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排序方式: 共有439条查询结果,搜索用时 15 毫秒
421.
FM Santorelli SC Mak M El-Schahawi C Casali S Shanske TZ Baram RE Madrid S DiMauro 《Canadian Metallurgical Quarterly》1996,58(5):933-939
A novel G8363A mutation in the mtDNA tRNA(Lys) gene was associated, in two unrelated families, with a syndrome consisting of encephalomyopathy, sensorineural hearing loss, and hypertrophic cardiomyopathy. Muscle biopsies from the probands showed mitochondrial proliferation and partial defects of complexes I, III, and IV of the electron-transport chain. The G8363A mutation was very abundant (>95%) in muscle samples from the probands and was less copious in blood from 18 maternal relatives (mean 81.3% +/- 8.5%). Single-muscle-fiber analysis showed significantly higher levels of mutant genomes in cytochrome (c) oxidase-negative fibers than in cytochrome (c) oxidase-positive fibers. The mutation was not found in >200 individuals, including normal controls and patients with other mitochondrial encephalomyopathies, thus fulfilling accepted criteria for pathogenicity. 相似文献
422.
423.
Primer tRNAs for reverse transcription 总被引:2,自引:0,他引:2
424.
We show how to determine the value of methanol and ethanol as gasoline additives in the liquid-fuel market, where the alcohol-gasoline blends compete with unleaded clear gasolines. It is found that the clear gasolines are cheaper to produce than the alcohol blends of equivalent octane under the same refinery constraints. The results are based on the use of a combined model of the oil-refining and transportation sectors with optimised refinery operation and transport fleet. In the context of the national lead phaseout program, optimisation provided a viable route to producing the unleaded gasoline without recourse to alcohol-blending, while investment in heavy-end processing and isomerisation capacity increases the economic advantage of this route. 相似文献
425.
Intracranial controlled release polymers have been used for drug delivery to the brain, bypassing the blood brain barrier (BBB). By understanding the rates and patterns of transport in the local tissues, it is possible to design delivery systems that provide the optimal spatial and temporal pattern of chemotherapy within the intracranial space. This paper reviews the kinetics of drug release from polymeric controlled release implants, and describes the fate of drug molecules following release into the brain interstitium. Potential improvements in drug delivery based on the understanding of the mechanisms of drug release, transport and elimination are discussed. 相似文献
426.
TWACS?, A Power Line Communication Technology for Power Distribution Network Control and Monitoring 总被引:1,自引:0,他引:1
The vital issues pertaining to Distribution Automation in the light of the TWACS? Communication Technology are presented and discussed in this paper. Reachability, selectivity, speed of response, link security, reliability, etc. which are vital for distribution automation functions from an operational standpoint, are impacted by distribution network conditions, configuration and the communication technology used. All the above issues are discussed in detail in this paper. 相似文献
427.
A production lot size inventory model for deteriorating items 总被引:3,自引:0,他引:3
K. L. Mak 《Computers & Industrial Engineering》1982,6(4):309-317
In this paper, an attempt has been made to develop a production lot size model which incorporates an unfilled-order backlog for an inventory system with exponential decaying items. Approximate expressions are obtained for the optimum production lot size, the production cycle time and the total cycle time. The theory is illustrated by considering a numerical example of this class. Also it is shown that earlier models developed by Ghare and Schrader [3] and Misra [5] can be obtained as particular cases by choosing appropriate values for the various parameters of the model. 相似文献
428.
We propose a medium access control protocol design for a vehicle to send safety messages to other vehicles. We develop a Quality-of-Service (QoS) model for safety messages that are consistent with the active vehicle safety systems literature. Each message has a range and useful lifetime. The QoS target has each message received with high probability within its specified lifetime by each vehicle within its specified range. The protocol design is based on rapidly rebroadcasting each message multiple times within its lifetime in combination with the 802.11 Distributed Coordination Function. This makes the design compatible with emerging standards for Dedicated Short-Range Communication. Six different design variations are proposed. We derive equations and develop a simulation tool to assess the performance of the designs. Using these, we identify the best and most easily implemented designs. Design performance depends on the number of rebroadcasts, power, modulation, coding, and vehicular traffic volumes. We show that under certain assumptions on the loss probability tolerated by safety applications, the design is able to transport safety messages in vehicular ad hoc networks 相似文献
429.
Hin Yu Mak Vladimir G. Chigrinov Hoi‐Sing Kwok 《Journal of the Society for Information Display》2007,15(7):527-531
Abstract— Two configurations, (i) a double‐cell‐gap twisted nematic (DTN) liquid‐crystal display (LCD) and (ii) a single‐cell‐gap twisted‐nematic (TN) liquid‐crystal display (LCD) using a twisted LC retarder, were optimized for transflective liquid‐crystal displays. For the DTN configuration, both the single‐cell‐gap approach and the double‐cell‐gap approach were considered. The optimized configurations exhibit a high contrast ratio, wide viewing angles, and achromatic (black/white) switching in both the transmissive and reflective modes. They are easy to fabricate and also possess a perfect dark state. Both are suitable for high‐quality transflective TFT‐LCDs. 相似文献
430.
K.L. Mak X.X. Wang 《The International Journal of Advanced Manufacturing Technology》2002,20(2):144-152
In this paper, an approach using the concept of genetic algorithms is proposed as a powerful but simple means of scheduling
the manufacturing operations of a virtual cellular manufacturing system (VCMS). A mathematical model is developed to describe
the characteristics of a VCMS, which includes the constraints related to the delivery due dates of the various products and
the maximum capacities of the manufacturing resources. The objectives are to set up virtual manufacturing cells and to formulate
feasible production schedules for all manufacturing operations, in order to minimise the total material and component travelling
distance incurred in manufacturing the products. A new genetic based scheduling algorithm is proposed as an optimisation tool
to determine the solution. The proposed algorithm differs from the conventional genetic algorithms in that the populations
of the candidate solutions consist of individuals from various age-groups, and each individual is incorporated with an age
attribute to enable its birth and survival rates to be governed by predefined ageing patterns. By generating the evolution
of the populations with the genetic operators of selection, crossover and mutation, the proposed approach provides excellent
results by maintaining a better balance between the exploitation and the exploration of the solution space, and thus improves
the computational speed and the solution quality. The condition ensuring stable search performance is also derived. The superiority
of the proposed algorithm is illustrated by solving the production-scheduling and cell-formation problems for a virtual cellular
manufacturing system, and the results are compared with those obtained by using a conventional optimisation technique. 相似文献