bluuebunny/crossref_metadata_2025 huggingface dataset:
Medical Priority Dispatch System Breathing Problems Protocol Key Question Combinations are Associated with Patient Acuity
Authors: Clawson Jeff , Barron Tracey , Scott Greg , Siriwardena A. Niroshan , Patterson Brett , Olola Christopher
Published: July 2012

Introduction

The Breathing Problems Chief Complaint (CC) protocol in the Medical Priority Dispatch System (MPDS) was the system's most frequently used protocol. While “severe breathing problems” is a significant predictor of cardiac arrest (CA), previous data have demonstrated that the DELTA-level determinant codes in this CC contain patients across a wide spectrum of acuity.

Hypothesis

The hypothesis in this study was that certain combinations of caller answers to the breathing problems protocol key questions (KQs) are correlated with different but specific patient acuities.

Methods

This was a retrospective study conducted at one International Academies of Emergency Dispatch (IAED) Accredited Center of Excellence. Key Question combinations were generated and analyzed from 11 months of dispatch data, and extracted from MPDS software and the computer assisted dispatch system. Descriptive statistics were used to evaluate measures between study groups.

Results

Forty-two thousand cases were recorded; 52% of patients were female and the median age was 61 years. Overall, based on the original MPDS Protocol (before generating KQ combinations), patients withabnormal breathingandclammyconditions were the youngest. The MPDS DELTA-level constituted the highest percentage of cases (74.0%) and thedifficulty speaking between breaths(DSBB) condition was the most prevalent (50.3%).Ineffective breathingandnot alertconditions had the highest cardiac arrest quotient (CAQ). Based on the KQ combinations, the CA patients who also had thenot alertcondition were significantly older than other patients. The percentage of CA outcomes in asthmatic patients was significantly higher inDSBBplusnot alert; DSBBplusnot alertpluschanging color;andDSBBplusnot alertplusclammyconditions cases, compared to asthmaticabnormal breathingcases.

Conclusions

The study findings demonstrated that MPDS KQ answer combinations relate to patient acuity. Cardiac arrest patients are significantly less likely to be asthmatic than those without CA, and vice versa. Using a prioritization scheme that accounts for the presence of either single or multiple signs and/or symptom combinations for the Breathing Problems CC protocol would be a more accurate method of assigning DELTA-level cases in the MPDS.

Clawson J, Barron T, Scott G, Siriwardena AN, Patterson B, Olola C. Medical Priority Dispatch System breathing problems protocol key question combinations are associated with patient acuity.Prehosp Disaster Med.2012;27(4):1-6.
Advances in Maser Theory
Authors: Strelnitski Vladimir
Published: July 2012

The groundwork of the cosmic maser theory was laid four decades ago. The elapsed time, including the few years after the last IAU symposium dedicated to masers, did not add much to the fundamentals. In this review, I will summarize some cornerstones of the theory, with an emphasis on issues that don't seem to have received due attention in the past. I will also comment on some new developments.
Maser polarization with ALMA
Authors: Pérez-Sánchez Andrés F. , Vlemmings Wouter
Published: July 2012

Once ALMA full polarization capabilities are offered, (sub-)mm polarization studies will enter a new era. It will become possible to perform detailed studies of polarized maser emission towards for example massive star forming regions and late-type stars such as (post-) Asymptotic Giant Branch stars and young Planetary Nebulae. In these environments, SiO, H2O and HCN are molecules that can naturally generate polarized maser emission observable by ALMA. The maser polarization can then be used to derive the strength and morphology of the magnetic field in the masing regions. However, in order to derive, in particular, the magnetic field orientation from maser linear polarization, a number of conditions involving the rate of stimulated emission, molecular state decay and Zeeman splitting need to be satisfied. In this work, we discuss these conditions for the maser transitions in the ALMA frequency range and highlight the optimum transitions to further our understanding of star formation and evolved star magnetic fields.
Water Maser Emission Around Low/Intermediate Mass Evolved Stars
Authors: Leal-Ferreira M. L. , Vlemmings W. H. T. , Diamond P. J. , Kemball A. , Amiri N. , Desmurs J.-F.
Published: July 2012

We present results of Very Long Baseline Array (VLBA) polarimetric 22 GHz H2O maser observations of a number of low/intermediate mass evolved stars. We observed 3 Miras (Ap Lyn, IK Tau and IRC+60370), 1 semi-regular variable (RT Vir) and 1 pPN (OH231.8+4.2). Circular polarization is detected in the H2O maser region of OH231.8+4.2 and we infer a magnetic field of |B||| = ~45 mG. This implies an extrapolated magnetic field of ~2.5 G on the surface of the central star. The preliminary results on RT Vir and IRC+60370 also indicate the first detection of weak H2O maser linear polarization.
Intermittent maser flare around the high-mass young stellar object G353.273+0.641
Authors: Motogi Kazuhito , Sorai Kazuo , Fujisawa Kenta , Sugiyama Koichiro , Honma Mareki
Published: July 2012

