• 제목/요약/키워드: Gradient envelope

검색결과 9건 처리시간 0.039초

Gradient Optimized Gradient-Echo Gradient Moment Nulling Sequences for Flow Compensation of Brain Images

  • Jahng, Geon-Ho;Stephen Pickup
    • Investigative Magnetic Resonance Imaging
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    • 제4권1호
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    • pp.20-26
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    • 2000
  • Gradient moment nulling techniques require the introduction of an additional gradient on each axis for each order of motion correction to be applied. The additional gradients introduce new constraints on the sequence design and increase the demands on the gradient system. The purpose of this paper is to demonstrate techniques for optimization of gradient echo gradient moment nulling sequences within the constraints of the gradient hardware. Flow compensated pulse sequences were designed and implemented on a clinical magnetic resonance imaging system. The design of the gradient moment nulling sequences requires the solution of a linear system of equations. A Mathematica package was developed that interactively solves the gradient moment nulling problem. The package allows the physicist to specify the desired order of motion compensation and the duration of the gradients in the sequence with different gradient envelopes. The gradient echo sequences with first, second, and third order motion compensation were implemented with minimum echo time. The sequences were optimized to take full advantage of the capabilities of the gradient hardware. The sequences were used to generate images of phantoms and human brains. The optimized sequences were found to have better motion compensation than comparable standard sequences.

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IMAGING THE CIRCUMSTELLAR ENVELOPES AROUND EVOLVED STARS WITH THE SMA

  • HIRANO NAOMI;CHIU PO-JIAN;MULLER SEBASTIEN;TRUNG DINH-V
    • 천문학회지
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    • 제38권2호
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    • pp.219-222
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    • 2005
  • We present the high-resolution (2"-4") images of the molecular envelopes surrounding the evolved stars, V Hya, VY CMa, and ${\pi}^1$ Gru observed with the Submillimeter Array. The CO J=2-1 and 3-2 images of the carbon star V Hya show that the circumstellar structure of this star consists of three kinematic components; there is a flattened disk-like envelope that is expanding with a velocity of ${\~}16 km\;s^{-1}$, the second component is the medium-velocity wind having a deprojected velocity of 40-120 km $s^{-l}$ moving along the disk plane, and the third one is the bipolar molecular jet having an extreme velocity of 70-185 km $s^{-l}$. The axis of this high velocity jet is perpendicular to the plane of the disk-like envelope. We found that the circumstellar structure of the S-star ${\pi}^1$ Gru traced by the CO J =2-1 resembles that of V Hya quite closely; the star is surrounded by the expanding disk-like envelope and is driving the medium-velocity wind along the disk plane. We also obtained the excellent images of VY CMa with the CO and $^{13}CO$ J=2-1 and $SO\;6_5-5_4$ lines. The maps of three molecular lines show that the envelope has a significant velocity gradient in the east-west direction, suggesting that the envelope surrounding VY CMa is also flattened and expanding along its radial direction. The high-resolution images obtained with the SMA show that some AGB stars are associated with the asymmetric mass loss including the equatorial wind and bipolar jet.

Markov Envelope를 이용한 지진동의 위상차 확률분포와 전파지연시간의 추정 (Inference of the Probability Distribution of Phase Difference and the Path Duration of Ground Motion from Markov Envelope)

