The complete description of the interaction between an external electromagnetic field and a charged particle causing it to radiate is one of the most fundamental problems in classical electrodynamics. Here we provide a simple coupled model that describes via the Lagrangian of the physical system the full radiation reaction process resulting from the particle–field interactions which simulate the electromagnetic ones. The particle and field evolution equations obtained from the Lagrangian are studied as an initial value problem giving (...) rise to the particle's radiation reaction equation, which includes the complete interaction with the field. Using stability theory we analyze this equation and prove that every solution is global uniform asymptotically stable, evidencing that the particle coupled to the field radiates. The model proves to be interesting, for it clearly illustrates the particle–field interaction process and shows the radiation's origin. (shrink)

In order to understand the rise of runaway solutions in the radiation reaction problem a mechanical model is used. An alternative demonstration of Daboul’s theorem, through Hurwitz’s criterion, is given. The origin of runaway solutions in electrodynamics is discussed. They arise when the particle has a negative mechanical mass or when approximations are used in the equation of motion. In the 1-dimensional mechanical model an exact and linear equation of motion for the particle is obtained, the corresponding (...) exact solution is again runaway when the mechanical mass is negative. The exact solution is not runaway when the mechanical mass is positive. However, the use of approximations leads to an equation of motion which has runaway solutions. It is exhibited that the use of approximations in the 3-dimensional mechanical model is completely necessary because the general equation of motion for the particle is non-linear. The analysis of this case proceeds in a very similar way to the one carried out in electrodynamics. This means that the number of dimensions also plays an important role in the analysis. (shrink)

It has been shown by Gupta and Padmanabhan that the radiation reaction force of the Abraham–Lorentz–Dirac equation can be obtained by a coordinate transformation from the inertial frame of an accelerating charged particle to that of the laboratory. We show that the problem may be formulated in a flat space of five dimensions, with five corresponding gauge fields in the framework of the classical version of a fully gauge covariant form of the Stueckelberg–Feynman–Schwinger covariant mechanics (the zero (...) mode fields of the 0, 1, 2, 3 components correspond to the Maxwell fields). Without additional constraints, the particles and fields are not confined to their mass shells. We show that in the mass-shell limit, the generalized Lorentz force obtained by means of the retarded Green's functions for the five dimensional field equations provides the classical Abraham–Lorentz–Dirac radiation reaction terms (with renormalized mass and charge). We also obtain general coupled equations for the orbit and the off-shell dynamical mass during the evolution as well as an autonomous non-linear equation of third order for the off-shell mass. The theory does not admit radiation if the particle does not move off-shell. The structure of the equations implies that mass-shell deviation is bounded when the external field is removed. (shrink)

We examine the problem of deducing the geodesic motion of test particles from Einstein's vacuum field equations and its extension to include gravitational radiation reaction. In the latter case we obtain an equation of motion for a particle which incorporates radiation reaction of the electrodynamical type, but due to shearing radiation, together with a mass-loss formula of the Bondi-Sachs type.

The self force of electrodynamics is derived from a scalar field. The resulting equation of motion is free of all of the problems that plague the Lorentz Abraham Dirac equation. The age-old problem of a particle in a constant field is solved and the solution has intuitive appeal.

We present a stochastic theory for the nonequilibriurn dynamics of charges moving in a quantum scalar field based on the worldline influence functional and the close-time-path (CTP or in-in) coarse-grained effective action method. We summarize (1) the steps leading to a derivation of a modified Abraham-Lorentz-Dirac equation whose solutions describe a causal semiclassical theory free of runaway solutions and without pre-acceleration patholigies, and (2) the transformation to a stochastic effective action, which generates Abraham-Lorentz-Dirac-Langevin equations depicting the fluctuations of a particle’s (...) worldline around its semiclassical trajectory. We point out the misconceptions in trying to directly relate radiation reaction to vacuum fluctuations, and discuss how, in the framework that we have developed, an array of phenomena, from classical radiation and radiation reaction to the Unruh effect, are interrelated to each other as manifestations at the classical, stochastic and quantum levels. Using this method we give a derivation of the Unruh effect for the spacetime worldline coordinates of an accelerating charge. Our stochastic particle-field model, which was inspired by earlier work in cosmological backreaction, can be used as an analog to the black hole backreaction problem describing the stochastic dynamics of a black hole event horizon. (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)

A point charge accelerating under the influence of an external force emits electromagnetic radiation that reduces the increase in its mechanical energy. This causes a reduction in the particle's acceleration. We derive the decrease in acceleration due to radiation reaction for a particle accelerating parallel to its velocity, and show that it has a negligible effect.

