High Polarization Fraction Research Articles

A Volume-limited Radio Search for Magnetic Activity in 140 Exoplanets with the Very Large Array

We present results from a search for radio emission in 77 stellar systems hosting 140 exoplanets, predominantly within 17.5 pc using the Very Large Array (VLA) at 4–8 GHz. This is the largest and most sensitive search to date for radio emission in exoplanetary systems in the GHz frequency range. We obtained new observations of 58 systems and analyzed archival observations of an additional 19 systems. Our choice of frequency and volume limit is motivated by radio detections of ultracool dwarfs (UCDs), including T dwarfs with masses at the exoplanet threshold of ∼13 M J. Our surveyed exoplanets span a mass range of ≈10−3–10 M J and semimajor axes of ≈10−2–10 au. We detect a single target—GJ 3323 (M4) hosting two exoplanets with minimum masses of 2 and 2.3 M ⊕—with a circular polarization fraction of ≈40%; the radio luminosity agrees with its known X-ray luminosity and the Güdel–Benz relation for stellar activity suggesting a likely stellar origin, but the high circular polarization fraction may also be indicative of star–planet interaction. For the remaining sources our 3σ upper limits are generally L ν ≲ 1012.5 erg s−1 Hz−1, comparable to the lowest radio luminosities in UCDs. Our results are consistent with previous targeted searches of individual systems at GHz frequencies while greatly expanding the sample size. Our sensitivity is comparable to predicted fluxes for some systems considered candidates for detectable star–planet interaction. Observations with future instruments such as the Square Kilometre Array and Next-Generation VLA will be necessary to further constrain emission mechanisms from exoplanet systems at GHz frequencies.

Sensitivity of Polarization to Grain Shape. II. Aggregates

A previous study (Paper I) investigated the polarization properties of a variety of simple convex grain shapes, some of which were found to be consistent with the observed polarization properties of interstellar dust from far-ultraviolet to far-infrared. Here, we study the optical properties of 45 nonconvex shapes, all aggregates of N equal-sized spheres. We consider N = 2, N = 3, and N = 256 random aggregates obtained from three different aggregation schemes. We also consider “trimmed” N = 256 aggregates obtained by systematically trimming initially random aggregates to increase either flattening or elongation. The “macroporosities” of the studied aggregates range from Pmacro=0.18 (for the N = 2 bisphere) to Pmacro≈0.85 (for the N = 256 “BA” aggregates). The only aggregates consistent with observations of starlight polarization and polarized thermal emission are shapes that have been trimmed to increase their asymmetry. If interstellar grains are high-porosity aggregates, there must be processes causing extreme elongation or flattening; if not, interstellar grains must be dominated by fairly compact structures, with at most moderate porosities. The ratio of polarization in the 10 μm silicate feature to starlight polarization in the optical is shown to be insensitive to porosity and shape. X-ray scattering may be the best tool to determine the porosity of interstellar grains. We propose that modest porosities of interstellar grains could be the result of “photolytic densification.” High polarization fractions observed in some Class 0 cores require processes to reduce porosities and/or increase asymmetries of aggregates in dense regions.

Dust Polarization of Prestellar and Protostellar Sources in OMC-3

We present the Atacama Large Millimeter/submillimeter Array observations of linearly polarized 1.1 mm continuum emission at ∼0.″14 (55 au) resolution and CO (J = 2−1) emission at ∼1.″5 (590 au) resolution toward one prestellar (MMS 4), four Class 0 (MMS 1, MMS 3, MMS 5, and MMS 6), one Class I (MMS 7), and one flat-spectrum (MMS 2) sources in the Orion Molecular Cloud 3 region. The dust disk-like structures and clear CO outflows are detected toward all sources except for MMS 4. The diameters of these disk-like structures, ranging from 16 to 97 au, are estimated based on the deconvolved full width half maximum (FWHM) values obtained from the multi-Gaussian fitting. Polarized emissions are detected toward MMS 2, MMS 5, MMS 6, and MMS 7, while no polarized emission is detected toward MMS 1, MMS 3, and MMS 4. MMS 2, MMS 5, and MMS 7 show organized polarization vectors aligned with the minor axes of the disk-like structures, with mean polarization fractions ranging from 0.6% to 1.2%. The strongest millimeter source, MMS 6, exhibits complex polarization orientations and a remarkably high polarization fraction of ∼10% around the Stokes I peak, and 15%–20% on the arm-like structure, as reported by Takahashi et al. (2019). The origins of the polarized emission, such as self-scattering and dust alignment due to the magnetic field or radiative torque, are discussed for individual sources. Some disk-like sources exhibit a polarized intensity peak shift toward the nearside of the disk, which supports that the polarized emission originates from self-scattering.

