Graphs are among the most frequently used structures in Computer Science. Some of the properties that must be checked in many applications are connectivity, acyclicity and the Eulerian and Hamiltonian properties. In this work, we analyze how we can express these four properties with modal logics. This involves two issues: whether each of the modal languages under consideration has enough expressive power to describe these properties and how complex it is to use these logics to actually test whether a given (...) graph has some desired property. First, we show that these properties are not definable in a basic modal logic or in any bisimulation-invariant extension of it, like the modal μ-calculus. We then show that it is possible to express some of the above properties in a basic hybrid logic. Unfortunately, the Hamiltonian and Eulerian properties still cannot be efficiently checked. In a second attempt, we propose an extension of CTL* with nominals and show that the Hamiltonian property can be more efficiently checked in this logic than in the previous one. In a third attempt, we extend the basic hybrid logic with the ↓ operator and show that we can check the Hamiltonian property with optimal complexity in this logic. Finally, we tackle the Eulerian property in two different ways. First, we develop a generic method to express edge-related properties in hybrid logics and use it to express the Eulerian property. Second, we express a necessary and sufficient condition for the Eulerian property to hold using a graded modal logic. (shrink)

This work introduces a two-dimensional modal logic to represent agents' Concurrent Common Knowledge in distributed systems. Unlike Common Knowledge, Concurrent Common Knowledge is a kind of agreement reachable in asynchronous environments. The formalization of such type of knowledge is based on a model for asynchronous systems and on the definition of Concurrent Knowledge introduced before in paper [5]. As a proper semantics, we review our concept of closed sub-product of modal logics which is based on the product of modal logics. (...) The key idea is to reason about Concurrent Knowledge under a two-dimensional approach, regarding asynchronous runs and consistent global states as dimensions. We present an axiomatic system for the logic and issue the corresponding soundness and completeness proofs. (shrink)

This paper introduces a two-dimensional modal logic to reason about knowledge in asynchronous multi-agent message-passing systems. We present a new theoretical definition for concurrent knowledge in order to describe the kind of knowledge typical in such asynchronous environments. To define concurrent knowledge, we propose the closed sub-product of modal logics: a two-dimensional formal semantics where one dimension corresponds to asynchronous runs, the other corresponds to consistent cuts and the concurrent knowledge is defined as the transitive closure over the product of (...) the former dimensions. We axiomatize the presented logic issuing proofs of soundness and completeness with respect to the class of closed sub-product of modal frames. (shrink)

In this paper we show that the class of fork squares has a complete orthodox axiomatization in fork arrow logic (FAL). This result may be seen as an orthodox counterpart of Venema's non-orthodox axiomatization for the class of squares in arrow logic. FAL is the modal logic of fork algebras (FAs) just as arrow logic is the modal logic of relation algebras (RAs). FAs extend RAs by a binary fork operator and are axiomatized by adding three equations to RAs equational (...) axiomatization. A proper FA is an algebra of relations where the fork is induced by an injective operation coding pair formation. In contrast to RAs, FAs are representable by proper ones and their equational theory has the expressive power of full first-order logic. A square semantics (the set of arrows is ᵎ x ᵎ for some set ᵎ) for arrow logic was defined by Y. Venema. Due to the negative results about the finite axiomatizability of representable RAs, Venema provided a non-orthodox finite axiomatization for arrow logic by adding a new rule governing the applications of a difference operator. We address here the question of extending the type of relational structures to define orthodox axiomatizations for the class of squares. Given the connections between this problem and the finitization problem addressed by I. Németi, we suspect that this cannot be done by using only logical operations. The modal version of the FA equations provides an orthodox axiomatization for FAL which is complete in view of the representability of FAs. Here we review this result and carry it further to prove that this orthodox axiomatization for FAL also axiomatizes the class of fork squares. (shrink)

