• 제목/요약/키워드: $M{\alpha}$ wave

검색결과 70건 처리시간 0.031초

Interface structure and anisotropic strain relaxation of nonpolar a-GaN on r-sapphire

  • 공보현;조형균;송근만;윤대호
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2010년도 하계학술대회 논문집
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    • pp.31-31
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    • 2010
  • The growth of the high-quality GaN epilayers is of significant technological importance because of their commercializedoptoelectronic applications as high-brightness light-emitting diodes (LEDs) and laser diodes (LDs) in the visible and ultraviolet spectral range. The GaN-based heterostructural epilayers have the polar c-axis of the hexagonal structure perpendicular to the interfaces of the active layers. The Ga and N atoms in the c-GaN are alternatively stacked along the polar [0001] crystallographic direction, which leads to spontaneous polarization. In addition, in the InGaN/GaN MQWs, the stress applied along the same axis contributes topiezoelectric polarization, and thus the total polarization is determined as the sum of spontaneous and piezoelectric polarizations. The total polarization in the c-GaN heterolayers, which can generate internal fields and spatial separation of the electron and hole wave functions and consequently a decrease of efficiency and peak shift. One of the possible solutions to eliminate these undesirable effects is to grow GaN-based epilayers in nonpolar orientations. The polarization effects in the GaN are eliminated by growing the films along the nonpolar [$11\bar{2}0$] ($\alpha$-GaN) or [$1\bar{1}00$] (m-GaN) orientation. Although the use of the nonpolar epilayers in wurtzite structure clearly removes the polarization matters, however, it induces another problem related to the formation of a high density of planar defects. The large lattice mismatch between sapphiresubstrates and GaN layers leads to a high density of defects (dislocations and stacking faults). The dominant defects observed in the GaN epilayers with wurtzite structure are one-dimensional (1D) dislocations and two-dimensional (2D) stacking faults. In particular, the 1D threading dislocations in the c-GaN are generated from the film/substrate interface due to their large lattice and thermal coefficient mismatch. However, because the c-GaN epilayers were grown along the normal direction to the basal slip planes, the generation of basal stacking faults (BSFs) is localized on the c-plane and the generated BSFs did not propagate into the surface during the growth. Thus, the primary defects in the c-GaN epilayers are 1D threading dislocations. Occasionally, the particular planar defects such as prismatic stacking faults (PSFs) and inversion domain boundaries are observed. However, since the basal slip planes in the $\alpha$-GaN are parallel to the growth direction unlike c-GaN, the BSFs with lower formation energy can be easily formed along the growth direction, where the BSFs propagate straightly into the surface. Consequently, the lattice mismatch between film and substrate in $\alpha$-GaN epilayers is mainly relaxed through the formation of BSFs. These 2D planar defects are placed along only one direction in the cross-sectional view. Thus, the nonpolar $\alpha$-GaN films have different atomic arrangements along the two orthogonal directions ($[0001]_{GaN}$ and $[\bar{1}100]_{GaN}$ axes) on the $\alpha$-plane, which are expected to induce anisotropic biaxial strain. In this study, the anisotropic strain relaxation behaviors in the nonpolar $\alpha$-GaN epilayers grown on ($1\bar{1}02$) r-plane sapphire substrates by metalorganic chemical vapor deposition (MOCVO) were investigated, and the formation mechanism of the abnormal zigzag shape PSFs was discussed using high-resolution transmission electron microscope (HRTEM).

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흰쥐의 적출배뇨근에서 baclofen의 콜린성신경 억제작용 (Effect of Baclofen on the Cholinergic Nerve Stimulation in Isolated Rat Detrusor)