B-fields and Dust in Interstellar Filaments Using Dust Polarization (BALLAD-POL). I. The Massive Filament G11.11–0.12 Observed by SOFIA/HAWC+

We report the first measurement of polarized thermal dust emission toward the entire infrared dark cloud G11.11−0.12 taken by the polarimeter SOFIA/HAWC+ at 214 μm. The obtained magnetic fields (B-fields) from the polarized emission of the early-stage and massive filament tend to be perpendicular to its spine. We produce a map of B-field strengths for the center region of the filament. The strengths vary in the range of 100–600 μG and are strongest along the filament's spine. The central region is sub-Alfvénic and mostly subcritical, meaning that B-fields dominate over turbulence and are strong enough to resist gravitational collapse. The alignment and properties of dust grains in the filament are studied using radiative torque (RAT) theory. We find the decrease of polarization degree P with emission intensity I, i.e., depolarization effect, of the form P ∝ I −α with α ∼ 0.8–0.9, implying a significant loss of grain alignment in the filament's spine. The depolarization can be explained by the decrease in RAT alignment efficiency toward the denser regions with weaker radiation field, which cannot be explained by B-field tangling. We study the effect of the enhanced magnetic relaxation by embedded iron inclusions on RAT alignment and find that the high polarization fraction P ∼ 20%–30% in the outer layer of the filament is potential evidence for the magnetically enhanced RAT alignment mechanism. This is the first time this effect is evaluated in a filament. Based on the polarization fraction and RAT alignment theory, we also find evidence for grain growth in the filament.

High frequency study of FRB 20180916B using the 100-m Effelsberg radio telescope

ABSTRACT FRB 20180916B is a repeating fast radio burst (FRB) with an activity period of 16.33 d. In previous observations ranging from ∼150−1400 MHz, the activity window was found to be frequency dependent, with lower frequency bursts occurring later. In this work, we present the highest frequency detections of bursts from this FRB, using the 100-m Effelsberg radio telescope at 4−8 GHz. We present the results from two observing campaigns. We performed the first campaign over an entire activity period which resulted in no detections. The second campaign was done in an active window at 4−8 GHz which we predicted from our modelling of chromaticity, resulting in eight burst detections. The bursts were detected in a window of 1.35 d, 3.6 d preceding the activity peak seen by Canadian hydrogen intensity mapping experiment, suggesting the chromaticity extends to higher frequency. The detected bursts have narrower temporal widths and larger spectral widths compared to lower frequencies. All of them have flat polarization position angle sweeps and high polarization fractions. The bursts also exhibit diffractive scintillation due to the Milky Way, following a f3.90 ± 0.05 scaling, and vary significantly over time. We find that burst rate across frequency scales as f−2.6 ± 0.2. Lastly, we examine implications of the frequency dependency on the source models.

