scholarly journals A critical discussion of different methods and models in Casimir effect

2022 ◽  
Author(s):  
Iver Brevik ◽  
Boris Shapiro
Keyword(s):  
Electromagnetic Fields ◽  
Dielectric Function ◽  
Casimir Effect ◽  
Critical Discussion ◽  
Plasma Model ◽  
Fundamental Interest ◽  
Neutral Material ◽  
Recent Developments ◽  
Material Bodies ◽  
Oriented Approach

Abstract The Casimir-Lifshitz force acts between neutral material bodies and is due to the fluctuations (around zero) of the electrical polarizations of the bodies. This force is a macroscopic manifestation of the van der Waals forces between atoms and molecules. In addition to being of fundamental interest, the Casimir-Lifshitz force plays an important role in surface physics, nanotechnology and biophysics. There are two different approaches in the theory of this force. One is centered on the fluctuations inside the bodies, as the source of the fluctuational electromagnetic fields and forces. The second approach is based on finding the eigenmodes of the field, while the material bodies are assumed to be passive and non-fluctuating. In spite of the fact that both approaches have a long history, there are still some misconceptions in the literature. In particular, there are claims that (hypothetical) materials with a strictly real dielectric function $\varepsilon(\omega)$ can give rise to fluctuational Casimir-Lifshitz forces. We review and compare the two approaches, using the simple example of the force in the absence of retardation. We point out that also in the second (the "field-oriented") approach one cannot avoid introducing an infinitesimal imaginary part into the dielectric function, i.e. introducing some dissipation. Furthermore, we emphasize that the requirement of analyticity of $ \varepsilon(\omega)$ in the upper half of the complex $\omega$ plane is not the only one for a viable dielectric function. There are other requirements as well. In particular, models that use a strictly real $\varepsilon(\omega)$ (for all real positive $\omega)$ are inadmissible and lead to various contradictions and inconsistencies. Specifically, we present a critical discussion of the "dissipation-less plasma model". Our emphasis is not on the most recent developments in the field but on some conceptual, not fully resolved issues.

scholarly journals Jesus Traditions and Masculinities in World Christianity

Exchange ◽  
2013 ◽  
Vol 42 (1) ◽  
pp. 1-15 ◽  
Author(s):  
Adriaan S. van Klinken ◽  
Peter-Ben Smit
Keyword(s):  
Jesus Christ ◽  
Critical Discussion ◽  
Early Christian ◽  
Global Christianity ◽  
Contemporary Christian ◽  
The New Testament ◽  
Recent Developments ◽  
World Christianity ◽  
Historical Trajectory ◽  
Men And Masculinities

Abstract This opening article offers an introduction to the theme of this special issue of Exchange: Jesus traditions and masculinities in world Christianity. Highlighting the historical trajectory of feminist theological debates on the maleness of Jesus Christ and its implications for configurations of gender (read: the position of women) in Christian traditions, the article particularly explores two recent developments: first, the critical discussion in academic, theological and ecumenical circles of men and masculinities in contemporary Christian contexts, and second, the growing body of scholarship on the masculinity (or better, masculinities) of Jesus Christ in the New Testament in relation to masculinities in the early Christian era. Building on these debates and this scholarship, the article identifies a new and critical field of inquiry that explores the complex and productive relationships between the ambiguous and unstable masculinity/ies of Jesus Christ and the multiple and changing masculinities that are found today in the local contexts of an increasingly diverse global Christianity.

Abstraction and Science

Philosophy ◽  
1927 ◽  
Vol 2 (5) ◽  
pp. 28-38
Author(s):  
L. S. Stebbing
Keyword(s):  
Nineteenth Century ◽  
Space Time ◽  
Physical Sciences ◽  
Recent Developments ◽  
Material Bodies ◽  
Ultimate Nature

