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101.
The effect of thiopentone/halothane anaesthesia on the release of endogenous opioid, adrenocorticotrophin, arginine vasopressin, cortisol and catecholamine was investigated in ponies. The contribution made by halothane itself was studied by maintaining six ponies with a constant 1.2 per cent end tidal halothane concentration and five with a concentration ranging between 0.8 and 1.2 per cent. Cardiorespiratory depression was more prolonged in the ponies receiving a constant 1.2 per cent end tidal halothane concentration than in those which received less halothane. Plasma lactate concentration increased and haematocrit decreased during halothane anaesthesia. The concentrations of met-enkephalin, dynorphin and catecholamines did not change and those of beta-endorphin, adrenocorticotrophin, arginine vasopressin and cortisol increased during halothane anaesthesia. Halothane appeared to be a major stimulus to pituitary adrenocortical activation because the adrenocortical secretion was proportional to the amount of halothane inhaled. Beta-endorphin increased proportionally more than adrenocorticotrophin and their plasma concentrations were not correlated, suggesting that they have independent secretion mechanisms.  相似文献   
102.
β-FeSi2 can be used for various optoelectronic devices owing to its superior material features including high optical absorption coefficient and direct band gap of about 0.8 eV. Due to its high refractive index (>5.6), however, suitable antireflection coating (ARC) is necessary for practical device applications. In order to increase the effective areas of optoelectronic devices, transparent electrodes should be also developed. In this work, Al-doped ZnO (AZO) films were fabricated by sputtering on β-FeSi2 thin films and were found suitable for both transparent electrodes and ARC films. Choosing optimum substrate temperature and sputtering rate, high quality AZO films were formed. The conductivity of AZO films was as high as 3×103 S/cm and ohmic contact was easily achieved between AZO and β-FeSi2 films, indicating AZO film as an ideal transparent electrode for β-FeSi2. The transmittance of 400-nm-thick AZO films was >80% and >70% in the wavelength ranges 400-1400 and 1400-1600 nm, respectively. By changing the thickness of AZO film, the central wavelength of minimum reflectance was adjusted to 1550 nm where the total reflectance of AZO/β-FeSi2/Si structure was reduced below 2%.  相似文献   
103.
Cats were initially trained to make operant conditioned food responses to light by an "active selection of reinforcement" method. Provision of low-quality (a mixture of meat and bread) or high-quality (meat) reinforcement depended on the animal pressing a pedal in response to switching on a light with a short (1 sec) or long (10 sec) delay. Some animals responded to long delays--group I, animals with "self control," while others responded with short delays--group II, "impulsive" animals. Implanted semimicroelectrodes were used in chronic experiments to record multineuron activity in the basolateral amygdala. Cross-correlation analysis was used to study interneuron interactions in the spike discharges of individual neurons, extracted from multineuron activity. The numbers of interneuron interactions were significantly higher in "impulsive" cats of group II in all behavioral situations than in animals with "self control," and were dominated in "impulsive" animals by the shortest connections, with latencies of 0-30 msec. The largest numbers of connections in both groups were seen on omission of the conditioned pedal-pressing movement response, i.e., when the reinforcement selection task was more difficult. These data indicate that the basolateral amygdala should be regarded as a structure determining the individual typological characteristics of the animals' behavior.  相似文献   
104.
User-Generated Content has become very popular since new web services such as YouTube allow for the distribution of user-produced media content. YouTube-like services are different from existing traditional VoD services in that the service provider has only limited control over the creation of new content. We analyze how content distribution in YouTube is realized and then conduct a measurement study of YouTube traffic in a large university campus network. Based on these measurements, we analyzed the duration and the data rate of streaming sessions, the popularity of videos, and access patterns for video clips from the clients in the campus network. The analysis of the traffic shows that trace statistics are relatively stable over short-term periods while long-term trends can be observed. We demonstrate how synthetic traces can be generated from the measured traces and show how these synthetic traces can be used as inputs to trace-driven simulations. We also analyze the benefits of alternative distribution infrastructures to improve the performance of a YouTube-like VoD service. The results of these simulations show that P2P-based distribution and proxy caching can reduce network traffic significantly and allow for faster access to video clips.  相似文献   
105.
P2Cast: peer-to-peer patching for video on demand service   总被引:1,自引:0,他引:1  
Providing video on demand (VoD) service over the Internet in a scalable way is a challenging problem. In this paper, we propose P2Cast—an architecture that uses a peer-to-peer approach to cooperatively stream video using patching techniques, while only relying on unicast connections among peers. We address the following two key technical issues in P2Cast: (1) constructing an application overlay appropriate for streaming; and (2) providing continuous stream playback (without glitches) in the face of disruption from an early departing client. Our simulation experiments show that P2Cast can serve many more clients than traditional client-server unicast service, and that it generally out-performs multicast-based patching if clients can cache more than 10% of a stream’s initial portion. We handle disruptions by delaying the start of playback and applying the shifted forwarding technique. The threshold in P2Cast, i.e., the length of time during which arriving clients form a single session, can serve as a “knob” to adjust the balance between the scalability and the clients’ viewing quality.
Don TowsleyEmail:
  相似文献   
106.