In this paper we show that the class of fork squares has a complete orthodox axiomatization in fork arrow logic (FAL). This result may be seen as an orthodox counterpart of Venema's non-orthodox axiomatization for the class of squares in arrow logic. FAL is the modal logic of fork algebras (FAs) just as arrow logic is the modal logic of relation algebras (RAs). FAs extend RAs by a binary fork operator and are axiomatized by adding three equations to RAs equational (...) axiomatization. A proper FA is an algebra of relations where the fork is induced by an injective operation coding pair formation. In contrast to RAs, FAs are representable by proper ones and their equational theory has the expressive power of full first-order logic. A square semantics (the set of arrows is U×U for some set U) for arrow logic was defined by Y. Venema. Due to the negative results about the finite axiomatizability of representable RAs, Venema provided a non-orthodox finite axiomatization for arrow logic by adding a new rule governing the applications of a difference operator. We address here the question of extending the type of relational structures to define orthodox axiomatizations for the class of squares. Given the connections between this problem and the finitization problem addressed by I. Németi, we suspect that this cannot be done by using only logical operations. The modal version of the FA equations provides an orthodox axiomatization for FAL which is complete in view of the representability of FAs. Here we review this result and carry it further to prove that this orthodox axiomatization for FAL also axiomatizes the class of fork squares. (shrink)

Vague notions, such as ‘generally’, ‘rarely’, ‘often’, ‘almost always’, ‘a meaningful subset of a whole’, ‘most’, etc., occur often in ordinary language and in some branches of science. We introduce modal logical systems, with generalized operators, for the precise treatment of assertions involving some versions of such vague notions. We examine modal logics, constructed in a modular fashion, with generalized operators corresponding to some versions of ‘generally’ and ‘rarely’.

We compare fork arrow logic, an extension of arrow logic, and its natural first-order counterpart (the correspondence language) and show that both have the same expressive power. Arrow logic is a modal logic for reasoning about arrow structures, its expressive power is limited to a bounded fragment of first-order logic. Fork arrow logic is obtained by adding to arrow logic the fork modality (related to parallelism and synchronization). As a result, fork arrow logic attains the expressive power of its first-order (...) correspondence language, so both can express the same input–output behavior of processes. (shrink)

We compare fork arrow logic, an extension of arrow logic, and its natural first-order counterpart (the correspondence language) and show that both have the same expressive power. Arrow logic is a modal logic for reasoning about arrow structures, its expressive power is limited to a bounded fragment of first-order logic. Fork arrow logic is obtained by adding to arrow logic the fork modality (related to parallelism and synchronization). As a result, fork arrow logic attains the expressive power of its first-order (...) correspondence language, so both can express the same input-output behavior of processes. (shrink)

While ancient civilizations worshipped strong, active emotions, modern societies have favored more peaceful attitudes, especially within the democratic process. We have largely forgotten the struggle to make use of _thymos_, the part of the soul that, following Plato, contains spirit, pride, and indignation. Rather, Christianity and psychoanalysis have promoted mutual understanding to overcome conflict. Through unique examples, Peter Sloterdijk, the preeminent posthumanist, argues exactly the opposite, showing how the history of Western civilization can be read as a suppression and return (...) of rage. By way of reinterpreting the _Iliad_, Alexandre Dumas's _Count of Monte Cristo_, and recent Islamic political riots in Paris, Sloterdijk proves the fallacy that rage is an emotion capable of control. Global terrorism and economic frustrations have rendered strong emotions visibly resurgent, and the consequences of violent outbursts will determine international relations for decades to come. To better respond to rage and its complexity, Sloterdijk daringly breaks with entrenched dogma and contructs a new theory for confronting conflict. His approach acknowledges and respects the proper place of rage and channels it into productive political struggle. (shrink)

The Unified Foundational Ontology (UFO) was developed over the last two decades by consistently putting together theories from areas such as formal ontology in philosophy, cognitive science, linguistics, and philosophical logics. It comprises a number of micro-theories addressing fundamental conceptual modeling notions, including entity types and relationship types. The aim of this paper is to summarize the current state of UFO, presenting a formalization of the ontology, along with the analysis of a number of cases to illustrate the application of (...) UFO and facilitate its comparison with other foundational ontologies in this special issue. (The cases originate from the First FOUST Workshop – the Foundational Stance, an international forum dedicated to Foundational Ontology research.). (shrink)

O filósofo Dominique Lecourt, nascido em 05 de fevereiro de 1944, em Paris, é professor da Universidade Paris Diderot-7, e discute questões como ética, política e ciência, atentando ao biocatastrofismo e ao cientificismo. Tais questões são pertinentes na presente obra, a qual é dividida em quatro capítulos.

