The nature of the pi1 colour mechanism of W.S. Stiles

The ppi1 colour mechanism was isolated by means of Stile's auxiliary field technique: that it is pi1 which is isolated is proven by both test and field action spectra. 2. The fundamental mechanisms of human trichromatic colour vision must satisfy Grassman's law of additivity. The hypothesis that pi1 is one of the three fundamentals is tested by experiments in which pairs (u1, u2) of monochromatic adapting fields are mixed 3. When two fields with wave-lengths in the neighbourhood of its primary mode (mu1, mu2 less than or equal to 500 nm) are combined, pi1 is field-additive, consistent with the hypothesis that this portion of the pi1 action spectrum is that of the short-wave-length-sensitive photoreceptors. 4. When a short-wave-length adaptation field (mu1 less than or equal to 500 nm) is mixed with a longer wave-length field (mu2 greater than or equal 550 nm) i1 is strongly non-additive. This result proves that the long-wave-length portion of the pi1 field spectrum is generated at least in part by a signal originating in the long- or middle-wave-length sensitive cones. 5. Analysis of the additivity failures supports a model of pi1 in which the signal to be detected is generated in the short-wave-length cones, and must pass serially through two gain stages: the gain in the first stage is controlled by the short-wave-length cones alone; the gain in the second stage is controlled by a signal originating in the middle, or long-wave-length cones, or both.     

Sources of several errors in DNA cytofluorimetry

It was shown that serious errors in DNA cytofluorimetry may be due to incorrect illumination of photocathode of the photomultiplier in the cytofluorimeters and non-observance of the requirements to the nuclear structures of the cells under measurement with respect to their chemical integrity and thickness. The methods of the optimal illumination of photocathode in the cytofluorimeters and the criteria of selection of the nuclear structures on slides are considered with the aim of obtaining the objective results of DNA cytofluorimetry.     

Oral premedication: diazepam, metoclopramide and a drink

A technique of premiedication using oral diazepam and metoclopramide with a drink is described and shown to provide better sedation and less vomiting than pethidine and atropine given intramuscularly without a drink to a group of similar patients.     

Effect of vaccine-induced immune activation on the performance of early-weaned pigs

Two groups of 96 pigs were studied to determine the influence of weaning age, nursery site and a challenge to their immune system on their performance. The weaning ages were 11 to 16 days and 16 to 21 days. One nursery was on-site and the second nursery was off-site. Immune activation was stimulated by the administration of infectious bovine rhinotracheitis virus (IBR) vaccine to half of the pigs at each site. Serum virus neutralisation titres to IBR and total immunoglobulins were monitored in some of the pigs in each group. Performance was measured in terms of feed intake, average daily gain in weight, and feed conversion ratio (FCR). The mean serum immunoglobulin concentrations of all the groups of pigs tended to decrease in the first two weeks after weaning and then increase. Twelve of 20 pigs vaccinated with IBR had neutralisation titres to the virus. The site of the nursery did not significantly affect average daily gain in weight, feed intake or FCR. Pigs weaned at 16 to 21 days of age had a significantly better daily gain in weight than the pigs weaned at 11 to 16 days of age. Immune stimulation of the older weaned pigs did not influence their performance, but it had a significantly (P < 0.016) negative effect on the performance of the younger weaned pigs.     

Fluctuations in tap water fluoride levels: a potential problem for practitioners

Prior to the early 1980s, two Winnipeg hospitals provided hemodialysis for all patients in Manitoba with chronic renal failure. Because no other hemodialysis centres existed, families were forced to relocate to the city. Because of these factors, the Manitoba Renal Failure Advisory Committee proposed the development of an outreach hemodialysis program. Under the auspices of the Health Sciences Centre in Winnipeg, this outreach program has evolved into the current Manitoba Local Centre Dialysis Program. Hemodialysis services are now available in an additional seven health care centres throughout Manitoba and northwestern Ontario. This program has benefited many and in some instances, families previously separated by distances of up to 500 miles have been reunited. Creativity has been one of the most essential ingredients in the evolution of this unique program.     

Queueing analysis of buffered slotted multiple access protocols

Much of the literature on the performance evaluation of multiple access protocols has assumed a buffer capacity of one unit. This assumption is not realistic. In practice the buffer capacities used are larger than one unit in order to reduce the probability of packet rejection. This is more crucial for multiple access protocols, which allow moderate to high values of the expected throughput (URN, Random TDMA etc.).In this paper, a model appropriate for the analysis of buffered slotted multiple access schemes is proposed. The method can be applied to several multiple access protocols such as the URN protocol, the ALOHA protocol, Random TDMA etc. The cases of infinite and finite buffer capacity are examined separately but under the same basic assumptions. The analysis is based on the assumption that each user process can be modelled as an M/G/1 queueing system. The proposed method requires a small amount of computation and is characterized by a high speed, a fact that simplifies the buffer's design as well. The solution obtained is extremely accurate and exhibits excellent agreement with simulation results, which corroborate the accuracy of the model. The special case when the buffer capacity is equal to 1 is examined. In that case, the present approach also allows for computation of the packet delay distribution.     

高温正向栅电流下Ti/Pt/Au栅SiC MESFET的栅退化机理

SiC MESFET器件的性能强烈依赖于栅肖特基结的特性,而栅肖特基接触的稳定性直接影响其可靠性.针对SiC MESFET器件在微波频率的应用中射频过驱动导致高栅电流密度的现象,设计了两种栅极大电流的条件,观察栅肖特基接触和器件特性的变化,并通过对试验数据的分析,确定了栅的寄生并联电阻的缓慢退化是导致栅肖特基结和器件特性退化,甚至器件烧毁失效的主要原因.     

超滤浓缩制备南瓜果胶的工艺研究

采用超滤浓缩后乙醇沉淀的方法制备南瓜果胶.通过单因素试验,确定优化超滤条件为:超滤膜截留分子量50 kD,压力0.08 MPa,温度25 ℃,溶液pH 7.0;在该条件下,将南瓜果胶提取液浓缩至原体积1/5,再加入80%乙醇溶液沉淀果胶并洗涤果胶1次,所得的南瓜果胶纯度为80.08%,得率为8.50%,凝胶度为120.25,酯化度为31.82,干燥失重为4.26%,总灰分为3.22%,半乳糖醛酸为88.10%,pH为2.7,铅及砷含量分别为1.2 mg/kg和0.036 mg/kg,各项指标均达到国家质量标准QB 2484--2000.