Smooth Continuum Research Articles

Transmural action potential repolarization heterogeneity develops postnatally in the rabbit

Introduction: In the hereditary long QT syndrome, arrhythmia risk changes with age despite the presence of an ion channel mutation throughout development. Age-dependent changes in the transmural dispersion of repolarization may modulate this vulnerability. We recorded cardiac action potentials in infant, periadolescent, and adult rabbit myocardium to determine if transmural heterogeneities in repolarization are developmentally determined. Methods and Results: Arterially perfused ventricular preparations were studied from 2-week (n = 7), 7-week (n = 7), and adult (n = 6) NZW rabbits. Action potentials were recorded with microelectrodes in five regions: epicardium (epi), subepicardium (subepi), midwall (mid), subendocardium (subendo), and endocardium (endo) during endocardial S1 pacing at cycle lengths of 2,000, 1,000, and 500 ms. At 2 weeks, the transmural APD90 profile was flat. With age, APD prolongation from subepi to endo created a transmural repolarization gradient. At 7 weeks, APD90 was significantly longer at subendo [204 ± 2 ms (mean ± SE) 2,000-ms cycle length, P < 0.05] vs both endo (193 ± 2 ms) and epi (172 ± 2 ms), causing a heterogeneous transmural APD90 gradient. In adults, the transmural gradient was a smooth continuum such that APD was shortest in epicardium and longest in endocardium. Conclusion: The transmural distribution of APD is developmentally determined. Tissue-specific age-dependent changes in APD can result in transmural repolarization heterogeneity. These age-related effects may modulate arrhythmia vulnerability during development. (J Cardiovasc Electrophysiol, Vol. 15, pp. 795-801, July 2004)

Finitary, Causal and Quantal Vacuum Einstein Gravity

We continue recent work (Mallios and Raptis, International Journal of Theoretical Physics40, 1885, 2001; in press) and formulate the gravitational vacuum Einstein equations over a locally finite space-time by using the basic axiomatics, techniques, ideas, and working philosophy of Abstract Differential Geometry. The main kinematical structure involved, originally introduced and explored in (Mallios and Raptis, International Journal of Theoretical Physics40, 1885, 2001), is a curved principal finitary space-time sheaf of incidence algebras, which have been interpreted as quantum causal sets, together with a nontrivial locally finite spin-Loretzian connection on it which lays the structural foundation for the formulation of a covariant dynamics of quantum causality in terms of sheaf morphisms. Our scheme is innately algebraic and it supports a categorical version of the principle of general covariance that is manifestly independent of a background \(\mathcal{C}^\infty\)-smooth space-time manifold M. Thus, we entertain the possibility of developing a “fully covariant” path integral-type of quantum dynamical scenario for these connections that avoids ab initio various problems that such a dynamics encounters in other current quantization schemes for gravity—either canonical (Hamiltonian) or covariant (Lagrangian)—involving an external, base differential space-time manifold, namely, the choice of a diffeomorphism-invariant measure on the moduli space of gauge-equivalent (self-dual) gravitational spin-Lorentzian connections and the (Hilbert space) inner product that could in principle be constructed relative to that measure in the quantum theory—the so-called “inner product problem,” as well as the “problem of time” that also involves the Diff(M) “structure group” of the classical \(\mathcal{C}^\infty\)-smooth space-time continuum of general relativity. Hence, by using the inherently algebraico—sheaf—theoretic and calculus-free ideas of Abstract Differential Geometry, we are able to draw preliminary, albeit suggestive, connections between certain nonperturbative (canonical or covariant) approaches to quantum general relativity (e.g., Ashtekar's new variables and the loop formalism that has been developed along with them) and Sorkin et al.'s causal set program. As it were, we “noncommutatively algebraize,” “differential geometrize” and, as a result, dynamically vary causal sets. At the end, we anticipate various consequences that such a scenario for a locally finite, causal and quantal vacuum Einstein gravity might have for the obstinate (from the viewpoint of the smooth continuum) problem of \(\mathcal{C}^\infty\)-smooth space-time singularities.

Electron density of semi-bridging carbonyls. Metamorphosis of CO ligands observed via experimental and theoretical investigations on [FeCo(CO)(8)](-).