Exploring Magnetic Loops and Serpentine Fields in the Quiet Sun with the GRIS-IFU

Synthetic observations produced from radiative magnetohydrodynamic simulations have predicted that higher polarization fractions in the quiet solar photosphere would be revealed by increasing the total integration time of observations at GREGOR resolutions. We present recently acquired disk center observations of the Fe i 15648.5 Å line obtained with the GREGOR telescope equipped with the GRIS-IFU during excellent seeing conditions, showing exceptionally high polarization fractions. Our observations reveal an internetwork region with a majority (>60%) of magnetized pixels displaying a clear transverse component of the magnetic field. This result is in stark contrast to previous disk center GRIS-IFU observations in this spectral line, which had predominantly vertical magnetic fields in the deep photosphere. At the same time, the median magnetic field strength is weaker than previous GRIS-IFU observations, indicating that the larger fraction of polarization signals cannot be explained by a more active target. We use the Stokes Inversion based on Response functions (SIR) code to analyze the data, performing over 45 million inversions, and interrogate the impact of two conflicting approaches to the treatment of noise on the retrieval of the magnetic inclination and azimuth. We present several case studies of the zoo of magnetic features present in these data, including small-scale magnetic loops that seem to be embedded in a sea of magnetism, and serpentine fields, focusing on regions where full-vector spectropolarimetry has been achieved. We also present a new open-source Python 3 analysis tool, SIR Explorer, which we use to examine the dynamics of these small-scale magnetic features.

Polarization properties of FRB 20201124A from detections with the Effelsberg 100-m radio telescope

ABSTRACT The repeating fast radio burst (FRB) source, FRB 20201124A, was found to be highly active in 2021 March and April. We observed the source with the Effelsberg 100-m radio telescope at 1.36 GHz on 2021 April 9 and detected 20 bursts. A downward drift in frequency over time is clearly seen from the majority of bursts in our sample. A structure-maximizing dispersion measure (DM) search on the multicomponent bursts in our sample yields a DM of 411.6 ± 0.6 pc cm−3. We find that the rotation measure (RM) of the bursts varies around their weighted mean value of −601 rad m−2 with a standard deviation of 11.1 rad m−2. This RM magnitude is 10 times larger than the expected Galactic contribution along this line of sight (LoS). We estimate an LoS magnetic field strength of 4–6 µG, assuming that the entire host galaxy DM contributes to the RM. Further polarization measurements will help determine FRB 20201124A’s RM stability. The bursts are highly linearly polarized, with some showing signs of circular polarization, the first for a repeating FRB. Their polarization position angles (PAs) are flat across the burst envelopes and vary between bursts. We argue that the varying polarization fractions and PAs of FRB 20201124A are similar to known magnetospheric emission from pulsars, while the observed circular polarization, combined with the RM variability, is hard to explain with Faraday conversion. The high linear polarization fractions, flat PAs, and downward drift from FRB 20201124A bursts are similar to previous repeating sources, while the observed circular polarization is a newly seen behaviour among repeaters.

Morphology of radio relics – II. Properties of polarized emission

ABSTRACTRadio relics are diffuse radio sources in galaxy clusters that are associated with merger shock waves. Detailed observations of radio relics in total intensity and in polarization show complex structures on kiloparsec scales. The relation between the observed features and the underlying morphology of the magnetic field is not clear. Using 3D magneto-hydrodynamical simulations, we study the polarized emission produced by a shock wave that propagates through a turbulent medium that resembles the intracluster medium. We model the polarized synchrotron emission on the basis of diffusive shock acceleration of cosmic ray electrons. We find that the synchrotron emission produced in a shocked turbulent medium can reproduce some of the observed features in radio relics. Shock compression can give rise to a high polarization fraction at the shock front and a partial alignment of the polarization E-vectors with the shock normal. Our work confirms that radio relics can also be formed in an environment with a tangled magnetic field. We also discuss the effect of Faraday rotation intrinsic to the source, and how our results depend on the angular resolution of observations.