We propose a formal framework to examine the relationship between models and observations. To make our analysis precise,models are reduced to first-order theories that represent both terminological knowledge – e.g., the laws that are supposed to regulate the domain under analysis and that allow for explanations, predictions, and simulations – and assertional knowledge – e.g., information about specific entities in the domain of interest. Observations are introduced into the domain of quantification of a distinct first-order theory that describes their nature (...) and their organization and takes track of the way they are experimentally acquired or intentionally elaborated. A model mainly represents the theoretical knowledge or hypotheses on a domain, while the theory of observations mainly represents the empirical knowledge and the given experimental practices. We propose a precise identity criterion for observations and we explore different links between models and observations by assuming a degree of independence between them. By exploiting some techniques developed in the field of social choice theory and judgment aggregation, we sketch some strategies to solve inconsistencies between a given set of observations and the assumed theoretical hypotheses. The solutions of these inconsistencies can impact both the observations – e.g., the theoretical knowledge and the analysis of the way observations are collected or produced may highlight some unreliable sources – and the models – e.g. empirical evidences may invalidate some theoretical laws. (shrink)

This paper examines two twenty-first-century developments in the enactive approach in philosophy and the cognitive sciences. The first is the surging interest in Hans Jonas, which begins with Weber and Varela's 'Life After Kant' (2002) and continues up to the present. The second is the 'social turn' that the enactive approach has taken, especially after De Jaegher and Di Paolo's (2007) work on participatory sense-making. We look at these two developments through the lens of the problem of other minds. We (...) argue that they are incompatible due to a residual solipsism in Jonasian phenomenology. Ultimately, this leaves enactive theory with a choice between embracing Jonas or embracing the social turn in enactive theory. We recommend replacing Jonasian influences with those from the late work of Maurice Merleau-Ponty. We argue that enactivism can evade the problem of other minds using Merleau-Ponty's discussion of 'flesh' and 'expression'. (shrink)

It is generally argued that if the wave-function in the de Broglie–Bohm theory is a physical field, it must be a field in configuration space. Nevertheless, it is possible to interpret the wave-function as a multi-field in three-dimensional space. This approach hasn’t received the attention yet it really deserves. The aim of this paper is threefold: first, we show that the wave-function is naturally and straightforwardly construed as a multi-field; second, we show why this interpretation is superior to other interpretations (...) discussed in the literature; third, we clarify common misconceptions. (shrink)

Em Ser e Tempo, Heidegger argumenta que o conhecimento primordial do Dasein se dá no manuseio de entes mundanos. Merleau-Ponty, por sua vez, descreve na Fenomenologia da Percepção que o conhecimento é, antes de tudo, uma intencionalidade corporal intraduzível em termos proposicionais. Mais tarde, em What Computers Can’t Do, Hubert Dreyfus usa a obra de ambos para apontar os equívocos do paradigma cognitivista, isto é, a abordagem dominante do então nascente campo da inteligência artificial. Finalmente, em The Embodied Mind: Cognitive (...) Science and Human Experience, a noção de enativismo - elaborada por Francisco Varela, Evan Thompson e Eleanor Rosch - surge como uma tentativa de tomar do cognitivismo e do conexionismo a hegemonia nas ciências cognitivas. Dito isso, o objetivo do artigo consiste em descrever o enativismo e apontar sua herança fenomenológica. (shrink)