The water maser site associated with G353.273+0.641 is classified as a dominant blueshifted H2O maser, which shows an extremely wide velocity range (± 100 km s−1) with almost all flux concentrated in the highly blueshifted emission. The previous study has proposed that this peculiar H2O maser site is excited by a pole-on jet from high mass protostellar object. We report on the monitoring of 22-GHz H2O maser emission from G353.273+0.641 with the VLBI Exploration of Radio Astrometry (VERA) and the Tomakamai 11-m radio telescope. Our VLBI imaging has shown that all maser features are distributed within a very small area of 200 × 200 au2, in spite of the wide velocity range (> 100 km s−1). The light curve obtained by weekly single-dish monitoring shows notably intermittent variation. We have detected three maser flares during three years. Frequent VLBI monitoring has revealed that these flare activities have been accompanied by a significant change of the maser alignments. We have also detected synchronized linear acceleration (−5 km s−1yr−1) of two isolated velocity components, suggesting a lower-limit momentum rate of 10−3 M⊙ km s−1yr−1 for the maser acceleration. All our results support the previously proposed pole-on jet scenario, and finally, a radio jet itself has been detected in our follow-up ATCA observation. If highly intermittent maser flares directly reflect episodic jet-launchings, G353.273+0.641 and similar dominant blueshifted water maser sources can be suitable targets for a time-resolved study of high mass protostellar jet.
VERA Observations of the H2O Maser Burst in Orion KL
Authors: Hirota Tomoya , Tsuboi Masato , Fujisawa Kenta , Honma Mareki , Kawaguchi Noriyuki , Kim Mi Kyoung , Kobayashi Hideyuki , Imai Hiroshi , Omodaka Toshihiro , Shibata Katsunori M. , Shimoikura Tomomi , Yonekura Yoshinori
Published: July 2012

In 2011 February, a burst of the 22 GHz H2O maser in Orion KL was reported. In order to identify the bursting maser features, we have been carrying out observations of the 22 GHz H2O maser in Orion KL with VERA, a Japanese VLBI network dedicated for astrometry. The bursting maser turns out to consist of two spatially different features at 7.58 and 6.95 km s−1. We determine their absolute positions and find that they are coincident with the shocked molecular gas called the Orion Compact Ridge. We tentatively detect the absolute proper motions of the bursting features toward the southwest direction, perpendicular to the elongation of the maser features. It is most likely that the outflow from the radio source I or another young stellar object interacting with Compact Ridge is a possible origin of the H2O maser burst. We will also carry out observations with ALMA in the cycle 0 period to monitor the submillimeter H2O maser lines in the Orion Compact Ridge region. These follow-up observations will provide novel information on the physical and chemical properties of the mastering region.
On the Methanol masers in G9.62+0.20E: Preliminary colliding-wind binary (CWB) calculations
Authors: van den Heever S. P. , van der Walt D. J. , Pittard J. M. , Hoare M. G.
Published: July 2012

A comparison between the observed periodic flaring of methanol maser sources in the star forming region G9.62+0.20E and the continuum emission from parts of a background HII region is made. Using a colliding wind binary (CWB) model preliminary calculations show that the CWB model results fit the maser light curves very well.
Methanol masers and millimetre lines: a common origin in protostellar envelopes
Authors: Torstensson Karl J. E. , van Langevelde Huib Jan , van der Tak Floris F. S. , Vlemmings Wouter H. T. , Kristensen Lars E. , Bourke Stephen , Bartkiewicz Anna
Published: July 2012

To understand the origin of the CH3OH maser emission, we map the distribution and excitation of the thermal CH3OH emission in a sample of 14 relatively nearby (<6 kpc) high-mass star forming regions that are identified through 6.7 GHz maser emission. The images are velocity-resolved and allow us to study the kinematics of the regions. Further, rotation diagrams are created to derive rotation temperatures and column densities of the large scale molecular gas. The effects of optical depth and subthermal excitation are studied with population diagrams. For eight of the sources in our sample the thermal CH3OH emission is compact and confined to a region <0.4 pc and with a central peak close (<0.03 pc) to the position of the CH3OH maser emission. Four sources have more extended thermal CH3OH emission without a clear peak, and for the remaining two sources, the emission is too weak to map. The compact sources have linear velocity gradients along the semi-major axis of the emission of 0.3 – 13 kms−1 pc−1. The rotation diagram analysis shows that in general the highest rotation temperature is found close to the maser position. The confined and centrally peaked CH3OH emission in the compact sources indicates a single source for the CH3OH gas and the velocity fields show signs of outflow in all but one of the sources. The high detection rate of the torsionally excited vt = 1 line and signs of high-K lines at the maser position indicate radiative pumping, though the general lack of measurable beam dilution effects may mean that the masing gas is not sampled well and originates in a very small region.
The infrared environment of methanol maser rings at high spatial resolution
Authors: De Buizer James M. , Bartkiewicz Anna , Szymczak Marian
Published: July 2012

The recent discovery of methanol maser emission coming from ring-like distributions has led to the plausible hypothesis that they may be tracing circumstellar disks around forming high mass stars. In this article we discuss the distribution of circumstellar material around such young and massive accreting (proto)stars, and what infrared emission geometries would be expected for different disk/outflow orientations. For four targets we then compare the expected infrared geometries (as inferred from the properties of the maser rings) with actual high spatial resolution near-infrared and mid-infrared images. We find that the observed infrared emission geometries are not consistent with the masers residing in circumstellar disks.
Masers as evolutionary tracers of high-mass star formation
Authors: Breen Shari L. , Ellingsen Simon P.
Published: July 2012

