchill, G. Yeomans and I. Channing, it seems possible to describe the main characteristics of this approach. In accordance with it, historical criminology can be thought of not as a subject area of criminological research and not as a criminological school, but as a set of requirements for the study of all components of the subject of criminology. They are based on two basic theoretical concepts: “historical time” and “historical thinking”. The main characteristics of historical time — change, eventfulness, fluidity, tension and embodiment — set the appropriate rules for conducting criminological research, including: the study of criminologically significant trends in the long term; attention to specific criminal and social events not only as a point that changes trends, but also as an independent temporal unit; using the complexity principle to explain crime. In the process of implementing these requirements, it is necessary to take into account that the present studied by criminologists is a multi-layered social phenomenon that combines not only recorded events and facts of today, but also persistent echoes of the past and anticipations of the future. It is the recognition of the unity of the past, present and future that serves as the principle of adequate historical thinking in criminology.

Introduction

Labor historiography in the contexts of modern racial slavery and emancipation has long placed changes in the status of work at the core of the very meaning of captivity and freedom, their epochal watersheds, and institutionalized or unintended overlaps. Reviewing, in this journal's pages, recent scholarship on the relations between slavery and capitalism, James Oakes summarized that the “crucial differences between the political economy of slave and free labor … ultimately led to a catastrophic Civil War and one of the most violent emancipations in the hemisphere.” The literature Oakes critically discussed exemplifies the growing academic interest in the multifarious functionality of coerced production for the development of global capitalism. The resulting picture reaches much further than mere questions of economic causality, or whether chattel slavery did kick-start the profitability of capitalism, rather than the other way around. At stake are explanations of how racial captivity—which liberal economic, political, and moral discourse deems an anachronism—shapes the very productive, financial, social, institutional, and philosophical foundations of the global present. Historic and contemporary activist resistance to recurring and ubiquitous waves of antiblack violence, as well as the increasingly self-confident affirmation of white supremacy across Western states and civil societies has rendered such dilemmas in starker terms, asking whether persistent echoes of racial slavery are symptoms that the system is “built this way” rather than being just “broken.”

Large networks of rational agents form persistent echo chambers

Echo chambers (ECs) are enclosed epistemic circles where like-minded people communicate and reinforce pre-existing beliefs. It remains unclear if cognitive errors are necessarily required for ECs to emerge, and then how ECs are able to persist in networks with available contrary information. We show that ECs can theoretically emerge amongst error-free Bayesian agents, and that larger networks encourage rather than ameliorate EC growth. This suggests that the network structure itself contributes to echo chamber formation. While cognitive and social biases might exacerbate EC emergence, they are not necessary conditions. In line with this, we test stylized interventions to reduce EC formation, finding that system-wide truthful ‘educational’ broadcasts ameliorate the effect, but do not remove it entirely. Such interventions are shown to be more effective on agents newer to the network. Critically, this work serves as a formal argument for the responsibility of system architects in mitigating EC formation and retention.

Can the elongated hindwing tails of fluttering moths serve as false sonar targets to divert bat attacks?

It has long been postulated that the elongated hindwing tails of many saturniid moths have evolved to create false sonar targets to divert the attack of echolocation-guided bat predators. However, rigorous echo-acoustic evidence to support this hypothesis has been lacking. In this study, fluttering luna moths (Actias luna), a species with elongated hindwing tails, were ensonified with frequency modulated chirp signals from all angles of orientation and across the wingbeat cycle. High-speed stereo videography was combined with pulse compression sonar processing to characterize the echo information available to foraging bats. Contrary to previous suggestions, the results show that the tail echoes are weak and do not dominate the sonar returns, compared to the large, planar wings and the moth body. However, the distinctive twisted morphology of the tails create persistent echoes across all angles of orientation, which may induce erroneous sonar target localization and disrupt accurate tracking by echolocating bats. These findings thus suggest a refinement of the false target hypothesis to emphasize sonar localization errors induced by the twisted tails, and highlight the importance of physics-based approaches to study the sensory information involved in the evolutionary arms race between moths and their bat predators.

Bayesian Echo Classification for Australian Single-Polarization Weather Radar with Application to Assimilation of Radial Velocity Observations

AbstractThe Australian Bureau of Meteorology’s operational weather radar network comprises a heterogeneous radar collection covering diverse geography and climate. A naïve Bayes classifier has been developed to identify a range of common echo types observed with these radars. The success of the classifier has been evaluated against its training dataset and by routine monitoring. The training data indicate that more than 90% of precipitation may be identified correctly. The echo types most difficult to distinguish from rainfall are smoke, chaff, and anomalous propagation ground and sea clutter. Their impact depends on their climatological frequency. Small quantities of frequently misclassified persistent echo (like permanent ground clutter or insects) can also cause quality control issues. The Bayes classifier is demonstrated to perform better than a simple threshold method, particularly for reducing misclassification of clutter as precipitation. However, the result depends on finding a balance between excluding precipitation and including erroneous echo. Unlike many single-polarization classifiers that are only intended to extract precipitation echo, the Bayes classifier also discriminates types of nonprecipitation echo. Therefore, the classifier provides the means to utilize clear air echo for applications like data assimilation, and the class information will permit separate data handling of different echo types.