The electron density distribution in a transition-metal dimer containing a semibridging carbonyl is determined through experimental X-ray diffraction and quantum chemical computations. The changes occurring during the evolution from terminal to bridging coordinations are described by a "structure-correlation-like" approach and by a theoretical investigation along the conversion path. The smooth continuum of conformations observed in the solid state is explained in terms of the mutual interplay of direct M-M and M-CO and indirect M- - -M and M- - -C interactions, which can be characterized by interatomic delocalization indexes, within the framework of Quantum Theory of Atoms in Molecules.

Fluid flow in nanopores: Accurate boundary conditions for carbon nanotubes

Steady-state Poiseuille flow of a simple fluid in carbon nanopores under a gravitylike force is simulated using a realistic empirical many-body potential model for carbon. Building on our previous study of slit carbon nanopores we show that fluid flow in a nanotube is also characterized by a large slip length. By analyzing temporal profiles of the velocity components of particles colliding with the wall we obtain values of the Maxwell coefficient defining the fraction of molecules thermalized by the wall and, for the first time, propose slip boundary conditions for smooth continuum surfaces such that they are equivalent in adsorption, diffusion, and fluid flow properties to fully dynamic atomistic models.

Obviously sequential, but continuous or staged? Refits and cognition in three late paleolithic assemblages from Japan

The cognitive basis of technological behavior is of major interest in modern archaeology, although addressing ancient cognition in objective, material terms is difficult. Since refitted portions of lithic debris found together reflect the work done at one sitting, patterns of refitted material expose the cognitive basis of lithic technology by showing how stoneworkers structured their efforts. Analysis of assemblages of refitted materials from three Late Paleolithic Japanese sites—Iwato, Isoyama, and Mosanru—shows that although stoneworking was highly patterned and could proceed as a smooth continuum, stoneworkers regularly made use of convenient interruption points to divide the reduction sequence. Analysis also shows that diversity existed within patterns of production and suggests that established archaeological models that focus on highly patterned sequential activities may not expose the diversity that existed in the execution of technological activities.

On the nature of internal wave spectra near a continental slope

Amongst the most energetic motions in the deep ocean are internal waves supported by stable vertical stratification in density. Previously, these waves were considered freely propagating as described by a smooth continuum internal wave band (IWB) frequency spectrum. We studied details of the IWB using yearlong current observations from the Bay of Biscay. Instead of observing continuum IWB spectra near a continental slope, we show that (at least) the first half‐decade of the IWB is dominated by motions at localized frequencies determined by strong non‐linear interactions between waves at the fundamental semidiurnal tidal and atmospherically induced inertial frequencies.

Care and Monitoring of the Anaesthetized Patient Including the Prevention of Injuries

Effective anaesthetic care aims to reduce the morbidity, mortality and complication rates from surgery. General anaesthesia renders the patient in a suitable state for surgery but, by interfering with control of vegetative functions, has many side effects. Sedation is often accomplished using lower doses of the same drugs used for general anaesthesia and forms part of a smooth continuum of increasing depth of general anaesthesia. The sedated patient should therefore be monitored just as diligently. Control of the airway is lost in general anaesthesia or ‘deep’ sedation by abolition of the protective reflexes which normally prevent aspiration. Control of breathing is impaired, leading to hypoventilation. Circulatory control is similarly blunted, with a tendency to vasodilatation whether general or regional anaesthesia is employed. Under general or regional anaesthesia, reflexes protecting the patient from noxious events are abolished (e.g. blinking, limb withdrawal, movement to relieve uncomfortable pressure points). Control of body temperature is impaired by both regional and general anaesthesia.

Self, Object, Neurobiology

After many years of teaching borderline psychodynamics on the basis of object relations theory, I came to something of a crisis. I discovered that I no longer believed in significant aspects of what I was doing. Traditional object relations theory provides an approach to the understanding of the borderline’s subjective state, but it fails to provide a plausible explanation of etiology. To get to etiology, one must go further. On must go to biology. This paper goes back to Darwin who was one of the first investigators to describe attachment behavior in a biologic frame. By applying the biology of attachment to object relations theory, one is lead to a very different perspective. What biology shows is that the progression from attachment to primitive affect to integrated self is not along a smooth continuum. There are biologic leaps. And if object relations theory is to go beyond the mere description of subjective experience, then it must combine the scientific study of attachment that began with Darwin and the study of the intrapsychic that began with Freud, in order to arrive at a neuropsychoanalysis that brings laboratory science to the study of mind.

