• Steel and Composite Structures
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• 제49권6호
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• pp.603-614
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• 2023

In this paper, frequency analysis of curved functionally graded (FG) nanobeam by consideration of deepness effect has been studied. Differential transform method (DTM) has been used to obtain frequency responses. The nonlocal theory of Eringen has been applied to consider nanoscales. Material properties are supposed to vary in radial direction according to power-law distribution. Differential equations and related boundary conditions have been derived using Hamilton's principle. Finally, by consideration of nonlocal theory, the governing equations have been derived. Natural frequencies have been obtained using semi analytical method (DTM) for different boundary conditions. In order to study the effect of deepness, the deepness term is considered in strain field. The effects of the gradient index, radius of curvature, the aspect ratio, the nonlocal parameter and interaction of aforementioned parameters on frequency value for different boundary conditions such as clamped-clamped (C-C), clamped-hinged (C-H), and clamped-free (C-F) have been investigated. In addition, the obtained results are compared with the results in previous literature in order to validate present study, a good agreement was observed in the present results.

• Asian-Australasian Journal of Animal Sciences
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• 제30권7호
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• pp.957-966
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• 2017

Objective: To understand the dynamic structure, function, and influence on nutrient metabolism in hosts, it was crucial to assess the genetic potential of gut microbial community in yaks of different ages. Methods: The denaturing gradient gel electrophoresis (DGGE) profiles and Illumina-based metagenomic sequencing on colon contents of 15 semi-domestic yaks were investigated. Unweighted pairwise grouping method with mathematical averages (UPGMA) clustering and principal component analysis (PCA) were used to analyze the DGGE fingerprint. The Illumina sequences were assembled, predicted to genes and functionally annotated, and then classified by querying protein sequences of the genes against the Kyoto encyclopedia of genes and genomes (KEGG) database. Results: Metagenomic sequencing showed that more than 85% of ribosomal RNA (rRNA) gene sequences belonged to the phylum Firmicutes and Bacteroidetes, indicating that the family Ruminococcaceae (46.5%), Rikenellaceae (11.3%), Lachnospiraceae (10.0%), and Bacteroidaceae (6.3%) were dominant gut microbes. Over 50% of non-rRNA gene sequences represented the metabolic pathways of amino acids (14.4%), proteins (12.3%), sugars (11.9%), nucleotides (6.8%), lipids (1.7%), xenobiotics (1.4%), coenzymes, and vitamins (3.6%). Gene functional classification showed that most of enzyme-coding genes were related to cellulose digestion and amino acids metabolic pathways. Conclusion: Yaks' age had a substantial effect on gut microbial composition. Comparative metagenomics of gut microbiota in 0.5-, 1.5-, and 2.5-year-old yaks revealed that the abundance of the class Clostridia, Bacteroidia, and Lentisphaeria, as well as the phylum Firmicutes, Bacteroidetes, Lentisphaerae, Tenericutes, and Cyanobacteria, varied more greatly during yaks' growth, especially in young animals (0.5 and 1.5 years old). Gut microbes, including Bacteroides, Clostridium, and Lentisphaeria, make a contribution to the energy metabolism and synthesis of amino acid, which are essential to the normal growth of yaks.

• Journal of Pharmaceutical Investigation
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• 제25권3호spc1호
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• pp.7-20
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• 1995

Taurine, a ${\beta}-amino$ acid, plays an important role as a neuromodulator and is necessary for the normal development of the brain. Since de novo synthesis of taurine in the brain is minimal and in vivo studies suggest that taurine dose not cross the blood-brain barrier, we examined whether the choroid plexus, the blood-cerebrospinal fluid (CSF) barrier, plays a role in taurine transport in the central nervous system. The uptake of $[^3H]-taurine$ into ATP depleted choroid plexus from rabbit was substantially greater in the presence of an inwardly directed $Na^+$ gradient taurine accumulation was negligible. A transient in side-negative potential gradient enhanced the $Na^+-driven$ uptake of taurine into the tissue slices, suggesting that the transport process is electrogenic, $Na^+-driven$ taurine uptake was saturable with an estimated $V_{max}$ of $111\;{\pm}\;20.2\;nmole/g/15\;min$ and a $K_M\;of\;99.8{\pm}29.9\;{\mu}M$. The estimated coupling ratio of $Na^+$ and taurine was $1.80\;{\pm}\;0.122.$ $Na^+-dependent$ taurine uptake was significantly inhibited by ${\beta}-amino$ acids, but not by ${\alpha}-amino$ acids, indicating that the transporter is selective for ${\beta}-amino$ acids. Since it is known that the physiological concentration of taurine in the CSF is lower than that in the plasma, the active transport system we characterized may face the brush border (i.e., CSF facing) side of the choroid plexus and actively transport taurine out of the CSF. Therefore, we examined in vivo elimination of taurine from the CSF in the rat to determine whether elimination kinetics of taurine from the CSF is consistent with the in vitro study. Using a stereotaxic device, cannulaes were placed into the lateral ventricle and the cisterna magna of the rat. Radio-labelled taurine and inulin (a marker of CSF flow) were injected into the lateral ventricle, and the concentrations of the labelled compounds in the CSF were monitored for upto 3 hrs in the cisterna magna. The apparent clearance of taurine from CSF was greater than the estimated CSF flow (p<0.005) indicating that there is a clearance process in addition to the CSF flow. Taurine distribution into the choroid plexus was at least 10 fold higher than that found in other brain areas (e. g., cerebellum, olfactory bulb and cortex). When unlabelled taurine was co-administered with radio-labelled taurine, the apparent clearance of taurine was reduced (p<0.0l), suggesting a saturable disposition of taurine from CSF. Distribution of taurine into the choroid plexus, cerebellum, olfactory bulb and cortex was similarly diminished, indicating that the saturable uptake of taurine into these tissues is responsible for the non-linear disposition. A pharmacokinetic model involving first order elimination and saturable distribution described these data adequately. The Michaelis-Menten rate constant estimated from in vivo elimination study is similar to that obtained in the in vitro uptake experiment. Collectively, our results demonstrate that taurine is transported in the choroid plexus via a $Na^+-dependent,saturable$ and apparently ${\beta}-amino$ acid selective mechanism. This process may be functionally relevant to taurine homeostasis in the brain.

