Radial Spread Research Articles

Anatomic correlates of painful tonic spasms in multiple sclerosis.

Painful tonic spasms (PTS) are now regarded as a typical symptom of multiple sclerosis but pathologic or radiologic findings rarely have been described. We report clinical and magnetic resonance imaging records of five original cases. In all of them, lesions likely responsible for unilateral PTS involved the motor pathway at the level of the posterior limb of the internal capsule or the cerebral peduncle on the opposite side. Closeness of motor fibers seems to be the most important underlying anatomic factor because it enables involvement of a higher proportion of axons by a single demyelinating lesion and radial spread of ephaptic activation. In turn, preservation of the underlying pyramidal-spinal tract could make it easier for the pathologic discharge to reach the peripheral effectors and generate PTS.

Radial localization of inositol 1,4,5-trisphosphate-sensitive Ca2+ release sites in Xenopus oocytes resolved by axial confocal linescan imaging.

The radial localization and properties of elementary calcium release events ("puffs") were studied in Xenopus oocytes using a confocal microscope equipped with a piezoelectric focussing unit to allow rapid (>100 Hz) imaging of calcium signals along a radial line into the cell with a spatial resolution of <0.7 micrometer. Weak photorelease of caged inositol 1,4,5-trisphosphate (InsP3) evoked puffs arising predominantly within a 6-micrometer thick band located within a few micrometers of the cell surface. Approximately 25% of puffs had a restricted radial spread, consistent with calcium release from a single site. Most puffs, however, exhibited a greater radial spread (3.25 micrometer), likely involving recruitment of radially neighboring release sites. Calcium waves evoked by just suprathreshold stimuli exhibited radial calcium distributions consistent with inward diffusion of calcium liberated at puff sites, whereas stronger flashes evoked strong, short-latency signals at depths inward from puff sites, indicating deep InsP3-sensitive stores activated at higher concentrations of InsP3. Immunolocalization of InsP3 receptors showed punctate staining throughout a region corresponding to the localization of puffs and subplasmalemmal endoplasmic reticulum. The radial organization of puff sites a few micrometers inward from the plasma membrane may have important consequences for activation of calcium-dependent ion channels and "capacitative" calcium influx. However, on the macroscopic (hundreds of micrometers) scale of global calcium waves, release can be considered to occur primarily within a thin, essentially two-dimensional subplasmalemmal shell.

Calculation of depth dose and dose per monitor unit for irregularly shaped electron fields

A new dosimetric quantity, the lateral build-up ratio (LBR), has been introduced to calculate depth dose distribution for any shaped field. Factors to account for change in incident fluence with collimation are applied separately. The LBR data for a small circular field are used to extract radial spread of the pencil beam, , as a function of depth and energy. By using the relationship between LBR, , energy and depth, a formalism is developed to calculate dose per monitor unit for any shaped field. Criteria for lateral scatter equilibrium are also developed which are useful in clinical dosimetry.

Air Dilution, under Calm, of Spreading Dense Vapor from an Instantaneous Spill of Volatile Liquid

We adopt depth-averaged, shallow-water gravity-wave theory to furnish a simplistic, tractable description of the lateral axisymmetric spreading of liquid and vapor in the aftermath of an accidental, instantaneous spill on level ground of a large quantity of volatile liquid. Our attention is focused on the spill of a flammable and/or toxic liquid (e.g., liquid petroleum gas, or liquid chlorine), such that the phase transition, facilitated primarily by heat transfer from the ground to the liquid, yields a vapor which, even upon equilibration to atmospheric temperature, remains appreciably denser than the surrounding air. Thus, the vapor remains confined to a ground-contiguous layer as the vapor laterally disperses (in the absence of obstacles, in the modeling). Our objective is to estimate the time after release until dilution with air of a combustible vapor results in the local concentration being everywhere below the fuel-lean flammability limit (or until the dilution of a toxic vapor results in the local concentration being everywhere tolerable for human occupation). We limit attention to no-wind conditions, for which the dilution is protracted (because the dispersion remains limited to the proximity of the spill site). For an instantaneous release of sufficient liquid volume, we anticipate (and can justify a posteriori) that a balance of inertial and buoyant forces constitutes an excellent approximation to the conservation of momentum for the gravity-current dynamics of the spilled liquid and evolved vapor [until the (cylindrical-)radial spread results in liquid and vapor layers so thin that a viscous–buoyant balance is more appropriate]. Whereas virtually all previous analyses of wind-free dense-fluid dispersion take the initial condition to be a uniform-fluid spill in the configuration of a right-circular cylinder, and eventually a selfsimilar behavior, based parametrically only on the fixed spill-occupied volume and the effective gravitational acceleration, evolves, we adopt an initial spilled-fluid configuration in the form of a finite-radius mound, with the layer thickness monotonically decreasing with increasing radial distance and smoothly vanishing at finite radius. We find that no selfsimilar behavior evolves: vestiges of the initial conditions persist and, asymptotically, the radial position of the spilled-fluid edge would increase linearly with time in the absence of vaporization; furthermore, we find that at all times the thickness of the spilled-fluid layer would decrease monotonically with radius, from the axis of symmetry to the spilled-fluid-layer front. Also, whereas virtually all simple gas-cloud models are of box type, and take the contents to be spatially homogeneous, we investigate the spatial inhomogeneity of the vapor content of a cloud formed by evaporation, and show that distribution of the ambient-air-diluted vapor is well approximated as decreasing with increasing height as a Gaussian function, with peak concentration on the axis at all times.