Determining an evolutionary clock for high-mass star formation is an important step towards realising a unified theory of star formation, as it will enable qualitative studies of the associated high-mass stars to be executed. We have carried out detailed studies of a large number of sources suspected of undergoing high-mass star formation and have found that common maser transitions offer the best opportunity to determine an evolutionary scheme for these objects. We have investigated the relative evolutionary phases of massive star formation associated with the presence or absence of combinations of water, methanol and main-line hydroxyl masers. The locations of the different maser species have been compared with the positions of 1.2 mm dust clumps, radio continuum, GLIMPSE point sources and Extended Green Objects. Comparison between the characteristics of coincident sources has revealed strong evidence for an evolutionary sequence for the different maser species in high-mass star formation regions. We present our proposed sequence for the presence of the common maser species associated with young high-mass stars and highlight recent advances. We discuss future investigations that will be made in this area by comparing data from the Methanol Multibeam (MMB) Survey with chemical clocks from the Millimetre Astronomy Legacy Team 90 GHz (MALT90) Survey.
Class I methanol masers in low-mass star formation regions
Authors: Kalenskii S. V. , Slysh V. I. , Johansson L. E. B. , Bergman P. , Kurtz S. , Hofner P. , Walmsley C. M.
Published: July 2012

Four Class I maser sources were detected at 44, 84, and 95 GHz toward chemically rich outflows in the regions of low-mass star formation NGC 1333I4A, NGC 1333I2A, HH25, and L1157. One more maser was found at 36 GHz toward a similar outflow, NGC 2023. Flux densities of the newly detected masers are no more than 18 Jy, being much lower than those of strong masers in regions of high-mass star formation. The brightness temperatures of the strongest peaks in NGC 1333I4A, HH25, and L1157 at 44 GHz are higher than 2000 K, whereas that of the peak in NGC 1333I2A is only 176 K. However, a rotational diagram analysis showed that the latter source is also a maser. The main properties of the newly detected masers are similar to those of Class I methanol masers in regions of massive star formation. The former masers are likely to be an extension of the latter maser population toward low luminosities of both the masers and the corresponding YSOs.
What is happening in G357.96-0.16?
Authors: Britton Tui R. , Voronkov Maxim A. , Moss Vanessa A.
Published: July 2012

In order to answer this question, we examine the relationship between the two sites of maser activity in G357.96-0.16. We also propose future observations for examining the dust properties of this interesting region of massive star formation.
10 years of 12.2 GHz methanol maser VLBI observations towards NGC 7538 IRS1 N: proper motions and maser saturation
Authors: Pestalozzi Michele , Jerkstrand Anders , Conway John
Published: July 2012

We present the outcomes of the consistent analysis of 6 epochs of VLBA 12.2 GHz data obtained between 1995 and 2005 towards the known high-mass star formation reigon NGC7538 IRS1 N. Our analysis concentrates on the study of the main spectral/spatial feature, which is 20 VLBA synthesized beams in size with a distinct velocity gradient. We looked for proper motion signals relative to the central peak which, in an edge-on disc framework, is expected to be stationary. We also study the peak flux and the spatial brightness profile of the main maser feature searching for maser variability. Our results are twofold: we detect a clear proper motion signal of three spatial features (0.21, 0.1, 0.65 mas yr−1) and conclude that these can be made consistent with previous modelling of a Keplerian disc seen edge-on around a high-mass protostar. We further detect a consistent decrease of the peak flux over the time-span 1995-2005 (~ 5.4 Jy yr−1), confirmed when taking into account earlier data (1986, 1987) as well as by the 6.7 GHz maser emission. Also, the width of the spatial brightness profile of the main feature seems to decrease between 1995 and 2005 by some 50%. We consider these observables as clear signs of partial maser saturation.
Internal Proper Motion of 6.7 GHz Methanol Masers in Ultra Compact HII Region S269
Authors: Sawada-Satoh S. , Fujisawa K. , Sugiyama K. , Wajima K. , Honma M.
Published: July 2012

We present the internal proper motion of 6.7-GHz methanol masers in S269, an Ultra Compact HII region. The maser distribution in S269 consists of several maser groups, and the spatial structure of the main groups A and B are consistent with the past VLBI image. The remarkable result of comparing the two VLBI maps is that 6.7-GHz methanol maser distribution and velocity range within each group have been kept for eight years. Angular separation between the two groups A and B increases by 3.6 mas, which corresponds to a velocity of 11.5 km s−1.
The radial velocity acceleration of the 6.7 GHz methanol maser in Mon R2 IRS3
Authors: Sugiyama K. , Fujisawa K. , Shino N. , Doi A.
Published: July 2012

We present the radial velocity acceleration of the 6.7 GHz methanol maser in a high-mass star-forming region Monoceros R2 (Mon R2). The methanol maser is associated with an infrared source IRS3. The methanol maser of Mon R2 shows at least three spectral features having radial velocities (Vlsr) of 10.8, 12.7, and 13.2 km s−1. The radial velocity of a feature at Vlsr = 12.7 km s−1 has changed during ten years from Aug. 1999 to Oct. 2009, corresponding to an acceleration of 0.08 km s−1 yr−1. We observed the 6.7 GHz methanol masers of Mon R2 in Oct. 2008 using the Japanese VLBI Network (JVN). Compared with the previous VLBI image obtained in Nov. 1998 using the European VLBI Network (EVN), the maser feature at Vlsr = 12.7 km s−1 showed relative proper motions of ~2.5 mas yr−1 (about 10 km s−1 at 0.83 kpc) toward the intensity peak of IRS3. The radial velocity acceleration could be caused by an inflow from a disk or envelope around a high-mass young stellar object (YSO) at IRS3.
The final 112-frame movie of the 43 GHz SiO masers around the Mira Variable TX Cam
Authors: Gonidakis Ioannis , Diamond Philip J. , Kemball Athol J.
Published: July 2012

