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排序方式: 共有10000条查询结果,搜索用时 281 毫秒
821.
T Tagami K Tanaka H Sugawa H Nakamura Y Miyoshi T Mori K Nakao 《Canadian Metallurgical Quarterly》1996,43(6):689-699
MIcrospheres containing diclofenac sodium (DS) were prepared using carboxymethylcellulose (CMC) as the main support material (1.0, 2.0, 3.0% (w/v)) and aluminum chloride as the crosslinker. Drug to polymer ratios of 1:1, 1:2 and 1:4 were used to obtain a range of microspheres. The microspheres were then coated with an enteric coating material, Eudragit S-100, efficiency, % yield value, particle sizes an in-vitro dissolution behaviour were investigated. The surface of the enteric coated microspheres seemed to be all covered with Eudragit S-100 from scanning electron microscopy observation. It was also observed that increasing the CMC concentration led to an increase in the encapsulation efficiency, % yield value and particle size and decreased the release rate. Eudragit S-100 coating did not significantly alter the size but the release rate was significantly lower even when the lower concentration solution was used. 相似文献
822.
M Suda K Tanaka K Natsui T Usui I Tanaka M Fukushima C Shigeno J Konishi S Narumiya A Ichikawa N Nakao 《Canadian Metallurgical Quarterly》1996,137(5):1698-1705
PGE2 is one of the key molecules in the osteoblast. It is the major prostanoid in the bone, and its production is under the control of both systemic and local factors. PGE2 has been reported to have multiple actions in the osteoblast, such as growth promotion and cell differentiation. To better understand the action of PGE2 in the osteoblast, we determined the PGE receptor subtypes in MC3T3-E1, an osteoblastic cell line derived from the normal mouse calvaria. Northern blot analysis revealed that EP1 and EP4 subtypes are expressed in MC3T3-E1. In contrast, EP3 subtype was not detected by either Northern blot analysis or RT-PCR. The contribution of each subtype was evaluated by studying the effects of subtype-specific analogs on osteoblastic function at confluency and 5 days after confluency. An EP1 agonist, 17-phenyl-omega-trinor PGE2, increased DNA synthesis and decreased alkaline phosphatase activity. 11-Deoxy-PGE1, and EP2 and EP4 agonist, decreased DNA synthesis and increased alkaline phosphatase activity at both stages. Butaprost, an EP2-selective agonist, showed effects similar to those of 11-deoxy-PGE1 only at confluency. Another and more differentiated osteoblastic marker, osteocalcin production, was detectable and was stimulated by 11-deoxy-PGE1 only 5 days after confluency. The exposure of these cells to EP1 agonist changed the cell shape to a more fibroblastic appearance. These results indicate that EP1, EP4, and probably EP2 are present in MC3T3-E1 cells; EP1 promotes cell growth, and EP2 and EP4 mediate differentiation of the osteoblast. Furthermore, the decreased response to EP2-specific agonist 5 days after confluency suggests that the expression of PGE receptor subtype is dependent on the stage of osteoblastic differentiation. This is the first report to determine PGE receptor subtypes in the bone. 相似文献
823.
C Botschev B Bondy M Hofmann T Kircher F Müller-Spahn 《Canadian Metallurgical Quarterly》1996,40(3):203-207
We describe a rapid and specific differential amplification system which can detect five of the most common cystic fibrosis mutations from a single cell. In the first round of the polymerase chain reaction (PCR), regions of exons 4, 10 and 11 of the cystic fibrosis transmembrane conductance regulator (CFTR) gene containing the mutations delta F508, G551D, R553X, G542X and 621+1G > T were co-amplified in a single multiplex PCR. To identify potential contamination, we included external amplification primers for the polymorphic human tyrosine hydroxylase (HUMTH01) locus as a fingerprint for the sample. In the second round of PCR, detection of any of the five mutations was achieved using the amplification refractory mutation system (ARMS) in two separate reactions, each containing nested amplification primers for either wild type or mutant sequence. A separate second round PCR for the fingerprinting was performed with nested HUMTH01 primers. Using this procedure we have successfully and accurately detected five cystic fibrosis mutations in 30 single cells with a failed amplification rate of 7% and a contamination rate of 4.6% and that PCR failure or possible contamination will also be easily detected. This procedure allows detection of the five most common point mutations and small deletions responsible for cystic fibrosis from a single cell in < 8 h which could be applicable to preimplantation diagnosis in human embryos. 相似文献
824.