Optical measurements of ion density in the second vacuum stage of an inductively coupled plasma mass spectrometer

A portion of the ion beam in the second stage of an inductively coupled plasma mass spectrometer was mapped using laser induced fluorescence (LIF). With LIF relative density measurements are made in real time with minimal interference to the ion beam. We report axial measurements of Ba and Sc ion density from 22 to 45 mm behind the tip of the skimmer cone. Additionally, maps of radial ion density with and without Pb and Mg matrices are given for the same two analyte species. The results reveal that earlier ion deposition experiments dramatically underestimated the extent of the radial spread of the ion beam and the influence of matrix on the ion beam.

Short-pulse high-intensity laser-generated fast electron transport into thick solid targets

The transport of fast electrons generated by 1 ps, 1 $\ensuremath{\mu}\mathrm{m}$ wavelength laser pulses focused to spot diameters of 20 $\ensuremath{\mu}\mathrm{m}$ and peak intensities of up to $2\ifmmode\times\else\texttimes\fi{}{10}^{18}$ W ${\mathrm{cm}}^{\ensuremath{-}2}$ on to solid aluminum targets is considered using a relativistic Fokker-Planck equation, which is solved by reducing it to an equivalent system of stochastic differential equations. The background is represented by $\mathbf{E}=\ensuremath{\eta}{\mathbf{j}}_{b},$ where $\ensuremath{\eta}$ is the resistivity and ${\mathbf{j}}_{b}$ is the background current density. Collisions, electric and magnetic fields, and changes in resistivity due to heating of the background are included. Rotational symmetry is assumed. The treatment is valid for fast electron number densities much less than that of the background, fast electron energies much greater than the background temperature, and time scales short enough that magnetic diffusion and thermal conduction are negligible. The neglect of ionization also limits the validity of the model. The intensities at which electric and magnetic fields become important are evaluated. The electric field lowers the energy of fast electrons penetrating the target. The magnetic field reduces the radial spread, increases the penetration of intermediate energy fast electrons, and reflects lower energy fast electrons. Changes in resistivity significantly affect the field generation. The implications for $K\ensuremath{\alpha}$ emission diagnostics are discussed.

Quantification of the Initial Lymphatic Network in Normal Human Forearm Skin Using Fluorescence Microlymphography and Stereological Methods

Fluorescence microlymphography enables the visualization of the initial lymphatic network in human dermisin vivo.In order to determine which objective, measurable parameters are likely to be of value in future studies, microlymphangiograms were obtained from normal forearm skin of eight men and nine women of a range of ages and analyzed stereologically to calculate: (1) lymphatic length density at a specified radial distance,r, from the site of injection of the fluorescent dye (LDr, cm−1); (2) maximum lymphatic density (LDmax, cm−1); (3) total length of filled lymphatic (LL, cm); (4) maximum radial spread of vessels (mm). There was no significant difference between the right and left arms for peak LDr, LDmax, LL, or spread. Mean values (±SD) for the right and left arms combined (n= 24) were 13.34 ± 7.61 cm−1; 19.31 ± 8.96 cm−1; 12.04 ± 10.04 cm; and 7.58 ± 3.30 mm, respectively. Unexpectedly, three of the four parameters were significantly lower in women compared to men. For women LDmaxwas 30% lower than for men (P= 0.04), LL was 59% lower (P= 0.032), and spread was 39% lower (P= 0.007). Peak LDrdid not differ significantly. Stereological analysis of fluorescent microlymphangiograms enables quantification of the dermal initial lymphatic network and hence the objective study of the influence of gender, age, and disease (including treatment interventions).

