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The rotationally modulated polarization of ξ Boo A
摘要： We have observed the active star ξ Boo A (HD 131156A) with high precision broadband linear polarimetry contemporaneously with circular spectropolarimetry. We find both signals are modulated by the 6.43 d rotation period of ξ Boo A. The signals from the two techniques are 0.25 out of phase, consistent with the broadband linear polarization resulting from differential saturation of spectral lines in the global transverse magnetic field. The mean magnitude of the linear polarization signal is ～4 ppm G–1 but its structure is complex and the amplitude of the variations suppressed relative to the longitudinal magnetic field. The result has important implications for current attempts to detect polarized light from hot Jupiters orbiting active stars in the combined light of the star and planet. In such work stellar activity will manifest as noise, both on the time-scale of stellar rotation, and on longer time-scales – where changes in activity level will manifest as a baseline shift between observing runs.
关键词： stars: individual HD 131156A,stars: magnetic field,polarization,stars: activity
更新于2025-09-23 15:22:29
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Brief History of the EML Symposia: 1980-2018
摘要： Following the pioneering research studies by individual inventors and teams from the 1840s to the 1960s on various aspects of electromagnetic launch using railguns, coilguns, and linear motors, there has been an explosion of interest since the 1970s. Much of this growth has been discussed at the International Electro-Magnetic Launcher Symposia that have taken place approximately every two years from 1980 to 2018. A brief description and a summary of the early work of pioneers in this field as well as the symposia is provided here. Selected papers from the symposia have been archived in the IEEE TRANSACTIONS ON MAGNETICS and the IEEE TRANSACTIONS ON PLASMA SCIENCE.
关键词： linear launchers,electro-magnetic launcher (EML) Symposia,railguns,pulsed power,electromagnetic (EM) launchers,Coilguns
更新于2025-09-23 15:22:29
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Diagnostic imaging and radiation exposure in inflammatory bowel disease
摘要： Diagnostic imaging plays a key role in the diagnosis and management of inflammatory bowel disease (IBD). However due to the relapsing nature of IBD, there is growing concern that IBD patients may be exposed to potentially harmful cumulative levels of ionising radiation in their lifetime, increasing malignant potential in a population already at risk. In this review we explore the proportion of IBD patients exposed to high cumulative radiation doses, the risk factors associated with higher radiation exposures, and we compare conventional diagnostic imaging with newer radiation-free imaging techniques used in the evaluation of patients with IBD. While computed tomography (CT) performs well as an imaging modality for IBD, the effective radiation dose is considerably higher than other abdominal imaging modalities. It is increasingly recognised that CT imaging remains responsible for the majority of diagnostic medical radiation to which IBD patients are exposed. Magnetic resonance imaging (MRI) and small intestine contrast enhanced ultrasonography (SICUS) have now emerged as suitable radiation-free alternatives to CT imaging, with comparable diagnostic accuracy. The routine use of MRI and SICUS for the clinical evaluation of patients with known or suspected small bowel Crohn’s disease is to be encouraged wherever possible. More provision is needed for out-of-hours radiation-free imaging modalities to reduce the need for CT.
关键词： Diagnostic medical radiation,Small intestine contrast-enhanced ultrasonography,Nuclear medicine,Computerised tomography,Inflammatory bowel disease,Magnetic resonance enterography,Small bowel follow-through
更新于2025-09-23 15:22:29
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Robust midgap states in band-inverted junctions under electric and magnetic fields
摘要： Several IV–VI semiconductor compounds made of heavy atoms, such as Pb1?xSnxTe, may undergo band-inversion at the L point of the Brillouin zone upon variation of their chemical composition. This inversion gives rise to topologically distinct phases, characterized by a change in a topological invariant. In the framework of the k·p theory, band-inversion can be viewed as a change of sign of the fundamental gap. A two-band model within the envelope-function approximation predicts the appearance of midgap interface states with Dirac cone dispersions in band-inverted junctions, namely, when the gap changes sign along the growth direction. We present a thorough study of these interface electron states in the presence of crossed electric and magnetic fields, the electric field being applied along the growth direction of a band-inverted junction. We show that the Dirac cone is robust and persists even if the fields are strong. In addition, we point out that Landau levels of electron states lying in the semiconductor bands can be tailored by the electric field. Tunable devices are thus likely to be realizable, exploiting the properties studied herein.