A Layered Debris Disk around M Star TWA 7 in Scattered Light

Abstract We have obtained Hubble Space Telescope (HST) coronagraphic observations of the circumstellar disk around M star TWA 7 using the Space Telescope Imaging Spectrograph (STIS) instrument in visible light. Together with archival observations, including HST/NICMOS using the F160W filter and Very Large Telescope/SPHERE at the H-band in polarized light, we investigate the system in scattered light. By studying this nearly face-on system using geometric disk models and Henyey–Greenstein phase functions, we report a new discovery of a tertiary ring and a clump. We identify a layered architecture: three rings, a spiral, and an ≈150 au2 elliptical clump. The most extended ring peaks at 28 au, and the other components are on its outskirts. Our point-source detection-limit calculations demonstrate the necessity of disk modeling in imaging fainter planets. Morphologically, we witness a clockwise spiral motion, and the motion pattern is consistent with both solid body motion and local Keplerian motion; we also observe underdensity regions for the secondary ring that might result from mean-motion resonance or moving shadows: both call for re-observations to determine their nature. Comparing multi-instrument observations, we obtain blue STIS-NICMOS color, a STIS-SPHERE radial distribution peak difference for the tertiary ring, and a high SPHERE-NICMOS polarization fraction; these aspects indicate that TWA 7 could retain small dust particles. By viewing the debris disk around M star TWA 7 at a nearly face-on vantage point, our study allows for the understanding of such disks in scattered light in both system architecture and dust property.

Distinctive Sources Govern Organic Aerosol Fractions with Different Degrees of Oxygenation in the Urban Atmosphere.

Understanding how the sources of an atmospheric organic aerosol (OA) govern its burden is crucial for assessing its impact on the environment and adopting proper control strategies. In this study, the sources of OA over Beijing were assessed year-around based on the combination of two separation approaches for OA, one from chemical fractionation into the high-polarity fraction of water-soluble organic matter (HP-WSOM), humic-like substances (HULIS), and water-insoluble organic matter (WISOM), and the other from statistical grouping using positive matrix factorization (PMF) of high-resolution aerosol mass spectra. Among the three OA fractions, HP-WSOM has the highest O/C ratio (1.36), followed by HULIS (0.56) and WISOM (0.17). The major sources of different OA fractions were distinct: HP-WSOM was dominated by more oxidized oxygenated OA (96%); HULIS by cooking-like OA (40%), less oxidized oxygenated OA (27%), and biomass burning OA (21%); and WISOM by fossil fuel OA (77%). In addition, our results provide evidence that mass spectral-based PMF factors are associated with specific substructures in molecules. These structures are further discussed in the context of the FT-IR results. This study presents an overall relationship of OA groups monitored by chemical and statistical approaches for the first time, providing insights for future source apportionment studies.

Polarimetric Properties of Event Horizon Telescope Targets from ALMA

Abstract We present the results from a full polarization study carried out with the Atacama Large Millimeter/submillimeter Array (ALMA) during the first Very Long Baseline Interferometry (VLBI) campaign, which was conducted in 2017 April in the λ3 mm and λ1.3 mm bands, in concert with the Global mm-VLBI Array (GMVA) and the Event Horizon Telescope (EHT), respectively. We determine the polarization and Faraday properties of all VLBI targets, including Sgr A*, M87, and a dozen radio-loud active galactic nuclei (AGNs), in the two bands at several epochs in a time window of 10 days. We detect high linear polarization fractions (2%–15%) and large rotation measures (RM > 103.3–105.5 rad m−2), confirming the trends of previous AGN studies at millimeter wavelengths. We find that blazars are more strongly polarized than other AGNs in the sample, while exhibiting (on average) order-of-magnitude lower RM values, consistent with the AGN viewing angle unification scheme. For Sgr A* we report a mean RM of (−4.2 ± 0.3) × 105 rad m−2 at 1.3 mm, consistent with measurements over the past decade and, for the first time, an RM of (–2.1 ± 0.1) × 105 rad m−2 at 3 mm, suggesting that about half of the Faraday rotation at 1.3 mm may occur between the 3 mm photosphere and the 1.3 mm source. We also report the first unambiguous measurement of RM toward the M87 nucleus at millimeter wavelengths, which undergoes significant changes in magnitude and sign reversals on a one year timescale, spanning the range from −1.2 to 0.3 × 105 rad m−2 at 3 mm and −4.1 to 1.5 × 105 rad m−2 at 1.3 mm. Given this time variability, we argue that, unlike the case of Sgr A*, the RM in M87 does not provide an accurate estimate of the mass accretion rate onto the black hole. We put forward a two-component model, comprised of a variable compact region and a static extended region, that can simultaneously explain the polarimetric properties observed by both the EHT (on horizon scales) and ALMA (which observes the combined emission from both components). These measurements provide critical constraints for the calibration, analysis, and interpretation of simultaneously obtained VLBI data with the EHT and GMVA.

