Occurrence Of Halos Research Articles

Dermoscopy findings of the axilla of women with frontal fibrosing alopecia

AbstractBackgroundFrontal fibrosing alopecia (FFA) is a form of inflammatory and cicatricial alopecia, presenting concomitantly with rarefaction of eyebrows and body hair. However, the involvement of body hair in FFA is still poorly investigated.ObjectivesTo compare the dermoscopy findings of axillary hairs in a group of women with FFA with a group of women without FFA.MethodsAn observational case‐control study was carried out on the dermoscopic findings of the axillary hair in this group of patients with FFA compared to a group of women without FFA, matched by age groups and skin phototypes.ResultsThirty women with a clinical and histopathological diagnosis of FFA were included in the study. Dermoscopy of the axilla in patients with FFA revealed the presence of axillary hair in 93.3% and all patients had hairless follicular openings. More than one wire per follicular ostium was observed in 70% of the patients and variability in the diameter of the hairs in 83.3% of the cases. Regarding dermoscopic inflammatory signs, a peripillary brownish halo was present in 83.3% of patients, peripillary scaling in 56.7%, diffuse scaling in 63.3% and pigmented network of the epidermis in 73.3% of the cases. When comparing the dermoscopic findings of the axilla of cases with controls, the chance of occurrence of brownish peripillary halos between cases was higher than double the chance of occurrence of these halos among controls (OR = 2.7; 95% CI: 1.1−7.6; p = 0.029). The rest of variables were not statistically associated with the FFA.ConclusionsDermoscopy of the axilla in patients with FFA revealed that brownish peripillary halos may be a diagnostic clue for FFA in the axillary region. The dermoscopy findings found in the present study allow characterizing the axillary involvement of patients with FFA and recognize the dermoscopic differences with other dermatoses involving this location.

Simulations of Halos Produced by Carbon Dioxide Ice Crystals in the Martian Atmosphere

AbstractIt has been known for decades that carbon dioxide (CO2) ice clouds exist in the Martian atmosphere. According to remote sensing observations and previous modeling studies, the Martian CO2 ice crystals may be sufficiently large to generate halos. However, observations of CO2 ice crystal halos have not been reported so far. This study simulates the scattering and polarized phase functions at a wavelength of 0.48 μm based on state‐of‐the‐art light‐scattering computational capabilities. The specific CO2 ice crystal habits considered in the simulations include cubes, octahedrons, cubo‐octahedrons, and truncated octahedrons of various sizes. The halos produced by CO2 ice crystals peak at approximately 29° and 42°. Moreover, large CO2 ice crystals may cause strong scattering peaks at 155° and 180°. An ensemble of water (H2O) ice crystals and CO2 ice crystals with appropriate mixing fractions might be responsible for a halo occurrence recently observed on Mars.

Unified mechanism behind the even-parity ground state and neutron halo of 11Be* *This work was partly supported by the Strategic Priority Research Program of Chinese Academy of Sciences (XDB34000000), the National Natural Science Foundation of China (12275111) and the Fundamental Research Funds for the Central Universities (lzujbky-2021–sp41, lzujbky-2021–sp36)

Using the axially deformed relativistic Hartree-Fock-Bogoliubov (D-RHFB) model, we explore the mechanism behind the parity inversion and halo occurrence in 11Be, which are well reproduced by the RHF Lagrangian PKA1. It is illustrated that evidently enhanced deformation effects by the π-pseudo-vector and ρ-tensor couplings in PKA1 are crucial for correctly describing both the even-parity ground state (GS) and the neutron halo of 11Be. Coupling with the deformation, the intrude component largely enhances the couplings between the even-parity orbit and the nuclear core to ensure an even-parity GS, whereas the component therein dominates the halo formation in 11Be. Moreover, the deformed halo in 11Be is found to be stabilized by the attractive inherent correlations between the and components of the halo orbit , instead of pairing correlations, which paves a new way for understanding the halo pictures in deformed unstable nuclei.

Influence of angle alpha on visual quality after implantation of extended depth of focus intraocular lenses