关键词： crystalline topological insulators,Landau levels,midgap states,electric and magnetic fields
更新于2025-09-23 15:22:29
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Three-Dimensional Scanning Hall Probe Microscopy for Final Stage of Crack Growth of Chromium Molybdenum Steel SCM440
摘要： Crack propagation around the stress concentration area causes fatigue failure. Non-destructive method is necessary for monitoring structure fatigue before destruction. We focused on a magnetic non-destructive evaluation method for crack growth. In order to understand the relation between crack propagation and changes in magnetic flux density, we observed the position of the positive and negative magnetic flux density distributions around the crack of tool steel (SCM440) plate using a scanning Hall probe microscope (SHPM). We found that the vertical component of the three-dimensional magnetic flux density moved as the crack growth. Furthermore, the magnetic component which is parallel to the tensile stress appeared just before destruction of the specimen.
关键词： Crack propagation,Scanning Hall probe microscope,Magnetic flux density
更新于2025-09-23 15:22:29
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Significance of Additional Non-Mass Enhancement in Patients with Breast Cancer on Preoperative 3T Dynamic Contrast Enhanced MRI of the Breast
摘要： Background: In preoperative assessment of breast cancer, MRI has been shown to identify more additional breast lesions than are detectable using conventional imaging techniques. The characterization of additional lesions is more important than detection for optimal surgical treatment. Additional breast lesions can be included in focus, mass, and non-mass enhancement (NME) on MRI. According to the fifth edition of the breast imaging reporting and data system (BI-RADS?), which includes several changes in the NME descriptors, few studies to date have evaluated NME in preoperative assessment of breast cancer. Objectives: We investigated the diagnostic accuracy of BI-RADS descriptors in predicting malignancy for additional NME lesions detected on preoperative 3T dynamic contrast enhanced MRI (DCE-MRI) in patients with newly diagnosed breast cancer. Patients and Methods: Between January 2008 and December 2012, 88 patients were enrolled in our study, all with NME lesions other than the index cancer on preoperative 3T DCE-MRI and all with accompanying histopathologic examination. The MRI findings were analyzed according to the BI-RADS MRI lexicon. We evaluated the size, distribution, internal enhancement pattern, and location of NME lesions relative to the index cancer (i.e., same quadrant, different quadrant, or contralateral breast). Results: On histopathologic analysis of the 88 NME lesions, 73 (83%) were malignant and 15 (17%) were benign. Lesion size did not differ significantly between malignant and benign lesions (P = 0.410). Malignancy was more frequent in linear (P = 0.005) and segmental (P = 0.011) distributions, and benignancy was more frequent in focal (P = 0.004) and regional (P < 0.001) NME lesions. The highest positive predictive value (PPV) for malignancy occurred in segmental (96.8%), linear (95.1%), clustered ring (100%), and clumped (92.0%) enhancement. Asymmetry demonstrated a high positive predictive value of 85.9%. The frequency of malignancy was higher for NME lesions located in the same quadrant with the index cancer (P = 0.006), and benignancy was higher in the contralateral breast (P = 0.015). On multivariate analysis, linear (P = 0.001) and segmental (P = 0.005) distributions were significant predictors of malignancy. Conclusion: The possibility of malignancy is strongly indicated when additional NME lesions show linear or segmental enhancement on preoperative 3T DCE-MRI in patients with recently diagnosed breast cancer.
关键词： Non-Mass Enhancement,Magnetic Resonance Imaging,Preoperative Care,Breast Neoplasms,Diagnosis
更新于2025-09-23 15:22:29
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The properties of solar radio spikes with harmonics and the associated EUV brightenings
摘要： Solar radio spikes are narrowband, short duration radio bursts. They are excited by the energetic electrons accelerated during small scale magnetic reconnections. Spikes play an important role in diagnosing magnetic reconnections and studying electron accelerations. In this paper, the solar radio spikes observed by the Chashan Solar Observatory (CSO) spectrograph combined with observations from the Solar Dynamics Observatory (SDO) are used to study the properties of spikes with harmonics. The CSO data show that the central frequency ratio of the third to the second harmonic is 1.35 ± 0.01 and the third harmonic has a larger absolute and relative bandwidth, but a shorter duration than the second one. By studying the correlation between light curves of the solar radio spike and those of bright points at different Extreme UltraViolet (EUV) passbands, the best associated EUV bright point and passbands are determined. The spike source properties are discussed based on the extrapolated magnetic field around the associated EUV bright point.