  • 이광윤;이근미;최은미;최형철;하정희;김원준
    • Journal of Yeungnam Medical Science
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    • 제12권2호
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    • pp.246-259
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    • 1995
  • 배뇨근의 운동성에 대한 baclofen의 억제작용의 기전을 탐구하기 위하여 다음과 같은 실험을 하였다. 흰쥐 (Sprague-Dawley)의 방광에서 적출한 배뇨근절편을 적출근편실험조에 현수하고, 등척성 장력측정기를 사용하여 그 수축력을 묘기하였다. 실험조내의 영양액의 온도는 $37^{\circ}C$로 유지시키고, 95% 산소와 5% 이산화탄소의 혼합기체를 공급하여 pH를 7.4로 유지하였다. 배뇨근절편은 전기장자극에 의해 수축하였는데, 8분간의 전기장자극 유발수축 중 최초의 급격한 수축반응은 mATP와 baclofen에 의해 약간 억제되는 경향을 보였으며, 후기 4분간의 수축반응은 콜린성 무스카린성 수용체 봉쇄제인 atropine과 $GABA_B$ 수용체 효현제인 baclofen에 의해 유의하게 억제되었다. Atropine은 배뇨근 절편의 acetylcholine 유발 수축을 길항하였고, mATP는 ATP 유발 수축을 완전히 봉쇄하였으나, baclofen 존재하에서는 acetylcholine이나 ATP 첨가에 의한 배뇨근의 수축이 영향을 받지 않았다. 이상의 결과를 종합하면, 흰쥐 방광에는 $GABA_B$ 수용체가 존재하며 baclofen은 이 수용체를 통하여 콜린성신경 말단에서의 신경전달체의 유리를 억제하여 배뇨근의 수축성을 감소시킨다고 사료된다.

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뇌파측정을 이용한 비염 환아와 정상아의 주의집중력에 관한 연구 (The Study of Cognitive Function and EEG Spectrum Difference between Allergic Rhinitis and Normal Children)

  • 이남열;김윤희;한재경
    • 대한한방소아과학회지
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    • 제21권2호
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    • pp.1-12
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    • 2007
  • Objectives : Allergic children have known to have multiple behavior problems. Among them, attentional ability disorder is one of the most common problems. This study is to examine relationship between learning ability and allergic rhinitis by analyzing EEG status of children. Methods : We analyzed cognitive functions of two different children groups; 21 children with allergic rhinitis and 19 normal children with CANS 3000(Central & Autonomic Nervous System, LAXTHA Inc., Korea), cognitive functions assessment program by EEG. Results : 1. According to mean active EEG rhythm of Theta, Alpha, SMR, M-beta, there were no significant difference between allergic rhinitis and the normal group. 2. According to mean active EEG rhythm of right H-beta, Gamma wave allergic rhinitis group's value was significantly higher than that of the normal group. 3. According to mean cognitive strength, response, concentration, left / right brain activity and learning ability score, there were no significant difference between allergic rhinitis and the normal group. 4. According to mean workload score, allergic rhinitis group's value was significantly higher than that of the normal group. Conclusions : It is likely that allergic rhinitis group, which showed relatively high frequency EEG rhythm, is more fragile to stress and less active on mental processing. Along side with physical examination, psychological assessment should also be conjugated on treating children with allergic rhinitis.

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폐석 및 석분 슬러지를 활용한 인조석판재의 제조 (Manufacture of Artificial stone using Wasts Stone and Powder Sludge)

  • 손정수;김병규;김치권
    • 자원리싸이클링
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    • 제4권1호
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    • pp.4-11
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    • 1995
  • 국내 각 채석장 및 석재 가공공정에서 발생되는 폐석과 석분 슬러지를 활용하여 장식재, 바닥재 및 내외장재 등에 쓰이는 인조 석판재 제조기술을 개발하고자 하였다. 인조석재는 폐석과 결합제 및 경화제 등을 혼합하여 제조하였으며 성형압력, 폐석 및 석분 슬러지의 결합비 그리고 결합제의 양 등의 변화에 따른 인조석재 각각의 특성을 비교하였다. 천연석재와 인조석재와의 물성을 비교하기 위하여 $\circled1$ 비중,$\circled2$ 흡수율, $\circled3$ 탄성파속도, $\circled4$ 압축강도, $\circled5$ 인장강도, $\circled6$ 반발경도, $\circled7$ 탄성계수 $\circled8$ 포아송비를 측정하였으며 $\circled9$ 내열성도 함께 조사하였는데 석재의 물성은 원료의 혼합정도, 성형압력 및 결합제의 양에 의해 좌우됨을 알 수 있었다. 본 인조석재의 제조에도 석분에 비해 고가인 결합제의 사용을 가능한한 최소로 하여 폐기물로 배출되는 폐석 및 석분슬러지를 최대한 활용할 수 있도록 하였으며 성형압력 $200kg/\textrm{cm}^2$, 결합제의 양 12~15wt.%의 제조조건에서 원하는 물성을 갖는 인조석재를 제조할 수 있었다.