Infrared spectroscopy of V4334 Sgr (Sakurai's Object)

IR spectroscopy and photometry in the 0.8–2.4 and 3–14 μmregions are reported for seven dates between March 21 1998 and July20 2000 UT. The shorter wavelength region displays a smooth continuum increasing to longerwavelengths that is indicative of the Wien tail of a Planck function. Only theHe I 1.0830 line is present early and it shows a P-Cygni profile which laterdisappears. The long wave spectra show a smooth continuum between 3 and 13μm that was well fit by a gray body at 1000 K. A weak, unidentifiedemission feature appears between 8 and 10 μm.

Care and Monitoring of the Anaesthetized Patient Including the Prevention of Injuries

Effective anaesthetic care aims to reduce the morbidity, mortality and complication rates from surgery. General anaesthesia renders the patient in a suitable state for surgery but, by interfering with control of vegetative functions, has many side effects. Sedation is often accomplished using lower doses of the same drugs used for general anaesthesia and forms part of a smooth continuum of increasing depth of general anaesthesia. The sedated patient should therefore be monitored just as diligently. Control of the airway is lost in general anaesthesia or ‘deep’ sedation by abolition of the protective reflexes which normally prevent aspiration. Control of breathing is impaired, leading to hypoventilation. Circulatory control is similarly blunted, with a tendency to vasodilatation whether general or regional anaesthesia is employed. Under general or regional anaesthesia, reflexes protecting the patient from noxious events are abolished (e.g. blinking, limb withdrawal, movement to relieve uncomfortable pressure points). Control of body temperature is impaired by both regional and general anaesthesia.

Implication of scaling hierarchy associated with nonequilibrium: field and particulate

The advent of nanotechnology has necessitated a better understanding of how material microstructure changes at the atomic level would affect the macroscopic properties that control the performance. Such a challenge has uncovered many phenomena that were not previously understood and taken for granted. Among them are the basic foundation of dislocation theories which are now known to be inadequate. Simplifying assumptions invoked at the macroscale may not be applicable at the micro- and/or nanoscale. There are implications of scaling hierrachy associated with inhomegeneity and nonequilibrium of physical systems. What is taken to be homogeneous and equilibrium at the macroscale may not be so when the physical size of the material is reduced to microns. These fundamental issues cannot be dispensed at will for the sake of convenience because they could alter the outcome of predictions. Even more unsatisfying is the lack of consistency in modeling physical systems. This could translate to the inability for identifying the relevant manufacturing parameters and rendering the end product unpractical because of high cost. Advanced composite and ceramic materials are cases in point. Discussed are potential pitfalls for applying models at both the atomic and continuum levels. No encouragement is made to unravel the truth of nature. Let it be partiuclates, a smooth continuum or a combination of both. The present trend of development in scaling tends to seek for different characteristic lengths of material microstructures with or without the influence of time effects. Much will be learned from atomistic simulation models to show how results could differ as boundary conditions and scales are changed. Quantum mechanics, continuum and cosmological models provide evidence that no general approach is in sight. Of immediate interest is perhaps the establishment of greater precision in terminology so as to better communicate results involving multiscale physical events.

Fuzzy logic methods in fatigue and creep

Fatigue and creep laboratory data for metals normally exhibit scatter, which implies an element of uncertainty or vagueness in the results. Such data are usually treated by empirical correlations or by mathematical models with some theoretical basis. Confidence limits are sometimes given based upon an assumed probability distribution. On a fine scale, fracture mechanics studies consider the mechanism of crack growth, assuming a uniformly smooth continuum. The treatments aim to provide design working stresses and also the reliability basis for the formulation of inspection and maintenance schedules. Further uncertainty in the interpretation of laboratory test data in terms of in-service material characteristics arises from a few other sources, even if the material types are nominally the same. Fuzzy logic is a natural means of expressing vague categories of information by means of fuzzy sets and also provides the means of performing logic operations on them. In this work, consideration is given to the application to some aspects of fatigue and creep. Some examples, including fuzzy boundaries between safe and unsafe states, are given to illustrate the methodology, the conclusions are also initially in the form of fuzzy sets. Compared with other methodologies, richer meaning is found in the results.