O livro "Humano pós-humano: a técnica e a vida" de Dominique Lecourt expõe as formas das aplicações da técnica e as mudanças que ela causou na vida humana e na sua natureza; na sua essência. Essa resenha visa explicitar suas ideias, expondo os argumentos de Lecourt para defender a sua tese de que o ser humano ultrapassou essa essência e tornou-se o pós-humano, no momento em que o homem aliou a técnica e a ciência não mais para suprir suas necessidades, (...) mas para construir máquinas que ultrapassem o seu modelo e seus limites biológicos, substituindo o homem em quase todas as suas atividades. Apresente como solução para esse problema a necessidade da aplicação da ética a cada inovação tecnológica. (shrink)

A partir da pergunta que dá título a este artigo, pretendemos posicionar o pensamento de Michel Foucault em relação ao materialismo através de uma análise que contemple as três fases de seu pensamento, a saber, a arqueologia, a genealogia e a ética. Mediante esta análise, concluímos não só pela filiação do pensamento de Michel Foucault no campo mais amplo e plural dos materialismos, mas também pela radicalidade que o filósofo assume em relação ao materialismo em todas as fases de seu (...) pensamento. Do ponto de vista da arqueologia, argumentamos que a tomada do discurso não em seu caráter representativo, significativo ou teleológico, mas na concretude e singularidade de seu aparecimento, reforça de forma significativa o materialismo; em relação à genealogia, mostramos como a microfísica do poder, ao voltar-se contra os efeitos de hegemonia que produzem a abstração dos Grandes Conceitos e das Grandes Coisas, revelam a materialidade de um jogo de forças sujeitado pelas formas oficiais do saber e do poder; por fim, do ponto de vista da ética, esclarecemos que o âmbito da análise da relação de si consigo não consiste no domínio da interioridade, refúgio último do imaterialismo, mas justamente no âmbito da produção de subjetividade determinada por uma relação com a exterioridade, a alteridade e o fora. Dessa forma, consideramos a noção de Materialismo Radical pertinente para compreendermos, de forma mais rigorosa, tanto certas características próprias ao pensamento de Michel Foucault, quanto sua indubitável filiação ao materialismo. (shrink)

No final da década de 1950, Merleau-Ponty desloca seu foco de investigação da fenomenologia à ontologia. Tal transição envolve a articulação de seus estudos prévios acerca da percepção e da corporeidade com os desdobramentos filosóficos dos postulados da física e da biologia da primeira metade do século. A partir de uma reformulação do conceito de natureza, fomentada não só pelas ciências supracitadas como pela metafísica de Whitehead, Merleau-Ponty propõe a admissão da natureza como um fluxo de expressividade temporal autoprodutora de (...) sentido, incorporando ao âmago do ser a temporalidade e a negatividade antes exclusivas ao para-si. A carne de Merleau-Ponty, como veremos, está em harmonia com a noção de processo de Whitehead, apontando assim um certo hilozoísmo pré-socrático na ontologia de ambos. Dito isso, o objetivo do artigo consiste em examinar a ontologia indireta de Merleau-Ponty, indicando sua convergência com a filosofia de Whitehead para, finalmente, introduzirmos uma crítica incipiente a partir da obra de Francisco Varela. Defende-se aqui que o conceito de autopoiesis pode indicar uma alternativa à noção merleau-pontiana de natureza. (shrink)

In Varieties of Religious Experience: A Study in Human Nature William James examines the role of mysticism in the development of religion. James argues that the root of all religions is precisely the experience of mystical states of consciousness. As we shall see, although James himself admits that his own psychological constitution shuts him out from these experiences, the acknowledgement of practical developments of mysticism within institutionalized religions illustrates the reality of these states of consciousness, a stance supported by James’ (...) pragmatism. Thus, the paper not only examines the nature of mysticism but presents James’ pragmatist view of religion. (shrink)

Stress has been being pointed as the evil of the current world and can affect as much adults as children. The disorders associated with stress are varied, and people who suffer from it frequently present physical and psychological problems, influencing their behavior and social environment. The care..

