Meaningful Boundary Research Articles

Numerical simulation of endovascular treatment options for cerebral aneurysms

AbstractPredicting the long‐term success of endovascular interventions in the clinical management of cerebral aneurysms requires detailed insight into the patient‐specific physiological conditions. In this work, we not only propose numerical representations of endovascular medical devices such as coils, flow diverters or Woven EndoBridge but also outline numerical models for the prediction of blood flow patterns in the aneurysm cavity right after a surgical intervention. Detailed knowledge about the postsurgical state then lays the basis to assess the chances of a stable occlusion of the aneurysm required for a long‐term treatment success. To this end, we propose mathematical and mechanical models of endovascular medical devices made out of thin metal wires. These can then be used for fully resolved flow simulations of the postsurgical blood flow, which in this work will be performed by means of a Lattice Boltzmann method applied to the incompressible Navier–Stokes equations and patient‐specific geometries. To probe the suitability of homogenized models, we also investigate poro‐elastic models to represent such medical devices. In particular, we examine the validity of this modeling approach for flow diverter placement across the opening of the aneurysm cavity. For both approaches, physiologically meaningful boundary conditions are provided from reduced‐order models of the vascular system. The present study demonstrates our capabilities to predict the postsurgical state and lays a solid foundation to tackle the prediction of thrombus formation and, thus, the aneurysm occlusion in a next step.

Quantitative phase-field model to simulate low carbon steel aqueous corrosion phenomena

A quantitative phase-field model has been developed to simulate aqueous corrosion on low carbon steel under chloride-based electrolytes at different pHs. All relevant transport phenomena are included through physically interpretable variables. In particular, both diffusion and migration charge transport are modelled. Separated electrical potentials for the electrolyte and the metal are considered, and physically meaningful boundary conditions are provided. Using this model, different polarization conditions can be predicted and many parameters not observable/challenging during experiments, can be obtained. Finally, since the proposed model includes different time scales, a segregated numerical integration algorithm is proposed to speed up simulations.

Probing the quantitative–qualitative divide in probabilistic reasoning

This paper explores the space of (propositional) probabilistic logical languages, ranging from a purely ‘qualitative’ comparative language to a highly ‘quantitative’ language involving arbitrary polynomials over probability terms. While talk of qualitative vs. quantitative may be suggestive, we identify a robust and meaningful boundary in the space by distinguishing systems that encode (at most) additive reasoning from those that encode additive and multiplicative reasoning. The latter includes not only languages with explicit multiplication but also languages expressing notions of dependence and conditionality. We show that the distinction tracks a divide in computational complexity: additive systems remain complete for NP, while multiplicative systems are robustly complete for ∃R. We also address axiomatic questions, offering several new completeness results as well as a proof of non-finite-axiomatizability for comparative probability. Repercussions of our results for conceptual and empirical questions are addressed, and open problems are discussed.

Sound categorization by crocodilians

Rapidly sorting the information contained in a stream of stimuli is a major challenge for animals. One cognitive mechanism for achieving this goal is categorization, where the receiving individual considers a continuous variation of a stimulus as belonging to discrete categories. Using playback experiments in a naturalistic setup, here we show that crocodiles confronted with an acoustic continuum ranging from a frog call to a crocodile call classify each acoustic variant into one of these two categories, establishing a meaningful boundary where no acoustic boundary exists. With GO/NO-GO experiments, we then observe that this boundary is defined along the continuum following learning. We further demonstrate that crocodilians rely on the spectral envelope of sounds to categorize stimuli. This study suggests that sound categorization in crocodilians is a pre-wired faculty allowing rapid decision-making and highlights the learning-dependent plasticity involved in defining the boundary between sound categories.

Out of bounds? The boundary specification problem for centrality in psychological networks.

The analysis of psychological networks has become common in multiple subfields including clinical, social, and personality psychology, where the focus is often on identifying highly central nodes that represent symptoms, beliefs, or traits. However, the boundaries of these networks are often ambiguous and relevant nodes are often missing from the network. In this article, we use a series of simulations to show that even under typical conditions of missingness, the centrality of nodes in an empirical psychological network are poorly correlated or uncorrelated with their centrality in a hypothetical "true" psychological network, and thus are invalid. We illustrate the implications of this lack of validity using an empirical example drawn from a recent study of political belief system networks, demonstrating that the original study would have drawn incorrect conclusions about American's most central political beliefs. We conclude by recommending that centrality measures should be computed and interpreted only in psychological networks that include (nearly) all the nodes inside a theoretically meaningful boundary. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