The proximity of the SiO masers to the star, makes them a powerful tool for studying the properties of the extended stellar atmosphere. This project is a long monitoring campaign of the 43 GHz SiO masers (v=1 J=1→0) around the Mira Variable TX Cam. The target source was observed with the Very Long Baseline Array (VLBA) from the 24th of May 1997 to the 25th of January 2002 in bi-weekly or monthly intervals, covering 3.06 stellar cycles. The time-span and frequency of observations helped us examine the long and short-term properties of the emission and study the dynamics of the gas, the existence of shock waves and their contribution to the morphology and kinematics. Maps from each epoch were concatenated into a 112-frame movie showing the evolution of the emission around TX Cam.
OH mainline maser polarisation properties of post-AGB stars
Authors: Chapman Jessica M. , Gonidakis Ioannis , Deacon Rachel M. , Green Anne
Published: July 2012

The Parkes 64-m telescope was used to study the OH mainline polarisation properties at 1665 and 1667 MHz for a sample of 36 evolved stars, identified by their far-infrared and OH 1612 MHz maser properties as likely post-AGB stars.
The Hamburg Database of Circumstellar OH Masers
Authors: Engels Dieter
Published: July 2012

A new version of the Hamburg Database of Circumstellar OH Masers at 1612, 1665, and 1667 MHz was released in 2012 January. The database now lists 13170 OH maser observations of stars in the Milky Way. They belong to 6318 different objects and 2324 of them were detected in at least one of the transitions. The database contains flux densities and velocities of the two strongest maser peaks, the expansion velocity of the shell and the radial velocity of the star. Compared to the first version presented in 2007 at the IAU Symposium 242 in Alice Springs new observations published 2008–2011 are included. Interferometric observations and monitoring programs of the maser emission were also added. Access to the database is possible over the Web (www.hs.uni-hamburg.de/maserdb), allowing cone searches for individual objects and lists of objects. A general object search is possible in selected regions of the sky and by defining ranges of flux densities and/or velocities.
Imaging the water masers toward the H2O-PN IRAS 18061–2505
Authors: Gómez Yolanda , Tafoya Daniel , Suárez Olga , Gómez Jose F. , Miranda Luis F. , Anglada Guillem , Torrelles Jóse M. , Vázquez Roberto
Published: July 2012

It has been suggested that the presence of disks or tori around the central stars of pre Planetary Nebulae and Planetary Nebulae is related to the collimation of the jet that are frequently observed in these sources. These disks or tori can be traced by the maser emission of some molecules such as water. In this work we present Very Large Array (VLA) observations of the water maser emission at 22 GHz toward the PN IRAS 18061–2505, for which the masers appear located on one side of the central star. For comparison with the observations, we present a simple kinematical model of a disk rotating and expanding around the central star. The model matches qualitatively the observations. However, since the masers appear only on one side of the disk, these results are not conclusive.
TWINKLING STARS The disappearing SiO masers of W Aql
Authors: Ramstedt Sofia , Vlemmings Wouter , Mohamed Shazrene , Choi Yoon Kyung , Olofsson Hans
Published: July 2012

W Aql is a binary S-type AGB star showing SiO maser emission. The dust distribution around the star is asymmetric, possibly indicating gravitational interaction between the binary pair. There are indications that the gas distribution also exhibits asymmetries. To investigate the source of the circumstellar structures, we applied for and were rewarded VLBI time to map the distribution of the SiO masers around this source and to constrain the presence and distribution of a possible magnetic field. Using VERA observations we also aim at measuring an accurate parallax to determine the binary separation, however, from showing peak emission of 21 Jy in June 2010, the SiO(1-0) v=1 line at 43 GHz has now disappeared. We find no correlation with the stellar pulsational period.
Water maser follow-up of the Methanol Multi-Beam Survey.
Authors: Titmarsh Anita , Ellingsen Simon , Breen Shari , Caswell James , Voronkov Maxim
Published: July 2012

The Australia Telescope Compact Array has been used to observe all the 603 6.7 GHz methanol masers detected in the Methanol Multi-Beam survey between l = 310° - 20°. To date we have measured positions with arcsecond accuracy for all the observations in the l = 6° - 20°.
SHOOTING STARS Masers from red giants
Authors: Ramstedt Sofia , Vlemmings Wouter , Humphreys Elizabeth , Alves Felipe
Published: July 2012

SiO maser emission probes the region close to the stellar surface where the wind is formed and is observed to better constrain the physical conditions in this region. We have started a long-term project where high-excitation 28SiO maser lines (i.e., J=5-4, v=1 and 2) are observed in a large sample of southern AGB stars. The primary goals are to put constraints on the physical conditions in the extended atmospheres, and to achieve a better understanding of the maser excitation process. Since the maser emission is strong and often highly linearly polarized, the detected sources could also complement the polarization calibrator catalogue for ALMA. Preliminary results show a high detection rate and that in approximately 20% of the sources, the v=2 transition emits stronger than the v=1 transition. We interpret this as possibly indicative of a hot dust shell very close to the stars.
Mrk 1419 - a new distance determination
Authors: Impellizzeri C. M. Violette , Braatz James A. , Kuo Cheng-Yu , Reid Mark J. , Lo K. Y. , Henkel Christian , Condon James J.
Published: July 2012

