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1.
Isolated rat hearts were subjected to 15, 45, or 60 minutes of global ischaemia and then fixed by perfusion at 37°C with glutaraldehyde containing various amounts of oxygen. This either had been bubbled with 100% oxygen (PO2 620 mm Hg) or with 100% nitrogen (PO2 40 mm Hg) immediately before use, or it had been routinely prepared and stored exposed to atmospheric oxygen (PO2 245 mm Hg). The ultrastructure of myocytes and endothelial cells subjected to 15 minutes of ischaemia was not affected by the treatment of the fixative. However, when the tissue subjected to longer periods of ischaemia was fixed with routinely prepared or oxygen-bubbled glutaraldehyde, ultrastructural changes characteristic of reoxygenation damage were uniformly evident in both the microvasculature and myocytes. These qualitatively distinct changes included mitochondrial swelling, cell swelling, endothelial bleb formation, and narrowing of capillary lumina. These abnormalities were not observed in tissue fixed with nitrogen-bubbled glutaraldehyde. These findings indicate that deliberate steps should be taken to reduce or eliminate dissolved oxygen from the fixatives used to study ischaemic tissues. Otherwise artefactual reoxygenation damage in vitro may occur and make valid ultrastructural interpretation difficult or impossible. 相似文献
2.
A microbubble-powered bioparticle actuator 总被引:4,自引:0,他引:4
Maxwell R.B. Gerhardt A.L. Toner M. Gray M.L. Schmidt M.A. 《Journal of microelectromechanical systems》2003,12(5):630-640
We present the results of a device that uses controllable microbubble actuation to manipulate bioparticles. In order to create a useful device for controlling the position of bioparticles, predictable microfluidic actuation is crucial. The goal of this project was to develop fundamental technology that can be used to manipulate single bioparticles (e.g., cells). We use a thermal bubble actuation method to accomplish this goal. Microbubbles have the advantages of relatively simple electronics and fabrication but can be difficult to control. In this paper, we describe two specific accomplishments: the use of micromachined nucleation cavities to precisely localize thermal bubbles and to achieve controllable bubble formation temperatures and bubble dissipation and the demonstration of controllable microbubbles in a new device for particle sorting. 相似文献
3.
Maxwell G.D. Kashyap R. Sherlock G. Collins J.V. Ainslie B.J. 《Electronics letters》1994,30(18):1486-1487
The authors report the first demonstration of a semiconductor external cavity waveguide laser, modulated at 2.5 Gbit/s over 100 km of standard optical fibre using a UV written grating in a planar silica waveguide as the feedback element 相似文献
4.
The widely used pretest–posttest design traditionally consists of a pretest and a posttest of equal lengths. However, greater statistical power can usually be achieved by using a posttest that is somewhat longer than the pretest. This article provides a method for calculating the optimal allocation of pretest and posttest assessment units so as to maximize power and presents the accompanying reduction in required sample size for a range of parameter values. When insufficient information is available to estimate the optimal location precisely, the effects of allocating 75% of the assessment units to the posttest are evaluated. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
5.
Pleros N. Zakynthinos P. Poustie A. Tsiokos D. Bakopoulos P. Petrantonakis D. Kanellos G.T. Maxwell G. Avramopoulos H. 《Optoelectronics, IET》2007,1(3):120-126
The use of discrete but interconnected SOA-MZI switches for performing logical and highly functional processing tasks, demonstrating the multi-functional potential of the photonic switching elements is discussed. An all-optical 3R burst-mode receiver consisting of four SOA-MZI switches and operating error-free with 40-Gb/s optical bursts, proving that interconnection of multiple switching units can lead to the realisation of key network node functionalities offering increased intelligence at the physical layer is presented. In order to allow for easier interconnectivity between the SOA-MZI switches and to provide compactness and cost effectiveness to the developed subsystems, the integration of multiple switches into the same platform is proposed. To this end, the implementation of the first integrated quadruple SOA-MZI switch array is reported, increasing the integration density level and reducing packaging and pigtailing costs. Finally, possible applications of integrated multiple switch arrays are discussed, indicating their suitability for producing compact circuits performing common processing tasks in a multi-wavelength environment, as well as their potential to lead to the development of an all-optical high-speed packet switched node by implementing critical packet switching functionalities in a compact and efficient way. 相似文献
6.