The radial spread and axial decay of temperature in turbulent condensing jets

Radial and axial time-averaged temperature distributions in turbulent steam jets discharged into ambient air under unchoked/choked and saturated/superheated nozzle exit conditions have been measured with the aid of a fine thermocouple. Centreline decay and half-width spreading rates were calculated for these two-phase (liquid and vapour), two-fluid (air and water) jets and compared with data from the literature for non-condensing jets. Condensing jets exhibit higher spreading rates but much lower decay rates compared to non-condensing jets. A significant temperature increase due to condensation was observed. This increase in temperature became smaller with increased superheat and hence reduced condensation. Preliminary computational fluid dynamics (CFD) simulations were also performed using various simplifying assumptions.

A Simple Theory for the Fate of Buoyant Coastal Discharges*

Abstract A simple theory that predicts the vertical structure and offshore spreading of a localized buoyant inflow onto a continental shelf is formulated. The theory is based on two competing mechanisms that move the buoyant fluid offshore: 1) the radial spread of the lighter water over the ambient water, being deflected by the Coriolis force and producing an anticyclonic cyclostrophic plume, and 2) offshore transport of buoyant water in the frictional bottom boundary layer that moves the entire plume offshore while maintaining contact with the bottom. The surface expression of the cyclostrophic plume moves offshore a distance ys = 2(3g′h0 + υ 2i)/(2g′h0 + υ 2i)1/2f,where g′ is reduced gravity based on the inflow density anomaly, h0 is the inflow depth, υi is the inflow velocity, and f is the Coriolis parameter. The plume remains attached to the bottom to a depth given by hb = (2Lυih0f/g′)1/2,where L is the inflow width. Both scales are based solely on parameters of the buoyant inflow at its source. There...

Effects of resonant magnetic perturbations on divertor target power loads in COMPASS-D

The effect of externally applied resonant magnetic perturbations on the power load to the divertor target is studied in the COMPASS-D tokamak. A theoretical model is constructed, based on detailed field-line tracing, allowing for cross-field transport in the scrape-off layer (SOL). In this model, the perturbations give rise to an `ergodic' layer that modifies the transport properties in the SOL, causing a net radial spread in the power loading. Spiral magnetic structures form on the divertor target, giving rise to `hotspots' near their toroidal turning points and a double peak structure to the inboard and outboard divertor strike zones. For the first time, detailed comparisons are made between model and experiment, obtaining good agreement when the amplification of the applied field, due to the requirements of pressure balance in the plasma, is included

Root System Characteristics of Young Papaya Plants

Excavation of field-grown `Red Lady' and `Tainung #2' papaya plants was begun 3 months after transplanting to the field to characterize development of the papaya root system. The roots were separated into the taproot system and lateral roots within three size categories: &lt;1, 1 to 5, and &gt;5 mm. Length of the taproot system and the larger lateral roots was measured directly, and that of the smaller roots was determined using the line-intersect method. Mass of the various size categories was measured after drying at 70°C. A typical plant 3 months after field-planting was ≈ 60 cm tall and exhibited a root system radial spread of 34,636 cm2, total root length of 9613 cm, and total dry mass of 17.3 g. The taproot system accounted for &gt;70% of the mass and &lt;5% of the length of the root system. Lateral roots &lt;1 mm in diameter accounted for &lt;10% of the mass and &gt;70% of the length of the root system. A typical plant during the heavy fruit set stage, about 6 months after field planting, was 175 cm tall and exhibited a root system radial spread of 101,736 cm2, total root length of 975 m, and total dry mass of 539 g. The taproot system accounted for ≈38% of the dry mass and &lt;1% of the length of the root system. Lateral roots &lt;1 mm in diameter accounted for ≈5% of the dry mass and 65% of the length of the root system. Plant age influenced root system characteristics more than cultivar, especially the proportional distribution of mass and length among the defined root classes.

Auditory epithelial migration: I. Macroscopic evidence of migration and pathways in rat.

