• Title/Summary/Keyword: Gradient envelope

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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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    • v.4 no.1
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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
    • Journal of The Korean Astronomical Society
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    • v.38 no.2
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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.

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

  • Choi, Hang;Yoon, Byung-Ick
    • Journal of the Earthquake Engineering Society of Korea
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    • v.26 no.5
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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
    • Journal of Aquaculture
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    • v.15 no.1
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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.

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

  • Nguyen, Hung N.;Kim, Jong-Myon
    • Journal of the Korea Society of Computer and Information
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    • v.18 no.7
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    • pp.23-35
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    • 2013
  • This paper proposes an effective technique that is used to automatically extract feature vectors from vibration signals for fault classification systems. Conventional mel-frequency cepstral coefficients (MFCCs) are sensitive to noise of vibration signals, degrading classification accuracy. To solve this problem, this paper proposes spectral envelope cepstral coefficients (SECC) analysis, where a 4-step filter bank based on spectral envelopes of vibration signals is used: (1) a linear predictive coding (LPC) algorithm is used to specify spectral envelopes of all faulty vibration signals, (2) all envelopes are averaged to get general spectral shape, (3) a gradient descent method is used to find extremes of the average envelope and its frequencies, (4) a non-overlapped filter is used to have centers calculated from distances between valley frequencies of the envelope. This 4-step filter bank is then used in cepstral coefficients computation to extract feature vectors. Finally, a multi-layer support vector machine (MLSVM) with various sigma values uses these special parameters to identify faulty types of induction motors. Experimental results indicate that the proposed extraction method outperforms other feature extraction algorithms, yielding more than about 99.65% of classification accuracy.

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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    • v.15 no.6
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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
    • Proceedings of the Korean Society of Crop Science Conference
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    • 2017.06a
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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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Prediction of Strength for Transversely Isotopic Rock Based on Critical Plane Approach (임계면법을 이용한 횡등방성 암석의 강도 예측)

  • Lee, Youn-Kyou
    • Tunnel and Underground Space
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    • v.17 no.2 s.67
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    • pp.119-127
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    • 2007
  • Based on the critical plane approach, a methodology far predicting the anisotropic strength ot transversely isotropic rock is Proposed. It is assumed that the rock failure is governed by Hoek-Brown failure criterion. In order to establish an anisotropic failure function, Mohr envelope equivalent to the original Hoek-Brown criterion is used and the strength parameters m, s are expressed as scalar functions of orientation. The conjugate gradient method, which is one of the robust optimization techniques, is applied to the failure function for searching the orientation giving the maximum value of the anisotropic function. While most of the existing anisotropic strength models can be applied only when the stress condition is the same as that of conventional triaxial compression test, the proposed model can be applied to the general 3-dimensional stress conditions. Through the simulation of triaxial compression tests for transversely isotropic rock sample, the validity of the proposed method is investigated by comparing the predicted triaxial strengths and inclinations of failure plane.

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

  • 류강선;김근영;강석원
    • Korean journal of applied entomology
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    • v.30 no.3
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    • pp.187-195
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    • 1991
  • This study was carried out to acquire some basic biological informations on the granulosis virus (GV) of Pieris rapae and Pieris brassicae. Purified fractions of GV capsules in an sucrose density gradient centrifugation yielded on homogenous and sharp peak without a shoulder. Electron microscopy revealed that GV capsules were mostly ovalglove in shape. P. rapae and P. rapae GV isolated from P. rapae comprised granules($396\pm38\times238\pm25nm$ for P. rapae GV. $375\pm40\times255\pm28nm$ for P. brassicae GV) which contained single virus particle. The virus particles were 250- $275{\times}63$ -73nm for P. rapae GV and 243-250 $\times$ 63-75nm for P. brassicae GV containing a nucleocapsid 225 $\times$ 31nm for P. rapae, 225 $\times$ 29nm for P. brassicae within an envelope. The virulent difference between the two viruses was very small in their virulence for P. rapae larvae showing the $LC_{50}$( -log) with 5.5673 for P. rapae GV and 5.8104 for P. brassicae GV. Also the $LT_{50}$ of the 3rd instar P. rapae larvae against $10^{-6}$ inoculum was 8.17 days for P. rapae GV and 7.16 days for P. brassicae GV.

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