An alternative approach to analyze the nonrelativistic quantum dynamics of a rigid and extended charged particle taking into account the radiation reaction is discussed with detail. Interpretation of the field operators as annihilation and creation ones, theory of perturbations and renormalization are not used. The analysis is carried out in the Heisenberg picture with the electromagnetic field expanded in a complete orthogonal basis set of functions which allows the electromagnetic field to satisfy arbitrary boundary conditions. The corresponding coefficients (...) are the field operators which satisfy the usual commutation relations. A nonlinear equation of motion for the charged particle is obtained. A careful consideration of the quantum effects allows the derivation of a linear equation of motion which is free of both runaway solutions and preacceleration, even for a point charge. Also, the electromagnetic mass, which is defined as the coefficient of the acceleration operator, vanishes for a point particle. However, this does not mean that the results are free of ambiguities which are exhibited and discussed. (shrink)

In this paper, we construct a parallel image of the conventional Maxwell theory by replacing the observer-time by the proper-time of the source. This formulation is mathematically, but not physically, equivalent to the conventional form. The change induces a new symmetry group which is distinct from, but closely related to the Lorentz group, and fixes the clock of the source for all observers. The new wave equation contains an additional term (dissipative), which arises instantaneously with acceleration. This shows that the (...) origin of radiation reaction is not the action of a “charge” on itself but arises from inertial resistance to changes in motion. This dissipative term is equivalent to an effective mass so that classical radiation has both a massless and a massive part. Hence, at the local level the theory is one of particles and fields but there is no self-energy divergence (nor any of the other problems). We also show that, for any closed system of particles, there is a global inertial frame and unique (invariant) global proper-time (for each observer) from which to observe the system. This global clock is intrinsically related to the proper clocks of the individual particles and provides a unique definition of simultaneity for all events associated with the system. We suggest that this clock is the historical clock of Horwitz, Piron, and Fanchi. At this level, the theory is of the action-at-a-distance type and the absorption hypothesis of Wheeler and Feynman follows from global conservation of energy. (shrink)

In the traditional frame of classical electrodynamics, a hydrogen atom would emit electromagnetic waves and thus constantly lose energy, resulting in the fall of the electron on the proton over a finite period of time. The corresponding results were derived under the assumption of the instantaneous interaction between the proton and the electron. In 2004, Raju published a paper where he removed the assumption of the instantaneous interaction and studied the role of a time delay in the classical hydrogen atom. (...) He introduced a model of this effect that can be solved analytically. He calculated the radius rsel of a selected orbit, for which this effect and the radiation reaction force would cancel each other with respect to the tangential acceleration. It turned out that rsel is by an order of magnitude smaller than the Bohr radius. In the present paper we use Raju’s model for the corresponding gravitational situation. In frames of Newton’s gravity, we calculate analytically the radius and the energy Esel of a selected orbit, for which the retardation effect and the radiation reaction force would cancel each other out with respect to the tangential acceleration. Then we compare our outcome with some results of Kaplan’s solution for the two-body gravitational problem based on the Schwarzschild’s field. We show that Esel is very close to the minimum energy of bound states obtained by Kaplan in Einstein’s gravity. We emphasize that the selected orbit from the present paper represents the second only physical situation where the radiation reaction force is zero, but the radiation-caused energy loss is not zero. (shrink)

In this paper the analysis of the classical dynamics of a charged particle is carried out without considering that the electromagnetic field necessarily goes to zero at infinity. A quite general non-linear equation of motion is obtained for an extended charged particle valid for any distribution of charge in the particle and for an electromagnetic field satisfying any boundary conditions. Some common approximations are analyzed with detail to determine how the usual difficulties arise.