BackgroundTo assess postoperative changes in angle alpha, and to evaluate the postoperative visual quality of patients with different angle alpha values after implantation of extended depth of focus (EDOF) intraocular lenses (IOLs).MethodsSeventy-nine eyes of 79 patients who had phacoemulsification with EDOF IOLs implantation were enrolled. A cut-off value of 0.3 mm, 0.4 mm, and 0.5 mm in preoperative angle alpha was chosen to divide eyes into groups. Distance, intermediate, and near visual acuities, modulation transfer function (MTF), and aberrations were recorded during a 6-month follow-up. A patient questionnaire was completed.ResultsThere were no significant differences in angle alpha postoperatively compared to preoperatively. No significant differences were found in visual acuity and MTF between all groups. With 5 mm pupil diameter, there were significant differences of higher-order aberrations and spherical aberration in ocular aberration and internal aberration between angle alpha<0.4 mm and angle alpha≥0.4 mm. Additionally, significant differences of coma were also added in cut-off value of 0.5 mm. When the value of angle alpha is 0.4 mm or higher, there were significant differences in the score of halos and glare.ConclusionsAngle alpha did not affect visual acuity, but the value of 0.4 mm or higher in angle alpha affected the visual quality under scotopic conditions and occurrence of halos and glare. For patients with 0.4 mm or higher in angle alpha, the choice to implant a EDOF IOL should be carefully considered.

Examining the influence of current waveform on the lightning electromagnetic field at the altitude of halo formation

In this paper, we extend the analysis of Lu (2006) to calculate the electric field (E-field) of lightning return stroke in the region of sprite initiation and halos using a transmission line model that uses various lightning stroke current measured during the triggered lightning experiment as the driving source to examine the individual components (i.e., electrostatic, induction, and radiation) of E-field perturbation. As the altitude increases, the maximum strength of electrostatic and induction field gradually decreases, and the induction field decays slower than electrostatic field above 80 km. The electrostatic and induction field in the region of halo formation have a much larger contribution to the total E-field than the radiation field. Therefore, it is proposed that in addition to the electrostatic field, the induction field (with amplitude more than half of total E-field) is the main component of the total E-field within the first half millisecond directly above the stroke. Our analysis indicates that the induction field might play a significant role in the halo formation and probably also the sprite initiation. The M-component, the longer rising edge, the wavy long tail, and the relatively long time scale of stroke current can increase the amplitude of electrostatic and induction field at the height of halos, and drive the occurrence of halos and the subsequent development of streamers, therefore forming sprites. Our results enrich the understanding on the mechanism of halo production and the lightning electromagnetic field in the middle and high-altitude atmosphere, and also pave the way for future accurate modeling of halo formation.

De-Hazing using Guided and L&lt;sub&gt;0&lt;/sub&gt; Gradient Minimization Filters

Objectives: Images captured under foggy or hazy conditions have low contrast and meager color. The proposed work is carried to improve the visibility of hazy images. Methods: The proposed method is based on ‘dark channel prior’ to remove haze, along with guided filter to refine the image due to the occurrence of halos. Even after refinement, halos are not completely removed. So, for further refinement edge preserving smoothing global filter L0 gradient minimization filter is used. Findings: This method has an advantage over conventional method by suppressing halos completely. Application/Improvements: The proposed method improves the contrast and increase in entropy reveals that the detail information is preserved effectively.

A comparative study of radio halo occurrence in SZ and X-ray selected galaxy cluster samples

We aim at an unbiased census of the radio halo population in galaxy clusters and test whether current low number counts of radio haloes have arisen from selection biases. We construct near-complete samples based on X-ray and Sunyaev–Zel'dovich (SZ) effect cluster catalogues and search for diffuse, extended (Mpc-scale) emission near the cluster centres by analysing data from the National Radio Astronomy Observatory Very Large Array Sky Survey. We remove compact sources using a matched filtering algorithm and model the diffuse emission using two independent methods. The relation between radio halo power at 1.4 GHz and mass observables is modelled using a power law, allowing for a ‘dropout’ population of clusters hosting no radio halo emission. An extensive suite of simulations is used to check for biases in our methods. Our findings suggest that the fraction of targets hosting radio haloes may have to be revised upwards for clusters selected using the SZ effect: while approximately 60 per cent of the X-ray selected targets are found to contain no extended radio emission, in agreement with previous findings, the corresponding fraction in the SZ selected samples is roughly 20 per cent. We propose a simple explanation for this selection difference based on the distinct time evolution of the SZ and X-ray observables during cluster mergers, and a bias towards relaxed, cool-core clusters in the X-ray selection.

Habitat engineering by decadal-scale bioturbation around shipwrecks on the Great Barrier Reef mid-shelf

