Radiation Asymmetry Research Articles

Investigation of the external-magnetic-field dependence of polarization transfer in a 8Li-6Li disordered nuclear system

Random walks in disorderedmedia are studied by considering the example of the delocalization of nuclear polarization in an ensemble of 8Li beta-active nuclei produced in (n, γ) reactions induced by polarized thermal neutrons in LiF single crystals. The process is initiated by magnetic dipole-dipole interactions. It consists in polarization transfer from a primarily polarized 8Li nucleus to the closest (stable) 6Li nuclei and in subsequent polarizationmigration over 6Li nuclei, the return of the polarization in question to the 8Li nucleus being possible. In order to obtain information about the polarization of 8Li nuclei, the asymmetry of beta radiation from them was measured with respect to the external magnetic field H0. The process was studied until it reached the diffusion asymptotic regime. The concentration of 6Li was varied between 3% and 10%, while the field strength H0 was changed from 200 to 1200 G. It is shown that microscopic theory is in satisfactory agreement with the experimental results obtained in the way outlined above. A comparison with the investigation of the mathematically allied process of the Forster electricdipole transfer of localized excitons is performed.

Asymmetric sky from the long mode modulations

The observed dipole asymmetry in Cosmic Microwave Background radiation may have originated from the modulations of super-horizon long wavelength modes. In this work we unveil different aspects of asymmetries generated from the long wavelength mode modulations. We show that the same mechanism which leads to the observed CMB power spectrum dipole asymmetry from the long mode modulations also yields dipole asymmetry in (a): tensor perturbations power spectrum and (b): the halo bias parameter. These are different phenomena relevant to different cosmological histories but both share the same underlying mechanism in generating asymmetries in the sky. We obtain the set of consistency conditions relating the amplitude of dipole asymmetries generated on tensor perturbations and halo bias parameter to the amplitude of dipole asymmetry generated on CMB power spectrum. In addition, we show that this mechanism does not produce dipole asymmetry in acceleration expansion in $\Lambda CDM$ universe because the super-horizon curvature perturbation is conserved in this background.

Hydrodynamic instabilities of laser indirect-drive inertial-confinement-fusion implosion

Hydrodynamic instabilities (HI) occurring at interfaces of a capsule in the process of laser indirect-drive inertial-confinement-fusion (ICF) implosion, plays an essential role in the success of the fusion ignition. In order to deeply understand the generation and growth of the HI and their influence on the fusion ignition, we have successfully developed the LARED-S code which is a high-order twodimensional (local three-dimensional) radiation hydrodynamic code. The LARED-S code has been improved in our research of the HI in the past decades. It is shown that the results of LARED-S code agree well with the results of the linear and weakly nonlinear theories and the nonlinear shock tube experiments. Using the LARED-S code, we carry out a lot of numerical simulation research, obtaining a large amount of important result and physical understanding of the growth and evolution of the HI. The analytic expressions of the linear growth rate of Rayleigh-Taylor (RT) and Kelvin-Helmholtz (KH) instabilities considering the profiles of density, velocity, and magnetic field, and the their weakly nonlinear solutions in the limit of incompressible fluids, are derived. The relation of the RT instability (RTI) competing against the KH instability (KHI) is clearly shown, at different Froude numbers and widths of the density transition layer and the velocity shear layer. It is found that the jet-like spike in the ablative RTI (ARTI) in the presence of weak preheating can be ruptured by the nonlinear growth of the second harmonic. Moreover, jet-like spike pattern can be formed in the ARTI with strong preheating where a bubble acceleration process can be observed. The growth of high harmonics initiated by single-mode perturbation of the ablative KHI (AKHI) is effectively mitigated and the flow is stabilized in comparison with its classical counterpart. However, with a two-mode perturbation, the vortex pairing of the AKHI is reinforced, which would strength the mixing of materials. A serial of ARTI experiments have been performed in the Shenguang Ⅱ laser facility of China. The simulation results from the LARED-S code for the planar foil trajectory experiment indicates that the energy flux at the hohlraum wall is obviously less than that at the laser entrance hole (LEH). Furthermore, the non-Planckian spectra of X-ray source can affect the dynamics of the foil flight and the perturbation growth. The image of evident growth of the ARTI initiated by a small-amplitude perturbation and the spike-bubble pattern initiated by large-amplitude perturbation are observed. The data of the growth of the second and the third harmonics is also obtained by increasing the spatial resolution in the experiments. The simulation results are in general consistent with the experimental results. The reliability of the LARRED-S code has been tested and validated through the comparison with experiment results. Based on the physical understanding mentioned above, we have achieved the physical research of ICF fusion ignition target, including the effects of the perturbation seeded on the outer and inner surfaces of the shell, of the radiation asymmetry, of the hot-spot boundary instability, of the M-band from the hohlraum radiation, and of the low-mode areal density inhomogeneity, on the ICF implosion. Regarding the perturbation seeded on the ablator outer surface and on the deuterium-tritium (DT) ice inner surface and the radiation asymmetry, we have obtained the growth rule of the instabilities and improved the full understandings of the influence of the hot-spot interfacial growth on the fusion ignition and of the effect of the M-band of the X-ray spectra on the implosion stability. The simulation results show that the areal density inhomogeneity of the DT fuel severely affects the efficiency of the conversion of the implosion kinetic energy into the fuel internal energy and the implosion inertial confinement time. Our studies will play an important role not only in the research of ICF implosion ignition, but also in fundamental understanding of the HI which occur at the nature phenomena and the celestial bodies.