It is shown that the well-known disparity in classical electrodynamics between the power losses calculated from the radiation reaction and that from Larmor’s formula, is succinctly understood when a proper distinction is made between quantities expressed in terms of a “real time” and those expressed in terms of a retarded time. It is explicitly shown that an accelerated charge, taken to be a sphere of vanishingly small radius \, experiences at any time a self-force proportional to the acceleration (...) it had at a time \ earlier, while the rate of work done on the charge is obtained by a scalar product of the self-force with the instantaneous value of its velocity. Now if the retarded value of acceleration is expressed in terms of the present values of acceleration, then we get the rate of work done according to the radiation reaction equation, however if we instead express the present value of velocity in terms of its time-retarded value, then we get back the familiar Larmor’s radiation formula. From this simple relation between the two we show that they differ because Larmor’s formula, in contrast with the radiation reaction, is written not in terms of the real-time values of quantities specifying the charge motion but is instead expressed in terms of the time-retarded values. Moreover, it is explicitly shown that the difference in the two formulas for radiative power loss exactly matches the difference in the temporal rate of the change of energy in the self-fields between the retarded and real times. From this it becomes obvious that the ad hoc introduction of an acceleration-dependent energy term, usually referred to in the prevalent literature as Schott-term, in order to make the two formulas comply with each other, is redundant. (shrink)

We investigate in detail the electromagnetic fields of a uniformly accelerated charge, in order to ascertain whether such a charge does ‘emit’ radiation, especially in view of the Poynting flow computed at large distances and taken as an evidence of radiation emitted by the charge. In this context, certain important aspects of the fields need to be taken into account. First and foremost is the fact that in the case of a uniformly accelerated charge, one cannot ignore the (...) velocity fields. This then leads to other equally vital points. The net field energy turns out to be exactly the same as that of a non-accelerated charge having a uniform velocity equal to the instantaneous velocity of the uniformly accelerated charge. Further, the Poynting vector, seen with respect to the ’present’ location of the uniformly accelerated charge, during the deceleration phase, possesses everywhere a radial component pointing inward toward the charge, becoming nil when the charge becomes momentarily stationary, and during the acceleration phase, points away from the charge position. Last, but not least, when the leading spherical front of the relativistically beamed Poynting flux, advances forward at a large time t to a far-off distance \, the charge too is not lagging far behind. In fact, these relativistically beamed fields, increasingly resemble fields of a charge moving in an inertial frame with a uniform velocity \, with a convective flow of fields in that frame along with the movement of the charge. There is no other Poynting flow in the far-zones that could be termed as radiation emitted by the charge which, in turn, is fully consistent with the absence of radiation reaction and is also fully conversant with the strong principle of equivalence. (shrink)

In this paper, I discuss from a philosophical viewpoint the so-called radiation problem that resulted from the Fukushima Daiichi Nuclear Power Station accident after the Great East Japan Earthquake in 2011. The starting point lies in the conceptual distinction between “damage due to radiation” and “damage caused by avoiding radiation.” We can recognize the direct “damage due to radiation” in Fukushima as not serious based on the empirical data so that I focus upon the (...) class='Hi'>problem of the “damage caused by avoiding radiation,” particularly the damage due to evacuation actions. Actually, evacuation actions caused more refugees to die of suicide and diseases than supposed. Obviously, there is a practical problem on whether the forceful and emergent evacuationwas needed. In addition, I will point out that some people psychologically had negative feelings about the radiation problem altogether, for example, absurdity, discomfort, anxiety, or distrust, where some of them tend to twistedly solve those by giving moral censure to people and the product in affected areas. This brought about serious harm to people in Fukushima. I will interpret some people’s careless adoption of precautionary principle and their misunderstanding of the legal standard in radiation protection as being latent in this tragedy. (shrink)

Based on the heterogeneous multiscale method, this paper presents a finite volume method to solve multiscale convection-diffusion-reaction problem. The paper constructs an algorithm of the optimal order convergence rate in H1-norm under periodic medias.

We revisit the nonrelativistic problem of a bound, charged particle subject to the random zero-point radiation field, with the purpose of revealing the mechanism that takes it from the initially classical description to the final quantum-mechanical one. The combined effect of the zpf and the radiation reaction force results, after a characteristic time lapse, in the loss of the initial conditions and the concomitant irreversible transition of the dynamics to a stationary regime controlled by the field. (...) In this regime, the canonical variables x, p become expressed in terms of the dipolar response functions to a set of field modes. A proper ordering of the response coefficients leads to the matrix representation of quantum mechanics, as was proposed in the early days of the theory, and to the basic commutator x^,p^=iħ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\left[ {\hat{x}},{\hat{p}}\right] =i\hbar $$\end{document}. Further, the connection with the corresponding Fokker–Planck equation valid in the Markov approximation, allows one to obtain the radiative corrections of qed. These results reaffirm the essentially electrodynamic and stochastic nature of the quantum phenomenon, as proposed by stochastic electrodynamics. (shrink)