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$ThMn_{12}$$NdFe_{10.7}Ti_{1.2}Mo_{0.1}$의 미세구조 및 자기적 성질 연구 (Magnetic Properties of $ThMn_{12}-type$$NdFe_{10.7}Ti_{1.2}Mo_{0.1}$>$Ti_{1.2}Mo_{0.1}$)

  • 안성용;이승화;김철성;김윤배;김창석
    • 한국자기학회지
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    • 제7권2호
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    • pp.90-96
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    • 1997
  • ThM $n_{12}$ 구조를 갖는 NdF $e_{10.7}$ $Ti_{1.2}$M $o_{0.1}$의 미세구조 및 자기적 성질을 Mossbauer 분광법과 X-선 회절 분석 그리고 VSM으로 연구하였다. NdF $e_{10.7}$ $Ti_{1.2}$M $o_{0.1}$ 합금은 알곤 가스 분위기의 아크 ㅇ용해로에서 제조하였으며, X-선 회절 분석 결과 결정구조는 상온에서 tetragonal 구조를 갖고 있으며, 격자상수는 $a_{0}$ = 8.637 .angs. , $c_{0}$ = 4.807 .angs. 으로 결정하였다. Mossbauer spectrum을 13 K에서 800 K 까지 취하였으며, Curie 온도는 600 K로 결정하였다. Mossbauer spectrum 분석은 Curie 온도 이하의 온도에서는 Fe-site가 (8 $i_{1}$, 8 $i_{2}$, 8 $j_{2}$, 8 $j_{1}$, 8f)의 5 site로 나타났으며, 400 K 근처에서 .alpha. -Fe 상이 나타나기 시작하여 온도가 증가함에 따라서 점진적으로 증가하여 Curie 온도에서 20.7%의 .alpha. -Fe 상이 존재함을 알았다. 각 site에서의 초미세 자기장은 온도가 증가함에 따라 감소하였으며, 그 크기는 $H_{hf}$(8i)> $H_{hf}$(8j)> $H_{hf}$(8f) 임을 알았고 spin파 여기에 의한 T/ $T_{c}$<0.7 이하에서의 평균 초미세 자기장 $H_{hf}$(T)의 변화는 [ $H_{hf}$(T)- $H_{hf}$(0)]/ $H_{hf}$(0)=-0.34(T/ $T_{c}$)$^{3}$2/-0.14(T/ $T_{c}$)$^{5}$ 2/로 나타났다. 또한 원자간 결합력을 알 수 있는 Debye 온도는 .THETA. = 340 .+-. 5 K로 나타났다.ETA. = 340 .+-. 5 K로 나타났다.

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전경골근 등척성 수축에 의한 경직성 뇌졸중 환자의 비복근 ${\alpha}$-운동 신경원 흥분 변화 (The Change of ${\alpha}$-motor neuron excitability in Spastic Stroke Patients by Pre-tibia Muscle Isometric Contraction)

