Thought experiments analogous to those discussed by Landau and Peierls are studied in the framework of a manifestly covariant relativistic quantum theory. It is shown that momentum and energy can be arbitrarily well defined, and that the drifts induced by measurement in the positions and times of occurrence of events remain within the (stable) spread of the wave packet in space-time. The structure of the Newton-Wigner position operator is studied in this framework, and it is shown that an analogous time (...) operator can be constructed which satisfies the canonical commutation relation with the energy E but does not commute (due to the presence of a time drift term) with the momentum p. The resulting commutation relation is used as a mathematical basis for the derivation of the Landau-Peierls relation Δt Δp≳ħ/c. (shrink)

The heme‐containing cytochromes P‐450 are a ubiquitous family of monooxygenase isozymes responsible for the oxidative metabolism of a wide variety of endogenous as well as exogenous compounds. Many of the compounds metabolized by this enzyme system are effectively detoxified and converted to derivatives more easily eliminated from the organism. However, some compounds can be activated to reactive species capable of eliciting a cascade of toxic lesions, including cancer. Since its discovery nearly 30 years ago, the cytochrome P‐450 enzyme system has (...) received a great deal of attention, particularly in the areas of their mechanisms of metabolism, range of substrate specificity, the purification and characterization of the multiple isozymes and, more recently, the regulation of expression of specific forms. This review will discuss current notions concerning the expression of at least one cytochrome P‐450 isozyme and future directions that should lead to a more complete understanding of cytochrome P‐450 gene expression in general, particularly as it impacts upon biochemical pharmacology. (shrink)

The dynamical equations of relativistic quantum mechanics prescribe the motion of wave packets for sets of events which trace out the world lines of the interacting particles. Electromagnetic theory suggests thatparticle world line densities be constructed from concatenation of event wave packets. These sequences are realized in terms of conserved probability currents. We show that these conserved currents provide a consistent particle and antiparticle interpretation for the asymptotic states in scattering processes. The relation between current conservation and unitarity is used (...) to establish relations between pair production and annihilation amplitudes and scattering. The discrete symmetriesC, T, P are studied and it is shown that no Dirac sea (for fermions where such a construction is possible, or bosons where it is not) is required for consistency of the theory. These currents, furthermore, represent the discrete symmetries in a way consistent with their interpretation as particle currents. (shrink)

Continuous recordings of brain electrical activity were obtained from a group of 176 patients throughout surgical procedures using general anesthesia. Artifact-free data from the 19 electrodes of the International 10/20 System were subjected to quantitative analysis of the electroencephalogram (QEEG). Induction was variously accomplished with etomidate, propofol or thiopental. Anesthesia was maintained throughout the procedures by isoflurane, desflurane or sevoflurane (N = 68), total intravenous anesthesia using propofol (N = 49), or nitrous oxide plus narcotics (N = 59). A set (...) of QEEG measures were found which reversibly displayed high heterogeneity of variance between four states as follows: (1) during induction; (2) just after loss of consciousness (LOC); (3) just before return of consciousness (ROC); (4) just after ROC. Homogeneity of variance across all agents within states was found. Topographic statistical probability images were compared between states. At LOC, power increased in all frequency bands in the power spectrum with the exception of a decrease in gamma activity, and there was a marked anteriorization of power. Additionally, a significant change occurred in hemispheric relationships, with prefrontal and frontal regions of each hemisphere becoming more closely coupled, and anterior and posterior regions on each hemisphere, as well as homologous regions between the two hemispheres, uncoupling. All of these changes reversed upon ROC. Variable resolution electromagnetic tomography (VARETA) was performed to localize salient features of power anteriorization in three dimensions. A common set of neuroanatomical regions appeared to be the locus of the most probable generators of the observed EEG changes. (shrink)

In many animal species, the early development of the embryo follows a stereotypic pattern of cell cleavage, lineage allocation and generation of tissue asymmetry leading to delineation of the body plan with three primary embryonic axes. The mammalian embryo has been regarded as an exception and primary body axes of the mouse embryo were thought to develop after implantation. However, recent findings have challenged this view. Asymmetry in the fertilised oocyte, as defined by the position of the second polar body (...) and the sperm entry point, can be correlated with the orientation of the animal–vegetal and the embryonic–abembryonic axes in the preimplantation blastocyst. Studies of the pattern of morphogenetic movement of cells and genetic activity in the peri‐implantation embryo suggest that the animal–vegetal axis of the blastocyst might presage the orientation of the anterior–posterior axis of the gastrula. This suggests that the asymmetry of the zygote that is established at fertilisation and early cleavage has a lasting impact on the delineation of body axes during embryogenesis. BioEssays 23:508–517, 2001. © 2001 John Wiley & Sons, Inc. (shrink)

In recent years, we have seen a new concern with ethics training for research and development professionals. Although ethics training has become more common, the effectiveness of the training being provided is open to question. In the present effort, a new ethics training course was developed that stresses the importance of the strategies people apply to make sense of ethical problems. The effectiveness of this training was assessed in a sample of 59 doctoral students working in the biological and social (...) sciences using a pre–post design with follow-up and a series of ethical decision-making measures serving as the outcome variable. Results showed not only that this training led to sizable gains in ethical decision making but also that these gains were maintained over time. The implications of these findings for ethics training in the sciences are discussed. (shrink)