  • 최항;윤병익
    • 한국지진공학회논문집
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    • 제26권5호
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    • pp.191-202
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    • 2022
  • Markov envelope as a theoretical solution of the parabolic wave equation with Markov approximation for the von Kármán type random medium is studied and approximated with the convolution of two probability density functions (pdf) of normal and gamma distributions considering the previous studies on the applications of Radiative Transfer Theory (RTT) and the analysis results of earthquake records. Through the approximation with gamma pdf, the constant shape parameter of 2 was determined regardless of the source distance ro. This finding means that the scattering process has the property of an inhomogeneous single-scattering Poisson process, unlike the previous studies, which resulted in a homogeneous multiple-scattering Poisson process. Approximated Markov envelope can be treated as the normalized mean square (MS) envelope for ground acceleration because of the flat source Fourier spectrum. Based on such characteristics, the path duration is estimated from the approximated MS envelope and compared to the empirical formula derived by Boore and Thompson. The results clearly show that the path duration increases proportionately to ro1/2-ro2, and the peak value of the RMS envelope is attenuated by exp (-0.0033ro), excluding the geometrical attenuation. The attenuation slope for ro≤100 km is quite similar to that of effective attenuation for shallow crustal earthquakes, and it may be difficult to distinguish the contribution of intrinsic attenuation from effective attenuation. Slowly varying dispersive delay, also called the medium effect, represented by regular pdf, governs the path duration for the source distance shorter than 100 km. Moreover, the diffraction term, also called the distance effect because of scattering, fully controls the path duration beyond the source distance of 300 km and has a steep gradient compared to the medium effect. Source distance 100-300 km is a transition range of the path duration governing effect from random medium to distance. This means that the scattering may not be the prime cause of peak attenuation and envelope broadening for the source distance of less than 200 km. Furthermore, it is also shown that normal distribution is appropriate for the probability distribution of phase difference, as asserted in the previous studies.

White Sport Syndrome Virus Disease of Shirmp and Diagnostic Methods

  • Zhan, Wen-Bin
    • 한국양식학회지
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    • 제15권1호
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    • pp.7-13
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    • 2002
  • Since 1993, the White Spot Syndrome Virus (WSSV) disease occurred in China among cultured shrimps resulting in mass mortality. Epizootiological surveys undertaken during the outbreak period of 1993-1994 indicated that all stages of Penaeus chinensis, P. japonicus and P. monodon were infected. Consequent to the transport of contaminated shrimp seedlings and seawater, the disease spread all over the farms of China. The disease was more rapidly transmitted at temperatures above $25^{\circ}C$. Challenge experiments showed the causative agent was highly virulent. White spots appeared on the carapace of both span-taneous and experimentally infected shrimps. Moribund shrimps contained turbid hemolymph, hypertrophied Iymphoid organ and a necrotic mid-gut gland. Electron microscopy showed the presence of viral particles in the gills, stomach, lymphoid organ, and epidermal tissue of the infected shrimp. The visions were slightly ovoid with an envelope and averaged 350 $\times$ 150 nm; nucleocapsids measured 375 $\times$ 157 nm. With discontinuous sucrose gradient of 35, 50 and 60% (w/v), the virus was separated from hemolymph of the infected shrimp. The estimated molecular weight of genomic DNA was 237 Kb with EcoR I, 247 Kb with Hind III and 241kb with Pst I. A total of 9 hybridoma colones secreting monoclonal antibodies (MAbs) were produced from mouse myeloma and spleen cells immunized with WSSV. The immunofluorescence assay of gill tissue showed that the MAbs reacted with diseased but not with healthy shrimp. The MAbs belonged to IgGl, IgG2b subclass and IgM class, all with kappa light Immune-electron-microscopy with colloidal gold marker showed the presence of 5 MAbs epitopes on the envelope and one on the capsid of the virus. Baculoviral mid-gut gland necrosis showed the specificity of the MAbs produced. For diagnosis 5 different methods were selected. Using Kimura primers for PCR, or MAbs for immunoblot, ELISA or FAT method, in situ hybridization was carried out to show the gene. All these methods detected WSSV in the organ samples of the diseased shrimp but not in healthy one.