Single-side microelectromechanical capacitive accelerometer

The advent of nanotechnology has necessitated a better understanding of how material microstructure changes at the atomic level would affect the macroscopic properties that control the performance. Such a challenge has uncovered many phenomena that were not previously understood and taken for granted. Among them are the basic foundation of dislocation theories which are now known to be inadequate. Simplifying assumptions invoked at the macroscale may not be applicable at the micro- and/or nanoscale. There are implications of scaling hierrachy associated with inhomegeneity and nonequilibrium of physical systems. What is taken to be homogeneous and equilibrium at the macroscale may not be so when the physical size of the material is reduced to microns. These fundamental issues cannot be dispensed at will for the sake of convenience because they could alter the outcome of predictions. Even more unsatisfying is the lack of consistency in modeling physical systems. This could translate to the inability for identifying the relevant manufacturing parameters and rendering the end product unpractical because of high cost. Advanced composite and ceramic materials are cases in point.Discussed are potential pitfalls for applying models at both the atomic and continuum levels. No encouragement is made to unravel the truth of nature. Let it be partiuclates, a smooth continuum or a combination of both. The present trend of development in scaling tends to seek for different characteristic lengths of material microstructures with or without the influence of time effects. Much will be learned from atomistic simulation models to show how results could differ as boundary conditions and scales are changed. Quantum mechanics, continuum and cosmological models provide evidence that no general approach is in sight. Of immediate interest is perhaps the establishment of greater precision in terminology so as to better communicate results involving multiscale physical events.

DIVERSITY AND DEVELOPMENT OF CIRCADIAN RHYTHMS IN THE EUROPEAN RABBIT

Three main concerns underlie this review: 1) The need to draw together the widely dispersed information available on the circadian biology of the rabbit. Although the rabbit is a classic laboratory mammal, this extensive body of information is often overlooked by chronobiologists, and despite several advantages of this species. In terms of its general biology the rabbit is the best studied laboratory mammal in the wild, it demonstrates a wide variety of robust circadian functions, and being a lagomorph, it provides a useful comparison with more commonly studied rodent species. 2) The need to more fully exploit a developmental approach to understanding circadian function, and the particular suitability of the rabbit for this. Female rabbits only visit their altricial young for a few minutes once every 24 h to nurse, and survival of the young depends on the tight circadian-controlled synchronization in behavior and physiology of the two parties. Patterns of circadian rhythmicity in neonatal pups associated with nursing do not form a smooth continuum into weaning and adult life, and may reflect the action of separate mechanisms operating in their own right. 3) Using information from the first two points, to emphasize the diversity and complexity of circadian rhythms underlying behavioral and physiological functions in adult and developing mammals. Information accruing on circadian functions in the rabbit makes it increasingly difficult to account for these in terms of one or two regulatory mechanisms or “oscillators.” Thus, it is argued that in addition to the reductionist, molecular approaches currently dominating much of chronobiology, the study of circadian systems as emergent characteristics of whole organisms operating in complex environments merits special attention. (Chronobiology International, 18(1), 1–26, 2001)

Pulse modulated high-pressure caesium discharge lamp

The high-pressure caesium discharge has a favourable spectraldistribution consisting of a smooth recombination continuum in the visiblerange. When operated on a continuous power source, the spectrum in thevisible region is close to blackbody radiation; however, the lamp efficacyis restrained by the self-reversed resonance lines occurring at 825 nm and894 nm. Pulse modulation significantly increases the core plasmatemperature, suppresses the near-infrared segment of the spectrum, stronglyenhances the continuous radiation in the visible region, and successfullyavoids overloading (<40 W cm-2) the arc tubes. Thespectrum in the visible appears to have the same shape as blackbodyradiation when the lamp is operated on a multiple pulse modulated powersource.The arc tube geometry, caesium/mercury compositions, and power supplywaveforms were optimized for photometric performance through a series ofcomparison tests. The lamp efficacy increased with narrower diameter arctubes, higher lamp currents, as well as higher current crest factors (ratioof current pulse peak to RMS current). The highest efficacy achieved forthe lamp operated on the pulse modulated power supply was 46 lpw. The lampexhibits excellent dimming characteristics and has a colour rendering index(CRI) very close to a thermal source such as a tungsten halogen lamp.This study provides a framework for the design of a new lamp/ballast systemwhich features excellent dimming characteristics, a near-perfect CRI, anefficacy above 40 lpw, and long life. The application for this light sourcecould be a replacement for a high-end tungsten halogen or a whitehigh-pressure sodium lamp.

