We present the results of a single-pointing survey of 207 dense cores embedded in Planck Galactic Cold Clumps distributed in five different environments (\(\lambda\) Orionis, Orion A, B, Galactic ...plane, and high latitudes) to identify dense cores on the verge of star formation for the study of the initial conditions of star formation. We observed these cores in eight molecular lines at 76-94 GHz using the Nobeyama 45-m telescope. We find that early-type molecules (e.g., CCS) have low detection rates and that late-type molecules (e.g., N\(_2\)H\(^+\), c-C\(_3\)H\(_2\)) and deuterated molecules (e.g., N\(_2\)D\(^+\), DNC) have high detection rates, suggesting that most of the cores are chemically evolved. The deuterium fraction (D/H) is found to decrease with increasing distance, indicating that it suffers from differential beam dilution between the D/H pair of lines for distant cores (\(>\)1 kpc). For \(\lambda\) Orionis, Orion A, and B located at similar distances, D/H is not significantly different, suggesting that there is no systematic difference in the observed chemical properties among these three regions. We identify at least eight high D/H cores in the Orion region and two at high latitudes, which are most likely to be close to the onset of star formation. There is no clear evidence of the evolutionary change in turbulence during the starless phase, suggesting that the dissipation of turbulence is not a major mechanism for the beginning of star formation as judged from observations with a beam size of 0.04 pc.
We mapped two molecular cloud cores in the Orion A cloud with the ALMA ACA 7-m Array and with the Nobeyama 45-m radio telescope. These cores have bright N\(_2\)D\(^+\) emission in single-pointing ...observations with the Nobeyama 45-m radio telescope, have relatively high deuterium fraction, and are thought to be close to the onset of star formation. One is a star-forming core, and the other is starless. These cores are located along filaments observed in N\(_2\)H\(^+\), and show narrow linewidths of 0.41 km s\(^{-1}\) and 0.45 km s\(^{-1}\) in N\(_2\)D\(^+\), respectively, with the Nobeyama 45-m telescope. Both cores were detected with the ALMA ACA 7m Array in the continuum and molecular lines at Band 6. The starless core G211 shows clumpy structure with several sub-cores, which in turn show chemical differences. Also, the sub-cores in G211 have internal motions that are almost purely thermal. The starless sub-core G211D, in particular, shows a hint of the inverse P Cygni profile, suggesting infall motion. The star-forming core G210 shows an interesting spatial feature of two N\(_2\)D\(^+\) peaks of similar intensity and radial velocity located symmetrically with respect to the single dust continuum peak. One interpretation is that the two N\(_2\)D\(^+\) peaks represent an edge-on pseudo-disk. The CO outflow lobes, however, are not directed perpendicular to the line connecting both N\(_2\)D\(^+\) peaks.
Efforts toward ideal microelectromechanical switches Jun-Bo Yoon; Yong-Hoon Yoon; Min-Ho Seo ...
2017 19th International Conference on Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS),
2017-June
Conference Proceeding
Since a microelectromechanical (MEM) switch with an electrostatically actuated cantilever was first demonstrated by Petersen in 1978 1, MEM switches have actively been researched by many research ...groups. However, comparing with the conventional metal-oxide-semiconductor fieldeffect transistor (MOSFET), MEM switches are still suffering from their high actuation voltage and insufficient operational reliability, which still remain as a difficult challenge to many MEMS researchers and hinder commercialization of the MEM switches. In this work, we look at what lies behind these difficulties in MEM switches and illustrate bright ideas that have been sought to enhance the actuation voltage and switch endurance (lifetime) problems.