  • 김종순;이현옥;안소윤
    • 대한정형도수물리치료학회지
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    • 제11권1호
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    • pp.11-28
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    • 2005
  • Spasticity has been defined as "a motor disorder characterized by a velocity-dependent increased in tonic stretch reflexes with exaggerated tendon jerks, resulting from hyperexcitability of the stretch reflex, as one components of the upper motorneuron syndrome". Spasticity is one of the common symptoms of stroke patients and frequently interferes with the motor functions such as gait, posture and activities of daily living. Therefore, its management is becoming a major issue in physical therapy. The purpose of this study was to determined the effects of reciprocal inhibition by isometric contraction of pre-tibia muscle on spasticity in hemiplegic patients through Hoffmann reflex. The subjects were consisted 45 patients who had hemiplegia due to stroke. All subjects randomly assigned to 3 group: manual reciprocal inhibition program group(manual group), neuromuscular electrical stimulation group(NMES group) and control group. The manual group received voluntary isometric contraction of pre-tibia muscle. The NMES group received neuromuscular electrical stimulation on tibialis anterior. The control group was not received any therapeutic intervention. Before and after experiments, Hoffmann reflex, M-wave and Modified Ashworth scale was measure in all patients. The data of 30 patients who complete experimental course were statistically analysed. Modified Ashworth scale were significantly decreased after experiment in manual group(p<.01). The Hmax/Mmax ratios were significantly decreased after experiment in manual group(p<.o1). There were no statistical difference between pre-test and post-test with modified Ashworth scale in NMES group(p>.01). There were no statistical difference between pre-test and post-test with Hmax/Mmax ratios in NMES group(p>.01). There were no statistical difference between pre-test and post-test with modified Ashworth scale in control group(p>.01). There were no statistical difference between pre-test and post-test with Hmax/Mmax ratios in control group(p>.01). The present results revealed that reciprocal inhibition which produced by voluntary isometric contraction of pre-tibia muscle can be reduce spasticity of gastrocnemius. Therefore, reciprocal inhibition is useful to improve functional activities in hemiplegic patient. Further study should be done to analyse the effects of intervention duration of reciprocal inhibition, appropriate muscle contraction, optimal time to apply the reciprocal inhibition in more long period.

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Cardiovascular Neurons Mediating Somatosympathetic Reflex in Rostral Ventrolateral Medulla

  • Goo, Yong-Sook;Kim, Sang-Jeong;Kim, Jun;Sung, Ho-Kyung
    • The Korean Journal of Physiology
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    • 제27권2호
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    • pp.185-197
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    • 1993
  • The rostral ventrolateral medulla (RVLM) includes vasopressor neurons, which transmit activation signals to the intermediolateral nucleus (IML) of the spinal cord, where the preganglionic sympathetic nucleus is located, to raise arterial blood pressure (BP). However, controversy exists as to the possible depressor area in the RVLM and the pathway involved. The present study persued evidence far the location of depressor neurons and the pathway by simultaneously observing changes in BP and the firing rate (FR) of cardiovascular neurons (CVNs) in the RVLM during the somatosympathetic reflex (SSR) elicited by peripheral nerve stimulation, since CVNs are known to contribute to the generation of the sympathetic nerve discharge. In 42 cats, anaesthetized with $\alpha-chloralose$, single unit recording was performed, using carbon filament electrodes inserted into the RVLM, enabling estimation of the post R wave unit histogram (PR-UNlT) and the spike triggered average of sympathetic nerve discharge (STA-SND), allowing identification of CVNs. Antidromic stimulation of spinal $T_2$ segment was followed to determine whether the identified CVN projects axonal endings to the spinal cord (reticulospinal neuron). The sciatic nerve was electrically stimulated at $A\delta-intensity$ (1 mA, 0.1 ms), 1 Hz and C-intensity (10 mA, 0.5 ms), 20 Hz to elicit the depressor, and pressor responses of the SSR, respectively. Simultaneous measurement of CVN firing rate was made. Experimental results are summarized as follows. 1) 20 out of 98 CVNs had axonal projections to the spinal cord and 17 out of 98 CVNs showed FR changes during SSR. 2) Response patterns of FR and BP during SSR were classified into 8 types. 3) These 8 different response patterns could be further classified into those from pressor and depressor neurons. These results demonstrate that some CVNs were identifiable as reticulospinal neurons responding to anti-dromic stimulation and that CVNs operating as depressor neurons as well as pressor neurons exist in the RVLM, both of which are involved with SSR mediation. Therefore, evidence was found that an independent depressor pathway might be involved in the mediation of SSR.