I want to combine two hitherto largely independent research projects, scientific understanding and mechanistic explanations. Understanding is not only achieved by answering why-questions, that is, by providing scientific explanations, but also by answering what-questions, that is, by providing what I call scientific descriptions. Based on this distinction, I develop three forms of understanding: understanding-what, understanding-why, and understanding-how. I argue that understanding-how is a particularly deep form of understanding, because it is based on mechanistic explanations, which answer why something happens in (...) virtue of what it is made of. I apply the three forms of understanding to two case studies: first, to the historical development of thermodynamics and, second, to the differences between the Clausius and the Boltzmann entropy in explaining thermodynamic processes. (shrink)

The ontological models framework distinguishes ψ-ontic from ψ-epistemic wave- functions. It is, in general, quite straightforward to categorize the wave-function of a certain quantum theory. Nevertheless, there has been a debate about the ontological status of the wave-function in the statistical interpretation of quantum mechanics: is it ψ-epistemic and incomplete or ψ-ontic and complete? I will argue that the wave- function in this interpretation is best regarded as ψ-ontic and incomplete.

Philosophers now seem to agree that frequentism is an untenable strategy to explain the meaning of probabilities. Nevertheless, I want to revive frequentism, and I will do so by grounding probabilities on typicality in the same way as the thermodynamic arrow of time can be grounded on typicality within statistical mechanics. This account, which I will call typicality frequentism, will evade the major criticisms raised against previous forms of frequentism. In this theory, probabilities arise within a physical theory from statistical (...) behavior of almost all initial conditions. The main advantage of typicality frequentism is that it shows which kinds of probabilities (that also have empirical relevance) can be derived from physics. Although one cannot recover all probability talk in this account, this is rather a virtue than a vice, because it shows which types of probabilities can in fact arise from physics and which types need to be explained in different ways, thereby opening the path for a pluralistic account of probabilities. (shrink)

What does it take to understand a phenomenon ideally, or to the highest conceivable extent? In this paper, we answer this question by arguing for five necessary conditions for ideal understanding: (i) representational accuracy, (ii) intelligibility, (iii) truth, (iv) reasonable endorsement, and (v) fitting. Even if one disagrees that there is some form of ideal understanding, these five conditions can be regarded as sufficient conditions for a particularly deep level of understanding. We then argue that grasping, novel predictions, and transparency (...) are not reasonable conditions for ideal understanding. (shrink)

pt. I. Matter: 1. Philosophy as worldview ; 2. Classical matter: bodies and fields ; 3. Quantum matter: weird but real ; 4. General concept of matter: to be is to become ; 5. Emergence and levels ; 6. Naturalism ; 7. Materialism -- pt. II. Mind: 8. The mind-body problem ; 9. Minding matter: the plastic brain ; 10. Mind and society ; 11. Cognition, consciousness, and free will ; 12. Brain and computer: the hardware/software dualism ; 13. Knowledge: (...) genuine and bogus -- pt. III. Appendices: 14. Appendix A: Objects ; 15. Appendix B. Truths. (shrink)

Name der Zeitschrift: Das Mittelalter Jahrgang: 22 Heft: 1 Seiten: 146-164.

Due to the prevalence, severity, and costs associated with autism spectrum disorders, it has become a public health issue. In response, state governments have adopted ASD-specific private insurance mandates requiring coverage of ASD screening, diagnosis, and treatment. Despite rapid uptake of these laws, differences exist in the type and levels of coverage, especially for allied health services including occupational therapy. We piloted a structured legal research methodology to code ASD insurance mandates that impact allied health service provisions. State private insurance (...) mandates were obtained from WestlawNext. A coding methodology was piloted on 14 states and included variables for age and service limits, treatments covered, and medical necessity. Coding methods were feasible and highly reliable among raters. Ten of 12 states had a coverage mandate, many with specific provisions for allied health providers. A full analysis of all 50 states is warranted to identify provisions affecting allied health providers serving individuals with ASD. (shrink)

Let M be an o-minimal expansion of a real closed field. Let G be a definably compact definably connected abelian n-dimensional group definable in M. We show the following: the o-minimal fundamental group of G is isomorphic to ℤn; for each k>0, the k-torsion subgroup of G is isomorphic to n, and the o-minimal cohomology algebra over ℚ of G is isomorphic to the exterior algebra over ℚ with n generators of degree one.