Polarization of accreting X-ray pulsars – II. Hercules X-1

ABSTRACT We employ our new model for the polarized emission of accreting X-ray pulsars to describe the emission from the luminous X-ray pulsar Hercules X-1. In contrast with previous works, our model predicts the polarization parameters independently of spectral formation, and considers the structure and dynamics of the accretion column, as well as the additional effects on propagation due to general relativity and quantum electrodynamics. We find that our model can describe the observed pulse fraction and the pulse shape of the main peak, as well as the modulation of the cyclotron line with phase. We pick two geometries, assuming a single accretion column or two columns at the magnetic poles, that can describe current observations of pulse shape and cyclotron modulation with phase. Both models predict a high polarization fraction, between 60 and 80 per cent in the 1–10 keV range, that is phase and energy dependent, and that peaks at the same phase as the intensity. The phase and energy dependence of the polarization fraction and of the polarization angle can help discern between the different geometries.

Understanding the Origin of the Magnetic Field Morphology in the Wide-binary Protostellar System BHR 71

Abstract We present 1.3 mm Atacama Large Millimeter/submillimeter Array observations of polarized dust emission toward the wide-binary protostellar system BHR 71 IRS1 and IRS2. IRS1 features what appears to be a natal, hourglass-shaped magnetic field. In contrast, IRS2 exhibits a magnetic field that has been affected by its bipolar outflow. Toward IRS2, the polarization is confined mainly to the outflow cavity walls. Along the northern edge of the redshifted outflow cavity of IRS2, the polarized emission is sandwiched between the outflow and a filament of cold, dense gas traced by N2D+, toward which no dust polarization is detected. This suggests that the origin of the enhanced polarization in IRS2 is the irradiation of the outflow cavity walls, which enables the alignment of dust grains with respect to the magnetic field—but only to a depth of ∼300 au, beyond which the dust is cold and unpolarized. However, in order to align grains deep enough in the cavity walls, and to produce the high polarization fraction seen in IRS2, the aligning photons are likely to be in the mid- to far-infrared range, which suggests a degree of grain growth beyond what is typically expected in very young, Class 0 sources. Finally, toward IRS1 we see a narrow, linear feature with a high (10%–20%) polarization fraction and a well-ordered magnetic field that is not associated with the bipolar outflow cavity. We speculate that this feature may be a magnetized accretion streamer; however, this has yet to be confirmed by kinematic observations of dense-gas tracers.

Extreme starlight polarization in a region with highly polarized dust emission

Context. Galactic dust emission is polarized at unexpectedly high levels, as revealed by Planck. Aims. The origin of the observed ≃20% polarization fractions can be identified by characterizing the properties of optical starlight polarization in a region with maximally polarized dust emission. Methods. We measure the R-band linear polarization of 22 stars in a region with a submillimeter polarization fraction of ≃20%. A subset of 6 stars is also measured in the B, V, and I bands to investigate the wavelength dependence of polarization. Results. We find that starlight is polarized at correspondingly high levels. Through multiband polarimetry we find that the high polarization fractions are unlikely to arise from unusual dust properties, such as enhanced grain alignment. Instead, a favorable magnetic field geometry is the most likely explanation, and is supported by observational probes of the magnetic field morphology. The observed starlight polarization exceeds the classical upper limit of [pV/E(B−V)]max = 9% mag−1 and is at least as high as 13% mag−1, as inferred from a joint analysis of Planck data, starlight polarization, and reddening measurements. Thus, we confirm that the intrinsic polarizing ability of dust grains at optical wavelengths has long been underestimated.

