389 research outputs found
UHF RFID Antenna: Printed Dipole Antenna with a CPS Matching Circuit and Inductively Coupled Feed
This paper presents simulated (WIPL‐D pro) and
measured results of a UHF RFID antenna realized with a
dipole matched to a CPS (Coplanar Stripline) and
inductively coupled with a small rectangular loop. Such a
design enables achieving and controlling high values of the
inductive reactance that is necessary for obtaining good
match of the antenna to an Application Specific Integrated
Circuit (ASIC) chip. The antenna is characterized by a simple
and robust design, which results in low‐cost realization
Warm Gas in the Inner Disks around Young Intermediate Mass Stars
The characterization of gas in the inner disks around young stars is of particular interest because of its connection to planet formation. In order to study the gas in inner disks, we have obtained high-resolution K-band and M-band spectroscopy of 14 intermediate mass young stars. In sources that have optically thick inner disks, i.e. E(K-L)>1, our detection rate of the ro-vibrational CO transitions is 100% and the gas is thermally excited. Of the five sources that do not have optically thick inner disks, we only detect the ro-vibrational CO transitions from HD 141569. In this case, we show that the gas is excited by UV fluorescence and that the inner disk is devoid of gas and dust. We discuss the plausibility of the various scenarios for forming this inner hole. Our modeling of the UV fluoresced gas suggests an additional method by which to search for and/or place stringent limits on gas in dust depleted regions in disks around Herbig Ae/Be stars
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Inter-comparison of MAX-DOAS measurements of tropospheric HONO slant column densities and vertical profiles during the CINDI-2 campaign
We present the inter-comparison of delta slant column densities (SCDs) and vertical profiles of nitrous acid (HONO) derived from measurements of different multi-axis differential optical absorption spectroscopy (MAX-DOAS) instruments and using different inversion algorithms during the Second Cabauw Inter-comparison campaign for Nitrogen Dioxide measuring Instruments (CINDI-2) in September 2016 at Cabauw, the Netherlands (51.97∘ N, 4.93∘ E). The HONO vertical profiles, vertical column densities (VCDs), and near-surface volume mixing ratios are compared between different MAX-DOAS instruments and profile inversion algorithms for the first time. Systematic and random discrepancies of the HONO results are derived from the comparisons of all data sets against their median values. Systematic discrepancies of HONO delta SCDs are observed in the range of ±0.3×1015 molec. cm−2, which is half of the typical random discrepancy of 0.6×1015 molec. cm−2. For a typical high HONO delta SCD of 2×1015 molec. cm−2, the relative systematic and random discrepancies are about 15 % and 30 %, respectively. The inter-comparison of HONO profiles shows that both systematic and random discrepancies of HONO VCDs and near-surface volume mixing ratios (VMRs) are mostly in the range of ∼±0.5×1014 molec. cm−2 and ∼±0.1 ppb (typically ∼20 %). Further we find that the discrepancies of the retrieved HONO profiles are dominated by discrepancies of the HONO delta SCDs. The profile retrievals only contribute to the discrepancies of the HONO profiles by ∼5 %. However, some data sets with substantially larger discrepancies than the typical values indicate that inappropriate implementations of profile inversion algorithms and configurations of radiative transfer models in the profile retrievals can also be an important uncertainty source. In addition, estimations of measurement uncertainties of HONO dSCDs, which can significantly impact profile retrievals using the optimal estimation method, need to consider not only DOAS fit errors, but also atmospheric variability, especially for an instrument with a DOAS fit error lower than ∼3×1014 molec. cm−2. The MAX-DOAS results during the CINDI-2 campaign indicate that the peak HONO levels (e.g. near-surface VMRs of ∼0.4 ppb) often appeared in the early morning and below 0.2 km. The near-surface VMRs retrieved from the MAX-DOAS observations are compared with those measured using a co-located long-path DOAS instrument. The systematic differences are smaller than 0.15 and 0.07 ppb during early morning and around noon, respectively. Since true HONO values at high altitudes are not known in the absence of real measurements, in order to evaluate the abilities of profile inversion algorithms to respond to different HONO profile shapes, we performed sensitivity studies using synthetic HONO delta SCDs simulated by a radiative transfer model with assumed HONO profiles. The tests indicate that the profile inversion algorithms based on the optimal estimation method with proper configurations can reproduce the different HONO profile shapes well. Therefore we conclude that the features of HONO accumulated near the surface derived from MAX-DOAS measurements are expected to represent the ambient HONO profiles well.