Water vapor megamasers from the center of active galaxies provide a powerful tool to trace accretion disks at sub-parsec resolution and, through an entirely geometrical method, measure direct distances to galaxies up to 200 Mpc. The Megamaser Cosmology Project (MCP) is formed by a team of astronomers with the aim of identifying new maser systems, and mapping their emission at high angular resolution to determine their distance. Two types of observations are necessary to measure a distance: single-dish monitoring to measure the acceleration of gas in the disk, and sensitive VLBI imaging to measure the angular size of the disk, measure the rotation curve, and model radial displacement of the maser feature. The ultimate goal of the MCP is to make a precise measurement of H0 by measuring such distances to at least 10 maser galaxies in the Hubble flow. We present here the preliminary results from a new maser system, Mrk 1419. Through a model of the rotation from the systemic masers assuming a narrow ring, and combining these results with the acceleration measurement from the Green Bank Telescope, we determine a distance to Mrk 1419 of 81 ± 10 Mpc. Given that the disk shows a significant warp that may not be entirely traced by our current observations, more sensitive observations and more sophisticated disk modeling will be essential to improve our distance estimation to this galaxy.
Optical Properties of the Host Galaxies of Extragalactic Nuclear H2O Masers
Authors: Zaw Ingyin , Zhu Guangtun , Blanton Michael , Greenhill Lincoln J.
Published: July 2012

Although most nuclear 22GHz (λ=1.35 cm) H2O masers are in Seyfert 2 and LINER galaxies, only a small fraction of such galaxies host water masers. We systematically study the optical properties of the galaxies with and without nuclear H2O maser emission to better understand the relationship between H2O maser emission and properties of the central supermassive black hole and improve the detection rates in future surveys. To this end, we cross-matched the galaxies from H2O maser surveys, both detections and non-detections, with the Sloan Digital Sky Survey (SDSS) low-redshift galaxy sample. We find that maser detection rates are higher at higher optical luminosity (MB), larger velocity dispersion (σ), and higher ion [O III] λ5007 luminosity, with [O III] λ5007 being the dominant factor, and that the isotropic maser luminosity is correlated with these variables. These correlations are natural if maser emission depends on the host SMBH mass and AGN activity. We also find that the detection rate is higher for galaxies with higher extinction. These results indicate that, by pre-selecting galaxies with high extinction-corrected [O III] λ5007 flux, future maser surveys can increase detections efficiencies by a factor of ~3 to ~5.
Long term Arecibo monitoring of the water megamaser in MG J0414+0534
Authors: Castangia Paola , Impellizzeri C. M. Violette , McKean John P. , Henkel Christian , Brunthaler Andreas , Roy Alan L. , Wucknitz Olaf
Published: July 2012

We monitored the 22 GHz maser line in the lensed quasar MG J0414+0534 at z = 2.64 with the 300-m Arecibo telescope for almost two years to detect possible additional maser components and to measure a potential velocity drift of the lines. The main maser line profile is complex and can be resolved into a number of broad features with line widths of 30-160 km s−1. A new maser component was tentatively detected in October 2008 at a velocity of +470 km s−1. After correcting for the estimated lens magnification, we find that the H2O isotropic luminosity of the maser in MG J0414+0534 is ~26,000 solar luminosities, making this source the most luminous ever discovered. Both the main line peak and continuum flux densities are surprisingly stable throughout the period of the observations. An upper limit on the velocity drift of the main peak of the line has been estimated from our observations and is of the order of 2 km s−1 per year. We discuss the results of the monitoring in terms of the possible nature of the maser emission, associated with an accretion disk or a radio jet. This is the first time that such a study is performed in a water maser source at high redshift, potentially allowing us to study the parsec-scale environment around a powerful radio source at cosmological distances.
Maser astrometry with VERA and Galactic structure
Authors: Honma Mareki , Nagayama Takumi , Hirota Tomoya , Matsumoto Naoko , Sakai Nobuyuki , Kawaguchi Noriyuki ,   VERA project members
Published: July 2012

Since 2007 VERA (VLBI Exploration of Radio Astrometry) has been producing astrometric results (distances and/or proper motions) for Galactic maser sources. Nearly 30 parallaxes have been obtained for star-forming regions and late-type stars. By using VERA's astrometric results for star-forming regions, combined with those obtained with VLBA and EVN, fundamental Galactic parameters and Galactic structure may be derived. Our results show that R0 = 8.4 ± 0.4 kpc and Ω⊙ ≡ Ω0 + V⊙/R0=30.7±0.8 km s−1 kpc−1, and also show that the rotation curve of the Galaxy is nearly flat. The determinations of Galactic parameters and structures demonstrate that the maser astrometry can not only contribute significantly to research of individual maser sources, but also to studies of the structure of the Galaxy.
Trigonometric Parallax of the Protoplanetary Nebula OH 231.8+4.2
Authors: Choi Y. K. , Brunthaler A. , Menten K. M. , Reid M. J.
Published: July 2012

We report a trigonometric parallax measurement for the H2O masers around the protoplanetary nebula OH 231.8+4.2 carried out with the Very Long Baseline Array (VLBA). Based on astrometric monitoring for 1 year, we measured a parallax of 0.65 ± 0.01 mas, corresponding to a distance of 1.54 +0.02−0.01 kpc. The spatial distribution of H2O masers is consistent with that found in the previous studies. After removing the average proper motion of 1.4 mas yr−1, corresponding to 10 km s−1, the internal motions of the H2O maser spots indicate a bipolar outflow.
Annual Parallax Measurements of an Infrared Dark Cloud MSXDC G034.43+00.24
Authors: Kurayama Tomoharu
Published: July 2012