Polarization radiation of vortex electrons with large orbital angular momentum

Vortex electrons, - freely propagating electrons whose wavefunction has helical wavefronts, - could become a novel tool in the physics of electromagnetic radiation. They carry a non-zero intrinsic orbital angular momentum (OAM) $\ell$ with respect to the propagation axis and, for \ell \gg 1, a large OAM-induced magnetic moment, \mu ~ \ell \mu_B (\mu_B is the Bohr magneton), which influences the radiation of electromagnetic waves. Here, we consider in detail the OAM-induced effects by such electrons in two forms of polarization radiation, namely in Cherenkov radiation and transition radiation. Thanks to the large \ell, we can neglect quantum or spin-induced effects, which are of the order of \hbar \omega/E_e \ll 1, but retain the magnetic moment contribution \ell \hbar \omega/E_e \lesssim 1, which makes the quasiclassical approach to polarization radiation applicable. We discuss the magnetic moment contribution to polarization radiation, which has never been experimentally observed, and study how its visibility depends on the kinematical parameters and the medium permittivity. In particular, it is shown that this contribution can, in principle, be detected in azimuthally non-symmetrical problems, for example when vortex electrons obliquely cross a metallic screen (transition radiation) or move nearby it (diffraction radiation). We predict a left-right angular asymmetry of the transition radiation (in the plane where the charge radiation distributions would stay symmetric), which appears due to an effective interference between the charge radiation field and the magnetic moment one. Numerical values of this asymmetry for vortex electrons with E_e = 300keV and \ell = O(100-1000) are O(0.1-1%), and we argue that this effect could be detected with existing technology. The finite conductivity of the target and frequency dispersion play the crucial roles in these predictions.

Effect of solar UV/EUV heating on the intensity and spatial distribution of Jupiter's synchrotron radiation

We analyzed the Very Large Array archived data observed in 2000 to determine whether solar ultraviolet (UV)/extreme ultraviolet (EUV) heating of the Jovian thermosphere causes variations in the total flux density and dawn‐dusk asymmetry (the characteristic differences between the peak emissions at dawn and dusk) of Jupiter's synchrotron radiation (JSR). The total flux density varied by 10% over 6 days of observations and accorded with theoretical expectations. The average dawn‐dusk peak emission ratio indicated that the dawn side emissions were brighter than those on the dusk side and this was expected to have been caused by diurnal wind induced by the solar UV/EUV. The daily variations in the dawn‐dusk ratio did not correspond to the solar UV/EUV, and this finding did not support the theoretical expectation that the dawn‐dusk ratio and diurnal wind velocity varies in correspondence with the solar UV/EUV. We tried to determine whether the average dawn‐dusk ratio could be explained by a reasonable diurnal wind velocity. We constructed an equatorial brightness distribution model of JSR using the revised Divine‐Garrett particle distribution model and used it to derive a relation between the dawn‐dusk ratio and diurnal wind velocity. The estimated diurnal wind velocity reasonably corresponded to a numerical simulation of the Jovian thermosphere. We also found that realistic changes in the diurnal wind velocity could not cause the daily variations in the dawn‐dusk ratio. Hence, we propose that the solar UV/EUV related variations were below the detection limit and some other processes dominated the daily variations in the dawn‐dusk ratio.

