41,461 research outputs found
Effect of heat treatment on the microstructural change of syndiotactic polystyrene/poly (styrene-co-vinyloxazolin)/clay nanocomposite
No full textThe fabrication of a syndiotactic polystyrene (sPS)/organoclay nanocomposite was conducted via a stepwise mixing process using poly(styrene-co-vinyloxazolin) (OPS), i.e. melt intercalation of OPS into organoclay followed by blending with sPS. The effects of several parameters. including type of organoclay and mixing temperature on the microstructure of the nanocomposite were investigated through Xray diffraction patterns and rheological properties. The microstructure of the nanocomposite mainly depended on the arrangement type of the organic modifiers in the clay gallery. Using organoclays having lateral a bilayer arrangement exfoliated structure was obtained, whereas intercalated structure were obtained when organoclay with a paraffinic monolayer arrangement was employed in our sPS/OPS/organoclay system. In this work, a simple heat treatment on a previously prepared OPS/organoclay nanocomposite induced microstructural evolution with a favorable direction from intercalation to exfoliation. This phenomenon is attributed to a strong interaction between OPS and the clay surfaces, which is revealed by plateau behavior of the storage modulus in rheological properties. When heat is applied to the OPS/organoclay, the OPS chains and clay layers move together by promoted thermal motion of OPS chains, which results in disordering of stacked clay layers and exfoliation. (C) 2003 Elsevier Ltd. All rights reserved
Dual mode phase measurement for optical heterodyne interferometry
No full textWe present a new digital phase measuring scheme for optical heterodyne interferometry, which provides high measurable velocity up to 6 m s(-1) with a fine displacement resolution of 0.1 nm. The main idea is combining two distinctive digital phase measuring techniques with mutually complementary characteristics; one is counting the Doppler shift frequency with a 20 MHz beat frequency for high velocity measurement and the other is synchronous phase demodulation with a 2.0 kHz beat frequency for extremely fine displacement resolution. The two techniques are operated in switching mode in accordance with the object speed in a synchronized way. Experimental results prove that the proposed dual mode phase measuring scheme is realized with a set of relatively simple electronic circuits for beat frequency shifting, heterodyne phase detection and low-pass filtering
Kim, Ji Eun
No full text학위논문(박사)--아주대학교 일반대학원 :의학과,2014. 8ABSTRACT ⅰ
TABLE OF CONTENTS ⅱ
LIST OF FIGURES ⅲ
LIST OF TABLES ⅳ
Ⅰ. INTRODUCTION 1
Ⅱ. MATERIALS AND METHODS 2
STATISTICAL ANALYSIS 2
Ⅲ. RESULTS 4
Ⅳ. DISCUSSION 17
Ⅴ. CONCLUSION 20
REFERENCES 21
국문요약 25DoctoralFentanyl-induced cough (FIC) is often observed after intravenous bolus administration of fentanyl during anesthesia induction. This meta-analysis assessed the efficacy of pharmacological and non-pharmacological interventions to reduce the incidence of FIC. We searched for randomized controlled trials comparing the pharmacological or non-pharmacological interventions with the controls to prevent FIC; we included 28 studies retrieved from Pub-Med, Embase, and Cochrane Library. Overall incidence of FIC was approximately 31%. Lidocaine [odds ratio (OR) = 0.29, 95% confidence interval (CI) 0.21 –0.39], N-methyl-D-aspartate (NMDA) receptor antagonists [OR = 0.09, 95% CI 0.02 – 0.42], propofol [OR = 0.07, 95% CI 0.01 – 0.36], α2 agonists [OR = 0.32, 95% CI 0.21 – 0.48], β2 agonists [OR = 0.10, 95% CI 0.03 – 0.30], fentanyl priming [OR = 0.33, 95% CI 0.19 – 0.56], and slow injection of fentanyl [OR = 0.25, 95% CI 0.11 – 0.58)] were effective in decreasing the incidence of FIC, whereas atropine [OR = 1.10, 95% CI 0.58 – 2.11] and benzodiazepines [OR = 2.04, 95% CI 1.33 – 3.13] were not effective. This meta-analysis found that lidocaine, NMDA receptor antagonists, propofol, α2 agonists, β2 agonists, and priming dose of fentanyl were effective in preventing FIC, but atropine and benzodiazepines were not. Slow injection of fentanyl was effective in preventing FIC, but results depend on the speed of administration
Thermal and mechanical properties of syndiotactic polystyrene/organoclay nanocomposites with different microstructures