유도전동기의 고장 진단을 위한 효과적인 특징 추출 방법 (An Effective Feature Extraction Method for Fault Diagnosis of Induction Motors)

  • 흥 뉘엔;김종면
    • 한국컴퓨터정보학회논문지
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    • 제18권7호
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    • pp.23-35
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    • 2013
  • 본 논문은 고장 분류 시스템을 위해 진동 신호로부터 특징 벡터를 자동적으로 추출하는 효과적인 기법을 제안한다. 기존의 멜-주파수 캡스트럼 계수는 진동신호의 노이즈에 민감하여 분류 정확도를 감소시키는 단점이 있다. 이러한 문제를 해결하기 위해 본 논문은 4단계 필터 뱅크로 구성된 스펙트럴 엔벨로프 캡스트럼 계수 분석을 제안하며, 4단계는 (1) 모든 진동 신호의 스펙트럴 엔벨로프를 기술하기 위한 선형 예측 코딩 알고리즘 사용 단계, (2) 일반적인 스펙트럴 모양을 얻기 위해 모든 엔벨로프의 평균화 단계, (3) 평균 엔벨로프와 그 주파수의 최대값을 찾기 위한 기울기 하강 방법 사용 단계, (4) 엔벨로프의 주파수 사이의 거리로부터 계산된 중앙값을 얻는데 사용되는 비 중첩 필터 뱅크 단계로 구성된다. 이4-단계필터뱅크는 특징벡터를 추출하기위해 캡스트럼 계수 계산에 사용된다. 마지막으로 유도전동기의 결함 형태를 구분하기 위해 이러한 특수 파라미터를 사용하는 다중 계층 서포트 벡터 머신을 사용한다. 모의실험 결과, 제안하는 방법은 약 99.65%의 분류 성능을 보이며, 동시에 기존 방법들보다 우수한 성능을 보인다.

Mature HIV-like Particles Produced from Single Semliki Forest Virus-Derived Expression Vector

  • KIM EUN;POO HAR-YOUNG;SUNG MOON-HEE;KIM CHUL-JOONG
    • Journal of Microbiology and Biotechnology
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    • 제15권6호
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    • pp.1229-1239
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    • 2005
  • Human immunodeficiency virus-like particles (HIVVLPs) with native conformations similar to that of the wild-type virion could be valid candidates for vaccine development. To this end, we used a Semliki Forest Virus (SFV) expression system to produce HIV- VLPs containing high quantities of native envelope proteins. Here, we described a single SFV replicon containing the HIV gagpol and env genes under the control of separate subgenomic promoters. Mature VLPs incorporating the Gag and Env proteins were detected in the supernatant of replicon-expressing cells by Western blot analysis. The HIV-VLPs showed the expected molecular density (1.14-1.18 g/ml) on a $20-60\%$ sucrose gradient; the particles were 100-120 nm in diameter and Env proteins were observed on their surfaces by immunogold electron microscopy. RT-PCR analysis of VLP-associated RNAs in mature HIV-VLPs revealed two SF V-derived RNA species (full-length and subgenomic). Immunization studies in Balb/c mice showed that these HIV-VLPs were capable of inducing both HIV-specific antibodies and cell-mediated immune responses. Taken together, our results indicate that the SFV replicon system is useful for the production of HIV-VLPs, which may be valuable candidates for an HIV vaccine.

The mitochondrial proteome analysis in wheat roots

  • Kim, Da-Eun;Roy, Swapan Kumar;Kamal, Abu Hena Mostafa;Kwon, Soo Jeong;Cho, Kun;Cho, Seong-Woo;Park, Chul-Soo;Woo, Sun-Hee
    • 한국작물학회:학술대회논문집
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    • 한국작물학회 2017년도 9th Asian Crop Science Association conference
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    • pp.126-126
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    • 2017
  • Mitochondria are important in wheat, as in all crops, as the main source of ATP for cell maintenance and growth including vitamin synthesis, amino acid metabolism and photorespiration. To investigate the mitochondrial proteome of the roots of wheat seedlings, a systematic and targeted analysis were carried out on the mitochondrial proteome from 15 day-old wheat seedling root material. Mitochondria were isolated by Percoll gradient centrifugation; and extracted proteins were separated and analyzed by Tricine SDS-PAGE along with LTQ-FTICR mass spectrometry. From the isolated the sample, 184 proteins were identified which is composed of 140 proteins as mitochondria and 44 proteins as other subcellular proteins that are predicted by the freeware subcellular predictor. The identified proteins in mitochondria were functionally classified into 12 classes using the ProtFun 2.2 server based on biological processes. Proteins were shown to be involved in amino acid biosynthesis (17.1%), biosynthesis of cofactors (6.4%), cell envelope (11.4%), central intermediary metabolism (10%), energy metabolism (20%), fatty acid metabolism (0.7%), purines and pyrimidines (5.7%), regulatory functions (0.7%), replication and transcription (1.4%), translation (22.1%), transport and binding (1.4%), and unknown (2.8%). These results indicate that many of the protein components present and functions of identifying proteins are common to other profiles of mitochondrial proteins performed to date. This dataset provides the first extensive picture, to our knowledge, of mitochondrial proteins from wheat roots. Future research is required on quantitative analysis of the wheat mitochondrial proteomes at the spatial and developmental level.