Rapid shutdown experiments with one and two gas jets on Alcator C-Mod

Massive gas injection rapid shutdown experiments have been conducted on the Alcator C-Mod tokamak using two toroidally separated gas injectors, in order to investigate the effect of multiple gas injection locations on the toroidal asymmetry in the radiated power. Toroidal radiation asymmetry is diagnosed by an array of six single-channel photodiodes mounted on the vessel wall. The presence of magnetohydrodynamic (MHD) activity is diagnosed using an array of magnetic pickup (Mirnov) coils, mounted on stalks on the vessel wall. Scans were conducted of the relative timing between the two jets, of the 95th percentile safety factor, and of the plasma elongation. It is observed that firing the two gas jets so that the injected impurities arrive at the plasma at nearly the same time produced an increase in the toroidal radiation asymmetry. In addition, the radiation asymmetry in the thermal quench phase correlates with the growth rate of low toroidal mode number MHD modes, indicating that these mode(s) are playing a role in setting the radiation asymmetry.

Small non-Gaussianity and dipole asymmetry in the cosmic microwave background

In this paper we provide a prescription for obtaining a small non-Gaussianity and the observed dipole asymmetry in the cosmic microwave background radiation. The observations inevitably lead to multifield inflationary dynamics, where each field can create positive or negative large non-Gaussianity, resulting in a fine cancellation but with an observable imprint on the hemispherical asymmetry. We discuss this possibility within a simple slow-roll scenario and find that it is hard to explain the observed dipole asymmetry. We briefly discuss some speculative scenarios where one can explain dipole asymmetry.

Impurity mixing and radiation asymmetry in massive gas injection simulations of DIII-D

Simulations of neon massive gas injection into DIII-D are performed with the 3D MHD code NIMROD. The poloidal and toroidal distribution of the impurity source is varied. This report will focus on the effects of the source variation on impurity mixing and radiated power asymmetry. Even toroidally symmetric impurity injection is found to produce asymmetric radiated power due to asymmetric convective heat flux produced by the 1/1 mode. When the gas source is toroidally localized, the phase relationship between the mode and the source location is important, affecting both radiation peaking and impurity mixing. Under certain circumstances, a single, localized gas jet could produce better radiation symmetry during the disruption thermal quench than evenly distributed impurities.

Phenomenon of Radiation Asymmetry in The Capillary Plane Air-Conditioning Systems

Based on the introduction characteristics of capillary plane radiation air conditioning systems, we focuse on the analysis phenomenon of radiation asymmetry in the radiant air conditioning systems in the engineering practice , and discuss the condition that produces this phenomenon, and establish mathematical model of radiation asymmetric in the capillary plane air conditioning systems. And we work out the radiation angle coefficient between the human body and the floor, south wall, north wall, east wall , west wall in air conditioning rooms, and expound the radiation asymmetry degree in different parts of air conditioning rooms. The result is of positive significance to research capillary plane radiation air conditioning systems deeply and to improve occupant comfort .

Neonatal posterior cerebral artery stroke: clinical presentation, MRI findings, and outcome

To report the clinical presentation, magnetic resonance imaging (MRI) findings, and follow-up data of newborn infants with perinatal arterial ischemic stroke in the territory of the posterior cerebral artery (PCA). Data on 18 newborn infants from three neonatal intensive care units (11 males, seven females) with an MRI-confirmed PCA stroke were analysed and reported. Infants were born at a mean gestational age of 38.7 weeks (SD 3.4) with a mean birthweight of 3244g (SD 850). Fourteen infants presented with clinical seizures. Five of these had associated hypoxic-ischemic encephalopathy, four had hypoglycaemia, and five had neither hypoxic-ischemic encephalopathy nor hypoglycaemia. Subclinical seizures were present in one infant with hypoxic-ischemic encephalopathy and one with meningitis. One preterm infant presented with apnoeas and one had hypoxic-ischemic encephalopathy without seizures. Neurodevelopmental follow-up of 17 children at a median age of 36 months (SD 28, range 12-120mo) showed five with a global delay. Two children with additional injury developed postneonatal epilepsy and one child with extensive injury developed hemiplegia. A visual field defect was observed in nine children (six hemianopia, three quadrantanopia). In the 11 children with a second MRI at 3 months, the asymmetry of the optic radiation correlated with the development of a visual field deficit. Outcome after PCA stroke is fairly good, depending on additional brain injury. Follow-up is required, as subsequent visual field defects are frequently observed. Further research will be needed to clarify the role of hypoglycaemia in perinatal arterial ischemic stroke.