The Gardner report, recently published in the UK, showing a correlation between incidence of childhood leukaemia and paternal exposure to ionising radiations (amongst fathers working in nuclear power plants) has added a new element to debates about both the risk factors in nuclear power plants and the relationships between ionising radiations and leukaemogenesis. The epidemiologic and genetic evidence concerning leukaemias is reviewed here and it is concluded that the leukaemogenic agent, whose existence is indicated in the Gardner report, is unlikely (...) to be paternal radiation dose per se but rather exposure to another factor that is correlated with paternal radiation dose received. (shrink)

The physicists of the early twentieth century were unaware of two aspects which are vital to understanding some aspects of modern physics within classical theory. The two aspects are: the presence of classical electromagnetic zero-point radiation, and the importance of special relativity. In classes in modern physics today, the problem of atomic collapse is still mentioned in the historical context of the early twentieth century. However, the classical problem of atomic collapse is currently being treated in the (...) presence of classical zero-point radiation where the problem has been transformed. The presence of classical zero-point radiation indeed keeps the electron from falling into the Coulomb potential center. However, the old collapse problem has been replaced by a new problem where the zero-point radiation may give too much energy to the electron so as to cause “self-ionization.” Special relativity may play a role in understanding this modern variation on the atomic collapse problem, just as relativity has proved crucial for a classical understanding of blackbody radiation. (shrink)

It is conjectured that a suitably modified Bondi-type expansion of the gravitational field in the radiation zone is a rapidly convergent series. It is also conjectured that the source behavior in the inner zone is insensitive to the initial conditions imposed on the gravitational field in solving the initial-value problem in this zone. Consequences of these conjectures for the problem of relating source motion to the Bondi news function are discussed.

This study examined whether parents’ attribution of their child’s emotions (internalizing, externalizing) to dispositional causes is associated with children’s problem behaviour (internalizing, externalizing). The mediating roles of parents’ emotion-dismissing and -coaching reactions and the moderating role of child’s gender was also examined. Participants were 241 US parents with a child (43% girls) between the ages of 5 and 7. Parents were presented with vignettes in which a gender-neutral child displayed internalizing and externalizing emotions and were asked to imagine their (...) own child in the vignettes. Subsequently, parents indicated whether they attributed the child’s emotion to dispositional causes and the likelihood of reacting in an emotion-dismissing and -coaching way in each situation. Child problem behaviour was measured using the CBCL. Results show that parental dispositional attributions were associated with child internalizing and externalizing problems, and this association was consistently mediated by emotion-dismissing reactions. The association between parental dispositional attributions and emotion-dismissing, as well as its indirect effect on child internalizing problems, was stronger for boys than for girls, whereas the indirect effect via emotion-coaching was stronger for girls than for boys. Thus, the parental attribution process seems to be different for boys and girls. (shrink)

A new scheme is proposed in order to deduce an equation of motion for a spinless charged point particle leading to an equivalent Landau–Lifshitz equation of motion. Consequently Larmor’s formula must be substituted by a new expression for the large distance radiation rate of energy. A constraint appears on the applicability of the Maxwell electromagnetic tensor. The particular case of a sudden force is analyzed in order to show the physical results predicted by the new model. A geometrical rearrangement (...) of the energy explains the balance. (shrink)

I first argue that, contrary to many atheistic philosophers, there is good reason to think the typical theistic philosopher’s retaining of her theism when faced with the Problem of Evil is comparatively epistemically upstanding even if both atheism is true and the typical theistic philosopher has no serious criticism of the atheist’s premises in the PoE argument. However, I then argue that, contrary to many theistic philosophers, even if theism is true, the typical theistic philosopher has no good non-theistic (...) reasons for rejecting any of the atheist’s premises, and she has good non-theistic reasons in favor of the atheist’s premises. In that respect, it’s extremely difficult for the theistic philosopher to respond to the PoE in an informative, non-question-begging way. I close by considering whether theistic philosophers should reject my second thesis. (shrink)