Improving the performance of microstrip-patch antennas 总被引:1,自引:0,他引:1
This paper describes a cavity-backed patch-antenna geometry, which features multiple dielectric layers and shorting posts. These features are exploited to design antennas which retain many of the desirable characteristics of conventional microstrip antennas, yet overcome some of their inherent disadvantages 相似文献
825.
Amador F.G. Berman D. Borning A. DeRose T. Finkelstein A. Neville D. Notkin D. Salesin D. Salisbury M. Sherman J. Sun Y. Weld D.S. Winkenbach G. 《Knowledge and Data Engineering, IEEE Transactions on》1993,5(4):611-618
The electronic encyclopedia exploratorium (E3) is a vision of a future computer system-an electronic book describing how thing work. Typical articles in E3 will describe such mechanisms as compression refrigerators, engines, telescopes, and mechanical linkages. Each article will provide simulations, three-dimensional animated graphics that the user can manipulate, laboratory areas that allow a user to modify the device or experiment with related artifacts, and a facility for asking questions and receiving customized, computer-generated English-language explanations. Some of the foundational technology is discussed, focusing on topics in artificial intelligence, graphics, and user interfaces. The initial prototype system and the technical lessons learned from it, as well as the second prototype currently under construction, are described 相似文献
826.
An analysis of a wide rectangular radiating slot excited by a microstrip line is described. Coupled integral equations are formulated to find the electric current distribution on the feed line and the electric field in the aperture. The solution is based on the method of moments and using the space domain Sommerfeld-type Green's function. The information about the input impedance or reflection coefficient is extracted from the electric current distribution on the microstrip line utilizing the matrix pencil technique. The theoretical analysis is described and data are presented and compared with other theoretical and experimental results 相似文献
827.
Perez A.T. Vazquez P.A. Castellanos A. 《Industry Applications, IEEE Transactions on》1995,31(4):761-767
The physical system to be considered is a blade-plane configuration in a dielectric liquid. For high electric fields, injection from the blade takes place with ions of the same polarity. The Coulomb force acting upon the injected charges originates an electrohydrodynamic (EHD) flow, referred in what follows as the charged jet. A laminar solution of this EHD jet is obtained using similarity analysis. If transport of charge is dominated by convection, i.e., neglecting molecular diffusion and ion drift, and the electric field is assumed constant, the problem is mathematically equivalent to the bidimensional thermal plume in the limit of large Prandtl numbers. The authors examine the stability of this EHD jet using linear theory and parallel-flow approximations. Neutral stability curves are computed numerically in terms of a nondimensional parameter which is the electrical analogous to the Grashof number. Finally, some experimental observations are presented, followed by a short discussion. The role played by the viscosity correlates reasonable well with the theoretical analysis 相似文献
828.
The authors highlight several possible ways in which the construction industry could lower present emissions of the greenhouse gas, carbon dioxide. It is an excellent discussion document and is recommended reading. 相似文献
829.
830.
The mechanism of “475°C embrittlement” of a duplex stainless steel was investigated using finite element modelling of the stress distribution at brittle fracture initiation. Brittle fracture initiated at a critical shear stress, which increased with ferrite hardness. The fracture stress was affected by the duplex microstructure. Fracture was nucleated by deformation twins, which were identified using electron back-scatter diffraction. The ductile-to-brittle fracture transition was sensitive to age-hardening and could be described simply by the effect of age-hardening and test temperature on the yield stress. 相似文献