Simulation of Heat Radiation Asymmetry with Maple

Simulation of Heat Radiation Asymmetry with Maple

Liberalism and Tradition in the Nineteenth-Century Balkans

The article sets off from a discussion of some methodological and theoretical issues pertinent to the study of ideological and institutional transfer between “centre” and “periphery” in nineteenth-century Europe. While taking into account the asymmetry in radiation and reception, it probes into the (Balkan) periphery’s political and cultural agency in reformulating and re-institutionalizing the “western model.” Rather than simply tracing movements, flows and circulation – the conventional concern of the transnational approach – the focus is on studying the transformations which occur in the process. This makes it possible to highlight the dynamics and versatility of ideational and institutional selection, interpretation, adaptation and transformation (or subversion) – in brief, the process of re-signification of ideas and institutions. The article then proceeds by exemplifying this approach in two directions. First, it examines several main channels and agents of transfer to and within the Balkan periphery illuminative of the ways ideas, practices and institutions traveled and mutated in the course of their journey; second, it surveys several characteristic instances of transfer of liberal ideas and institutions in the Balkans focusing on their legitimization and “domestication” which underscore the semantic and functional reinterpretations of modernity and tradition in the process.

Simulation of Heat Radiation Asymmetry With Maple

AbstractA new method was developed for determination of radiated temperature asymmetry. Application of the method resulted in more accurate data, where the plane dividing the two half spaces of the surface element at the test point separates the thermally active (coldest and warmest) surfaces in all cases and determines the irradiation factor through drawing. The present method of asymmetry calculation enables a more accurate calculation of the “one side radiation asymmetry” parameter and provides a further characteristic parameter of the comfort of rooms in case of cold and warm surfaces being within the same plane.

Radiation loads onto plasma-facing components of JET during transient events – Experimental results and implications for ITER

This contribution examines the impact on plasma radiation and on power load to the divertor (i) of large type I ELMs with energies 0.25–1.3MJ in high current H-mode JET discharges and (ii) of disruptions.(i)The ELMs provoke strong radiation losses, mostly confined to the inner divertor region. Large type I ELMs with ΔWELM⩾0.72MJ show enhanced radiation losses which are associated with the ablation of carbon layers in the inner divertor. Such large ELMs are usually followed by a phase of type III ELMs with an increased radiation in the plasma core.(ii)The unmitigated disruptions exhibit small radiation fractions with strong poloidal radiation asymmetry during the thermal quench, which could cause Be melting by radiation in ITER. In dedicated experiments on massive gas injection, about 60% of the thermal energy and a significant part of the magnetic energy was converted in radiation and spread uniformly over the first walls.

Physiological modeling for technical clinical and research applications

Various and disparate technical disciplines have identified a growing need for tools to predict human thermal and thermoregulatory responses to environmental heating and cooling and other thermal challenges such as anesthesia and non-ionizing radiation. In this contribution, a dynamic simulation model is presented and used to predict human thermophysiological and perceptual responses for different applications and situations. The multi-segmental, multi-layered mathematical model predicts body temperatures, thermoregulatory responses, and components of the environmental heat exchange in cold, moderate, as well as hot stress conditions. The incorporated comfort model uses physiological states of the human body to predict thermal sensation responses to steady state and transient conditions. Different validation studies involving climate-chamber physiological and thermal comfort experiments, exposures to uncontrolled outdoor weather conditions, extreme climatic and radiation asymmetry scenarios revealed the model to predict physiological and perceptual responses typically within the standard deviation of the experimental observations. Applications of the model in biometeorology, clothing research, the car industry, clinical and safety applications are presented and discussed.

Rotational asymmetry of pulsar profiles

We analyse the influence of rotation on shapes of pulse profiles of fast-rotating (millisecond) pulsars. Corotation has two opposing effects: 1) the caustic enhancement of the trailing side (TS) by aberration and retardation (AR), which squeezes the emission into a narrower phase interval; 2) the weakening of the TS caused by the asymmetry of curvature radiation about the dipole axis. Analysis of the radii of curvature of electron trajectories in the inertial observer's frame (IOF) enables these two effects to be considered together. We demonstrate that for dipolar magnetic field lines on the TS there exists a `caustic phase' beyond which no emission can be observed. This phase corresponds to the zero (or minimum) curvature of the IOF trajectories and maximum bunching of the emission. The maximum gradient of polarisation angle (PA) in the S-shaped PA curve is also associated with the curvature minimum and occurs at exactly the same phase. The asymmetry of trajectory curvature with respect to the dipole axis affects the curvature emissivity and the efficiency of pair production, suggesting a minimum at the caustic phase. Emission over a fixed range of altitudes, as expected in millisecond pulsars, leads to broad leading profiles and sharp peaks with a cutoff phase on the TS. We apply our results to the main pulse of the 5 ms pulsar J1012+5307.