Isolated rat liver mitochondria were incubated under various metabolic conditions to determine their membrane potential (MMP) as measured continuously by a tetraphenylphosphonium (TPP+)-selective electrode. By flow cytometry, a parallel analysis of fluorescence emissions observing single mitochondria stained with the lipophilic cation 5,5',6,6'-tetrachloro-1,1'3,3'-tetraethylbenzimidazolcarbocyanine iodide (JC-1) revealed linear correlation between the median orange fluorescence (FL2) due to J-aggregate formations and MMP values measured by TPP+. No correlation was detected with the green fluorescence (FL1) emission. A significantly higher correlation appeared between the FL2/FL1 ratio and MMP values. Within the same mitochondrial population, cytofluorimetric analysis revealed the presence of various classes of organelles with different MMP, whose distribution was dependent on metabolic condition. The highest functional heterogeneity was found in deenergized mitochondria, while the highest homogeneity was observed during the first phase of the phosphorylative process. Thus, these data suggest that the cytofluorimetric use of JC-1 provides direct experimental evidence for the hypothesis of functional mitochondrial heterogeneity, at least with respect to their membrane potential. 相似文献
7.
Intensity modulated radiation therapy (IMRT) is one of the most effective modalities for modern cancer treatment. The key to successful IMRT treatment hinges on the delivery of a two-dimensional discrete radiation intensity matrix using a device called a multileaf collimator (MLC). Mathematically, the delivery of an intensity matrix using an MLC can be viewed as the problem of representing a non-negative integral matrix (i.e., the intensity matrix) by a linear combination of certain special non-negative integral matrices called segments, where each such segment corresponds to one of the allowed states of the MLC. The problem of representing the intensity matrix with the minimum number of segments is known to be NP-complete. In this paper, we present two approximation algorithms for this matrix representation problem. To the best of our knowledge, these are the first algorithms to achieve non-trivial performance guarantees for multi-row intensity matrices. 相似文献
8.
Incremental Evolution in ANNs: Neural Nets which Grow 总被引:1,自引:1,他引:0
This paper explains the optimisation of neuralnetwork topology using Incremental Evolution;that is, by allowing the network to expand byadding to its structure. This method allows anetwork to grow from a simple to a complexstructure until it is capable of fulfilling itsintended function. The approach is somewhatanalogous to the growth of an embryo or theevolution of a fossil line through time, it istherefore sometimes referred to as anembryology or embryological algorithm. Thepaper begins with a general introduction,comparing this method to other competingtechniques such as The Genetic Algorithm, otherEvolutionary Algorithms and SimulatedAnnealing. A literature survey of previous workis included, followed by an extensive newframework for application of the technique.Finally, examples of applications and a generaldiscussion are presented. 相似文献
9.
10.
A real-time vision module for interactive perceptual agents 总被引:2,自引:0,他引:2
Bruce A. Maxwell Nathaniel Fairfield Nikolas Johnson Pukar Malla Paul Dickson Suor Kim Stephanie Wojtkowski Thomas Stepleton 《Machine Vision and Applications》2003,14(1):72-82
Abstract. Interactive robotics demands real-time visual information about the environment. Real-time vision processing, however, places
a heavy load on the robot's limited resources, which must accommodate multiple other processes running simultaneously. This
paper describes a vision module capable of providing real-time information from ten or more operators while maintaining at
least a 20-Hz frame rate and leaving sufficient processor time for a robot's other capabilities. The vision module uses a
probabilistic scheduling algorithm to ensure both timely information flow and a fast frame capture. In addition, it tightly
integrates the vision operators with control of a pan-tilt-zoom camera. The vision module makes its information available
to other modules in the robot architecture through a shared memory structure. The information provided by the vision module
includes the operator information along with a time stamp indicating information relevance. Because of this design, our robots
are able to react in a timely manner to a wide variety of visual events. 相似文献