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Microwave를 이용한 심방세동의 치료 (Treatment of Atrial Fibrillation with Microwave)

  • 조광현;최강주;강도균;전희재;윤영철;이양행;황윤호
    • Journal of Chest Surgery
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    • 제36권5호
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    • pp.329-334
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    • 2003
  • 배경: 심방세동을 치료하기 위해 주로 radiofrequency 또는 cryoablation의 방법을 이용해왔다. Microwave를 이용하여 심방조직을 파괴하는 방법은 다른 방법과 비교하여 조직투과성이 좋다는 보고가 있다. 보고자는 심방세동의 치료에 microwave를 이용하였기에 그 결과를 보고하는 바이다. 대상 및 방법: 2001년 12월부터 2002년 7월까지 8명의 환자를 대상으로 하였다. 성별로는 남자 3명, 여자 5명이었고 평균나이는 43세, 평균체포면적은 $1.5m^2$이었다. 대상환자 중 7명에서 승모판막치환술을 시행하였고 1명에서는 승모판막치환술과 대동맥판막치환술을 함께 시행하였다. Microwave ablation은 심정지상태에서 1회 45 watts 25초로 시행하였다. 수술 전, 수술 직후, 수술 후 약 6개월 뒤에 각각 심장초음파와 심전도를 이용하여 좌심방의 크기와 동율동의 회복정도를 조사하였다. 결과: 수술합병증이나 사망률은 없었다. 수술 중 대동맥차단시간은 평균 104.6$\pm$25.0분, 체외순환시간은 평균 130.5$\pm$28.7분이었다. 수술 후 동율동의 회복은 평균 5.6개월 후에 75%이었다. 수술 전후 초음파로 측정한 좌심방의 크기는 차이가 없었다. 수술 후 평균 5.6개월에 측정한 승모판막의 $\alpha$파는 평균 77.0$\pm$24.8 cm/sec이었고 A/E 는 평균 0.46$\pm$0.17이었다. 결론: Microwave를 이용한 심방세동 차단술의 조기결과는 다른 방법의 결과와 큰 차이가 없었다. 수술 시 적용의 편리함과 심박동 시에도 적용할 수 있는 장점으로 인해 향후 그 적용이 늘어날 것으로 예측된다.

Synthesis of Binuclear Bismacrocyclic Iron(II) Complex by the Aerobic Oxidation of Iron(II) Complex of 1,4,8,11-Tetraazacyclotetradecane

  • Myunghyun Paik Suh;Gee-Yeon Kong;Il-Soon Kim
    • Bulletin of the Korean Chemical Society
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    • 제14권4호
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    • pp.439-444
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    • 1993
  • The aerobic oxidation of the Fe(II) complex of 1,4,8,11-tetraazacyclotetradecane, [Fe(cyclam)$(CH_3CN)_2](ClO_4)_2$, in MeCN in the presence of a few drops of $HClO_4$ leads to low spin Fe(III) species [Fe(cyclam)$(CH_3CN)_2](ClO_4)_3$. The Fe(III) cyclam complex is further oxidized in the air in the presence of a trace of water to produce the deep green binuclear bismacrocyclic Fe(II) complex $[Fe_2(C_{20}H_{36}N_8)(CH_3CN)_4](ClO_4)_4{\cdot}2CH_3CN$. The Fe(II) ions of the complex are six-coordinated and the bismacrocyclic ligand is extensively unsaturated. $[Fe_2(C_{20}H_{36}N_8)(CH_3CN)_4](ClO_4)_4{\cdot}2CH_3CN$ crystallizes in the monoclinic space group $P2_1/n$ with a= 13.099 (1) ${\AA}$, b= 10.930 (1) ${\AA}$, c= 17.859 (1) ${\AA}$, ${\beta}$= 95.315 $(7)^{\circ}$, and Z= 2. The structure was solved by heavy atom methods and refined anisotropically to R values of R= 0.0633 and $R_w$= 0.0702 for 1819 observed reflections with F > $4{\sigma}$ (F) measured with Mo K${\alpha}$ radiation on a CAD-4 diffractometer. The two macrocyclic units are coupled through the bridgehead carbons of ${\beta}$-diimitie moieties by a double bond. The double bonds in each macrocycle unit are localized. The average bond distances of $Fe(II)-N_{imine}$, $Fe(II)-N_{amine}$, and $Fe(II)-N_{MeCN}$ are 1.890 (5), 2.001 (5), and 1.925 (6) ${\AA}$, respectively. The complex is diamagnetic, containing two low spin Fe(II) ions in the molecule. The complex shows extremely intense charge transfer band in the near infrared at 868 nm with ${\varepsilon}$= 25,000 $M^{-1}cm^{-1}$. The complex shows a one-electron oxidation wave at +0.83 volts and two one-electron reduction waves at -0.43 and-0.72 volts vs. Ag/AgCl reference electrode. The complex reacts with carbon monoxide in $MeNO_2$ to form carbonyl adducts, whose $v_{CO}$ value (2010 $cm^{-1}$) indicates the ${\pi}$-accepting property of the present bismacrocyclic ligand.

