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181.
182.
One of the fundamental snags often encountered in the development of expert systems is the difficulty of effective liaison between the knowledge engineer and the specialists for whom the system is designed, especially when the latter have no engineering background. In our case, this problem has arisen in the course of working towards a comprehensive system for the automatic diagnosis and prognosis of fetal condition during labor, an important task which has traditionally been carried out by visual inspection of fetal heart rate and uterine pressure traces. Although the use of syntactic pattern recognition methods has enabled the system as it stands to achieve success rates of around 95 percent, its further improvement hinges on case-by-case interaction with obstetricians untrained in the concepts of discriminant analysis or formal grammar.  相似文献   
183.
The reasons underpinning search biases in 2 species of macaque monkeys (Macaca mulatta and Macaca arctoides) were explored over the course of 3 experiments requiring monkeys to search for a hidden food reward. The results reveal that monkeys are adept at exploiting perceptual cues to locate a food reward but are unable to use physical constraints such as solidity as cues to the reward's location. Monkeys prefer to search for a food reward beneath a solid shelf, not because they have an expectation that the reward should be there, but rather because, in the absence of usable cues, this bias emerges as a default search option. It is hypothesized that this bias may have its roots in a history of competition for food resources. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
184.
0 引言 为了在用能效率上作出工程努力,Cortagena技术大学去年4月已决定实施一项雄心勃勃的计划,要在此后的4年中削减用电费用。为了证实不同政策的可行性和成本效益,应用于原海军医院(工业工程高等技术学校总部)的许多展示活动将在最近期内完成。当然,在此建筑中合理用电的对象将集中在两个主要的电气末端即:电  相似文献   
185.
The present data show a dramatic decline in the circulating levels of dehydroepiandrosterone (DHEA), DHEA-sulfate (DHEA-S), androst-5-ene-3 beta,17 beta-diol (5-diol), 5-diol-sulfate, 5-diol-fatty acid esters, and androstenedione in both men and women between the ages of 20-80 yr. In the 50- to 60-yr-old group, serum DHEA decreased by 74% and 70% from its peak values in 20- to 30-yr-old men and women, respectively. the serum concentrations of the conjugated metabolites of dihydrotestosterone (DHT), namely androsterone (ADT)-G, androstane-3 alpha,17 beta-diol (3 alpha-diol-G), androstane-3 beta,17 beta-diol (3 beta-diol-G), and ADT-sulfate are the most reliable parameters of the total androgen pool in both men and women, whereas serum testosterone and DHT can be used as markers of testicular secretion in men and interstitial ovarian secretion in women. The serum concentration of these various conjugated androgen metabolites decreased by 40.8% to 72.8% between the 20- to 30-yr-old and 70- to 80-yr-old age groups in men and women, respectively, thus suggesting a parallel decrease in the total androgen pool with age. As estimated by measurement of the circulating levels of these conjugated metabolites of DHT, it is noteworthy that women produce approximately 66% of the total androgens found in men. In women, most of these androgens originate from the transformation of DHEA and DHEA-S into testosterone and DHT in peripheral intracrine tissues, whereas in men the testes and DHEA and DHEA-S provide approximately equal amounts of androgens at the age of 50-60 yr. An additional potentially highly significant observation is that the majority of the marked decline in circulating adrenal C19 steroids and their resulting androgen metabolites takes place between the age groups of 20- to 30-yr olds and 50- to 60-yr-olds, with smaller changes are observed after the age of 60 yr.  相似文献   
186.
The slow-channel congenital myasthenic syndrome (SCCMS) is a dominantly inherited disorder of neuromuscular transmission characterized by delayed closure of the skeletal muscle acetylcholine receptor (AChR) ion channel and degeneration of the neuromuscular junction. The identification of a series of AChR subunit mutations in the SCCMS supports the hypothesis that the altered kinetics of the endplate currents in this disease are attributable to inherited abnormalities of the AChR. To investigate the role of these mutant AChR subunits in the development of the synaptic degeneration seen in the SCCMS, we have studied the properties of the AChR mutation, epsilonL269F, found in a family with SCCMS, using both in vitro and in vivo expression systems. The mutation causes a sixfold increase in the open time of AChRs expressed in vitro, similar to the phenotype of other reported mutants. Transgenic mice expressing this mutant develop a syndrome that is highly reminiscent of the SCCMS. Mice have fatigability of limb muscles, electrophysiological evidence of slow AChR ion channels, and defective neuromuscular transmission. Pathologically, the motor endplates show focal accumulation of calcium and striking ultrastructural changes, including enlargement and degeneration of the subsynaptic mitochondria and nuclei. These findings clearly demonstrate the role of this mutation in the spectrum of abnormalities associated with the SCCMS and point to the subsynaptic organelles as principal targets in this disease. These transgenic mice provide a useful model for the study of excitotoxic synaptic degeneration.  相似文献   
187.