Empirical thermal comfort evaluation of single and double skin façades

In this paper, the topic of thermal comfort for buildings with double skin façades and single skin façades is demonstrated and discussed. A long-term monitoring was performed in 280 office rooms distributed over 28 buildings in Germany. The survey methods were based on sensor measurements and data simultaneously gathered from questionnaire given to office users. The authors take into consideration the operative temperature, vertical gradient temperature, draught rate, radiation asymmetry, relative humidity and carbon dioxide concentration. The aim is to determine the individual sensory perception of the indoor environment and compare it to the actually measured indoor climate in buildings with double skin façades and single skin façades. In regards to the thermal comfort results, in general, it is shown that double skin façades buildings have slight advantages in relation to single skin façades buildings.

Asymmetry Correction in the Irradiated Breast: Outcomes of Reduction Mammaplasty and Mastopexy After Breast-Conserving Therapy

There is relatively scant evidence concerning radiation effects on reduction mammaplasty and mastopexy, two procedures which are often used in the irradiated breast to restore symmetry following breast-conserving therapy (BCT). The purpose of this study is to further examine outcomes of reduction mammaplasty and mastopexy in breast cancer patients previously treated with BCT and radiation. A retrospective search at Baystate Medical Center (Springfield, MA) identified 12 patients who had received external beam radiation and either reduction mammaplasty or mastopexy. Overall radiation doses, including tumor bed boost, ranged from 5000 to 6600 cGy. The mean time between completion of radiation therapy and asymmetry correction was 63 months (range, 5 to 169 months). An overall average of 910 g of tissue was removed from the irradiated breast (range, 180 to 2925 g). The average length follow-up after asymmetry correction was 9 months (range, 1 to 44 months). In our patients, there were no major complications such as flap loss, tissue necrosis, heavy scarring, infection, or severe deformity. Minor complications in the irradiated breast occurred in 25% of patients and included prolonged edema (n = 1), delayed wound closure (n = 1), and minor scarring (n = 1). Histopathology was unremarkable except for one patient who was found to have recurrent ductal carcinoma in situ. In the cases reviewed, we did not observe any complications commonly associated with operating in an irradiated field. Good cosmesis and acceptable symmetry were achieved in all patients. Our data suggest that reduction mammaplasty and mastopexy after radiation therapy are relatively safe procedures with risks not significantly higher than either operation performed in patients without radiation.

Suprathermal electron studies in the TCV tokamak: Design of a tomographic hard-x-ray spectrometer

Electron cyclotron resonance heating and electron cyclotron current drive, disruptive events, and sawtooth activity are all known to produce suprathermal electrons in fusion devices, motivating increasingly detailed studies of the generation and dynamics of this suprathermal population. Measurements have been performed in the past years in the tokamak a configuration variable (TCV) tokamak using a single pinhole hard-x-ray (HXR) camera and electron-cyclotron-emission radiometers, leading, in particular, to the identification of the crucial role of spatial transport in the physics of ECCD. The observation of a poloidal asymmetry in the emitted suprathermal bremsstrahlung radiation motivates the design of a proposed new tomographic HXR spectrometer reported in this paper. The design, which is based on a compact modified Soller collimator concept, is being aided by simulations of tomographic reconstruction. Quantitative criteria have been developed to optimize the design for the greatly variable shapes and positions of TCV plasmas.

Transition radiation in the pre-wave zone for an oblique incidence of a particle on the flat target

Backward transition radiation of an electron with an arbitrary energy is studied when an ideally-conducting target is flat and its normal is not collinear with the particle velocity (oblique incidence). A model for radiation registered with a small flat detector placed at a finite distance (including the radiation in the pre-wave zone) in the vicinity of specular reflection direction is developed. Characteristics of the radiation in the far-field zone are in complete agreement with well-known results. The calculations for pre-wave zone show that the angular distribution of the radiation intensity is distorted compared to the far-field case, and the radiation asymmetry (having a place in the far-field for moderately relativistic energies) is also preserved in the pre-wave zone. Some numerical estimations of the radiation asymmetry at a finite distance are also given. The technique developed may be used for estimations of coherent transition radiation intensity in the mm-wavelength range.