Conspicuous, systematic patterns of holes in soft sediment around wreck sites on the Great Barrier Reef mid-shelf are documented. Multibeam bathymetry data show concentric 'halos of holes' extending hundreds of meters around the wrecks. These halos at 5 wreck sites between 16 and 111 yr old consist of hundreds of tightly spaced depressions with diameters of up to 10 m. Seafloor imagery clearly indicates a biogenic origin of the holes. The halos of the 2 youngest wrecks (<25 yr) have fewer holes than older wrecks, suggesting a relationship between wreck age and excavation activity. Conversely, the size of a wreck does not appear to control the sediment turnover activity. Holes are comparatively long-lived, and some of them are actively maintained by bioturbation activity. The spatial distribution of holes is consistent with resource depletion by a central-place forager, albeit on yearly to decadal time scales. Tow-camera data show that some holes support diverse sessile faunal assemblages of sponges, soft corals, and hard corals in an otherwise flat seafloor devoid of sessile fauna. The (to date unknown) bioturbator(s) are thus allogenic habitat engineers. The systematic occurrence of halos around wrecks suggests that 'the ecosystem wreck' extends beyond the spatial confines of the hull of a wreck to the seafloor, by a distance 10-fold greater than the size of a wreck itself. This has implications for the evaluation of ecological effects of artificial reefs such as wrecks and offshore wind farms on decadal time scales.

Exploring Scaling Laws of Valence Neutron Distributions for Medium Nuclei

The root-mean-square radii of the valence neutron distributions for many nuclei in He-Mo mass range are calculated in the framework of the single-particle potential model. The scaling laws of valence neutron distributions are obtained by analyzing the relations between the radii and the binding energies of the valence neutrons. Based on these scaling laws, the necessary conditions for the occurrence of neuron halos in 2s1/2, 1p3/2, 1p1/2, 2p3/2, 2p1/2, 1d5/2 and 1d3/2 states are deduced, respectively. The derived quantitative conditions for halo occurrence can provide reference for the searching of neutron halos up to medium nuclei.

Phase transition theory of sprite halo

We present the phase transition theory for sprite halo using measurable lightning parameters (charge moment and discharge time) on the basis of steady state thermodynamics. A halo is located at the upper part of the tree‐like structure of a sprite and is produced through electron impact excitation of neutral species under the lightning‐induced electric field. We proposed in our previous studies that the occurrence criteria for halos and sprites are characterized by the above lightning parameters, and additionally, the intensity of a halo weakens rapidly with an increase in the discharge time T. We assume that this phenomenon is quite similar to the phase transition between the vapor and the liquid states of water; here the analogy is between the accelerated electrons and the water molecules. We demonstrate analytically a phase transition for a simply modeled halo based on the quasistatic theory of lightning‐induced electric field. Choosing the luminosity of a halo as an order parameter, we show that it has a dependence of T−0.25 − Tc−0.25 near the critical point Tc, which is characteristic of the phase transition. Furthermore, the critical time scale Tc ≈ 5.5 ms is provided naturally from our modeling and is somewhat larger than the typical time scale of the halo luminosity in observations. We consider that this kind of formalism is useful in understanding the detailed relationship between lightning activity and occurrence of halos. We discuss this point for future observations along with the possibilities of the transition model of column and carrot structures.

NUCLEAR HALO AND ITS SCALING LAWS IN THE EXCITED STATES OF NUCLEI NEAR THE β-STABILITY LINE

The excited states of some odd A nuclei near the stability line have been systematically investigated from light to intermediate mass with the spherical relativistic mean field (RMF) model. The ratio between the valence nucleon root-mean-square (RMS) radius and the core rms radius, the separation energy and the density distribution have been deduced as signatures for halo or skin structure. We have presented the scaling laws of the ratio of valence particle rms radii and square-potential radii versus the scaled separation energies. The probability for a valence particle being out of the binding potential has also been extracted. We proposed a relaxed necessary condition for nuclear halo occurrence.

Theoretical Investigation of the Exotic Structure of the MirrorNuclei17Ne and 17N

The exotic structures of the ground state of the mirror nuclei17Ne and 17N are investigated by means of theasymptotic normalization coefficient (ANC) method to explore the roleof the Coulomb interaction. The probabilities of a valence nucleonoutside the binding-potential are P = 56.69±7.462.98% for17Ne and P = 45.51±5.812.32% for 17N. The rms radiiare ⟨r2⟩1/2 = 5.06±0.300.11 fm and⟨r2⟩1/2 = 4.24±0.160.06 fm, respectively.The results obtained are nearly independent of the potential parameters.According to the halo occurrence conditions, it is suggested that17Ne is a two-proton halo and 17N is a two-neutron skin.Moreover, two effects of the Coulomb interaction on the exoticstructure are analysed. From the present results, the exotic structureof the nucleus in the proton-rich side is more obvious than that of itsmirror nucleus because of the Coulomb interaction.