This paper investigates the historical origin and ancestors of typicality, which is now a central concept in Boltzmannian Statistical Mechanics and Bohmian Mechanics. Although Ludwig Boltzmann did not use the word typicality, its main idea, namely, that something happens almost always or is valid for almost all cases, plays a crucial role for his explanation of how thermodynamic systems approach equilibrium. At the beginning of the 20th century, the focus on almost always or almost everywhere was fruitful for developing measure (...) theory and probability theory. It was apparently Hugh Everett III who first mentioned typicality in physics in 1957 while searching for a justification of the Born rule in his interpretation of quantum mechanics. The historically closest concept before these developments is moral certainty, which was invented by the medieval French theologian Jean Gerson, and it became a standard concept at least until the Age of Enlightenment, when Jakob Bernoulli proved the Law of Large numbers. (shrink)

Predictivists use the no miracle argument to argue that “novel” predictions are decisive evidence for theories, while mere accommodation of “old” data cannot confirm to a significant degree. But deductivists claim that since confirmation is a logical theory-data relationship, predicted data cannot confirm more than merely deduced data, and cite historical cases in which known data confirmed theories quite strongly. On the other hand, the advantage of prediction over accommodation is needed by scientific realists to resist Laudan’s criticisms of the (...) no miracle argument. So, if the deductivists are right, the most powerful argument for realism collapses. There seems to be an inescapable contradiction between these prima facie plausible arguments of predictivists and deductivists; but this puzzle can be solved by understanding what exactly counts as novelty, if novel predictions must support the no miracle argument, i.e., if they must be explainable only by the truth of theories. Taking my cues from the use-novelty tradition, I argue that (1) the predicted data must not be used essentially in building the theory or choosing the auxiliary assumptions. This is possible if the theory and its auxiliary assumptions are plausible independently of the predicted data, and I analyze the consequences of this requirement in terms of best explanation of diverse bodies of data. Moreover, the predicted data must be (2) a priori improbable, and (3) heterogeneous to the essentially used data. My proposed notion of novelty, therefore, is not historical, but functional. Hence, deductivists are right that confirmation is independent of time and of historical contingencies such as if the theorist knew a datum, used it, or intended to accommodate it. Predictivists, however, are right that not all consequences confirm equally, and confirmation is not purely a logical theory-data relation, as it crucially involves background epistemic conditions and the notion of best explanation. Conditions (1)–(3) make the difference between prediction and accommodation, and account for the confirming power of theoretical virtues such as non ad-hocness, non-fudging, non-overfitting, independence and consilience. I thus show that functional novelty (a) avoids the deductivist objections to predictivism, (b) is a gradual notion, in accordance with the common intuition that confirmation comes in degrees, and (c) supports the no miracle argument, so vindicating scientific realism. (shrink)

This collection of essays deals with three clusters of problems in the philo sophy of science: scientific method, conceptual models, and ontological underpinnings. The disjointedness of topics is more apparent than real, since the whole book is concerned with the scientific knowledge of fact. Now, the aim of factual knowledge is the conceptual grasping of being, and this understanding is provided by theories of whatever there may be. If the theories are testable and specific, such as a theory of a (...) particular chemical reaction, then they are often called 'theoretical models' and clas sed as scientific. If the theories are extremely general, like a theory of syn thesis and dissociation without any reference to a particular kind of stuff, then they may be called 'metaphysical' - as well as 'scientific' if they are consonant with science. Between these two extremes there is a whole gamut of kinds of factual theories. Thus the entire spectrum should be dominated by the scientific method, quite irrespective of the subject matter. This is the leitmotiv of the present book. The introductory chapter, on method in the philosophy of science, tackles the question 'Why don't scientists listen to their philosophers?'. (shrink)

O estudo teve como objetivo comparar e correlacionar indicadores de habilidades sociais e do envolvimento de pais com filhos portadores de retardo mental. Participaram 27 casais com filhos portadores de retardo mental. Os pais responderam os questionários "Critério Brasil", "Qualidade da interação f..