Auditory epithelial migration (AEM) was studied in the rat for up to 42 days following the application of dye on the tympanic membrane (TM) and external auditory canal (EAC). Migratory pathways were similar to those in the human. In the pars tensa (PT), pathways were radially and centrifugally oriented from the handle of the malleus (HM) toward the annulus. However, the pathway along the HM from the umbo to the pars flaccida (PF), as reported in the human, was not observed in the rat; instead, a shallow downward pathway along the HM. In the PF, the radial spread of dye-markings from the proximal part of the HM to the upper wall of the EAC, as found in the human, was also observed in the rat. We conclude that the TM and EAC of the rat constitute an appropriate experimental model with which to study the human type of AEM.

A technique to estimate the radial extent of active mineral absorption by individual plants in carrot stands

Campbell and Grime (1989) developed a novel technique to establish zones of nutrient enrichment in sand without the use of physical partitions. It is shown here that this technique can be applied to estimate the radial spread of the functional root system from individual plants in monocultures. A model is presented which allows the radial extent of the functioning root system to be estimated from the change in shoot bromide concentration with distance from a boundary between bromide-enriched and non-enriched zones in a sand medium.

Dose calculations in proton beams: range straggling corrections and energy scaling

Three-dimensional dose planning systems employing accurate proton transport algorithms are essential for calculating absorbed dose distributions in proton therapy. In this paper, a pencil beam algorithm for the transport of protons in materials of interest for radiation therapy is developed. The Fermi-Eyges multiple-scattering theory is used to derive transport equations for calculating proton fluence and absorbed dose distributions. The multiple-scattering theory of Moliere is used to predict mean square scattering angles and to develop an expression for calculating the root mean square (RMS) radial spread of a proton pencil beam, as a function of depth, in an arbitrary scattering material. A correction factor is suggested to account for the decrease in the radial spread at the end of the range due to range straggling. The effects of neglecting large-angle scattering events and the possibility of incorporating such events into the pencil beam algorithm are discussed. An energy scaling technique for determining the water-equivalent surface energy at a given depth in a heterogeneous scattering medium is developed. The water-equivalent energy, giving the same Moliere scattering parameter B in water, is determined and the 1/e angle in water is scaled to the appropriate width in the scattering material. By using stored analytically or Monte Carlo calculated pencil beam distributions in water, the large-angle single-scattering events may be incorporated by approximating the scattering in an arbitrary material by the scattering in water for protons of the appropriate water-equivalent surface energy.

Three-dimensional codes for simulating electron beam transport and free-electron laser operation including space-charge effects

Three-dimensional models which describe the electron beam transport and electromagnetic (EM) interaction in a Free-electron laser (FEL) are presented. The models are based on single particle force equations, and take into account emittance and space-charge effects in the e-beam, and transverse spatial variation in the radiation field. In the e-beam transport problem, a cylindrically symmetrical transverse density distribution is assumed, having an arbitrary az-imuthal and radial angular spread. The particle trajectories are obtained by solving numerically the equation of motion for a general electric and magnetic field in the presence of space-charge forces. The parameters of the particles in the beam are then displayed in real space and phase space. In the FEL model, the total electromagnetic field (including the RF space-charge field) is expanded in terms of normal modes of the waveguide (including the cut-off modes). The field interaction with the e-beam is described by the force equation for electrons...

972-106 Intramural Activation Patterns of Focal Ventricular Tachycardia Induced by Programmed Stimulation During Experimental Subacute Myocardial Infarction

The purpose of this study was to elucidate the three dimensional (3-D) activation patterns of focal excitation during induced ventricular tachycardia (VT) in subacute myocardial infarction in canines. In 30 dogs 5 days after LAD occlusion and reperfusion, intramural electrograms were simultaneously recorded from 240 bipolar sites through 60 plunge needles inserted into both ventricles. Computerized 3-D color-coded isochronal activation maps were generated. At the given resolution, focal VT was diagsnosed when the site of latest activation was anatomically remote from the site of impulse origin. In 12 of 26 experiments, reproducibly induced sustained monomorphic VTs were attributed to a focal mechanism. Activation patterns were the following: 1) Radial spread of excitation (n = 5). Ventricular activation was completed in approximately 100 ms followed by about 100 ms of electrical quiescence. 2) Progressive slow conduction (n = 2). A focal excitation pattern was associated with progressive prolongation of intramural conduction times. 3) Presystolic activity and unidirectional exit block(n = 2). The site of impulse origin was surrounded by areas of unidirectional conduction block with intramural conduction delay. 4) Pan diastolic activity (n = 3). Myocardial activation was present throughout the entire systolic and diastolic intervals without regional slow conduction or block. In conclusion, multiple intramural activation patterns are present in focal VTs induced by programmed stimulation. Delayed diastolic activity does not constitute a direct evidence for macro-reentry. Triggered activity with or without conduction delay may be the underlying mechanism of these induced arrhythmias.