关键词： Radio emission, active regions,Radio bursts, meter-wavelengths and longer, spikes,Magnetic fields, corona
更新于2025-09-23 15:22:29
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Half-metallic, Magnetic, and Optical Properties for the (001) Surface of Binary Heusler Alloy MgCl3
摘要： The half-metallic (HM), magnetic, and optical properties for the (001) surface of binary Heusler alloy MgCl3 were investigated by the first-principles method. The Mg*Mg*-term and Mg*Mg-term had the lower surface energies among the ClCl-term, Mg*Mg*-term, ClMg-term, ClCl*-term, and Mg*Mg-term (001) surfaces, thus, they were the more stable surfaces. The band decomposed charge density showed clearly the valence band maximum was contributed not only by the ClB-3p states but also the ClA-3p and ClC-3p states. The HM character was destroyed in all the five terminations of the (001) surface. The stable Mg*Mg*-term (001) surface had the largest spin polarization (≈ 83.0%). The hydrogen-termination effect showed an effective method to enlarge the spin polarizations for the ClCl-term and ClCl*-term surfaces to produce thin films which had potential applications in spintronics. There were great changes of atomic magnetic moments for Cl atoms in any layer. In energy range of 1.6–3.1 eV for the visible light, the Mg*Mg*-term had superiority in the absorption for purple light.
关键词： binary Heusler alloy,Half-metallic property,magnetic property,optical property
更新于2025-09-23 15:22:29
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Different approaches for the solar photocatalytic removal of micro-contaminants from aqueous environment: Titania vs. hybrid magnetic iron oxides
摘要： This work reports on the light-induced heterogeneous photodegradation of four micro-contaminants (MCs): Carbamazepine (C), Flumequine (F), Ibuprofen (I), and Sulfamethoxazole (S), using two different heterogeneous advanced oxidation processes. The first one is the semiconductor photocatalysis, run in the presence of the suspension of a home prepared TiO2 (TiO2 HP); the second one is an heterogeneous photo-Fenton process run in the presence of a hybrid magnetic nanomaterial (MB3) with an iron oxides core and an organic shell made of bio-based substances (BBS) isolated from urban biowaste. The two materials work upon two different mechanisms and were already tested (and the action mechanism hypothesized) at the lab scale under model conditions: TiO2 acts as photocatalyst through the photo-generation of hole/electron pairs able to give rise to oxidation and reduction reactions, whereas hybrid magnetic nanomaterial acts in the presence of H2O2 by a photo-Fenton like mechanism. The results evidenced the better performances of TiO2 HP (also better than the well-known reference TiO2 P25). Preliminary photodegradation experiments carried out in a pilot plant under natural solar radiation confirmed the good results obtained with TiO2 HP. Moreover, in the adopted experimental conditions, the Fe(II) leached from MB3 can be considered as responsible of the MCs degradation through a homogeneous photo-Fenton reaction, where MB3 act as iron reservoir.
关键词： TiO2,Micro-contaminants,Photo-Fenton,Photocatalysis,Water treatments,Magnetic materials.
更新于2025-09-23 15:22:29
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Co2+ Substituted ZnCuFe2O4 (0.0?≤?x?≤?0.5) Ferrites: Synthesis, Magneto-structural and Optical Properties for Their Photocatalytic Performance
摘要： The cobalt (Co2+) has been successively substituted in ZnCuFe2O4 to obtain Zn0.5?xCoxCu0.5Fe2O4 (0.0 ≤ x ≤ 0.5) ferrites by auto-combustion technique. Prior to photocatalytic degradation, all as-synthesized ferrites were characterized to study their structure, composition, morphology, magnetic and optical behavior. The shifting of tetrahedral as well as octahedral stretching peaks towards higher frequencies observed in the Fourier transform infrared spectroscopy indicates that Co2+ ion is substituted in ZnCuFe2O4. X-ray diffraction pattern confirms the formation of single-phase cubic spinel with decrease in average lattice constant from 8.3915 to 8.3224 ? with increase in Co2+ substitution. The photocatalytic performance of obtained ferrite catalyst was determined using methylene blue (MB) as model dye under visible light and direct sunlight. The degradation of MB with as-obtained photocatalyst under sunlight improves (91%) which proves the effective utilization of visible light active magnetic photocatalyst.
关键词： Photocatalytic degradation,Magnetic materials,Methylene blue,Sol-gel method,Spinel ZnCuFe2O4
更新于2025-09-23 15:22:29