Let R be an o-minimal expansion of an ordered group R has no poles, R cannot define a real closed field with domain R and order R is eventually linear and every R -definable set is a finite union of cones. As a corollary we get that Th has quantifier elimination and universal axiomatization in the language with symbols for the ordered group operations, bounded R -definable sets and a symbol for each definable endomorphism of the group.

There are two possible realist defense strategies against the pessimistic meta-induction and Laudan’s meta-modus tollens: the selective strategy, claiming that discarded theories are partially true, and the discontinuity strategy, denying that pessimism about past theories can be extended to current ones. A radical version of discontinuity realism is proposed by Gerald Doppelt: rather than discriminating between true and false components within theories, he holds that superseded theories cannot be shown to be even partially true, while present best theories are demonstrably (...) completely true. I argue that this position, running counter both the cumulativity of science and fallibilism, is untenable; it cannot account for the success of past theories, nor for the failures of current theories, and rather than shutting the door to the pessimistic historical objections it opens it wide. The best strategy, instead, joins the selective idea there was both some truth and some falsity in discarded theories, like in current ones, with the moderate discontinuity idea that the truth rate in present best theories is much greater than in past ones. (shrink)

We argue that the asymmetry between diverging and converging electromagnetic waves is just one of many asymmetries in observed phenomena that can be explained by a past hypothesis and statistical postulate (together assigning probabilities to different states of matter and field in the early universe). The arrow of electromagnetic radiation is thus absorbed into a broader account of temporal asymmetries in nature. We give an accessible introduction to the problem of explaining the arrow of radiation and compare our preferred strategy (...) for explaining the arrow to three alternatives: (i) modifying the laws of electromagnetism by adding a radiation condition requiring that electromagnetic fields always be attributable to past sources, (ii) removing electromagnetic fields and having particles interact directly with one another through retarded action-at-a-distance, (iii) adopting the Wheeler-Feynman approach and having particles interact directly through half-retarded half-advanced action-at-a-distance. In addition to the asymmetry between diverging and converging waves, we also consider the related asymmetry of radiation reaction. (shrink)

Background The perception of organ donation and brain death among Syrian population has not been previously explored. The goal of this study is to evaluate the attitude and knowledge of organ donation among Syrians and the willingness of this population to donate their organs. Methods We conducted a survey-based cross-sectional study in four hospitals in Aleppo, Syria in November 2019. Patient demographic, awareness of brain death; and attitude toward organ donation were collected and analyzed. Results A total of 350 individuals (...) were invited to participate in the survey among whom 303 agreed to participate in the study. The majority of our participants heard about organ donation with television, social media, and the internet being the most common sources of information. When assessing knowledge about brain death, only 40% answered 3 or more questions correctly. Fifty-eight percent of respondents agreed with the idea of organ donation and 183 would like to donate their organs one day. The leading motivation to organ donation was the desire to help, while the most common reason to refuse donation was the refusal to disfigure a dead body by removing an organ. Religious reasons were cited as motivation for organ donation by 43% of participants, and a reason for refusing to donate organs by 24%. Most respondents were unaware of the laws and legislations related to organ donation in Syria. When asked if religion and law were encouraging organ donation, 76% of respondents would donate their organs. Although more positive attitude was found in those with better brain death knowledge, this did not translate into more willingness to donate organs in this group of participants. Conclusions The promotion of organ donations from deceased donors is a necessity given the rising shortage of organs. The information provided by this study could help policy makers build future strategies to promote deceased organ donation programs and overcome current obstacles preventing such initiatives from achieving their goals. (shrink)