A CYANOACETYLENE STUDY OF THE MOLECULAR DISK IN STAR FORMING REGIONS

  • Chung, H.S.;Kameya, Osamu;Morimoto, Masaki
    • 천문학회지
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    • 제24권2호
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    • pp.217-271
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    • 1991
  • We have observed dense core around young stellar objects, DR21, S140, Orion-KL, and L1551 using four millimeter-wave transitions of $HC_3N\;J$=4-3, J=5-4, J=10-9, and J=12-11. The spatial distribution of $HC_3N$ emission closely resembles the morphology of the previous CS observations that trace high density gas. These observations reveal the existence of $HC_3N$ dense cores around central IR source, elliptical in shape and almost perpendicular to the CO bipolar outflow axis. Small differences can be explained by that $HC_3N$ molecular line is more optically thin and is seen to be more detailed structure in the neighborhood of central IR sources. In S140 and Orion-KL, massive(${\sim}10\;M_{\odot}$), slowly rotating dense cores lie near at the central IR sources of bipolar outflows. The velocity channel maps of DR21 show that the bipolar outflow gas may have a correlation with the dense core of DR21. We analyzed intensities of the four lines to derive physical conditions in dense core from two methods, LTE and LVG. The column density of $HC_3N$, $N(HC_3N)$, between LTE and LVG calculations agree well with each other. The abundances of $HC_3N$ in each observing source have been estimated using the average values of $n(H_2)$ and $N(HC_3N)$ and assuming the size of dense core. The fractional $HC_3N$ abundances in massive dense cores of DR21, S140, and Orion-KL have a range of $(2-7){\times}10^{-10}$, while that of low mass dense core, L1551, has one order of magnitude greater value of $2{\times}10^{-9}$. This should be considered good agreement with the result by Morris et al.(1976). It may be considered that dense cores of DR21, S140, and Orion-KL may have almost same stage of chemical evolution, and their abundances have a small values relative to that of L1551. The column density $N(HC_3N)$ decreases with increasing distance from the densest part of the cloud, the central infrared source, and have the relation of $N(HC_3N){\varpropto}R^{\alpha}$, where a has a range of 0.65 to 0.89. The values of $n(H_2)$ are not varied with increasing distance from the dense core, and have almost same values. Therefore, it is considered that the dense cores in these regions probably consist of dense clumps in diffuse molecular gas medium, and $n(H_2)$ of each clump is ${\sim}10^5\;cm^{-3}$. Levels in the $T_{ex}$ increases with $n(H_2)$. It is considered that the $HC_3N$ dense cores are not completely thermalized. We examine the relationships between the luminosity of central infrared sources versus mass of the dense cores, and the luminosity of central infrared sources versus molecular hydrogen column density. Luminosities of the central IR sources show good correlation with mass and hydrogen column density of the dense core. Same has been found from CS observations. However, mass and size derived from $HC_3N$ observations are one order of magnitude smaller than those from CS. It can be interpreted that we see more central part of the cloud cores in $NC_3N$ lines than CS lines.

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