“What’s it really worth?” A meta-analysis of customer-perceived relationship value in B2B markets

PurposeResearch on customer-perceived relationship value (CPRV) in business-to-business (B2B) markets has flourished over the past two decades. This paper aims to meta-analytically take stock of this research stream. It creates a comprehensive overview of the theoretical bases of CPRV research and establishes CPRV in its nomological network. The latter includes relationship benefits and sacrifices, offer quality, trust, switching costs, satisfaction, commitment, loyalty and salience of alternatives. Meaningful boundary conditions of the links to and from CPRV emerge from this research.Design/methodology/approachTo locate suitable primary studies for inclusion in this meta-analysis, a comprehensive literature search was performed. Selection criteria ensured that only suitable B2B samples were included. Meta-analytical random and mixed-effects models were performed on a sample of k = 83 independent data sets from 94 primary publications, with a total n = 22,305.FindingsAll constructs are strongly related to CPRV in the expected direction, except for switching costs and salience of alternatives with a moderate relationship and relationship sacrifices with a non-significant mean association. Firm type (manufacturing, non-manufacturing), key informant role (purchaser, non-purchaser), supplier offering type (goods, services) and measurement approach (reflective, formative) function as boundary conditions in the moderation analysis.Originality/valueThis study is one of the very rare meta-analyses that draws exclusively from B2B marketing primary studies. It summarizes and solidifies the current theoretical and empirical knowledge on CPRV in business markets. The novel inclusion of boundary conditions offers additional insight over primary studies and makes for interesting new research directions.

Novel Approach to Well Tests Data Processing

A new bounded well function is suggested for processing well tests data. A solution of the basic partial differential equation with physically meaningful initial and boundary conditions is given using its Laplace transform simultaneously with the proof of its unicity. A model for distance-dependence of drawdown is suggested. Results reveal the link between unsteady and steady state of pumping. Related computational problems are discussed. Examples of processing actual data using these results are presented. They illustrate high accuracy of results and a considerable increase of information obtainable from a well test.

Challenges in Modeling Hemodynamics in Cerebral Aneurysms Related to Arteriovenous Malformations.

The significantly higher incidence of aneurysms in patients with arteriovenous malformations (AVMs) suggests a strong hemodynamic relationship between these lesions. The presence of an AVM alters hemodynamics in proximal vessels by drastically changing the distal resistance, thus affecting intra-aneurysmal flow. This study discusses the challenges associated with patient-specific modeling of aneurysms in the presence of AVMs. We explore how the presence of a generic distal AVM affects upstream aneurysms by examining the relationship between distal resistance and aneurysmal wall shear stress using physiologically realistic estimates for the influence of the AVM on hemodynamics. Using image-based computational models of aneurysms and surrounding vasculature, aneurysmal wall-shear stress is calculated for a range of distal resistances corresponding to the presence of AVMs of various sizes and compared with a control case representing the absence of an AVM. In the patient cases considered, the alteration in aneurysmal wall shear stress due to the presence of an AVM is considerable, as much as 19 times the base case wall shear stress. Furthermore, the relationship between aneurysmal wall shear stress and distal resistance is shown to be highly geometry-dependent and nonlinear. In most cases, the range of physiologically realistic possibilities for AVM-related distal resistance are so large that patient-specific flow measurements are necessary for meaningful predictions of wall shear stress. The presented work offers insight on the impact of distal AVMs on aneurysmal wall shear stress using physiologically realistic computational models. Patient-specific modeling of hemodynamics in aneurysms and associated AVMs has great potential for understanding lesion pathogenesis, surgical planning, and assessing the effect of treatment of one lesion relative to another. However, we show that modeling approaches cannot usually meaningfully quantify the impact of AVMs if based solely on imaging data from CT and X-ray angiography, currently used in clinical practice. Based on recent studies, it appears that 4D flow MRI is one promising approach to obtaining meaningful patient-specific flow boundary conditions that improve modeling fidelity.