Full List of Authors:
Yang Wang1, Arnoud Apituley2, Alkiviadis Bais3, Steffen Beirle1, Nuria Benavent4, Alexander Borovski5, Ilya Bruchkouski6, Ka Lok Chan7,8, Sebastian Donner1, Theano Drosoglou3, Henning Finkenzeller9,10, Martina M. Friedrich11, Udo Frieß12, David Garcia-Nieto4, Laura Gómez-Martín13, François Hendrick11, Andreas Hilboll14, Junli Jin15, Paul Johnston16, Theodore K. Koenig9,10, Karin Kreher17, Vinod Kumar1, Aleksandra Kyuberis18, Johannes Lampel12,19, Cheng Liu20, Haoran Liu20, Jianzhong Ma21, Oleg L. Polyansky18,22, Oleg Postylyakov5, Richard Querel16, Alfonso Saiz-Lopez4, Stefan Schmitt12, Xin Tian23,24, Jan-Lukas Tirpitz12, Michel Van Roozendael11, Rainer Volkamer9,10, Zhuoru Wang8, Pinhua Xie24, Chengzhi Xing25, Jin Xu24, Margarita Yela13, Chengxin Zhang25, and Thomas Wagner11Max Planck Institute for Chemistry, Mainz, Germany
2Royal Netherlands Meteorological Institute (KNMI), De Bilt, the Netherlands
3Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki, Thessaloniki, Greece
4Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano (CSIC), Madrid, Spain
5A. M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, Moscow, Russia
6National Ozone Monitoring Research and Education Center BSU (NOMREC BSU), Belarusian State University, Minsk, Belarus
7Meteorologisches Institut, Ludwig-Maximilians-Universität München, Munich, Germany
8Remote Sensing Technology Institute, German Aerospace Center (DLR), Oberpfaffenhofen, Germany
9Department of Chemistry, University of Colorado Boulder, Boulder, CO, USA
10Cooperative Institute for Research in Environmental Sciences, Boulder, CO, USA
11Royal Belgian Institute for Space Aeronomy, Brussels, Belgium
12Institute of Environmental Physics, University of Heidelberg, Heidelberg, Germany
13National Institute of Aerospatial Technology, Madrid, Spain
14Institute of Environmental Physics, University of Bremen, Bremen, Germany
15Meteorological Observation Center, China Meteorological Administration, Beijing, China
16National Institute of Water & Atmospheric Research (NIWA), Lauder, New Zealand
17BK Scientific, Mainz, Germany
18Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia
19Airyx GmbH, Justus-von-Liebig-Str. 14, 69214 Eppelheim, Germany
20Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei, Anhui, China
21Chinese Academy of Meteorology Science, China Meteorological Administration, Beijing, China
22Department of Physics and Astronomy, University College London, Gower St, London, WC1E 6BT, UK
23Institutes of Physical Science and Information Technology, Anhui University, Hefei, 230601, China
24Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei, China
25School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui, China
</ul
Sequential and Spontaneous Star Formation Around the Mid-Infrared Halo HII Region KR 140
We use 2MASS and MSX infrared observations, along with new molecular line
(CO) observations, to examine the distribution of young stellar objects (YSOs)
in the molecular cloud surrounding the halo HII region KR 140 in order to
determine if the ongoing star-formation activity in this region is dominated by
sequential star formation within the photodissociation region (PDR) surrounding
the HII region. We find that KR 140 has an extensive population of YSOs that
have spontaneously formed due to processes not related to the expansion of the
HII region. Much of the YSO population in the molecular cloud is concentrated
along a dense filamentary molecular structure, traced by C18O, that has not
been erased by the formation of the exciting O star. Some of the previously
observed submillimetre clumps surrounding the HII region are shown to be sites
of recent intermediate and low-mass star formation while other massive starless
clumps clearly associated with the PDR may be the next sites of sequential star
formation.Comment: Accepted for publication in MNRAS, 8 pages, 10 figure