Based on the 850 $\mu$m dust continuum data from SCUBA-2 at James Clerk
Maxwell Telescope (JCMT), we compare overall properties of Planck Galactic Cold
Clumps (PGCCs) in the $\lambda$ Orionis cloud ...to those of PGCCs in the Orion A
and B clouds. The Orion A and B clouds are well known active star-forming
regions, while the $\lambda$ Orionis cloud has a different environment as a
consequence of the interaction with a prominent OB association and a giant Hii
region. PGCCs in the $\lambda$ Orionis cloud have higher dust temperatures
($Td=16.13\pm0.15$ K) and lower values of dust emissivity spectral index ($
\beta=1.65\pm0.02$) than PGCCs in the Orion A (Td=13.79$\pm 0.21$K,
$\beta=2.07\pm0.03$) and Orion B ($Td=13.82\pm0.19$K, $\beta=1.96\pm0.02$)
clouds. We find 119 sub-structures within the 40 detected PGCCs and identify
them as cores. Of total 119 cores, 15 cores are discovered in the $\lambda$
Orionis cloud, while 74 and 30 cores are found in the Orion A and B clouds,
respectively. The cores in the $\lambda$ Orionis cloud show much lower mean
values of size R=0.08 pc, column density N(H2)=$(9.5\pm1.2) \times 10^{22}$
cm$^{-2}$, number density n(H2)=$(2.9 \pm 0.4)\times10^{5}$ cm$^{-3}$, and mass
$M_{core}$=$1.0\pm0.3$ M$_{\odot}$ compared to the cores in the Orion A
(R=0.11pc, $N(H2)=(2.3\pm0.3) \times 10^{23}$ cm$^{-2}$, n(H2)=$(3.8\pm0.5)
\times 10^{5}$cm$^{-3}$, and $M_{core}$=$2.4 \pm 0.3$ M$_{\odot}$) and Orion B
(R=0.16pc, N(H2)=$(3.8 \pm 0.4) \times 10^{23}$cm$^{-2}$,
n(H2)=$(15.6\pm1.8)\times10^{5}$ cm$^{-3}$, and $M_{core}$= $2.7\pm0.3$
M$_{\odot}$) clouds. These core properties in the $\lambda$ Orionis cloud can
be attributed to the photodissociation and external heating by the nearby Hii
region, which may prevent the PGCCs from forming gravitationally bound
structures and eventually disperse them. These results support the idea of
negative stellar feedback on core formation.
We are performing a series of observations with ground-based telescopes
toward Planck Galactic cold clumps (PGCCs) in the $\lambda$ Orionis complex in
order to systematically investigate the effects ...of stellar feedback. In the
particular case of PGCC G192.32-11.88, we discovered an extremely young Class 0
protostellar object (G192N) and a proto-brown dwarf candidate (G192S). G192N
and G192S are located in a gravitationally bound bright-rimmed clump. The
velocity and temperature gradients seen in line emission of CO isotopologues
indicate that PGCC G192.32-11.88 is externally heated and compressed. G192N
probably has the lowest bolometric luminosity ($\sim0.8$ L$_{\sun}$) and
accretion rate (6.3$\times10^{-7}$ M$_{\sun}$~yr$^{-1}$) when compared with
other young Class 0 sources (e.g. PACS Bright Red sources (PBRs)) in the Orion
complex. It has slightly larger internal luminosity ($0.21\pm0.01$ L$_{\sun}$)
and outflow velocity ($\sim$14 km~s$^{-1}$) than the predictions of first
hydrostatic cores (FHSCs). G192N might be among the youngest Class 0 sources,
which are slightly more evolved than a FHSC. Considering its low internal
luminosity ($0.08\pm0.01$ L$_{\odot}$) and accretion rate (2.8$\times10^{-8}$
M$_{\sun}$~yr$^{-1}$), G192S is an ideal proto-brown dwarf candidate. The star
formation efficiency ($\sim$0.3\%-0.4\%) and core formation efficiency
($\sim$1\%) in PGCC G192.32-11.88 are significantly smaller than in other giant
molecular clouds or filaments, indicating that the star formation therein is
greatly suppressed due to stellar feedback.