Consider the concept combination ‘pet human’. In word association experiments, human subjects produce the associate ‘slave’ in relation to this combination. The striking aspect of this associate is that it is not produced as an associate of ‘pet’, or ‘human’ in isolation. In other words, the associate ‘slave’ seems to be emergent. Such emergent associations sometimes have a creative character and cognitive science is largely silent about how we produce them. Departing from a dimensional model of human conceptual space, this (...) article will explore concept combinations, and will argue that emergent associations are a result of abductive reasoning within conceptual space, that is, below the symbolic level of cognition. A tensor-based approach is used to model concept combinations allowing such combinations to be formalized as interacting quantum systems. Free association norm data is used to motivate the underlying basis of the conceptual space. It is shown by analogy how some concept combinations may behave like quantum-entangled particles. Two methods of analysis were presented for empirically validating the presence of non-separable concept combinations in human cognition. One method is based on quantum theory and another based on comparing a joint probability distribution with another distribution based on a separability assumption using a chi-square goodness-of-fit test. Although these methods were inconclusive in relation to an empirical study of bi-ambiguous concept combinations, avenues for further refinement of these methods are identified. (shrink)

The current article aims to provide an up-to-date synopsis of available techniques to study affect dynamics using intensive longitudinal data. We do so by introducing the following eight dichotomies that help elucidate what kind of data one has, what process aspects are of interest, and what research questions are being considered: single- versus multiple-person data; univariate versus multivariate models; stationary versus nonstationary models; linear versus nonlinear models; discrete time versus continuous time models; discrete versus continuous variables; time versus frequency domain; (...) and modeling the process versus computing descriptives. In addition, we discuss what we believe to be the most urging future challenges regarding the modeling of affect dynamics. (shrink)

BackgroundLarge-scale, centralized data repositories are playing a critical and unprecedented role in fostering innovative health research, leading to new opportunities as well as dilemmas for the medical sciences. Uncovering the reasons as to why citizens do or do not contribute to such repositories, for example, to population-based biobanks, is therefore crucial. We investigated and compared the views of existing participants and non-participants on contributing to large-scale, centralized health research data repositories with those of ex-participants regarding the decision to end their (...) participation. This comparison could yield new insights into motives of participation and non-participation, in particular the behavioural change of withdrawal.MethodsWe conducted 36 in-depth interviews with ex-participants, participants, and non-participants of a three-generation, population-based biobank in the Netherlands. The interviews focused on the respondents’ decision-making processes relating to their participation in a large-scale, centralized repository for health research data.ResultsThe decision of participants and non-participants to contribute to the biobank was motivated by a desire to help others. Whereas participants perceived only benefits relating to their participation and were unconcerned about potential risks, non-participants and ex-participants raised concerns about the threat of large-scale, centralized public data repositories and public institutes, such as social exclusion or commercialization. Our analysis of ex-participants’ perceptions suggests that intrapersonal characteristics, such as levels of trust in society, participation conceived as a social norm, and basic societal values account for differences between participants and non-participants.ConclusionsOur findings indicate the fluidity of motives centring on helping others in decisions to participate in large-scale, centralized health research data repositories. Efforts to improve participation should focus on enhancing the trustworthiness of such data repositories and developing layered strategies for communication with participants and with the public. Accordingly, personalized approaches for recruiting participants and transmitting information along with appropriate regulatory frameworks are required, which have important implications for current data management and informed consent procedures. (shrink)

The disappearance of the imperial biographies written by Marius Maximus is one of the more frustrating losses of Latin literature, for various reasons: the well-known testimony of Ammianus, the interest of Marius Maximus' attested contribution to the Historia Augusta, his importance, much in dispute, to the writer of that work, the lack of information on much of the period he covered, and, not least, the fascinating role assigned to him by modern scholars, remodelling a previous duality of sources, of bad (...) biographer in contrast to the good Ignotus. It has recently become common practice for the evidence of Ausonius' Caesares to be used in the search for this biographer. The suggestion goes back to a dissertation of F. della Corte in 1956/7, and was taken up in his edition of Ausonius' works by Pastorino, and discussed in the following year by Cazzaniga who, though uncertain about the dependence of Ausonius on Marius Maximus, does misleadingly assert ‘e certo che l'ultima epigramma tocca Elagabalo, che chiude la silloge’. More recently, della Corte has returned to the question and sketched a possible model for the growth of the whole extant collection of Ausonius' Caesares, on the basis of the manuscript tradition. The same volume contains a contribution to the question by S. d'Elia and includes, by a felicitous piece of editing, an extended footnote in which d'Elia is able to comment on the relevant part of della Corte's paper. Meanwhile, outside Italy, there have been parallel and independent developments. (shrink)

The preparation of layers of amorphous Se by plasma-enhanced CVD using the hydride H2Se as precursor gas is described. Information concerning the structure of the films was obtained from Raman spectroscopy. The spectra of amorphous Se indicated that the dominant molecular structure is the eight-membered ring and/or a chain with Se8 molecular fragments. This material exhibited reversible photodarkening when illuminated at 77 K. In order to explain this phenomenon, we propose a mechanism which takes into account the role of the (...) lone-pair electron orbitals of Se in their contribution to structural ordering. Illumination can cause a distortion in the normal bonding direction between nearest-neighbour Se atoms and induce in this way intrinsic defect states located at the band edges. In the photo-darkened state, optical transition will occur between these defect states. (shrink)