Mutual Information-Based Non-Local Total Variation Denoiser for Low-Dose Cone-Beam Computed Tomography

Conventional non-local total variation (NLTV) approaches use the weight of a non-local means (NLM) filter, which degrades performance in low-dose cone-beam computed tomography (CBCT) images generated with a low milliampere-seconds (mAs) parameter value because a local patch used to determine the pixel weights comprises noisy-damaged pixels that reduce the similarity between corresponding patches. In this paper, we propose a novel type of NLTV based on a combination of mutual information (MI): MI-NLTV. It is based on a statistical measure for a similarity calculation between the corresponding bins of non-local patches vs. a reference patch. The weight is determined in terms of a statistical measure comprising the MI value between corresponding non-local patches and the reference-patch entropy. The MI-NLTV denoising process is applied to CBCT images generated by the analytical reconstruction algorithm using a ray-driven backprojector (RDB). The MI-NLTV objective function is minimized based on the steepest gradient descent optimization to augment the difference between a real structure and noise, cleaning noisy pixels without significant loss of the fine structure and details that remain in the reconstructed images. The proposed method was evaluated using patient data and actual phantom measurement data acquired with lower mAs. The results show that integrating the RDB further enhances the MI-NLTV denoising-based analytical reconstruction algorithm to achieve a higher CBCT image quality when compared with those generated by NLTV denoising-based approach, with an average of 15.97% higher contrast-to-noise ratio, 2.67% lower root mean square error, 0.12% lower spatial non-uniformity, 1.14% higher correlation, and an average of 18.11% higher detectability index. These quantitative results indicate that the incorporation of MI makes the NLTV more stable and robust than the conventional NLM filter for low-dose CBCT imaging. In addition, achieving clinically acceptable CBCT image quality despite low-mAs projection acquisition can reduce the burden on common online CBCT imaging, improving patient safety throughout the course of radiotherapy.

Negotiating attachments to plastic

Drawing on ethnographic research conducted in the office and warehouse of an organic wholesaler in Germany, this article presents a trans-sequential analysis of an innovation that aimed to reduce the use of plastic wrap. During the analytical reconstruction of the innovation process, the substitution of plastic wrap turned out to be a precarious process of negotiating attachments to plastic. Against this background, innovation is not simply about the implementation and substitution of technology by human actors, but about negotiating attachments that humans have towards objects within socio-technical assemblages. Drawing on actor-network theory and the sociology of attachment, the article highlights the dynamic interplay between persistence and problematization of plastic wrap, which characterizes the innovation process. This interplay is seen along several steps during the innovation process: from (1) the problematization of plastic dependency to (2) the mobilization of alternatives, to (3) resistance against measures to be implemented and (4) the enforcement of reusable strings as technological substitution and (5) to conclusive retrospection on the innovation process. The trans-sequential analysis shows that ‘getting rid of something’ might be an imperfect approach to dealing with unsustainable object relations. Instead, withdrawing is a double-sided process of detaching and attaching, removing constraints and building new ones.

Cognitive linguistic aspects of the most important functions of language

A figurative fantasy function presented in the article is meant to provide a link between language and imagination by sparing consciousness copresence. The article reflects the scholars’ controversy concerning the determination of a key function of language. A communicative function of language is replaced by an adaptive one with ever increasing frequency, and language capacity is considered as a biological property of a living organism. The adaptive function of language implies the modification of the behavior of communicants such that the reality provides them with the best conditions for interaction. A communicant modifies their speech behavior, enhancing their general adaptational capacity in the surrounding. Thus, linguistic signs perform the function of orienting toward a more effective type of interpersonal interaction. The method of analytical reconstruction made it possible to obtain a systematic understanding of verbal and cogitative processes and conceptualization of semantic experience through the prism of understanding the functions of language.

Two-loop five-parton leading-colour finite remainders in the spinor-helicity formalism

We present all two-loop five-parton leading-colour finite remainders in the spinor-helicity formalism by analysing numerical evaluations of their known expressions in terms of Mandelstam invariants. Recasting them in terms of spinor-helicity variables allows us to obtain expressions which are more compact, faster to evaluate, numerically more stable and manifestly free from poles of higher order than necessary. At the same time, due to the better scaling of our reconstruction strategy with the complexity of the input, we required one order of magnitude fewer numerical samples to complete the analytical reconstruction than were needed by the authors of ref. [1], albeit using higher numerical working precision. This places our reconstruction technique as an alternative to the finite-field single-numerator reconstruction for future applications.

THE IMPACT OF COVID-19 ON CHILDREN’S RIGHTS

In emergency situations, the people most affected are often those who are already vulnerable, and this certainly includes children. The “new normal” we are living in to defend ourselves against this tiny yet dangerous enemy has serious repercussions on children’s lives. This becomes even more evident if we think of those children who are doubly vulnerable – they are even more fragile because they live in conditions of particular hardship when they live outside their family, have a disability, or live in poverty. Since the beginning of the Covid-19 pandemic, we have witnessed the proliferation of numerous initiatives by various national and international children’s rights institutions, which have called for urgent measures to protect children’s rights. At this precise moment, the concept of the child’s best interests is also reinterpreted as a result of a reasonable compression of certain children’s rights and the prevalence of others. The present paper will attempt an analytical reconstruction of children’s fundamental rights by analyzing how these rights have changed during the pandemic. In fact, it is necessary to know if and/or how much have the rights of minors changed as a result of the emergency. The second part of the paper is dedicated to the question of which children’s rights will be most compromised or changed in the post-Covid-19 era. In reflecting on the inevitable consequences that the pandemic will leave on the delicate balance of the development of children’s rights, the author will offer some proposals on how to contain the encountered difficulties.

Analytical reconstruction formula with efficient implementation for a modality of Compton scattering tomography with translational geometry

<p style='text-indent:20px;'>In this paper, we address an alternative formulation for the exact inverse formula of the Radon transform on circle arcs arising in a modality of Compton Scattering Tomography in translational geometry proposed by Webber and Miller (Inverse Problems (36)2, 025007, 2020). The original study proposes a first method of reconstruction, using the theory of Volterra integral equations. The numerical realization of such a type of inverse formula may exhibit some difficulties, mainly due to stability issues. Here, we provide a suitable formulation for exact inversion that can be straightforwardly implemented in the Fourier domain. Simulations are carried out to illustrate the efficiency of the proposed reconstruction algorithm.</p>

Sociology of Migration in Latin America

Since the middle of the twentieth century, the study of migration in Latin America has evolved in response to the themes and debates dominating the social sciences at specific points in time. This chapter provides an overview of the field of sociology of migration in Latin America. It covers some of the principal debates within and contributions from the sociological research carried out by social scientists from various disciplines and by experts working in national academic institutions as well as a variety of international organizations. In short, this introduction presents an analytical reconstruction of the development of and the differentiation achieved in the specialization of the studies of migratory processes from various sociological approaches. This overview demonstrates that the field of migration studies is broad, heterogeneous, and, above all, inextricably multidisciplinary.