The Molecular Gas Environment around Two Herbig Ae/Be Stars: Resolving the Outflows of LkHa 198 and LkHa 225S
Observations of outflows associated with pre-main-sequence stars reveal
details about morphology, binarity and evolutionary states of young stellar
objects. We present molecular line data from the Berkeley-Illinois-Maryland
Association array and Five Colleges Radio Astronomical Observatory toward the
regions containing the Herbig Ae/Be stars LkHa 198 and LkHa 225S. Single dish
observations of 12CO 1-0, 13CO 1-0, N2H+ 1-0 and CS 2-1 were made over a field
of 4.3' x 4.3' for each species. 12CO data from FCRAO were combined with high
resolution BIMA array data to achieve a naturally-weighted synthesized beam of
6.75'' x 5.5'' toward LkHa 198 and 5.7'' x 3.95'' toward LkHa 225S,
representing resolution improvements of factors of approximately 10 and 5 over
existing data. By using uniform weighting, we achieved another factor of two
improvement. The outflow around LkHa 198 resolves into at least four outflows,
none of which are centered on LkHa 198-IR, but even at our resolution, we
cannot exclude the possibility of an outflow associated with this source. In
the LkHa 225S region, we find evidence for two outflows associated with LkHa
225S itself and a third outflow is likely driven by this source. Identification
of the driving sources is still resolution-limited and is also complicated by
the presence of three clouds along the line of sight toward the Cygnus
molecular cloud. 13CO is present in the environments of both stars along with
cold, dense gas as traced by CS and (in LkHa 225S) N2H+. No 2.6 mm continuum is
detected in either region in relatively shallow maps compared to existing
continuum observations.Comment: 14 pages, 10 figures (5 color), accepted for publication in Ap
A GLIMPSE into the Nature of Galactic Mid-IR Excesses
We investigate the nature of the mid-IR excess for 31 intermediate-mass stars
that exhibit an 8 micron excess in either the Galactic Legacy Infrared
Mid-Plane Survey Extraordinaire or the Mid-Course Space Experiment using high
resolution optical spectra to identify stars surrounded by warm circumstellar
dust. From these data we determine projected stellar rotational velocities and
estimate stellar effective temperatures for the sample. We estimate stellar
ages from these temperatures, parallactic distances, and evolutionary models.
Using MIPS [24] measurements and stellar parameters we determine the nature of
the infrared excess for 19 GLIMPSE stars. We find that 15 stars exhibit Halpha
emission and four exhibit Halpha absorption. Assuming that the mid-IR excesses
arise in circumstellar disks, we use the Halpha fluxes to model and estimate
the relative contributions of dust and free-free emission. Six stars exhibit
Halpha fluxes that imply free-free emission can plausibly explain the infrared
excess at [24]. These stars are candidate classical Be stars. Nine stars
exhibit Halpha emission, but their Halpha fluxes are insufficient to explain
the infrared excesses at [24], suggesting the presence of a circumstellar dust
component. After the removal of the free-free component in these sources, we
determine probable disk dust temperatures of Tdisk~300-800 K and fractional
infrared luminosities of L(IR)/L(*)~10^-3. These nine stars may be
pre-main-sequence stars with transitional disks undergoing disk clearing. Three
of the four sources showing Halpha absorption exhibit circumstellar disk
temperatures ~300-400 K, L(IR)/L(*)~10^-3, IR colors K-[24]< 3.3, and are warm
debris disk candidates. One of the four Halpha absorption sources has K-[24]>
3.3 implying an optically thick outer disk and is a transition disk candidate.Comment: 17 figures. Accepted for publication in Ap
Evolution of emission line activity in intermediate mass young stars
We present optical spectra of 45 intermediate mass Herbig Ae/Be stars.