No full textThe fabrication of syndiotactic polystyrene (sPS)/organoclay nanocomposite was conducted via a stepwise mixing process with poly(styrene-co-vinyloxazolin) (OPS), that is, melt intercalation of OPS into organoclay followed by blending with sPS. The microstructure of nanocomposite mainly depended on the arrangement type of the organic modifier in clay gallery. When organoclays that have a lateral bilayer arrangement were used, an exfoliated structure was obtained, whereas an intercalated structure was obtained when organoclay with a paraffinic monolayer arrangement were used. The thermal and mechanical properties of sPS nanocomposites were investigated in relation to their microstructures. From the thermograms of nonisothermal crystallization and melting, nanocomposites exhibited an enhanced overall crystallization rate but had less reduced crystallinity than a matrix polymer. Clay layers dispersed in a matrix polymer may serve as a nucleating agent and hinder the crystal growth of polymer chains. As a comparison of the two nanocomposites with different microstructures, because of the high degree of dispersion of its clay layer the exfoliated nanocomposite exhibited a faster crystallization rate and a lower degree of crystallinity than the intercalated one. Nanocomposites exhibited higher mechanical properties, such as strength and stiffness, than the matrix polymer as observed in the dynamic mechanical analysis and tensile tests. Exfoliated nanocomposites showed more enhanced mechanical properties than intercalated ones because of the uniformly dispersed clay layers. (C) 2004 Wiley Periodicals, Inc
ANALYSIS ON THE APPARENT SLIP AND DEPLETED LAYER OF POLYMER FLOW IN NARROW-BORE CAPILLARIES
No full textPolymer solutions flowing through small-diameter capillaries of which length scale is much larger than that of polymers were experimentally demonstrated to have the enhanced flow rate as compared to in bulk flow. This apparent slip phenomenon was analyzed by obtaining the slip velocity and concentration depleted layer thickness. Hydrolyzed polyacrylamide (HPAM) of highly flexible polymer and Xanthan of rigid rodlike polymer were made to flow through stainless steel capillaries having the diameter range of about 100 to 250 mum. The results showed that both slip velocity and depleted layer thickness decreased markedly with increasing polymer concentration. This behavior can be interpreted as being due to the reduction of diffusion coefficient and flexibility of polymer chains as the concentration is increased. The depleted layer thickness of HPAM was much larger than the polymeric length scale and was shown to increase with increasing wall shear stress. This is considered as an evidence of the stress-induced diffusion of polymer chains being a dominant factor for the apparent slip of flexible polymer solution. On the other hand, the depleted layer thickness of Xanthan solution was almost constant with the wall shear stress, which can not be explained by the stress-induced diffusion mechanism alone
Predictive Value of Urinary KIM-1, TIMP-2 and sTREM-1 for Contrast-Induced Acute Kidney Injury in Elderly Patients After Percutaneous Coronary Intervention
No full textWu Huang, Rong Wang, Ping Zhang Department of Geriatric Medicine, The Second Xiangya Hospital of Central South University, Changsha, Hunan, 410011, People’s Republic of ChinaCorrespondence: Rong Wang, Department of Geriatric Medicine, The Second Xiangya Hospital of Central South University, 139 Renmin Middle Road, Changsha, Hunan, 410011, People’s Republic of China, Tel +86-0731-85295173, Email [email protected]: We aimed to address the predictive value of urinary kidney injury molecule-1 (KIM-1), tissue inhibitor of metalloproteinases-2 (TIMP-2) and soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) for contrast-induced acute kidney injury (CI-AKI) in elderly patients after percutaneous coronary intervention (PCI).Methods: One hundred thirty-six patients who underwent PCI were separated into the CI-AKI group (n = 36) and the non-CI-AKI group (n = 100) based on CI-AKI occurrence after operation, and their general data were collected. Blood and urine specimens were collected before operation (at the time of admission) and 6 h, 12 h, 24 h and 48 h after the operation and preserved for future use. Serum creatinine (Scr) levels were tested and an estimated glomerular filtration rate (eGFR) was counted. Urinary KIM-1, TIMP-2 and sTREM-1 levels were assessed and the preoperative and general data as well as postoperative urinary KIM-1, TIMP-2 and sTREM-1 levels were compared. The early diagnostic value of urinary KIM-1, TIMP-2 and sTREM-1 at 6 hours postoperatively for CI-AKI was analyzed by receiver operating characteristic (ROC) curve.Results: After 48 h of operation, Scr in the CI-AKI group