We have measured the annual parallax of the H2O maser associated with an infrared dark cloud, MSXDC G034.43+00.24, with VERA. The parallax is 0.643 ± 0.049 mas, corresponding to a distance of 1.56+0.12−0.11 kpc. This value is less than half of the previous kinematic distance of 3.7 kpc. We revised the core-mass estimates of MSXDC G034.43+00.24 from the previous estimations of 1000M⊙ to hundreds of M⊙. The spectral type is still consistent with that of the massive star.
Distance and Maser Outflows of the Galactic Star-forming Region W51 Main/South
Authors: Sato Mayumi , Reid Mark J. , Brunthaler Andreas , Menten Karl M.
Published: July 2012

We report on high-resolution astrometry of 22 GHz H2O maser emission in the Galactic massive star-forming region W51 Main/South using the Very Long Baseline Array. We measured the trigonometric parallax of W51 Main/South to be 0.185 ± 0.010 mas, corresponding to a distance of 5.41+0.31−0.28 kpc. The H2O maser emission in W51 Main/South traces four powerful bipolar outflows within a 0.4 pc size region, three of which are associated with dusty molecular hot cores and/or hyper- or ultra-compact Hii regions. The maser outflows in W51 Main/South have a relatively small range of internal 3D speeds, suggesting that multiple speed maser outflows in other Galactic massive star-forming regions may come from separate young stellar objects closely spaced on the sky.
Trigonometric Parallax of RCW 122
Authors: Wu Y. W. , Xu Y. , Menten K. M. , Zheng X. W. , Reid M. J.
Published: July 2012

As a part of the BeSSeL (Bar and Spiral Structure Legacy) survey, we report a trigonometric parallax for the massive star-forming region G348.70–1.04. Its distance is 3.38−0.27+0.33 kpc, indicating that it is in the Scutum-Centaurus arm. Its proper motion is −0.73 ± 0.04 mas yr−1 toward the east and −2.83 ± 0.50 mas yr−1 toward the north.
New class I methanol masers
Authors: Voronkov M. A. , Caswell J. L. , Ellingsen S. P. , Breen S. L. , Britton T. R. , Green J. A. , Sobolev A. M. , Walsh A. J.
Published: July 2012

We review properties of all known collisionally pumped (class I) methanol maser series based on observations with the Australia Telescope Compact Array (ATCA) and the Mopra radio telescope. Masers at 36, 84, 44 and 95 GHz are most widespread, while 9.9, 25, 23.4 and 104 GHz masers are much rarer, tracing the most energetic shocks. A survey of many southern masers at 36 and 44 GHz suggests that these two transitions are highly complementary. The 23.4 GHz maser is a new type of rare class I methanol maser, detected only in two high-mass star-forming regions, G357.97-0.16 and G343.12-0.06, and showing a behaviour similar to 9.9, 25 and 104 GHz masers. Interferometric positions suggest that shocks responsible for class I masers could arise from a range of phenomena, not merely an outflow scenario. For example, some masers might be caused by interaction of an expanding Hii region with its surrounding molecular cloud. This has implications for evolutionary sequences incorporating class I methanol masers if they appear more than once during the evolution of the star-forming region. We also make predictions for candidate maser transitions in the ALMA frequency range.
OH Masers and Supernova Remnants
Authors: Wardle Mark , McDonnell Korinne
Published: July 2012

OH(1720 MHz) masers are created by the interaction of supernova remnants with molecular clouds. These masers are pumped by collisions in warm, shocked molecular gas with OH column densities in the range 1016–1017, cm−2. Excitation calculations suggest that inversion of the 6049 MHz OH line may occur at the higher column densities that have been inferred from main-line absorption studies of supernova remnants with the Green Bank Telescope. OH(6049 MHz) masers have therefore been proposed as a complementary indicator of remnant-cloud interaction.

This motivated searches for 6049 MHz maser emission from supernova remnants using the Parkes 63 m and Effelsberg 100 m telescopes, and the Australia Telescope Compact Array. A total of forty-one remnants have been examined by one or more of these surveys, but without success. To check the accuracy of the OH column densities inferred from the single-dish observations we modelled OH absorption at 1667 MHz observed with the Very Large Array towards three supernova remnants, IC 443, W44 and 3C 391. The results are mixed – the OH column is revised upwards in IC443, downwards in 3C391, and is somewhat reduced in W44. We conclude that OH columns exceeding 1017 cm−2 are indeed present in some supernova remnants and so the lack of any detections is not explained by low OH column density. We discuss the possibility that non-local line overlap is responsible for suppressing the inversion of the 6049 MHz line.
Unveiling the kinematics of the disk and the ionized stellar wind of the massive star MWC349A through RRL masers
Authors: Báez-Rubio Alejandro , Martín-Pintado Jesús
Published: July 2012

The kinematics of photoevaporating disks and their associated ionized outflows around massive stars are fundamental to understand how these stars are formed and they evolve in their early phases of their evolution. To date, the important advances have been provided by studying the UC-HII region of MWC349A thanks to their strong maser emission at Hydrogen radio-recombination lines (RRLs). This B[e] star is one of the best prototypes of massive star with an ionized outflow expanding at nearly constant velocity. A 3D radiative transfer model applied to the H30α line has allowed to constrain the disk kinematics, which seems to follow pure Keplerian rotation in its outer parts. The model has also allowed us to constraints the launching radius of the outflow. Our results are supported by the agreement of our model predictions with the observations for other observed RRLs. Recent high-frequency observations of RRL masers with the Herschel Space Telescope (HIFI) show that the kinematics of the disk inner regions is not well understood. Modeling of these lines will constrain the formation of the ionized winds.
Intrinsic Sizes of the W3 (OH) Masers via Short Time Scale Variability
Authors: Laskar Tanmoy , Goss W. M. , Zauderer B. Ashley
Published: July 2012