Boundary talk in Life (dis)Orientation: Collaborative conversations across Higher Education Institutions

Life Orientation (LO) as a compulsory subject in the South African school curriculum (Grades 7–12) aims to develop the learner’s self-in-society. This implies a holistic approach that includes the personal, social and physical development of the learner. In most Higher Education Institutions (HEIs), LO is not offered as a specialisation that includes these three broad aspects of development. In many cases, the emphasis rests with personal development, focusing, in particular, on modules taken in Psychology. Physical Education, if it is included in any LO programme, usually falls within the ambit of Sports/Human Movement Science programmes. The social development aspect is, by and large, omitted and Human Rights Education, including Religion Education and Citizenship Education, is neglected. Alternatively, pre-service teachers are required to select from a smorgasbord of modules and they often graduate without having included all three broad aspects of this specialisation. This article speaks to the importance of collaborative relationships across HEIs with a view to meaningful boundary talk that can be transformative in nature and provide the platform for research ventures. This collaboration that commenced as a community of two in conversation, led to a community of many in conversation, in the form of a national colloquium in 2020 that focused on LO in the HEI space. This article presents the themes emerging from this colloquium and recommends that transdisciplinary knowledge can lead to transdisciplinary education that serves the mandate of the LO specialisation in HEIs, namely, to prepare pre-service LO teachers.

Meaningful boundaries create boundary conditions for control.

Recent research demonstrated that control states learned via experience in inducer locations were retrieved in novel, unbiased (i.e., diagnostic) locations positioned nearby. Such transfer has been observed even in the presence of a visual boundary (a line) separating inducer and diagnostic locations. One aim of the present study was to assess whether a meaningful boundary might disrupt retrieval of control states in diagnostic locations. Supporting this possibility, in Experiment 1 learned control states did not transfer from inducer locations superimposed on a university's quad to diagnostic locations superimposed on buildings outside the quad. Similarly, in Experiment 2 transfer was not observed for diagnostic locations positioned on a track outside of the field where inducer locations were positioned; however, transfer was also not observed for diagnostic locations on the field (inside the boundary). The latter finding helped motivate Experiments 3a and 3b, which tackled the second aim by examining whether a meaningful boundary might attenuate learning of control states for inducer locations within the boundary. Consistent with this hypothesis, a CSPC effect was observed only when a meaningful boundary was not present. Taken together, the findings provide evidence that meaningful boundaries influence how conflict experiences are organized during a task thereby impacting learning and transfer of context-specific control states.

When it really counts: Investigating the relation between trait mindfulness and actual prosocial behavior

Meta-analytical findings suggested a positive link between trait mindfulness and prosociality. However, most correlational studies on mindfulness and prosociality have relied on self-report measures. The present work aimed to address this serious limitation by investigating actual prosocial behavior. We further focused on mindfulness as a multi-dimensional personality trait to disentangle effects of different mindfulness aspects. In addition, we tested whether the relation between trait mindfulness and prosocial behavior emerges under a theoretical meaningful experimental boundary condition (i.e., feelings of guilt). In two studies (using four different samples; N = 1240), we did not find support for a positive link between trait mindfulness and (a) charitable donation and (b) behavior in an incentivized economic game, respectively. Evidence for manipulated guilt-level as a moderator was inconclusive. Taken together, the findings point to a more complex role of trait mindfulness for prosocial behavior. Limitations and ideas for further research are discussed.

The lack of meaningful boundary differences between journal impact factor quartiles undermines their independent use in research evaluation

Journal impact factor (JIF) quartiles are often used as a convenient means of conducting research evaluation, abstracting the underlying JIF values. We highlight and investigate an intrinsic problem associated with this approach: the differences between quartile boundary JIF values are usually very small and often so small that journals in different quartiles cannot be considered meaningfully different with respect to impact. By systematically investigating JIF values in recent editions of the Journal Citation Reports (JCR) we determine it is typical to see between 10 and 30% poorly differentiated journals in the JCR categories. Social sciences are more affected than science categories. However, this global result conceals important variation and we also provide a detailed account of poor quartile boundary differentiation by constructing in-depth local quartile similarity profiles for each JCR category. Further systematic analyses show that poor quartile boundary differentiation tends to follow poor overall differentiation which naturally varies by field. In addition, in most categories the journals that experience a quartile shift are the same journals that are poorly differentiated. Our work provides sui generis documentation of the continuing phenomenon of impact factor inflation and also explains and reinforces some recent findings on the ranking stability of journals and on the JIF-based comparison of papers. Conceptually there is a fundamental problem in the fact that JIF quartile classes artificially magnify underlying differences that can be insignificant. We in fact argue that the singular use of JIF quartiles is a second order ecological fallacy. We recommend the abandonment of the quartiles reification as an independent method for the research assessment of individual scholars.