The man in the street to-day is aware that recent developments in the physical sciences have necessitated a fundamental revision of the concepts of physics; he finds that Einstein is no less upsetting to his ideas than was Copernicus to those of his own time or than Darwin was to Bishop Wilberforce. The plain man who has “ philosophical leanings ” is aware that questions previously regarded as metaphysical—and about which philosophers have written much that is unintelligible—are now recognized as falling within the scope of physics. Every reader of this Journal is aware that the criticism to which the main concepts of physics—space, time, matter—have been subjected is so fundamental that it is no longer possible to say that there are material bodies in space, which have events happening to them at a given time. We must substitute the conception of a fourfold continuum within which space, time and matter are inextricably involved. Finally, we are told that this new way of regarding the classical trinity suggests the consequence that we know nothing about the “ inner nature ” of the terms with which we deal, we can make no assertions as to the ultimate nature of that to which they may refer. In this respect the prevailing temper of the present-day scientist is to be contrasted with the cocksureness of most nineteenth-century physicists l who, even if they did not go so far as to say “ we know what matter is,” at least suggested that only the metaphysician had, or could have, any doubts as to its nature and reality^

scholarly journals Energy Densification of Biomass-Derived Furfurals to Furanic Biofuels by Catalytic Hydrogenation and Hydrodeoxygenation Reactions

2021 ◽  
Vol 2 (3) ◽  
pp. 521-549
Author(s):  
Nivedha Vinod ◽  
Saikat Dutta
Keyword(s):  
Catalytic Hydrogenation ◽  
Critical Discussion ◽  
Catalyst Design ◽  
Hydrogen Gas ◽  
Hydrogen Donor ◽  
Hydroxymethyl Furfural ◽  
Recent Developments ◽  
Potential Applications ◽  
Furanic Compounds

The concomitant hydrolysis and dehydration of biomass-derived cellulose and hemicellulose to furfural (FUR) and 5-(hydroxymethyl)furfural (HMF) under acid catalysis allows a dramatic reduction in the oxygen content of the parent sugar molecules with a 100% carbon economy. However, most applications of FUR or HMF necessitate synthetic modifications. Catalytic hydrogenation and hydrogenolysis have been recognized as efficient strategies for the selective deoxygenation and energy densification of biomass-derived furfurals generating water as the sole byproduct. Efficient and eco-friendly catalysts have been developed for the selective hydrogenation of furfurals affording renewable furanic compounds such as 2-methylfuran, 2,5-dimethylfuran and 2-methyltetrahydrofuran with potential applications as biofuel, solvent and chemical feedstock. Hydrogen gas or hydrogen donor molecules, required for the above processes, can also be renewably obtained from biomass using catalytic processes, enabling a circular economy. In this review, the recent developments in the energy densification of furfurals to furanic compounds of commercial significance are elaborated, emphasizing the role of catalyst and the reaction parameters employed. Critical discussion on sourcing hydrogen gas required for the processes, using hydrogen donor solvents, catalyst design and the potential markets of furanic intermediates have been made. Critical evaluations of the accomplishments and challenges in this field are also provided.

scholarly journals Strategies for Molecular Imprinting and the Evolution of MIP Nanoparticles as Plastic Antibodies—Synthesis and Applications

2019 ◽  
Vol 20 (24) ◽  
pp. 6304 ◽  
Author(s):  
Doaa Refaat ◽  
Mohamed G. Aggour ◽  
Ahmed A. Farghali ◽  
Rashmi Mahajan ◽  
Jesper G. Wiklander ◽  
...  
Keyword(s):  
Molecular Imprinting ◽  
Molecularly Imprinted Polymers ◽  
Binding Sites ◽  
Specific Binding ◽  
Polymeric Materials ◽  
Critical Discussion ◽  
Current State ◽  
Aqueous Environments ◽  
Real World Applications ◽  
Recent Developments

Materials that can mimic the molecular recognition-based functions found in biology are a significant goal for science and technology. Molecular imprinting is a technology that addresses this challenge by providing polymeric materials with antibody-like recognition characteristics. Recently, significant progress has been achieved in solving many of the practical problems traditionally associated with molecularly imprinted polymers (MIPs), such as difficulties with imprinting of proteins, poor compatibility with aqueous environments, template leakage, and the presence of heterogeneous populations of binding sites in the polymers that contribute to high levels of non-specific binding. This success is closely related to the technology-driven shift in MIP research from traditional bulk polymer formats into the nanomaterial domain. The aim of this article is to throw light on recent developments in this field and to present a critical discussion of the current state of molecular imprinting and its potential in real world applications.

scholarly journals Current Challenges and Opportunities in Microstructure-Related Properties of Advanced High-Strength Steels