Collision-Induced Absorption in the Region of the O2 Fundamental: Bandshapes and Dimeric Features

The oxygen fundamental collision-induced absorption bandshapes are simulated for temperatures between 90 and 296 K. It is shown that the use of line-mixing formalism allows nice simulation of the observed bandshapes including minor regular ripples superimposed on the smooth continuum in the region of the S and O branches. Weak absorption due to tightly bound oxygen dimers manifests itself as pseudodiatomic PR-like structure atop the monomer Q branch. Consideration of the temperature variations of this structure allows the oxygen-dimer effective rotational constant 〈B〉 to be roughly characterized. The value of 〈B〉 is notably lower than the ground state value B0 retrieved recently by high-resolution laser probe of oxygen dimers formed in a supersonic slit expansion. This may be considered an indication of significant deviation of the (O2)2 structure averaged over the ensemble of thermally excited dimers from that characterizing the ground state.

Pediatric asthma disease management.

The prevalence of asthma in children in the United States is estimated at more than 5% of the population, and it has risen more than 40% in the previous decade. Several guidelines for the management of acute and chronic asthma exist, and they all emphasize several basic components including state-of-the-art pharmacologic treatment, trigger avoidance, and patient self-management skills. This Article highlights the necessary components for pediatric asthma disease management to insure a smooth continuum of care across all disciplines and settings.

Ultra smooth continua are smooth

In this paper we to define and study a class of metric continua called ultra smooth, which (by the definition) form a subclass of the class of continua being hereditarily unicoherent at some point. The major result is that every ultra smooth continuum is smooth.

RelationTrγ5=0and the index theorem in lattice gauge theory

The relation $\mathrm{Tr}{\ensuremath{\gamma}}_{5}=0$ implies the contribution to the trace from unphysical (would-be) species doublers in lattice gauge theory. This statement is also true for Pauli-Villars regularization in continuum theory. If one insists on $\mathrm{Tr}{\ensuremath{\gamma}}_{5}=0,$ one thus inevitably includes unphysical states in Hilbert space. If one truncates the trace to the contribution from physical species only, one obtains $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{T}\mathrm{r}{\ensuremath{\gamma}}_{5}{=n}_{+}\ensuremath{-}{n}_{\ensuremath{-}}$ which is equal to the Pontryagin index. A smooth continuum limit of $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{T}\mathrm{r}{\ensuremath{\gamma}}_{5}=\mathrm{Tr}{\ensuremath{\gamma}}_{5}[1\ensuremath{-}(a/2)D]{=n}_{+}\ensuremath{-}{n}_{\ensuremath{-}}$ for the Dirac operator D satisfying the Ginsparg-Wilson relation leads to a natural treatment of a chiral anomaly in the continuum path integral. In contrast, the continuum limit of $\mathrm{Tr}{\ensuremath{\gamma}}_{5}=0$ is not defined consistently. It is shown that the nondecoupling of heavy fermions in the anomaly calculation is crucial to understand the consistency of the customary lattice calculation of the anomaly where $\mathrm{Tr}{\ensuremath{\gamma}}_{5}=0$ is used. We also comment on a closely related phenomenon in the analysis of the photon phase operator where the notion of index and the modification of index by a finite cutoff play a crucial role.

Theoretical study of the collision-induced fundamental absorption spectra of O 2–O2 pairs for temperatures between 193 and 273 K

A theoretical analysis of the collision-induced fundamental absorption spectra of O 2–O 2 pairs is presented for temperatures between 193 and 273 K. Most of the absorption arises from the long-range quadrupole and hexadecapole-induced dipole mechanisms for which accurate matrix elements are available from various other experimental measurements or from ab initio calculations. The line shape used is that obtained from quantum computations of the far infrared collision-induced absorption of N 2, modified to include dips resulting from the effects of intercollisional interference. Several refinements, including contributions from back-reaction and short-range induced-dipole moments, can improve the agreement in certain spectral regions but do not lead to significant improvement in the global fits to the experimental data. The small structural features superimposed on the smooth continuum can be modeled by the modified line shape but the half-widths of the dips have a density dependence inconsistent with that arising from interference. On the other hand, difference spectra obtained by subtracting the theoretical results from the experimental data appear quite similar to those obtained previously at low temperatures, leading to the conclusion that this structure is due to dimers. Further experimental results at higher temperatures and for O 2–N 2 pairs would be useful to validate this interpretation.