In their ‘Ethical and Technical Challenges in Compensating for Harm Due to Solar Radiation Management Geoengineering’ (2014), Toby Svoboda and Peter Irvine (S&I) argue that there are significant technical and ethical challenges that stand in the way of crafting a just solar radiation management (SRM) compensation system. My aim in this article is to contribute to the project of addressing these problems. I do so by focusing on one of S&I’s important ethical challenges, their claim that the polluter (...) pays principle (PPP) is too problematic to be useful in determining responsibility for SRM compensation. Their argument for the latter claim consists in a series of allegations, mostly in the form of questions, that are thought to indicate serious difficulties standing in the way of using the PPP to craft a just compensation system. I argue that S&I fail to substantiate these allegations: the PPP is not as problematic as S&I suggest, and moreover, is a viable candidate for determining responsibility for SRM compensation. S&I raise five allegations against the PPP. I discuss each in turn. (shrink)

Ionizing radiation is present in various situations in the contemporary world. Defining the quantities and units for this field is a complex scientific task, especially the quantities used in radiological protection (RP) to estimate the damage caused to individuals exposed to radiation (detriment). This article highlights the lack of consensus in the scientific RP community regarding the quantities and units employed in practice from the perspective of the philosophy of science. The basic concepts related to the system of (...) quantities are presented, followed by the problems and criticisms addressed by experts in the field. Several reasons for these problems are identified. The article discusses the scant interest on the part of philosophy of science in RP. The philosophy of science is still dominated by an analytical–conceptual perspective that pays little attention to the actual influence of certain structures better understood when considered from the institutional viewpoint, which is here exemplified by the International Commission on Radiological Protection (ICRP) and the International Atomic Energy Agency (IAEA). (shrink)

Some of the major problems in radiation protection are closely connected to issues that have a long, independent tradition in moral philosophy. This contribution focuses on two of these issues. One is the relationship between the protection of individuals and optimisation on the collective level, and the other is the relative valuation of future versus immediate damage. Some of the intellectual tools that have been developed by philosophers can be useful in radiation protection. On the other hand, philosophers (...) have much to learn from radiation protectors, not least when it comes to finding pragmatic solutions to problems that may be intractable in principle. (shrink)

The physical, mathematical, and philosophical foundations of the quantum theory of free Bose fields in fixed general relativistic spacetimes are examined. It is argued that the theory is logically and mathematically consistent whereas semiclassical prescriptions for incorporating the back-reaction of the quantum field on the geometry lead to inconsistencies. Still, the relations and heuristic value of the semiclassical approach to canonical and covariant schemes of quantum gravity-plus-matter are assessed. Both conventional and rigorous formulations of the theory and of its (...) principal predictions, cosmological particle creation and horizon radiation, are expounded and compared. Special attention is devoted to spacetime properties needed for the existence or uniqueness of the relevant theoretical elements , renormalization of the stress tensor). The emergence of unitarily inequivalent representations in a single dynamical context is used as motivation for the introduction of the abstract $\rm C\sp{\*}$-algebraic axiomatic formalism. The operationalist and conventionalist claims of the original abstract algebraic program are criticized in favor of its tempered outgrowth, local quantum physics. The interpretation of the theory as a wave mechanics of classical field configurations, deriving from the Schrodinger representations of the abstract algebra, is discussed and is found superior, at least on the level of analogy, to particle or harmonic oscillator interpretations. Further, it is argued that the various detector results and the Fulling nonuniqueness problem do not undermine the particle concept in the ways commonly claimed. In particular, arguments are offered against the attribution of particle status to the Rindler quanta, against the physical realizability of the Rindler vacuum, and against the more general notion of observer-dependence as to the definition of 'particle' or 'vacuum'. However, the question of the ontological status of particles is raised in terms of the consistency of quantum field theory with non-reductive realism about particles, the latter being conceived as entities exhibiting attributes of discreteness and localizability. Two arguments against non-reductive realism about particles, one from axiomatic algebraic local quantum theory in Minkowski spacetime and one from quantum field theory in curved spacetime, are developed. (shrink)

In this paper, a reaction is presented to Siegel’s claim that the pragma-dialectical theory of argumentation ignores or neglects epistemological viewpoints that he finds vital to any normative theory of argumentation. The focus is on the most important problems in Siegel’s argument: 1) the ambiguity of the term ‘argument’ and the alleged negligence of this ambiguity in pragma-dialectics; 2) the critical rational perspective of the pragma-dialectical account; and 3) the alleged negligence of the “abstract propositional sense” of argument in (...) pragma-dialectics. (shrink)