• 한국재료학회지
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• 제3권3호
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• pp.261-271
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• 1993

4.5 Pb($Zn_{1/3}Nb_{2/3})O_3-40.5Pb(Ni_{1/3}Nb_{2/3})O_3$-55PZT와 PLZT(10/70/30, 11/60/40)를 경사조성으로 하여 경사기능 재료를 제조하였으며, 그 유전 특성과 압전 변형율 특성을 조사하였다. 경사기능재료는 A/B/A의 세층으로 성형하고 소결한 후 한 층을 연마해내어 제작하였다. 닥터블레이드용 슬립에는 acrylic계 유기 결합제가 34-36wt% 혼합되었으며, 건조 후 균열이 없는 양호한 thick film을 제조하였다. $1250^{\circ}C$, 2시간의 소성에 의해 경사기능화된 시편은 Nb와 La등의 조성 차이에 의한 구배를 이루었으며, 구배영역은 약 30${\mu}$m 정도였다. 경사기능재료에서 유전상수나 큐리온도롸 같은 유전특성은 조합한 조성층의 특성들사이의 값을 나타내었다. 인가 전압에 따른 변형율 특성은 단일 조성의 시편보다 현저하게 증가하였다. 실제로 경사기능 압전엑튜에이터를 제조한 결과 약 3${\mu}$m/100V 정도의 변위향을 나타내었다.

• Steel and Composite Structures
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• 제21권1호
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• pp.1-36
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• 2016

In the present study, the nonlinear magneto-electro-mechanical free vibration behavior of rectangular double-bonded sandwich microbeams based on the modified strain gradient theory (MSGT) is investigated. It is noted that the top and bottom sandwich microbeams are considered with boron nitride nanotube reinforced composite face sheets (BNNTRC-SB) with electrical properties and carbon nanotube reinforced composite face sheets (CNTRC-SB) with magnetic fields, respectively, and also the homogenous core is used for both sandwich beams. The connections of every sandwich beam with its surrounding medium and also between them have been carried out by considering Pasternak foundations. To take size effect into account, the MSGT is introduced into the classical Timoshenko beam theory (CT) to develop a size-dependent beam model containing three additional material length scale parameters. For the CNTRC and BNNTRC face sheets of sandwich microbeams, uniform distribution (UD) and functionally graded (FG) distribution patterns of CNTs or BNNTs in four cases FG-X, FG-O, FG-A, and FG-V are employed. It is assumed that the material properties of face sheets for both sandwich beams are varied in the thickness direction and estimated through the extended rule of mixture. On the basis of the Hamilton's principle, the size-dependent nonlinear governing differential equations of motion and associated boundary conditions are derived and then discretized by using generalized differential quadrature method (GDQM). A detailed parametric study is presented to indicate the influences of electric and magnetic fields, slenderness ratio, thickness ratio of both sandwich microbeams, thickness ratio of every sandwich microbeam, dimensionless three material length scale parameters, Winkler spring modulus and various distribution types of face sheets on the first two natural frequencies of double-bonded sandwich microbeams. Furthermore, a comparison between the various beam models on the basis of the CT, modified couple stress theory (MCST), and MSGT is performed. It is illustrated that the thickness ratio of sandwich microbeams plays an important role in the vibrational behavior of the double-bonded sandwich microstructures. Meanwhile, it is concluded that by increasing H/lm, the values of first two natural frequencies tend to decrease for all amounts of the Winkler spring modulus.