We present a study of short time-scale variability of OH masers within a contiguous 15-hour Very Long Baseline Array observation of the high-mass star-forming region, W3 (OH). With an angular resolution of ~7 mas and a velocity resolution of 53 m s−1, we isolate emission from masers in the field into individual Gaussian-shaped components, each a few milliarcseconds in size. We compute dynamic spectra for individual maser features with a time resolution of 1 minute by fitting for the flux density of all sources in the field simultaneously in the uv-domain. We isolate intrinsic maser variability from interstellar scintillation and instrumental effects. We find fluctuations in the maser line shape on time scales of 5 to 20 minutes, corresponding to maser column lengths of 0.5 to 2.0 Astronomical Units.
Methanol masers in the Herschel era Putting them in the star formation context
Authors: Pestalozzi Michele
Published: July 2012

Methanol masers are known to be among the most reliable tracers of high-mass stars in early stages of evolution. A number of searches across the Galaxy has yielded to date, a complete census of those masers in two thirds of the Milky Way, providing a catalogue of some 800 sources to be studied in depth. In particular, it is important to characterise the physical properties of the objects hosting methanol masers, and this is possible today using data from the Herschel Space Observatory (HSO). The exceptional spatial resolution of HSO and its wavelength coverage are perfectly tuned to put the methanol maser phase into its star formation context. This paper presents results on the characterisation of methanol maser hosts using Herschel data from the Hi-GAL project, an Open Time Key Project to survey the inner Galactic plane at 5 wavelengths between 70 and 500 μm.
Early results from a diagnostic 1.3 cm survey of massive young protostars
Authors: Brogan Crystal L. , Hunter Todd R. , Cyganowski Claudia J. , Indebetouw Remy , Friesen Rachel , Chandler Claire
Published: July 2012

We have used the recently-upgraded Karl G. Jansky Very Large Array (JVLA) to conduct a K-band (~24 GHz) study of 22 massive young stellar objects in 1.3 cm continuum and a comprehensive set of diagnostic lines. This survey is unique in that it samples a wide range of massive star formation signposts simultaneously for the first time. In this proceeding we present preliminary results for the 11 sources in the 2-4 kpc distance bin. We detect compact NH3 cores in all of the fields, with many showing emission up through the (6,6) transition. Maser emission in the 25 GHz CH3OH ladder is present in 7 of 11 sources. We also detect non-thermal emission in the NH3 (3,3) transition in 7 of 11 sources.
Adolescent understanding of DOHaD concepts: a school-based intervention to support knowledge translation and behaviour change
Authors: Bay J. L. , Mora H. A. , Sloboda D. M. , Morton S. M. , Vickers M. H. , Gluckman P. D.
Published: July 2012

A life-course approach to reduction of risk of non-communicable diseases (NCD) suggests that early-life interventions may be more effective than lifestyle modifications in middle age. Knowledge translation to develop understanding of the Developmental Origins of Health and Disease (DOHaD) within the community offers the potential to encourage informed diet and lifestyle choices supporting reduction of NCD risk in current and future generations. Many women do not make sustained dietary change before or during pregnancy, therefore appropriate nutritional behaviours need to be established prior to adulthood. This makes adolescence an appropriate stage for interventions to establish suitable dietary and lifestyle behaviours. Therefore, we engaged adolescents in a school-based educational intervention, and assessed the value of this in development of understanding of DOHaD concepts to support behaviour change that could lead to NCD risk reduction in the next generation. Modules of course work were written for 11–14 year olds and trialled in nine schools. Matched pre- and post-intervention questionnaire responses from 238 students and 99 parents, and post-intervention interviews evaluated the intervention. Understanding of a link between maternal diet during pregnancy and the health of the foetus in adulthood increased from 46% to 76% following intervention. Post-intervention evidence suggests the programme facilitated discussion of diet, lifestyle and DOHaD concepts in most families. The intervention was effective in improving understanding of DOHaD concepts and in some cases led to appropriate behaviour change. However, the sustainability of these changes remains to be determined through on-going evaluation of attitudes and behaviour within this cohort.
Hybrid simulation of the shock wave trailing the Moon
Authors: Israelevich P. , Ofman L.
Published: July 2012

A standing shock wave behind the Moon was predicted by Michel (1967) but never observed nor simulated. We use 1D hybrid code in order to simulate the collapse of the plasma‐free cavity behind the Moon and for the first time to model the formation of this shock. Starting immediately downstream of the obstacle we consider the evolution of plasma expansion into the cavity in the frame of reference moving along with the solar wind. Well‐known effects as electric charging of the cavity affecting the plasma flow and counterstreaming ion beams in the wake are reproduced. Near the apex of the inner Mach cone where the plasma flows from the opposite sides of the obstacle meet, a shock wave arises. We expect the shock to be produced at periods of high electron temperature solar wind streams (Ti ≪ Te ∼ 100 eV). The shock is produced by the interaction of oppositely directed proton beams in the plane containing solar wind velocity and interplanetary magnetic field vectors. In the direction across the magnetic field and the solar wind velocity, the shock results from the interaction of the plasma flow with the region of the enhanced magnetic field inside the cavity that plays the role of the magnetic barrier. The appearance of the standing shock wave is expected at the distance of ∼7RM downstream of the Moon.
Space‐based retrievals of air‐sea gas transfer velocities using altimeters: Calibration for dimethyl sulfide
Authors: Goddijn‐Murphy Lonneke , Woolf David K. , Marandino Christa
Published: July 2012