DESCRIPTION OF DRIP-LINE NUCLEI WITHIN THE RELATIVISTIC MEAN FIELD PLUS BCS APPROACH

Recently, it has been demonstrated, considering Ni and Ca isotopes as prototypes, that the relativistic mean-field plus BCS (RMF+BCS) approach wherein the single particle continuum corresponding to the RMF is replaced by a set of discrete positive energy states for the calculation of pairing energy provides a good approximation to the full relativistic Hartree–Bogoliubov (RHB) description of the ground state properties of drip-line neutron rich nuclei. The applicability of the RMF+BCS approach even for the drip-line nuclei is essentially due to the fact that the main contribution to the pairing correlations for the neutron rich nuclei is provided by the low-lying resonant states, in addition to the contributions coming from the states close to the Fermi surface. In order to show the general validity of this approach we present the results of our detailed calculations for the ground state properties of the chains of isotopes of O, Ca, Ni, Zr, Sn and Pb nuclei. The TMA force parameter set has been used for the effective mean-field Lagrangian with nonlinear terms for the sigma and omega mesons. Further, to check the validity of our treatment for different mean-field descriptions, calculations have also been carried out for the NL-SH force parametrization usually employed for the description of drip-line nuclei. Comprehensive results for the two neutron separation energy, rms radii, single particle pairing gaps and pairing energies etc. are presented. In particular, the Ca isotopes are found to exhibit distinct features near the neutron drip line whereby it is found that further addition of neutrons causes a rapid increase in the neutron rms radius with almost no increase in the binding energy, indicating the occurrence of halos. This is mainly caused by the pairing correlations and results in the existence of bound states of extremely neutron rich exotic nuclei. Similar characteristics, though less pronounced, are also exhibited by neutron rich Zr isotopes. A comparison of these results with the available experimental data and with the recent continuum relativistic Hartree–Bogoliubov (RCHB) calculations amply demonstrates the validity and usefulness of this fast RMF+BCS approach for the description of nuclei including those near the drip-lines.

Nuclear halo and its scaling laws

We have proposed a procedure to extract the probability for valence particle being out of the binding potential from the measured nuclear asymptotic normalization coefficients. With this procedure, available data regarding the nuclear halo candidates are systematically analyzed and a number of halo nuclei are confirmed. Based on these results we have got a much relaxed condition for nuclear halo occurrence. Furthermore, we have presented the scaling laws for the dimensionless quantity $<r^{2}>/R^{2}$ of nuclear halo in terms of the analytical expressions of the expectation value for the operator $r^{2}$ in a finite square-well potential.

Towards necessary and sufficient conditions for halo occurrence

We define nuclear halos states and derive and discuss occurrence conditions leading to constraints on neutron N and proton Z numbers, the total nuclear excitation energy E ∗ and the binding energy B of the halo state. Only extremely small values of E ∗ allow halo formation, which also requires small B. Low N and Z seems to be favored. We give upper limits for B for E ∗=0 .

ICE Particle Size and Shape Effect on Solar Energy Scattering Angular Distribution

The rare occurrence of te halos produced by cirrus ice crystals in nature has been investigated by modelling the incident solar (visible) light scattering angular distribution using the Monte Carlo/ray tracing method. The results show that the irregular shapes of ice crystals and large population of small ice particles in cirrus are responsible for the rare occurrence of halos.

Ejecta correlations with spatial crater density and Venus resurfacing history

We examine the alternative hypotheses that on Venus (i) the spatial randomness of the crater population reflects predominantly the spatially stochastic nature of impact crater formation or (ii) a significant amount of spatial variation in crater density is due to variations in the geological rate of crater removal. Three endmember models of resurfacing are formulated: Case I assumes that a single‐age production surface accounts for the spatial distribution of craters. Case II assumes that variations in spatial crater density reflect local production surface ages, while Case III assumes that individual craters are removed regionally, so that variations in spatial crater density reflect local retention ages. These endmember models are tested by examining correlations of crater properties with crater spatial density, ρ. We analyze the distribution of embayed and tectonized craters and the relative abundances of extended ejecta deposits (termed “halos”). The three endmembers provide specific predictions as to the occurrence of halos as a function of ρ. For ρ ≲ 1.5 craters per 106 km², Case III provides the best explanation for the deficiency of halos as well as the relative abundances of modified craters. For the interval 1.5 ≲ ρ ≲ 2.5, Case II is applicable but with only a modest spread in production ages. For densities ≳2.5, Case II is the only endmember model that matches the global observations, suggesting that regions with these high densities represent a series of distinct production surfaces with ages increasing from the planetary mean retention age.

AC breakdown characteristics of in-service aged XLPE distribution cables

AC breakdown tests were performed on field-aged XLPE distribution cables. For these measurements, a special test assembly consisting of air/distilled water terminations was developed. The tested cable specimens were examined for the occurrence of halos and water trees. The results suggest a correlation between the AC breakdown strength and operating stress. The incidence of halos is also found to be related to the AC breakdown strength, but no such relation appears to exist for the water tree length or density. >