Fractured J-Wire Stylet Presenting as an Intrauterine Foreign Body

A 32-year old gravida 0 was noted to have a persistent echo dense reflection on her transvaginal ultrasound after undergoing saline infused sonohysterography during IVF work-up. Diagnostic hysteroscopy discovered a 1-cm remnant of a J-wire embryo transfer catheter embedded in a false passage created just below the apparently normal uterine cavity.

Mitral mechanical heart valves: in vitro studies of their closure, vortex and microbubble formation with possible medical implications.

The goal of the present work was to create the closest possible in vitro fluid dynamic environment in which prosthetic mitral valves in the patients' hearts function, in order to demonstrate whether microbubbles are generated, and if yes, under what conditions and at which stage of the cardiac cycle. Microbubbles were observed in the blood of patients with mitral mechanical heart valves (MHV) by means of echocardiography. The phenomenon, often referred to as high-intensity transient signals (HITS), appears as bright, intense, high-velocity and persistent echoes detected by Doppler echocardiography at the instant of valve closure. The question is no longer whether microbubbles are being formed in patients with MHV. as an inherent aspect of their design, but rather how they evolve and when. The answer to this question was the objective of the present paper. Hemodynamic conditions in which microbubbles were observed in patients with mitral MHV were simulated in our laboratory. We were able to describe the bubble formation process, as one consisting of nucleation and microbubble growth. While mild growth of nuclei is governed by diffusion, extensive growth of microbubbles is controlled by pressure drop during deceleration of the leaflets on the housing on the atrial side of the mitral MHV. The present study has shown that bubbles form in a fluid at the instant of closure of mechanical valves. The formation of vortices after valve closure, although clinically not yet observed, was also demonstrated in the present in vitro studies. We believe that impact of such vortices on the endothelial layer of the left atrial wall may have clinical significance. These two phenomena were not observed in bioprosthetic valves. As demonstrated, there exist two distinct phenomena characteristic of mechanical heart valves, which take place during valve closure, namely, that of vortex formation and that of microbubble growth. Both phenomena may have far reaching clinical implications.

A physical model describing the mechanism for formation of gas microbubbles in patients with mitral mechanical heart valves.

This study was aimed at developing a physical model, supported by experimental observations, to describe the formation and growth of microbubbles seen in patients with mitral mechanical heart valves (MHV). This phenomenon, often referred to as high intensity transient signals (HITS), appears as bright, intense, high-velocity and persistent echoes detected by Doppler ultrasonography at the instant of closure. The long-term clinical implications of HITS has yet to be determined. However, there are reports of a certain degree of neurological disorder in patients with mitral MHV. The numerical analysis has shown the existence of a twofold process (1) nucleation and (2) microbubble growth as a result of cavitation. While mild growth of nuclei is governed by diffusion, explosive growth of microbubbles is controlled by pressure drop on the atrial side of mitral MHV. It was demonstrated that there exist limits on both microbubble size and regurgitant velocity, above which microbubbles grow explosively, and below which growth is almost nonexistent. Therefore, prevention of excessive pressure drops induced by high closing velocities related to the dynamics of closure of mitral MHV may offer design changes in the future generations of mechanical valves.

Typical sonographic appearance of duodenal diverticulum.

During routine transabdominal ultrasonography of the hepatobiliary tract an occasional persistent bright linear or concave echo was detected that disrupted the normal images we routinely obtained of the pancreatic head. We began to suspect this echo to be the sonographic representation of a duodenal diverticulum. To confirm our suspicions we performed a prospective study. Over a 20 month period, 30 consecutive patients with a sonographically suspected duodenal diverticulum were followed up with either an upper gastrointestinal series, gastroscopy, or, depending on the patient's clinical symptoms, endoscopic retrograde cholangiopancreaticography. One patient was examined with simultaneous fluoroscopy and ultrasonography. The results of these examinations were then compared to the respective ultrasonograms by a qualified radiologist and sonographer. The suspected duodenal diverticulum, detected primarily with ultrasonography, was confirmed with follow-up examinations in all 30 patients. The persistent echo detected sonographically had the same anatomic position as the diverticulum seen during fluoroscopy. We concluded that duodenal diverticulum located near the pancreatic head has a rather typical sonographic appearance.

Progressive spastic paraplegia due to persistent echo virus encephalomyelitis in a child with X-linked hypogammaglobulinaemia.

Progressive spastic paraplegia due to persistent echo virus encephalomyelitis in a child with X-linked hypogammaglobulinaemia.

Interpretation of Radio Echoes from Polar Auroras

In a recent communication, Lovell, Clegg and Ellyett1 describe radio echoes from polar auroras. A remarkable feature was a persistent echo on 6·5 metres wave-length (46 Mc./s.) with an amplitude three times the noise-level and a distance of 480 km. The echo was not observed on 4 metres wave-length; it finally disappeared when striations occurred in the aurora.