This paper discusses the problem of gravitational perturbations of radiating spacetimes. We lay out the theoretical framework for describing the interaction of external gravitational fields with a radiating spacetime. This is done by deriving the field perturbation equations for a radiating metric. The equations are then specialized to a Vaidya spacetime. For the Hiscock ansatz of a linear mass model of a radiating blackhole the equations are found separable. Further, the resulting ordinary differential equations are found to admit analytic (...) solutions. We obtain the solutions and discuss their characteristics. (shrink)

In this paper, a reaction is presented to Siegel’s claim that the pragma-dialectical theory of argumentation ignores or neglects epistemological viewpoints that he finds vital to any normative theory of argumentation. The focus is on the most important problems in Siegel’s argument: 1) the ambiguity of the term ‘argument’ and the alleged negligence of this ambiguity in pragma-dialectics; 2) the critical rational perspective of the pragma-dialectical account; and 3) the alleged negligence of the “abstract propositional sense” of argument in (...) pragma-dialectics. (shrink)

Basically, I agree with Chen Lai's views on the difficulties of translating ancient Chinese thinking into modern Western idioms. The problem is not only due to the dependence of the meaning of terms upon their use in a specific context. The problem is already there for Chinese scholars themselves: It is the translation of words or concepts from a traditional learned context related to specific questions into modern Chinese language. In order to succeed, one has to realize, first, (...) that modern colloquial Chinese is divorced from classical Chinese categories and, secondly, that philosophical vocabulary in modern Chinese is contaminated by Western philosophical categories. (shrink)

The equivalence principle as well as the spin-two character of the weak gravitational field lead to difficulties in the measurability analysis of this field which are not encountered in Bohr and Rosenfeld's corresponding inquiry into the electromagnetic field. To meet these difficulties, atomic elastic structures are proposed as gravitational field detectors whose parameters (masses, total volumes, lattice and elastic constants) are adjustable. The limitations imposed by the uncertainty principle and by the radiation reaction of the detectors on the (...) determination of the amplitude, frequency, and direction of the field are then exhibited. Finally, the relevance of the present work to the investigation of DeWitt and to Einstein's full theory of gravitation is briefly considered. (shrink)

Ionizing radiation is present in various situations in the contemporary world. Defining the quantities and units for this field is a complex scientific task, especially the quantities used in radiological protection (RP) to estimate the damage caused to individuals exposed to radiation (detriment). This article highlights the lack of consensus in the scientific RP community regarding the quantities and units employed in practice from the perspective of the philosophy of science. The basic concepts related to the system of (...) quantities are presented, followed by the problems and criticisms addressed by experts in the field. Several reasons for these problems are identified. The article discusses the scant interest on the part of philosophy of science in RP. The philosophy of science is still dominated by an analytical–conceptual perspective that pays little attention to the actual influence of certain structures better understood when considered from the institutional viewpoint, which is here exemplified by the International Commission on Radiological Protection (ICRP) and the International Atomic Energy Agency (IAEA). (shrink)

This article addresses the problem of the impact of a major change in the "instrumentation space" of a given scientific domain. The domain under scrutiny is turbulent combustion. It has the peculcarcty of being developed, essentially since the 1940s, by the progressive interpenetration of two autonomous fields, the chemistry of combustion and the mechanics of turbulence. The analyzed change in instrumentation is a major one in that the new laser-based optical diagnostic techniques which, since the 1970s, invaded turbulent combustcon, (...) allowed for the first time the quantitative characterization of turbulent reacting flows. The impact of this new instrumentation on the relations between experimental and theoretical lines of work is analyzed. These relations concern both the global organization of the workplace and the scientific "division of labor" between theoreticians and experimentalists. The impact of the sudden availability of new experimental information on the cognitive structure of this borderland domain is also explored. (shrink)

The Enzymatic control reactions model was presented within the scope of fractional calculus. In order to accommodate the usual initial conditions, the fractional derivative used is in Caputo sense. The methodologies of the three analytical methods were used to derive approximate solution of the fractional nonlinear system of differential equations. Two methods use integral operator and the other one uses just an integral. Numerical results obtained exhibit biological behavior of real world problem.

The Enzymatic control reactions model was presented within the scope of fractional calculus. In order to accommodate the usual initial conditions, the fractional derivative used is in Caputo sense. The methodologies of the three analytical methods were used to derive approximate solution of the fractional nonlinear system of differential equations. Two methods use integral operator and the other one uses just an integral. Numerical results obtained exhibit biological behavior of real world problem.