TIM (Zeppelin Chirurgische Instrumente GmbH, 82 049 Pullach, Germany) is a tomographic imaging system which enables surgeons to visualize the pathologic lesions three dimensionally in relationship to the surrounding structures. The distance and the angle between the pathologic lesion and the anatomical and/or bony landmarks as well as the volume of the mass lesion can be measured. Therefore an accurate localization of the lesion is possible with this technique. It is very applicable for planning of surgery on skull base tumors. The surgical procedure for small and well-defined, intrinsic pathologic deep-seated brain lesions, however, becomes much easier by using the stereotactic techniques of this system. The target point and the direction brain-surface-to-lesion can be determined within seconds. Before the aiming probe is inserted to the target, the cortical motor area is mapped by direct electrical stimulation. The approach can be varied depending on the results of these neurophysiologic investigations of the brain surface. The dissection is made along the aiming probe up to the target point. Because of the fixation of the brain with the needle, a brain shifting due to the dissection as well as to CSF release is diminished. Forty patients with deep-seated intracerebral lesions were operated on during a 13 months period by these combined techniques in our service. Using this technique, we never made a negative exploration. In all but three patients, total removal of the mass lesion was achieved. Permanent neurological deficits were observed in two patients only. In our opinion, this combined imaging and neurophysiological technique is easy to perform, and of major benefit for the patients due to its accuracy and is preferable in comparison with other single computer localizer techniques without neurophysiological monitoring.  相似文献   
188.
The chemistry of 2‐acetyl‐1,3‐cycloalkanediones has acquired increased applied importance because of the great number of applications in the agroalimentary industry. The keto‐enol ratios and equilibrium constants for proton reactions of 2‐acetyl‐1,3‐cyclopentanedione have been determined in solution using nuclear magnetic resonance and spectrophotometric methods. Chromium(iii ) is an essential nutrient and it seems that high chromium supplementation improves glucose tolerance. Chromium chelates have been shown to have a significant beneficial effect on metal status by increasing metal bioavailability in human diets. The composition and log β‐value of the complex formed in aqueous solution by chromium(iii ) with the ligand mentioned above have been determined. A detailed reaction scheme is proposed for the 1 : 1 chelation process. The kinetic data are consistent with a mechanism in which the mono‐enol tautomer of the ligand reacts with both metallic species, the fully hydrated metal ion and the Cr(OH)2+. The results are discussed in the light of previous work.  相似文献   
189.
The protective effect of experimental immunization was studied in guinea pigs exposed to vectorial infection by Trypanosoma cruzi. Immunized animals received an inoculum of live-attenuated T. cruzi epimastigotes into a granuloma previously induced by Freund's complete adjuvant in the hind footpad. Seven days later, a delayed-type hypersensitivity reaction was triggered by reinjection of the parasites in the front footpad. The animals were then placed in Triatoma infestans-colonized corrals and exposed to vectorial T. cruzi transmission of the parasite for up to 200 days. The effectiveness of this immunizing protocol was controlled in terms of the number of bites necessary for infection (NBNI) in immunized as compared with control animals. Periodic entomological census allowed for the determination of vector biting and infection rates and the calculation of NBNI. Although this measurement was quite variable between yards, an overall average of 4,973 bites was enough to infect a control guinea pig in 4 separate experiments. The corresponding figure for the experimental group was 21,307 bites, implying that immunized animals could resist a 4.28-fold increase (range: 1.99-8.32) in the number of vector bites before becoming infected.  相似文献   
190.
OBJECTIVE: It is necessary to have thorough knowledge of the survival of extreme low birth weight infants (ELBWI) in order to make it easier for obstetricians, neonatologists and the family to make a decision. PATIENTS AND METHODS: A revision of the 100 ELBWI in our service between 1988 and 1995, considering live births, those deceased in the same birthing room and those followed until their discharge from the hospital, was performed. The differences between the periods before and after the introduction of pulmonary surfactant in 1992 were analyzed. RESULTS: The total survival was 37% for those with a birth weight superior to 750 g or 26 weeks gestation. There were 44.2% males and 28.9% females. The total survival improved from 26.1% during 1988-1991 to 46.3% during the period of 1992-1995. During this period (1992-1995), the newborns weighing more than 750 g had a survival rate of 72.4% and for those of 26 weeks gestation it was 73.3%. Those born at 28 weeks gestation and those with 25 weeks of gestation and weighing more than 750 g, the total survival was 63% and the survival rate in the last four years was 75.9%. CONCLUSIONS: The mortality of the ELBWI descends in similar proportion to the remainder fo the ELBWI. In order to predict the prognosis, it would be necessary to carry out a correct ultrasound estimation of the gestational age and weight. It is necessary to offer a mother in the process of childbirth with a fetus of 28 weeks gestation or with 25 weeks gestation and a fetus with an ultrasound weight greater than 750 g, intrapartum fetal monitoring and to finish by Cesarean section in case of acute fetal distress, as well as intense and immediate neonatal attention as indicated by the index of survival reached in the group mentioned during the later years.  相似文献   
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