Anti-parasitic effects of water-soluble alkaloid fractions from ethanolic extracts of Sophora moorcroftiana seeds in Caenorhabditis elegans

Parasite infections of humans and animals remain a major global health problem, with limited choice of drugs being available to the treatment of parasitosis in the clinic. Sophora moorcroftiana (S. moorcroftiana) is a shrub that grows in Tibet Plateau of China. Decoction of the seeds has been used as a traditional Tibetan medicine to treat parasitosis for years. But the anti-parasitic effects of water-soluble fractions in the seeds need further investigation. In the present study, the water-soluble alkaloid fractions (E2) were obtained from S. moorcroftiana seeds by refluxing extraction with 60% ethanol and low polarity fraction (E2-a) and high polarity fraction (E2-b) were subsequently isolated from E2 using column chromatography. As a parasite model, Caenorhabditis elegans (C. elegans) were treated with different fractions and their survivals were recorded. The results showed that that E2-a induced a lower survival rate in C. elegans than E2-b and E2. The protoscoleces of Echinococcus granulosus (E. granulosus) were cultured in the presence of E2-a. Compared with E2-b and E2, protoscoleces exhibited decreased survival rate following E2-a treatment. Furtherly, the effects of E2-a on the behavior, brood size, and lifespan of the worms were investigated. Body bend frequencies of the worms treated with the high concentration of E2-a were reduced by two-thirds compared with the control group (P < 0.01). Compared with non-E2-a-treated group, exposure of nematodes to E2-a led to a decrease in head thrashes and pharyngeal pumps frequency (P < 0.01). E2-a treatment resulted in a significantly lower brood size (P < 0.01). Additional E2-a treatment induced a significantly shortened lifespan, compared with the control (P < 0.05). These findings indicated that water-soluble fraction E2-a from S. moorcroftiana seeds was a potential helminthic agent.

Large-Scale Features of the Radio Sky and a Model for Loop I

The large-scale radio/microwave sky has been mapped over a range of frequencies from tens of MHz to tens of GHz, in intensity and polarization. The emission is primarily synchrotron radiation from cosmic ray electrons spiralling in the Galactic magnetic field, in addition to free–free radiation from warm ionized gas. Away from the Galactic plane, the radio sky is dominated by very large (tens of degrees) loops, arcs, spurs and filaments, including the well-known North Polar Spur (NPS), which forms part of Loop I with a diameter of ∼ 120 ∘ . In polarization data, such features are often more discernible due to their high polarization fractions suggesting ordered magnetic fields, while the polarization angles suggest fields that are parallel to the filament. The exact nature of these features are poorly understood. We give a brief review of these features, focussing on the NPS/Loop I, whose polarization directions can be explained using a simple expanding shell model, placing the centre of the shell at a distance of ∼100–200 pc. However, there is significant evidence for a larger distance in the range ∼500–1000 pc, while larger distances including the Galactic Centre are unlikely. We also briefly discuss other large-scale curiosities in the radio sky such as the microwave haze and anti-correlation of H α filaments and synchrotron polarized intensity.

The magnetic environment of the Orion-Eridanus superbubble as revealed by Planck

Using the 353-GHz polarization observations by the Planck satellite we characterize the magnetic field in the Orion-Eridanus superbubble, a nearby expanding structure that spans more than 1600 square degrees in the sky. We identify a region of both low dispersion of polarization orientations and high polarization fraction associated with the outer wall of the superbubble identified in the most recent models of the large-scale shape of the region. We use the Davis-Chandrasekhar-Fermi method to derive plane-of-the-sky magnetic field strengths of tens of μG toward the southern edge of the bubble. The comparison of these values with existing Zeeman splitting observations of HI in emission suggests that the large-scale magnetic field in the region was primarily shaped by the expanding superbubble.