This research is motivated by large-scale pervasive sensing applications. We examine the benefits and costs of caching data for such applications. We propose and evaluate several approaches to querying for, and then caching data in a sensor field data server. We show that for some application requirements (i.e., when delay drives data quality), policies that emulate cache hits by computing and returning approximate values for sensor data yield a simultaneous quality improvement and cost saving. This win–win is because when system delay is sufficiently important, the benefit to both query cost and data quality achieved by using approximate values outweighs the negative impact on quality due to the approximation. In contrast, when data accuracy drives quality, a linear trade-off between query cost and data quality emerges. We also identify caching and lookup policies for which the sensor field query rate is bounded when servicing an arbitrary workload of user queries. This upper bound is achieved by having multiple user queries share the cost of a single sensor field query. Finally, we demonstrate that our results are robust to the manner in which the environment being monitored changes using models for two different sensing systems.  相似文献   
107.
Loss of heterozygosity (LOH) of chromosome 10q is observed in approximately 40% of endometrial cancers. Mutations in PTEN/MMAC1, a gene recently isolated from the 10q23 region, are responsible for two dominantly inherited neoplastic syndromes, Cowden disease and Bannayan-Zonana syndrome. Somatic mutations of this gene have also been detected in sporadic cancers of the brain, prostate and breast. To investigate the potential role of this putative tumor suppressor gene in endometrial carcinogenesis as well, we examined 46 primary endometrial cancers for LOH at the 10q23 region, and for mutations in the entire coding region and exon-intron boundaries of the PTEN/MMAC1 gene. LOH was identified in half of the 38 informative cases, and subtle somatic mutations were detected in 15 tumors (33%). Our results suggest that of the genes studied so far in endometrial carcinomas, PTEN/MMAC1 is the most commonly mutated one, and that inactivation of both copies by allelic loss and/or mutation, a pattern that defines genes as "tumor suppressors," contributes to tumorigenesis in endometrial cancers.  相似文献   
108.
The degree of saturation of ground is conventionally measured at discrete points using transducers, soil moisture sensors, etc. In this paper, a novel method was developed to directly measure the degree of saturation of continuous region of ground by noting the variation in color of the ground as the amount of moisture in the soil changes. In this research, a series of experiments was conducted for the purpose of developing a method to measure the degree of saturation of ground by digital image processing. From photo images taken at various soil moisture contents, the colors of the images were converted into numerical values which were then related to known degrees of saturation. The results of the experiments showed that a method to measure the degree of saturation of ground by image processing was possible. The relation between degree of saturation and luminance value can be expressed in terms of second degree function. Good results were obtained for two soil samples with different colors and grain size distributions. The margin of error was in the order of ±5%. The method was validated through vertical seepage tests, where good agreements were obtained between the measured degrees of saturation by tensiometers and those estimated from the proposed method. The method illustrates the possibility of measuring the degree of saturation of a larger portion of the ground, which is difficult to perform using conventional procedures. With this method, contour diagrams of degree of saturation can be produced, making it possible to visualize the propagation of the saturated region.  相似文献   
109.
Coal is an important energy resource for meeting the future demand for electricity, as coal reserves are much more abundant than those of other fossil fuels. In this study, the percolation model, which can account for swelling due to devolatilization and ash agglomeration, is applied to particulate matter formation process in coal combustion, and the effects of coal properties, ambient temperature, ambient pressure and initial coal size on the characteristics of a burning coal particle are studied. The devolatilization rate of coal is given by the first-order reaction model with FLASHCHAIN® model [Niksa, S., Combust. Flame, 100, (1995) 384-394.]. The characteristics of a burning coal particle are investigated under the atmospheric and high pressure conditions. The results show that in the atmospheric pressure condition, the characteristics of the burning coal particle obtained by the percolation model are in general agreement with the experimental data. The particle diameter of Newlands coal with higher fuel ratio and ash content is larger than that of Plateau coal in the char-combustion-dominant process. As the ambient temperature increases, the particle diameter becomes small in the early stage of the char-combustion-dominant process, but becomes large afterward. The porosity in the char-combustion-dominant process decreases with decreasing the initial coal size. It is also observed that the effect of ambient pressure is prominent in the char-combustion-dominant process. The particle diameter and porosity in the pressurized condition are greater than those in the atmospheric pressure condition. These behaviors can be explained by the interaction between char reaction and ash agglomeration.  相似文献   
110.
Ryoichi Kurose  Hisao Makino 《Fuel》2004,83(6):693-703
A three-dimensional numerical simulation is applied to a pulverized coal combustion field in a test furnace equipped with an advanced low-NOx burner called CI-α burner, and the detailed combustion characteristics are investigated. In addition, the validities of the existing NOx formation and reduction models are examined. The results show that a recirculation flow is formed in the high-gas-temperature region near the CI-α burner outlet, and this lengthens the residence time of coal particles in this high-temperature region, promotes the evolution of volatile matter and the progress of char reaction, and produces an extremely low-O2 region for effective NO reduction. It is also found that, by lessening the effect of NO reduction in Levy et al.'s model and taking the NO formation from char N into account, the accuracy of the NO prediction is improved. The efficiency factor of the conversion of char N to NO affects the total NO concentration downstream after the injection of staged combustion air.  相似文献   
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