Together with the multi-epoch spectroscopic and photometric data compiled for a
large sample of these stars and ages estimated for individual stars by using
pre-main sequence evolutionary tracks, we have studied the evolution of
emission line activity in them. We find that, on average, the H_alpha emission
line strength decreases with increasing stellar age in HAeBe stars, indicating
that the accretion activity gradually declines during the PMS phase. This would
hint at a relatively long-lived (a few Myr) process being responsible for the
cessation of accretion in Herbig Ae/Be stars. We also find that the accretion
activity in these stars drops substantially by ~ 3 Myr. This is comparable to
the timescale in which most intermediate mass stars are thought to lose their
inner disks, suggesting that inner disks in intermediate mass stars are
dissipated rapidly after the accretion activity has fallen below a certain
level. We, further find a relatively tight correlation between strength of the
emission line and near-infrared excess due to inner disks in HAeBe stars,
indicating that the disks around Herbig Ae/Be stars cannot be entirely passive.
We suggest that this correlation can be understood within the frame work of the
puffed-up inner rim disk models if the radiation from the accretion shock is
also responsible for the disk heating.Comment: 39 pages, accepted for publication in Ap
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The driving factors of new particle formation and growth in the polluted boundary layer
New particle formation (NPF) is a significant source of atmospheric particles, affecting climate and air quality. Understanding the mechanisms involved in urban aerosols is important to develop effective mitigation strategies. However, NPF rates reported in the polluted boundary layer span more than 4 orders of magnitude, and the reasons behind this variability are the subject of intense scientific debate. Multiple atmospheric vapours have been postulated to participate in NPF, including sulfuric acid, ammonia, amines and organics, but their relative roles remain unclear. We investigated NPF in the CLOUD chamber using mixtures of anthropogenic vapours that simulate polluted boundary layer conditions. We demonstrate that NPF in polluted environments is largely driven by the formation of sulfuric acid–base clusters, stabilized by the presence of amines, high ammonia concentrations and lower temperatures. Aromatic oxidation products, despite their extremely low volatility, play a minor role in NPF in the chosen urban environment but can be important for particle growth and hence for the survival of newly formed particles. Our measurements quantitatively account for NPF in highly diverse urban environments and explain its large observed variability. Such quantitative information obtained under controlled laboratory conditions will help the interpretation of future ambient observations of NPF rates in polluted atmospheres.
Full List of Authors:
Mao Xiao1, Christopher R. Hoyle1,2, Lubna Dada3, Dominik Stolzenburg4, Andreas Kürten5, Mingyi Wang6, Houssni Lamkaddam1, Olga Garmash3, Bernhard Mentler7, Ugo Molteni1, Andrea Baccarini1, Mario Simon5, Xu-Cheng He3, Katrianne Lehtipalo3,8, Lauri R. Ahonen3, Rima Baalbaki3, Paulus S. Bauer4, Lisa Beck3, David Bell1, Federico Bianchi3, Sophia Brilke4, Dexian Chen6, Randall Chiu9, António Dias10, Jonathan Duplissy3,11, Henning Finkenzeller9, Hamish Gordon6, Victoria Hofbauer6, Changhyuk Kim13,14, Theodore K. Koenig9,a, Janne Lampilahti3, Chuan Ping Lee1, Zijun Li15, Huajun Mai13, Vladimir Makhmutov16, Hanna E. Manninen17, Ruby Marten1, Serge Mathot17, Roy L. Mauldin18,19, Wei Nie20, Antti Onnela17, Eva Partoll7, Tuukka Petäjä3, Joschka Pfeifer5,17, Veronika Pospisilova1, Lauriane L. J. Quéléver3, Matti Rissanen3,b, Siegfried Schobesberger15, Simone Schuchmann17,c, Yuri Stozhkov16, Christian Tauber4, Yee Jun Tham3, António Tomé21, Miguel Vazquez-Pufleau4, Andrea C. Wagner5,9,d, Robert Wagner3, Yonghong Wang3, Lena Weitz5, Daniela Wimmer3,4, Yusheng Wu3, Chao Yan3, Penglin Ye6,22, Qing Ye6, Qiaozhi Zha3, Xueqin Zhou5, Antonio Amorim10, Ken Carslaw12, Joachim Curtius5, Armin Hansel7, Rainer Volkamer9,19, Paul M. Winkler4, Richard C. Flagan13, Markku Kulmala3,11,20,23, Douglas R. Worsnop3,22, Jasper Kirkby5,17, Neil M. Donahue6, Urs Baltensperger1, Imad El Haddad1, and Josef Dommen1
1Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
2Institute for Atmospheric and Climate Science, ETH Zurich, 8092 Zurich, Switzerland
3Institute for Atmospheric and Earth System Research (INAR)/Physics, University of Helsinki, 00014 Helsinki, Finland
4Faculty of Physics, University of Vienna, 1090 Vienna, Austria
5Institute for Atmospheric and Environmental Sciences, Goethe University Frankfurt, 60438 Frankfurt am Main, Germany
6Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA 15213, USA
7Institute of Ion Physics and Applied Physics, University of Innsbruck, 6020 Innsbruck, Austria
8Atmospheric Composition Research Unit, Finnish Meteorological Institute, 00560 Helsinki, Finland
9Department of Chemistry & CIRES, University of Colorado Boulder, Boulder, CO 80309, USA
10CENTRA and FCUL, University of Lisbon, 1749-016 Lisbon, Portugal
11Helsinki Institute of Physics, University of Helsinki, 00014 Helsinki, Finland
12School of Earth and Environment, University of Leeds, LS2 9JT Leeds, United Kingdom
13Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
14School of Civil and Environmental Engineering, Pusan National University, 46241 Busan, Republic of Korea
15Department of Applied Physics, University of Eastern Finland, 70211 Kuopio, Finland
16Solar and Cosmic Ray Physics Laboratory, P.N. Lebedev Physical Institute of the Russian Academy of Sciences, 119991 Moscow, Russian Federation
17CERN, 1211 Geneva, Switzerland
18Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213, USA
19Department of Oceanic and Atmospheric Sciences, University of Colorado Boulder, Boulder, CO 80309, USA
20Joint International Research Laboratory of Atmospheric and Earth System Sciences, School of Atmospheric Sciences, Nanjing University, Nanjing, Jiangsu Province, China
21IDL-Universidade da Beira Interior, Covilhã, Portugal
22Aerodyne Research Inc., Billerica, MA 01821-3976, USA
23Aerosol and Haze Laboratory, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing, China
anow at: College of Environmental Sciences and Engineering, Peking University, 100871 Beijing, China
bnow at: Aerosol Physics Laboratory, Physics Unit, Faculty of Engineering and Natural Sciences, Tampere University, 33720 Tampere, Finland
cnow at: Experimentelle Teilchen- und Astroteilchenphysik, Johannes Gutenberg University Mainz, 55128 Mainz, Germany
dnow at: Department of Chemistry & CIRES, University of Colorado Boulder, Boulder, CO 80305, USA
Correspondence: Urs Baltensperger ([email protected]) and Imad El Haddad ([email protected])</p
The Stellar Composition of the Star Formation Region CMa R1 -- III. A new outburst of the Be star component in Z CMa
We report on a recent event in which, after more than a decade of slowly
fading, the visual brightness of the massive young binary Z CMa suddenly
started to rise by about 1 magnitude in December 1999, followed by a rapid
decline to its previous brightness over the next six months. This behaviour is
similar to that exhibited by this system around its eruption in February 1987.
A comparison of the intrinsic luminosities of the system with recent
evolutionary calculations shows that Z CMa may consist of a 16 M_sun B0 IIIe
primary star and a ~ 3 M_sun FUOr secondary with a common age of ~ 3 x 10^5 yr.
We also compare new high-resolution spectra obtained in Jan. and Feb. 2000,
during the recent rise in brightness, with archive data from 1991 and 1996. The
spectra are rich in emission lines, which originate from the envelope of the
early B-type primary star. The strength of these emission lines increased
strongly with the brightness of Z CMa. We interpret the collected spectral data
in terms of an accretion disc with atmosphere around the Herbig B0e component
of Z CMa, which has expanded during the outbursts of 1987 and 2000. A high
resolution profile of the 6300 A [O I] emission line, obtained by us in March
2002 shows an increase in flux and a prominent blue shoulder to the feature
extending to ~ -700 km/s, which was much fainter in the pre-outburst spectra.
We propose that this change in profile is a result of a strong change in the
collimation of a jet, as a result of the outburst at the start of this century.Comment: 22 pages, 12 figures, accepted for publication in MNRA
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