On a consistent rod theory for a linearized anisotropic elastic material: I. Asymptotic reduction method

An asymptotic reduction method is introduced to construct a rod theory for a linearized general anisotropic elastic material for space deformation. The starting point is Taylor expansions about the central line in rectangular coordinates, and the goal is to eliminate the two cross-section spatial variables in order to obtain a closed system for displacement coefficients. This is first achieved, in an ‘asymptotically inconsistent’ way, by deducing the relations between stress coefficients from a Fourier series for the lateral traction condition and the three-dimensional (3D) field equation in a pointwise manner. The closed system consists of 10 vector unknowns, and further refinements through elaborated calculations are performed to extract bending and torsion terms and to obtain recursive relations for the first- and second-order displacement coefficients. Eventually, a system of four asymptotically consistent rod equations for four unknowns (the three components of the central-line displacement and the twist angle) are obtained. Six physically meaningful boundary conditions at each edge are obtained from the edge term in the 3D virtual work principle, and a one-dimensional rod virtual work principle is also deduced from the weak forms of the rod equations.

Reduced order methods for parametric optimal flow control in coronary bypass grafts, toward patient-specific data assimilation.

Coronary artery bypass grafts (CABG) surgery is an invasive procedure performed to circumvent partial or complete blood flow blockage in coronary artery disease. In this work, we apply a numerical optimal flow control model to patient-specific geometries of CABG, reconstructed from clinical images of real-life surgical cases, in parameterized settings. The aim of these applications is to match known physiological data with numerical hemodynamics corresponding to different scenarios, arisen by tuning some parameters. Such applications are an initial step toward matching patient-specific physiological data in patient-specific vascular geometries as best as possible. Two critical challenges that reportedly arise in such problems are: (a) lack of robust quantification of meaningful boundary conditions required to match known data as best as possible and (b) high computational cost. In this work, we utilize unknown control variables in the optimal flow control problems to take care of the first challenge. Moreover, to address the second challenge, we propose a time-efficient and reliable computational environment for such parameterized problems by projecting them onto a low-dimensional solution manifold through proper orthogonal decomposition-Galerkin.

Are waves with negative spatial damping unstable?

Conventional plane harmonic waves decay in direction of propagation, but unconventional harmonic waves grow in the direction of propagation. While a single unconventional wave cannot be a solution to a physically meaningful boundary value problem, these waves may have an essential contribution to the overall solution of a problem as long as this is a superposition of unconventional and conventional waves. A fourth order diffusion equation with proper thermodynamic structure, and the Burnett equations of rarefied gas dynamics exhibit conventional and unconventional waves. Steady state oscillating boundary value problems are considered to discuss the interplay of conventional and unconventional waves. Results show that as long as the second law of thermodynamics is valid, unconventional waves may contribute to the overall solution, which, however is dominated by conventional waves, and behaves as these.

A Three-Variable Geometrically Nonlinear New First-Order Shear Deformation Theory for Isotropic Plates: Formulation and Buckling Analysis

This paper presents a displacement-based geometrically nonlinear first-order shear deformation theory for the analysis of shear deformable isotropic plates. Nonlinear strain–displacement relations as utilized by the von Karman plate theory and linear stress–strain constitutive relations are used to formulate this theory. Governing equations of this theory are derived by utilizing equilibrium equations for an infinitesimal plate element. Commonly occurring plate edge boundary conditions are described based on the physical understanding of the plate deformation. As against other geometrically nonlinear first-order shear deformation plate theories reported in the literature, main contributions of this theory are that (1) it incorporates the rotation-free shear deformation plate kinematics of the first order; (2) this theory involves only three governing equations involving only three unknown functions; (3) expressions of governing equations of this theory have a striking resemblance to corresponding expressions of the von Karman plate theory; (4) this theory describes two unique, physically meaningful plate clamped edge boundary conditions. Illustrative examples pertaining to the buckling of shear deformable isotropic Levy-type plates and the comparison of the results obtained with the corresponding results reported in the literature demonstrate the efficacy of the proposed theory.