Based on the 850 \(\mu\)m dust continuum data from SCUBA-2 at James Clerk Maxwell Telescope (JCMT), we compare overall properties of Planck Galactic Cold Clumps (PGCCs) in the \(\lambda\) Orionis ...cloud to those of PGCCs in the Orion A and B clouds. The Orion A and B clouds are well known active star-forming regions, while the \(\lambda\) Orionis cloud has a different environment as a consequence of the interaction with a prominent OB association and a giant Hii region. PGCCs in the \(\lambda\) Orionis cloud have higher dust temperatures (\(Td=16.13\pm0.15\) K) and lower values of dust emissivity spectral index (\( \beta=1.65\pm0.02\)) than PGCCs in the Orion A (Td=13.79\(\pm 0.21\)K, \(\beta=2.07\pm0.03\)) and Orion B (\(Td=13.82\pm0.19\)K, \(\beta=1.96\pm0.02\)) clouds. We find 119 sub-structures within the 40 detected PGCCs and identify them as cores. Of total 119 cores, 15 cores are discovered in the \(\lambda\) Orionis cloud, while 74 and 30 cores are found in the Orion A and B clouds, respectively. The cores in the \(\lambda\) Orionis cloud show much lower mean values of size R=0.08 pc, column density N(H2)=\((9.5\pm1.2) \times 10^{22}\) cm\(^{-2}\), number density n(H2)=\((2.9 \pm 0.4)\times10^{5}\) cm\(^{-3}\), and mass \(M_{core}\)=\(1.0\pm0.3\) M\(_{\odot}\) compared to the cores in the Orion A (R=0.11pc, \(N(H2)=(2.3\pm0.3) \times 10^{23}\) cm\(^{-2}\), n(H2)=\((3.8\pm0.5) \times 10^{5}\)cm\(^{-3}\), and \(M_{core}\)=\(2.4 \pm 0.3\) M\(_{\odot}\)) and Orion B (R=0.16pc, N(H2)=\((3.8 \pm 0.4) \times 10^{23}\)cm\(^{-2}\), n(H2)=\((15.6\pm1.8)\times10^{5}\) cm\(^{-3}\), and \(M_{core}\)= \(2.7\pm0.3\) M\(_{\odot}\)) clouds. These core properties in the \(\lambda\) Orionis cloud can be attributed to the photodissociation and external heating by the nearby Hii region, which may prevent the PGCCs from forming gravitationally bound structures and eventually disperse them. These results support the idea of negative stellar feedback on core formation.
We are performing a series of observations with ground-based telescopes toward Planck Galactic cold clumps (PGCCs) in the \(\lambda\) Orionis complex in order to systematically investigate the ...effects of stellar feedback. In the particular case of PGCC G192.32-11.88, we discovered an extremely young Class 0 protostellar object (G192N) and a proto-brown dwarf candidate (G192S). G192N and G192S are located in a gravitationally bound bright-rimmed clump. The velocity and temperature gradients seen in line emission of CO isotopologues indicate that PGCC G192.32-11.88 is externally heated and compressed. G192N probably has the lowest bolometric luminosity (\(\sim0.8\) L\(_{\sun}\)) and accretion rate (6.3\(\times10^{-7}\) M\(_{\sun}\)~yr\(^{-1}\)) when compared with other young Class 0 sources (e.g. PACS Bright Red sources (PBRs)) in the Orion complex. It has slightly larger internal luminosity (\(0.21\pm0.01\) L\(_{\sun}\)) and outflow velocity (\(\sim\)14 km~s\(^{-1}\)) than the predictions of first hydrostatic cores (FHSCs). G192N might be among the youngest Class 0 sources, which are slightly more evolved than a FHSC. Considering its low internal luminosity (\(0.08\pm0.01\) L\(_{\odot}\)) and accretion rate (2.8\(\times10^{-8}\) M\(_{\sun}\)~yr\(^{-1}\)), G192S is an ideal proto-brown dwarf candidate. The star formation efficiency (\(\sim\)0.3\%-0.4\%) and core formation efficiency (\(\sim\)1\%) in PGCC G192.32-11.88 are significantly smaller than in other giant molecular clouds or filaments, indicating that the star formation therein is greatly suppressed due to stellar feedback.
십이지장의 원발성 선암종 김인철; In Chul Kim; 김부성 ...
The Korean journal of gastroenterology,
01/1989, Letnik:
21, Številka:
3
Journal Article
Recenzirano
Primary Cancer of the duodenum is rare. The rarity and the non-specific symptoms of this cancer make the diagnosis difficult and are major factors contributing to its poor prognosis. As the prognosis ...of primary cancer of the duodenum, once metastasized, is poor, a greater awareness of the possibility of a duodenal cancer must accompany aggressive diagnostic and surgical procedures. We report our experience of a patient with primary adenocarcinoma of the duodenum with a brief review of literatures.