Radial spread of sodium lauryl sulfate after topical application.

Since topical application of sodium lauryl sulfate (SLS) has been reported to elevate transepidermal water loss and decrease skin capacitance in areas immediately adjacent to the applied site, studies were carried out to quantify the extent of radial spread of SLS below a topically exposed site in a hairless rat model. Fixed sites were demarcated and the levels of SLS measured around the applied site in the epidermis, dermis and the subcutaneous tissues. Underlying deep tissue penetration and radial spread of SLS in the presence and absence of a vasoconstrictor, phenylephrine, was also quantified. In a typical 24 hour study, the radial spread of SLS was observed to a distance of approximately 0.75 cm from the applied site. The use of phenylephrine (1:20000), did not significantly enhance either the local underlying tissue (apart from underlying epidermis) concentration or radial spread of SLS relative to no vasoconstrictor treatment. Given that SLS impairs barrier function of the skin, its radial spread could be explained by a passive diffusion process. Vasoconstrictor did not remarkably alter SLS penetration and radial spread possibly due to the competing effects of vasodilation (caused by SLS) and vasoconstriction (caused by phenylephrine).

Effect of negative ions on electrical breakdown in a nonuniform air gap between a wire and a plane

Electrical breakdown of an axisymmetric, atmospheric pressure air gap between a wire and a plane has been investigated for a gap length of 0.5 mm. O− and O−2 have been identified as the negative ions affecting the discharge development in air, besides electrons and positive ions, and have been included in the electrical breakdown model. Five coupled two-dimensional transient partial differential equations describing the discharge evolution in the air gap have been solved using a finite difference algorithm developed earlier. Temporal development of the charged particle number densities, electrostatic potential, electric field, and current at both the electrodes is presented when the wire is negatively biased at 2500 V. The impact of negative ions on gap breakdown has been assessed by comparing the results of analyses with and without negative ions. It is concluded that the negative ions have negligible effect during the early stages of the discharge development. However, as the discharge evolves, the negative ions cause a net loss of electrons from the discharge. The effect is most pronounced away from the discharge axis, where peaks in the electron density occur as breakdown proceeds. Radial spread of discharge and current growth rate are relatively unaffected by the presence of negative ions, but the magnitude of total current at the electrodes has been found to decrease by a decade when the negative ions are present.

Interplanetary dust particles and solar radiation

The problem of the action of the solar radiation on the motion of interplanetary dust particle is discussed. Differences between the action of electromagnetic solar radiation and that of the solar wind are explained not only from the point of view of the physical nature of these phenomena but also from the point of view of dust particle's orbital evolution. As for the electromagnetic solar radiation, general equation of motion for the particle is written and the most important consequences are: (i) the process of inspiralling toward the Sun is not the only possible motion - even spiralling from the Sun is also possible, and, (ii) the orbital plane of the particle (its inclination) may change in time. As for the solar wind, the effect corresponding to the fact that solar wind particles spread out from the Sun in nonradial direction causes that the process of inspiralling toward the Sun is in more than 50% less effective than for radial spread out; in the region of the asteroid belt (long period orbits) the process of inspiralling is changed into offspiralling. Also shift in the perihelion of dust particle's orbit exists.

Theory and design of a high-harmonic gyrofrequency multiplier

In a gyrofrequency multiplier, the entire electron beam enters the output cavity optimally phased to lose energy in a first-order interaction (in contrast to the second-order standard gyrotron process) resulting in a high conversion efficiency. Because the electrons radiate at a high harmonic of the cyclotron frequency, a gyrofrequency multiplier is capable of efficiently generating power in the millimeter to submillimeter wave region. The operational principles of the gyrofrequency multiplier are described in this paper. Results from nonlinear simulation show that radial guiding-center spread of the beam can dramatically affect the device's efficiency while velocity spread effects are negligible. The design is presented for a 150 kW, 17.4 GHz, sixth-harmonic gyrofrequency multiplier which is under construction and is predicted to yield 31% conversion efficiency of the electron beam into the output wave. The 300 keV, 1.67 A axis-encircling beam is produced by a 1 MW, 2.9 GHz gyroresonant RF accelerator. >