Improved CNN Classification Method for Groups of Buildings Damaged by Earthquake, Based on High Resolution Remote Sensing Images

Effective extraction of disaster information of buildings from remote sensing images is of great importance to supporting disaster relief and casualty reduction. In high-resolution remote sensing images, object-oriented methods present problems such as unsatisfactory image segmentation and difficult feature selection, which makes it difficult to quickly assess the damage sustained by groups of buildings. In this context, this paper proposed an improved Convolution Neural Network (CNN) Inception V3 architecture combining remote sensing images and block vector data to evaluate the damage degree of groups of buildings in post-earthquake remote sensing images. By using CNN, the best features can be automatically selected, solving the problem of difficult feature selection. Moreover, block boundaries can form a meaningful boundary for groups of buildings, which can effectively replace image segmentation and avoid its fragmentary and unsatisfactory results. By adding Separate and Combination layers, our method improves the Inception V3 network for easier processing of large remote sensing images. The method was tested by the classification of damaged groups of buildings in 0.5 m-resolution aerial imagery after the earthquake of Yushu. The test accuracy was 90.07% with a Kappa Coefficient of 0.81, and, compared with the traditional multi-feature machine learning classifier constructed by artificial feature extraction, this represented an improvement of 18% in accuracy. Our results showed that this improved method could effectively extract the damage degree of groups of buildings in each block in post-earthquake remote sensing images.

A single-variable first-order shear deformation nonlocal theory for the flexure of isotropic nanobeams

In this paper, a displacement-based single-variable first-order shear deformation nonlocal theory for the flexure of isotropic nanobeams is presented. In the present theory, the beam axial displacement consists of a bending component, whereas the beam transverse displacement consists of a bending component and a shearing component. Bending components do not take part in the cross-sectional shearing force, and the shearing component does not take part in the cross-sectional bending moment. The present theory utilizes linear strain–displacement relations. The displacement functions of the present theory give rise to the constant transverse shear strain through the beam thickness. Hence as is the case with the nonlocal Timoshenko beam theory, the present theory also requires a shear correction factor. In the present theory, nonlocal differential stress–strain constitutive relations of Eringen are utilized in order to take into account the size-dependent behaviour of nanobeams. In the present theory, beam gross equilibrium equations are utilized to derive the governing differential equation. As against other first-order shear deformation nonlocal beam theories, the present theory involves only one governing differential equation of fourth order and has only one unknown function. There exists a strong resemblance between expressions of the cross-sectional shearing force, cross-sectional bending moment and governing differential equation of the present theory and corresponding expressions of the nonlocal Bernoulli–Euler beam theory based on the nonlocal elasticity theory of Eringen. For the present theory, boundary conditions are described. The present theory also describes two distinct and physically meaningful clamped boundary conditions. Illustrative examples pertaining to the flexure of shear deformable isotropic nanobeams demonstrate the efficacy of the present theory.

Carbon nanotube based dielectric spectroscopy of tumor secretion; electrochemical lipidomics for cancer diagnosis

Cell free diagnosis of cancer is one of the crucial fields in new generation of medical technology. In this regard, cancer detection based on coastal fluids secreted from the tissues (named as secretome) has attracted a lot of attention. Lipids are important macromolecules could be found with much higher concentrations in secretome of cancer tissues vs. normal ones. On the other hand, lipids are the main dielectric components of the secretome with respect to proteins and ions. Here for the first time we introduced an electrochemical lipidomics based on electrical impedance spectroscopy (EIS) of the secretomes to detect the cancerous samples due to the lipidic content of their secretions. The EIS sensor was fabricated by multiwall carbon nanotube (MWCNT) arrays as conductive and super hydrophobic materials to have great interactive surface with the lipidic content of the solution. Results of the tests on the secretions of more than 100 human biopsied breast tissues showed the promising match between the charge transfer resistance (RCT) of samples’ secretions and pathological states of the tissues with meaningful boundary (up to 8 kΩ for normal and more than 13 kΩ for cancer samples). Mass spectroscopic analyses confirmed the higher content of lipids in cancer secretomes. Electrical lipidomics of the secretome shed new lights in cell free cancer diagnosis and could be applied as a complementary clinical approach in all of biopsy based diagnoses in future.

Healthcare Rationing Cutoffs and Sorites Indeterminacy.

Rationing is an unavoidable mechanism for reining in healthcare costs. It entails establishing cutoff points that distinguish between what is and is not offered or available to patients. When the resource to be distributed is defined by vague and indeterminate terms such as "beneficial," "effective," or even "futile," the ability to draw meaningful boundary lines that are both ethically and medically sound is problematic. In this article, I draw a parallel between the challenges posed by this problem and the ancient Greek philosophical conundrum known as the "sorites paradox." I argue, like the paradox, that the dilemma is unsolvable by conventional means of logical analysis. However, I propose another approach that may offer a practical solution that could be applicable to real-life situations in which cutoffs must be decided (such as rationing).