• Preventive Nutrition and Food Science
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• 제3권3호
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• pp.211-215
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• 1998

Preparative isolation of lipid granules from Fhodotorula glutinis, which has been studied for long time to produce edible lipids, was carried out by flotation method in Ficoll-Linear density gradient. When the isolated lipid granules were suspended in a series of solutions containing varying concentration of osmotic stabilizer (sorbitoal and mannitol) ranging from 0.8M to 0M, the lipid granules appeared to be disrupted at a concentration between 0.8M and 0.7, and again at a concentration below 0.1M, suggesting that lipid granules have a membraneous structure and that at least two types of lipid granules are present. Compositional analysis of lipids from lipid granules revealed that lipids are composed mainly of neutral lipids (87.8% of total lipids), predominantly as triacylglycerols (71.89%). Marked differences were observed inphospholipids between lipids of lipid granules and those of whole cells . The major components of phospholipids in lipid granules and inwhole cells are phosphatidylcholine(38.6%) and phosphatidylserine(42.8%), respectively. In addition, significant differences were also observed in the fatty acid composition of phospholipids. As phospholipids are important structural components of membranes, these differences lead to the suggesting that the membrane of lipid granules may be distinct functionally and structurally from other membranes of yeast cells. The major fatty acid components of neutral lipidss of whole cells and lipid granules are palmitic , oleic and linoleic acid. However , degreeof fatty acid unsaturation of neutal lipids of lipid granules was much lower than that of neutral lipids of whole cells.

• 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.

• Structural Engineering and Mechanics
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• 제64권3호
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• pp.361-379
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• 2017

In this article, the vibration behavior of double-bonded sandwich microplates with homogeneous core and nanocomposite facesheets reinforced by carbon nanotube and boron nitride nanotube under multi physical fields such as 2D magnetic and electric fields is investigated. Symmetric and un-symmetric distributions of nanotubes are considered for facesheets of sandwich microplates such as uniform distribution and various functionally graded distributions. The double-bonded sandwich microplates rest on visco-Pasternak foundation. Material properties of sandwich microplates are obtained by the extended rule of mixture. The sinusoidal shear deformation theory (SSDT) is employed to describe displacement fields of sandwich microplates. Also, the dimensionless natural frequency is obtained by classical plate theory (CPT) and compared with the obtained results by SSDT. It can be seen that the obtained dimensionless natural frequencies by CPT are higher than SSDT. In order to study the material length scale parameters, modified strain gradient theory at micro scale is utilized and then, the equations of motion are derived using Hamilton's principle. The effects of different parameters such as foundation parameters including Winkler, shear layer and damping coefficients, various distributions and volume fraction of nanotubes, core to facesheet thickness ratio, aspect and side ratios on the dimensionless natural frequencies are discussed in details. The results of present work can be used to optimum design and control of similar systems such as micro-electro-mechanical and nano-electro-mechanical devices.

• Composites Research
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• 제16권3호
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• pp.68-74
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• 2003

본 논문에서는 Ni과 Al 금속박판 사이의 자전고온반응을 이용한 금속간화합물/금속 적층복합재료의 제조시 제조공정 조건이 최종 미세조직에 미치는 영향을 연구하였다. 열분석을 통하여 Ni과 Al사이의 반응은 먼저 NiA1$_3$가 핵생성­성장 기구에 의해 생성된 후 다시 Ni$_2$A1$_3$로 확산변태됨을 확인하였다. 자전고온반응을 열역학적으로 해석하여 금속박판의 두께비(Ni:Al) 및 반응전 열처리와 반응후 미세조직에서 잔류한 Al의 부피분율과의 관계를 정립하였다. 후열처리 공정에 의해 Ni/Nl$_3$Al/NiAl의 적층구조와 각 두께비에서 82%(1:1), 59.5%(2:1), 40%(4:1)의 부피분율을 가지는 금속간화합물/금속적층복합재료를 얻을 수 있었다.

• 한국항공우주학회지
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• 제47권4호
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• pp.309-318
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• 2019

한국형 달 궤도선(Korea Pathfinder Lunar Orbiter, KPLO)에 탑재되는 달 표면지형 광학관측기(Lunar Terrian Imager, LUTI)의 열설계를 수행하고, 열해석을 통하여 열설계의 건전성을 검증하였다. 달 임무궤도의 열환경은 지구궤도와 달리 달 표면의 IR 복사가 중요하므로 이를 열설계에 반영하여야 한다. 위성 외부에 노출되는 부품이나 모듈은 가능한 MLI로 단열시키지만 경통이나 방열판은 기능상 노출되므로 복사형상계수의 개념을 이용한 thermal shield를 전면에 장착함으로써 IR 복사를 완화시킨다. 태양복사를 거의 받지 않는 방열판의 전면부는 IR 방사율이 중요하며, 경통과 같이 열변형에 취약한 부품은 복사히터를 사용하여 온도구배를 최소화시킨다. 열해석 결과분석을 통하여 LUTI의 열설계는 다양한 상황에서 안정적임을 확인하였다.