Environmental heterogeneity is invoked as a key explanatory factor in the adaptive evolution of a surprisingly wide range of phenomena. This article aims to analyze this explanatory scheme of categorizing traits or properties as adaptations to environmental heterogeneity. First it is suggested that this scheme can be understood as a reaction to how heterogeneity adaptations were discounted or ignored in the modern synthesis. Then a positive account is proposed, distinguishing between two broad categories of adaptation to environmental heterogeneity: properties (...) selected for by well-defined patterns of environmental heterogeneity, and properties that help organisms exploit novel patterns of environmental heterogeneity. (shrink)

The controversy over spontaneous generation and the theory of evolution was part of the broader issue of the nature of life. It was the vitalists, who had originally accepted the doctrine of heterogenesis, who now were forced to reject abiogenesis. Their commitment to the view that life was unique and autonomous was so strong that, once the link between evolution and the abiogenetic origin of life had been made, they were almost constrained to reject evolution. It is not surprising that (...) one finds this extreme position among German scientists, for it was only in Germany that the strong connection had been made. In Britain, with its strong empirical tradition, the theory of evolution was never completely tied to the doctrine of abiogenesis.Many nonvitalistic biologists were equally committed to the view that there was a gradation between the living and the nonliving, and saw in the doctrine of evolution a vindication of these views. To many of this school, abiogenesis was an a priori necessity requiring no empirical proof. If they sought for any empirical justification for their views on abiogenesis, one feels that such proof was never of great importance to them. Many—particularly the Germans—regarded those who denied abiogenesis because of the lack of proof to be guilty of following an outdated methodology: “that modern scientists still put so uncommon value on the inductive proof of spontaneous generation, is the clearest indication that few place confidence in the first principle of the theory of knowledge.” To them an acceptance of abiogenesis was necessary “in order to understand nature according to the laws of causality.” 105. (shrink)

The Coronavirus Covid 19 pandemic has produced terrible effects in the world economy and is shaking social and political stability around the world. The world of sport has obviously been severely affected by the pandemic, as authorities progressively canceled all level of competitions, including the 2020 Olympic Games in Tokyo. In Spain, the initial government-lockdown closed the Sports High-performance Centers, and many other sports facilities. In order to support athlete's health and performance at crises like these, an online questionnaire named (...) RECOVID-19, was designed to assess how athletes were living their lives during such periods of home confinement. The main purpose of the questionnaire was to assess the impact of prolongued confinement on athlete's psychological, emotional, and behavioral performance. One thousand, two hundred forty-eight athletes participated in the survey. They had the fllowing characteristics:, who compete at National and International level. Results showed that during the confinement period, those athletes who lacked motivation reported a higher level of stressful thoughts, more behavioral problems, and greater emotional upheaval. However, those athletes who accepted confinement measures as necessary, and were in favor of respecting the rules of social isolation, fostered positive emotional states such as feelings of friendship. In addition, the availability of some sport equipment together with the ability to continue some training, were protective factors against emotional stress, lack of motivation and behavioral problems; and they were associated with greater respect for, and adherence to, confinement rules. Gender differences, tested by multigroup analysis, revealed that coping activities were more often associated to negative emotional states among women, whereas the ongoing availability of training information and future conditions were equally protective factors for both genders. This study also showed that receiving coaching, support and completing frequent training routines seem to be valuable tools to prevent or reduce some of the harmful effects of isolation on athlete's emotional well-being. The conclusions derived from this research would possibly help sport authorities to design supporting policies and plans to support athletes and trainers in future disruptive health crises. (shrink)

A physically consistent semi-classical treatment of black holes requires universality arguments to deal with the `trans-Planckian' problem where quantum spacetime effects appear to be amplified such that they undermine the entire semi-classical modelling framework. We evaluate three families of such arguments in comparison with Wilsonian renormalization group universality arguments found in the context of condensed matter physics. Our analysis is framed by the crucial distinction between robustness and universality. Particular emphasis is placed on the quality whereby the various arguments (...) are underpinned by `integrated' notions of robustness and universality. Whereas the principal strength of Wilsonian universality arguments can be understood in terms of the presence of such integration, the principal weakness of all three universality arguments for Hawking radiation is its absence. (shrink)