was higher versus the non-CI-AKI group. At 24 h and 48 h postoperatively, eGFR in the CI-AKI group was lower versus the non-CI-AKI group; urinary KIM-1 and sTREM-1 in the CI-AKI group were higher in contrast to the non-CI-AKI group; TIMP-2 in the CI-AKI group was higher versus that in the non-CI-AKI group. ROC curve analysis showed that the areas under the curve (AUCs) for urine KIM-1, TIMP-2, and sTREM-1 in diagnosing CI-AKI at 6 hours postoperatively were 0.852 (95% CI: 0.768– 0.936), 0.810 (95% CI: 0.723– 0.898), and 0.874 (95% CI: 0.804– 0.943), and the cut-off values were 45.93 ng/L, 1.63 ng/mL, and 61.48 ng/L, respectively, with sensitivities of 66.70%, 58.30%, and 72.20%, and specificities of 95.00%, 93.00%, and 91.00%, respectively (all P < 0.05).Conclusion: Urinary KIM-1, TIMP-2 and sTREM-1 can respond to early changes in renal function after PCI and have good application value in the early diagnosis of CI-AKI.Keywords: percutaneous coronary intervention, kidney injury molecule-1, tissue inhibitor of metalloproteinases-2, soluble triggering receptor expressed on myeloid cells-1, contrast-induced acute kidney injur
Synthesis and material properties of syndiotactic polystyrene/organophilic clay nanocomposites
No full textSyndiotactic polystyrene (sPS)/organophilic clay nanocomposites were fabricated by direct-melt intercalation method. To overcome the thermal instability of organophilic clay at high-melt processing temperatures of sPS, an organophilic clay modified by alkyl phosphonium was adopted, which is known to be thermally stable. By using the newly synthesized clay, we could fabricate sPS intercalated nanocomposites. The microstructures of nanocomposites were confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The crystallization rate of nanocomposites investigated by differential scanning calorimetry (DSC) does not increase despite the presence of clay, which may be due to the physical hindrance of organic modifiers in the clay dispersion. Nanocomposites exhibited enhanced mechanical properties such as strength and stiffness relative to the virgin polymer. In addition, thermal stability was confirmed to be improved by thermogravimetric analysis (TGA). (C) 2004 Wiley Periodicals, Inc
Phased RGSS: An improved disk array scheduling for continuous media retrieval
No full textThis paper proposed a disk array scheduling algorithm called Phased RGSS which improves the initial service latency over RGSS presented by Kang and Park [IEICE Trans. Inform. Systems E81-D (8) (1998)] without increasing the buffer requirement for jitter-free service for continuous media retrieval. A specific data layout should be provided in order for Phased RGSS to be applied. The data layout makes disk arm movement more effective. The characteristics of Phased RGSS are proved by analysis of buffer requirement as well as initial startup delay. (C) 2001 Elsevier Science B.V. All rights reserved.X11sciescopu
Balanced RM2: An improved data placement scheme for tolerating double disk failures in disk arrays
No full textThere is a growing demand for high data reliability beyond what current RAIDs can provide and users need various levels of data reliability. In order to meet these requirements, an efficient data placement scheme called RM2 has been proposed in [1], which enables a disk array system to tolerate double disk failures. However, RM2 has high data reconstruction overhead due to data dependency between parity groups in the case of double disk failures, suffering from large performance fluctuation according to disk failure patterns. To minimize the reconstruction overhead, this paper presents an improved data placement scheme called Balanced RM2. Experimental results show that the performance fluctuation of the Balanced RM2 becomes much less than that of the RM2 regardless of read or write. It is also shown that Balanced RM2 provides better performance than RM2 by 5 similar to 20% in the case of double disk failures.X11sciescopu
mNFS: Multicast-based NFS cluster
No full textNFS is a distributed file system which is widely used in UNIX environments. Many studies have been worked to improve its I/O performance and scalability. However, existing architectures, which have either single load balancer or meta server, could suffer from single-point-of-failure and unnecessary network delay. We propose a new NFS architecture called mNFS cluster to improve its scalability. Experimental results show that mNFS outperforms both Linux NFS and NFSp by 64% and 99%, respectively.X11sciescopu
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