The Fan Region at 1.5 GHz – I. Polarized synchrotron emission extending beyond the Perseus Arm

The Fan Region is one of the dominant features in the polarized radio sky, long thought to be a local (distance < 500 pc) synchrotron feature. We present 1.3-1.8 GHz polarized radio continuum observations of the region from the Global Magneto-Ionic Medium Survey (GMIMS) and compare them to maps of Halpha and polarized radio continuum intensity from 0.408-353 GHz. The high-frequency (> 1 GHz) and low-frequency (< 600 MHz) emission have different morphologies, suggesting a different physical origin. Portions of the 1.5 GHz Fan Region emission are depolarized by about 30% by ionized gas structures in the Perseus Arm, indicating that this fraction of the emission originates >2 kpc away. We argue for the same conclusion based on the high polarization fraction at 1.5 GHz (about 40%). The Fan Region is offset with respect to the Galactic plane, covering -5{\deg} < b < +10{\deg}; we attribute this offset to the warp in the outer Galaxy. We discuss origins of the polarized emission, including the spiral Galactic magnetic field. This idea is a plausible contributing factor although no model to date readily reproduces all of the observations. We conclude that models of the Galactic magnetic field should account for the > 1 GHz emission from the Fan Region as a Galactic-scale, not purely local, feature.

INTERFEROMETRIC UPPER LIMITS ON MILLIMETER POLARIZATION OF THE DISKS AROUND DG Tau, GM Aur, AND MWC 480

Millimeter-wavelength polarization measurements offer a promising method for probing the geometry of magnetic fields in circumstellar disks. Single dish observations and theoretical work have hinted that magnetic field geometries might be predominantly toroidal, and that disks should exhibit millimeter polarization fractions of 2-3%. While subsequent work has not confirmed these high polarization fractions, either the wavelength of observation or the target sources differed from the original observations. Here we present new polarimetric observations of three nearby circumstellar disks at 2" resolution with the Submillimeter Array (SMA) and the Combined Array for Research in Millimeter Astronomy (CARMA). We reobserve GM Aur and DG Tau, the systems in which millimeter polarization detections have been claimed. Despite higher resolution and sensitivity at wavelengths similar to the previous observations, the new observations do not show significant polarization. We also add observations of a new HAeBe system, MWC 480. These observations demonstrate that a very low (<0.5%) polarization fraction is probably common at large (>100 AU) scales in bright circumstellar disks. We suggest that high-resolution observations may be worthwhile to probe magnetic field structure on linear distances smaller than the disk scale height, as well as in regions closer to the star that may have larger MRI-induced magnetic field strengths.

Immunostimulatory activities of polysaccharide extract isolated from Curcuma longa

Several curcuminoids and sesquiterpenoids isolated from Curcuma longa (CL) have been shown to have many pharmacological activities. In the present study, the immunomodulatory activities of the polar fractions of CL hot water extracts were investigated using human peripheral blood mononuclear cells (PBMC). Our results showed that the high polarity fraction of the hot water extract exhibited stimulatory effects on PBMC proliferation as shown in [methyl- 3H]-thymidine incorporation assay. In an attempt to isolate the active components responsible for the activities, further partition with ethyl acetate, n-butanol and ethanol, progressively were performed. The cytokine productions (TGF-β, TNF-α, GM-CSF, IL-1α, IL-5, IL-6, IL-8, IL-10, IL-13, etc.) have been modulated by a polysaccharide-enriched fraction as shown in ELISA and cytokine protein array. The proportion of CD14 positive stained PBMC was increased by such fraction. The composition of monosaccharide of the active fraction has been determined by GC–MS and gel permeation chromatography. The immunostimulatory effects of C. longa polysaccharides on PBMC were shown for the first time. The findings revealed the potential use of C. longa crude extract (containing curcuminoids and polysaccharides) as an adjuvant supplement for cancer patients, whose immune activities were suppressed during chemotherapies.