This study is the first to directly correlate gas transfer velocity, measured at sea using the eddy‐correlation (EC) technique, and satellite altimeter backscattering. During eight research cruises in different parts of the world, gas transfer velocity of dimethyl sulfide (DMS) was measured. The sample times and locations were compared with overpass times and locations of remote sensing satellites carrying Ku‐band altimeters: ERS‐1, ERS‐2, TOPEX, POSEIDON, GEOSAT Follow‐On, JASON‐1, JASON‐2 and ENVISAT. The result was 179 pairs of gas transfer velocity measurements and backscattering coefficients. An inter‐calibration of the different altimeters significantly reduced data scatter. The inter‐calibrated data was best fitted to a quadratic relation between the inverse of the backscattering coefficients and the gas transfer velocity measurements. A gas transfer parameterization based on backscattering, corresponding with sea surface roughness, might be expected to perform better than wind speed‐based parameterizations. Our results, however, did not show improvement compared to direct correlation of shipboard wind speeds. The relationship of gas transfer velocity to satellite‐derived backscatter, or wind speed, is useful to provide retrieval algorithms. Gas transfer velocity (cm/hr), corrected to a Schmidt number of 660, is proportional to wind speed (m/s). The measured gas transfer velocity is controlled by both the individual water‐side and air‐side gas transfer velocities. We calculated the latter using a numerical scheme, to derive water‐side gas transfer velocity. DMS is sufficiently soluble to neglect bubble‐mediated gas transfer, thus, the DMS transfer velocities could be applied to estimate water‐side gas transfer velocities through the unbroken surface of any other gas.
On the variations of sea surface pCO2 in the northern South China Sea: A remote sensing based neural network approach
Authors: Jo Young‐Heon , Dai Minhan , Zhai Weidong , Yan Xiao‐Hai , Shang Shaoling
Published: July 2012

Using a neural networking (NN) approach, we developed an algorithm primarily based upon sea surface temperature (SST) and chlorophyll (Chla) to estimate the partial pressure of carbon dioxide (pCO2) at the sea surface in the northern South China Sea (NSCS). Randomly selected in situ data collected from May 2001, February and July 2004 cruises were used to develop and test the predictive capabilities of the NN based algorithm with four inputs (SST, Chla, longitudes and latitudes). The comparison revealed a high correlation coefficient of 0.98 with a root mean square error (RMSE) of 6.9 μatm. We subsequently applied our NN algorithm to satellite SST and Chla measurements, with associated longitudes and latitudes, to obtain surface water pCO2. The resulting monthly mean pCO2 map derived from the satellite measurements agreed reasonably well with the in situ observations showing a generally homogeneous distribution in the offshore regions. The pCO2 exerts a very dynamic feature in nearshore regions, especially in the coastal upwelling and estuarine plume regions. We identified three low pCO2 zones (<330 μatm), two of which are influenced by coastal upwelling: off Hainan island in the western part of the NSCS; and off Guangdong province in the eastern part of the NSCS. The path of the Pearl River plume on the shelf was another zone with low pCO2. For the monthly mean pCO2variations estimated based on the MODIS‐SST and ‐Chla values, an RMSE of ∼6 μatm may be attributable to the measurement errors associated with MODIS measurements. As a first order estimation, we used the same sampling periods of remote sensing and in situ measurements, and were able to estimate pCO2 with an accuracy of 12.05 μatm for onshore regions and 13.0 μatm for offshore regions, but with combined uncertainties associated with the NN Testing algorithm and MODIS SST and Chla measurements.
Wind‐driven lateral circulation in a stratified estuary and its effects on the along‐channel flow
Authors: Li Yun , Li Ming
Published: July 2012

In the stratified rotating estuary of Chesapeake Bay, the Ekman transport drives a counterclockwise lateral circulation under down‐estuary winds and a clockwise lateral circulation under up‐estuary winds (looking into estuary). The clockwise circulation is about twice as strong as the counterclockwise circulation. Analysis of the streamwise vorticity equation reveals a balance among three terms: titling of the planetary vorticity by vertical shear in the along‐channel current, baroclinic forcing due to sloping isopycnals at cross‐channel sections, and turbulent diffusion. The baroclinic forcing is highly asymmetric between the down‐ and up‐estuary winds. While the counter‐clockwise lateral circulation tilts isopycnals vertically and creates lateral barolinic pressure gradient to oppose the Ekman transport under the down‐estuary wind, the clockwise circulation initially flattens the isopycnals and the baroclinic forcing reinforces the Ekman transport under the up‐estuary wind. The Coriolis acceleration associated with the lateral flows is of the first‐order importance in the along‐channel momentum balance. It has a sign opposite to the stress divergence in the surface layer and the pressure gradient in the bottom layer, thereby reducing the shear in the along‐channel current. Compared with the non‐rotating system, the shear reduction is about 30–40%. Two summary diagrams are constructed to show how the averaged streamwise vorticity and along‐channel current shear vary with the Wedderburn (W) and Kelvin (Ke) numbers.