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임계면법을 이용한 횡등방성 암석의 강도 예측 (Prediction of Strength for Transversely Isotopic Rock Based on Critical Plane Approach)

  • 이연규
    • 터널과지하공간
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    • 제17권2호
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    • pp.119-127
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    • 2007
  • 임계면법을 적용하여 횡등방성 암석의 강도이방성을 해석하는 방법을 제안하였다. 암석의 파괴는 Hoek-Brown 파괴기준을 따르는 것으로 가정하였다. Hoek-Brown의 경험적 파괴기준식에 대응되는 Mohr 포착선식을 이용하고 강도상수인 m과 s를 방향에 따른 스칼라 함수로 정의하여 이방성 파괴함수를 구성하였다. 이방성 파괴함수를 최대고 하는 임계면의 방향을 찾기 위하여 직접 최적화기법의 하나인 공액구배법을 적용하였다. 횡등방성 안석에 대한 기존 이방성 강도모델이 대부분 삼축압축실험과 동일한 응력조건에서만 적용할 수 있는데 반하여 이 연구에서 제안된 방법은 일반적인 3차원 응력조건에도 쉽게 적용할 수 있다는 장점을 가지고 있다. 삼축압축실험의 모사를 통하여 얻어진 삼축압축강도와 파괴면의 경사에 분석을 통하여 제안된 방법의 적합성을 검토하였다.

배추흰나비 과립병바이러스의 정제 및 병원성 (Purification and Pathogenicity of the Granulosis Viruses of Common Cabbage Worm, Pieris rapae and Pieris brassicae)

  • 류강선;김근영;강석원
    • 한국응용곤충학회지
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    • 제30권3호
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    • pp.187-195
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    • 1991
  • 배추흰나비 P. rapae와 P. brassicae GV의 정제조건, 형태 및 P. rapae 유충을 숙주로한 병원성을 비교하였다. 바이러스봉입체 자당밀도구배원심법(52,000g, 2시간)으로 정제하여 순도 높은 바이러스를 얻을 수 있었다. 봉입체의 크기는 P. rapae GV의 경우 396$\pm$38$\times$238$\pm$25nm, P. brassicae GV의 375$\pm$40$\times$255$\pm$28nm였으며, 바이러스 입자는 P. rapae GV가 250-275$\times$63-73 nm이며, P. brassicae GV가 243-250$\times$63-75 nm였다. 한편 nucleocapsid는 P. rapae GV가 225$\times$31 nm, P. brassicae GV가 225$\times$29 nm로 관찰되었다. P. rapae를 숙주로 하여 P. rapae GV와 P. brassicae GV의 병원성을 검정한 결과, P. rapae GV의 {TEX}$LC_{50}${/TEX}(-log)식은 5.5673, P. brassicae GV의 경우는 5.8104로 P. brassicae GV의 병원성이 약간 간하게 나타났으며, {TEX}$LT_{50}${/TEX}(바이러스농도 {TEX}$10^{-6}${/TEX})의 경우는 P. rapae GV는 8.17일 P.brassicae GV에서는 7.16일로 P. brassicae GV에서 약간 짧았다.

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