Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 1990-1994  (4)
  • Angiotensin II  (2)
  • learning imprecise concepts  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Learning Two-Tiered Descriptions of Flexible Concepts: The POSEIDON System (1992)
    Springer
    Machine learning 8 (1992), S. 5-43 
    Details
    ISSN: 0885-6125
    Keywords: Concept learning ; learning imprecise concepts ; inductive learning ; learning flexible concepts ; two-tiered concept representation ; flexible matching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper describes a method for learning flexible concepts, by which are meant concepts that lack precise definition and are context-dependent. To describe such concepts, the method employs a two-tiered representation, in which the first tier captures explicitly basic concept properties, and the second tier characterizes allowable concept's modifications and context dependency. In the proposed method, the first tier, called Base Concept Representation (BCR), is created in two phases. In phase 1, the AQ-15 rule learning program is applied to induce a complete and consistent concept description from supplied examples. In phase 2, this description is optimized according to a domain-dependent quality criterion. The second tier, called the inferential concept interpretation (ICI), consists of a procedure for flexible matching, and a set of inference rules. The proposed method has been implemented in the POSEIDON system, and experimentally tested on two real-world problems: learning the concept of an acceptable union contract, and learning voting patterns of Republicans and Democrats in the U.S. Congress. For comparison, a few other learning methods were also applied to the same problems. These methods included simple variants of exemplar-based learning, and an ID-3-type decision tree learning, implemented in the ASSISTANT program. In the experiments, POSEIDON generated concept descriptions that were both, more accurate and also substantially simpler than those produced by the other methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022682318197
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Learning two-tiered descriptions of flexible concepts: The POSEIDON system (1992)
    Springer
    Machine learning 8 (1992), S. 5-43 
    Details
    ISSN: 0885-6125
    Keywords: Concept learning ; learning imprecise concepts ; inductive learning ; learning flexible concepts ; two-tiered concept representation ; flexible matching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper describes a method for learningflexible concepts, by which are meant concepts that lack precise definition and are context-dependent. To describe such concepts, the method employs atwo-tiered representation, in which the first tier captures explicitly basic concept properties, and the second tier characterizes allowable concept's modifications and context dependency. In the proposed method, the first tier, calledBase Concept Representation (BCR), is created in two phases. In phase 1, the AQ-15 rule learning program is applied to induce a complete and consistent concept description from supplied examples. In phase 2, this description is optimized according to a domain-dependent quality criterion. The second tier, called theinferential concept interpretation (ICI), consists of a procedure forflexible matching, and a set of inference rules. The proposed method has been implemented in the POSEIDON system, and experimentally tested on two real-world problems: learning the concept of an acceptable union contract, and learning voting patterns of Republicans and Democrats in the U.S. Congress. For comparison, a few other learning methods were also applied to the same problems. These methods included simple variants of exemplar-based learning, and an ID-3-type decision tree learning, implemented in the ASSISTANT program. In the experiments, POSEIDON generated concept descriptions that were both, more accurate and also substantially simpler than those produced by the other methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00994004
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Positive inotropic action of angiotensin II in the pithed rat (1993)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 347 (1993), S. 658-663 
    Details
    ISSN: 1432-1912
    Keywords: Angiotensin II ; Myocardial contraction ; Pithed rat ; AT1 receptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The cardiovascular effects of angiotensin II were examined in aortic blood pressure-controlled and-uncontrolled pithed rats. Angiotensin II induced a dose-dependent increase in diastolic blood pressure, left ventricular pressure (LVP), dP/dt (the first derivative of LVP) and heart rate in pithed rats. The maximal responses for these parameters were similar to those to noradrenaline, except for the rise in diastolic blood pressure, where noradrenaline caused a greater increase than angiotensin II. After treatment with propranolol, the positive chronotropic effect of angiotensin II was abolished. Angiotensin II produced a dose-dependent increase in diastolic blood pressure, which was similar to that of vasopressin, and an increase in dP/dtmax, which proved much greater than that of vasopressin. When aortic blood pressure was controlled and the β-receptors were blocked by propranolol, angiotensin II caused a dose-dependent increase in dP/dtmax without affecting the left ventricular enddiastolic pressure. The same results were obtained after both β- and α-adrenoceptors were blocked by propranolol and phentolamine. Losartan but not PD 123177 caused parallel rightward shifts of the dose-response curve of angiotensin II for dP/dtmax in the aortic blood pressure controlled pithed rat without altering the maximal response. It is concluded that in the pithed rat angiotensin II produced an increase in myocardial contractile force which is not mediated by β- or α-adrenoceptors. The inotropic effect appears to be mediated by angiotensin receptors, of the AT1-subtype.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00166950
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Inhibitory effect of dithiothreitol on angiotensin II-induced contractions mediated by AT1-receptors in rat portal vein and rabbit aorta (1994)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 349 (1994), S. 538-542 
    Details
    ISSN: 1432-1912
    Keywords: AT1-receptors ; Angiotensin II ; Dithiothreitol ; Losartan ; Rat portal vein ; Rabbit aorta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The disulfide-reducing agent dithiothreitol (DTT) has been shown to reduce angiotensin II (Ang II) subtype 1 receptor (AT,) binding sites in various tissues. Its effect on Ang II-induced contractions was studied in the rat portal vein and rabbit aorta. In the isolated rat portal vein, DTT shifted the concentration-response curve for Ang II to the right (DTT 0.5–3 mmol/l) and depressed the maximal response (DTT 1–3 mmol/l). DTT 5 mmol/l almost abolished the effect of Ang II. In the isolated rabbit aorta, the inhibitory effect of DTT was more pronounced and its pattern of effect was different,since DTT 0.3 and 0.5 mmol/l caused a progressive flattening of the concentration-response curve of Ang II. DTT (1 mmol/l) fully suppressed the effect of Ang II. A biphasic curve consisting of a high sensitivity component and a component of low sensitivity for Ang II was observed after pretreatment with DTT 1 mmol/l in the rat portal vein but not in the rabbit aorta. In the presence of DTT 1 mmol/l, the AT1-receptor antagonist losartan antagonized the high sensitivity response to Ang II in a competitive manner with a pA2 value very similar to that obtained in the absence of DTT, suggesting that this response to Ang II is mediated by those AT1-receptors which were not inactivated by DTT The biphasic curve may be explained by the occurrence of a single AT1-receptor subtype existing in two different states. Another possibility might be the involvement of two AT1-receptor subpopulations. It is concluded that disulfide bonds are critical for the functional role of AT1-receptors in Ang II-induced contractions in the rat portal vein and rabbit aorta.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169144
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...