2020 ◽  
Vol 51 (11) ◽  
pp. 5517-5586 ◽  
Author(s):  
Dierk Raabe ◽  
Binhan Sun ◽  
Alisson Kwiatkowski Da Silva ◽  
Baptiste Gault ◽  
Hung-Wei Yen ◽  
...  
Keyword(s):  
Recent Progress ◽  
High Strength Steels ◽  
High Strength ◽  
Advanced Characterization ◽  
Critical Discussion ◽  
Press Hardening ◽  
Advanced High Strength Steels ◽  
Bainitic Steels ◽  
Challenges And Opportunities ◽  
Recent Developments

Abstract This is a viewpoint paper on recent progress in the understanding of the microstructure–property relations of advanced high-strength steels (AHSS). These alloys constitute a class of high-strength, formable steels that are designed mainly as sheet products for the transportation sector. AHSS have often very complex and hierarchical microstructures consisting of ferrite, austenite, bainite, or martensite matrix or of duplex or even multiphase mixtures of these constituents, sometimes enriched with precipitates. This complexity makes it challenging to establish reliable and mechanism-based microstructure–property relationships. A number of excellent studies already exist about the different types of AHSS (such as dual-phase steels, complex phase steels, transformation-induced plasticity steels, twinning-induced plasticity steels, bainitic steels, quenching and partitioning steels, press hardening steels, etc.) and several overviews appeared in which their engineering features related to mechanical properties and forming were discussed. This article reviews recent progress in the understanding of microstructures and alloy design in this field, placing particular attention on the deformation and strain hardening mechanisms of Mn-containing steels that utilize complex dislocation substructures, nanoscale precipitation patterns, deformation-driven transformation, and twinning effects. Recent developments on microalloyed nanoprecipitation hardened and press hardening steels are also reviewed. Besides providing a critical discussion of their microstructures and properties, vital features such as their resistance to hydrogen embrittlement and damage formation are also evaluated. We also present latest progress in advanced characterization and modeling techniques applied to AHSS. Finally, emerging topics such as machine learning, through-process simulation, and additive manufacturing of AHSS are discussed. The aim of this viewpoint is to identify similarities in the deformation and damage mechanisms among these various types of advanced steels and to use these observations for their further development and maturation.

scholarly journals Computer-Assisted Diagnosis of the Sleep Apnea-Hypopnea Syndrome: A Review

2015 ◽  
Vol 2015 ◽  
pp. 1-33 ◽  
Author(s):  
Diego Alvarez-Estevez ◽  
Vicente Moret-Bonillo
Keyword(s):  
Sleep Apnea ◽  
Critical Discussion ◽  
Computer Assisted ◽  
Diagnostic Systems ◽  
Computer Assisted Diagnosis ◽  
Current State ◽  
Respiratory Events ◽  
Recent Developments ◽  
Assisted Diagnosis ◽  
Hypopnea Syndrome

Automatic diagnosis of the Sleep Apnea-Hypopnea Syndrome (SAHS) has become an important area of research due to the growing interest in the field of sleep medicine and the costs associated with its manual diagnosis. The increment and heterogeneity of the different techniques, however, make it somewhat difficult to adequately follow the recent developments. A literature review within the area of computer-assisted diagnosis of SAHS has been performed comprising the last 15 years of research in the field. Screening approaches, methods for the detection and classification of respiratory events, comprehensive diagnostic systems, and an outline of current commercial approaches are reviewed. An overview of the different methods is presented together with validation analysis and critical discussion of the current state of the art.

scholarly journals Casimir Effect between Superconducting Plates in the Mixed State

2021 ◽  
Vol 3 (4) ◽  
pp. 731-745
Author(s):  
Norio Inui
Keyword(s):  
Magnetic Field ◽  
Mixed State ◽  
Imaginary Axis ◽  
Casimir Force ◽  
Casimir Effect ◽  
Normal Phase ◽  
Superconducting Phase ◽  
Type Ii ◽  
Plasma Model ◽  
The Magnetic Field

The Casimir effect between type-II superconducting plates in the coexisting phase of a superconducting phase and a normal phase is investigated. The dependence of the optical conductivity of the superconducting plates on the external magnetic field is described in terms of the penetration depth of the incident electromagnetic field, and the permittivity along the imaginary axis is represented by a linear combination of the permittivities for the plasma model and Drude models. The characteristic frequency in each model is determined using the force parameters for the motion of the magnetic field vortices. The Casimir force between parallel YBCO plates in the mixed state is calculated, and the dependence on the applied magnetic field and temperature is considered.

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