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181.
Betchen  SA; Doty  RL 《Chemical senses》1998,23(4):453-457
Several fundamental questions remain enigmatic concerning human olfactory sensitivity, including (i) whether detection threshold differences exist between the two sides of the nose (and, if so, whether such differences are influenced by handedness) and (ii) whether bilateral (i.e. binasal) stimulation leads to lower thresholds than unilateral stimulation (and, if so, whether the degree of facilitation is inversely related to general olfactory ability). In this study, and well-validated single staircase procedure was used to establish bilateral and unilateral detection thresholds for the cranial nerve I stimulant phenyl ethyl alcohol in 130 right- and 33 left-handed subjects. No differences in sensitivity between the left and right sides of the nose were observed in either group. Bilateral thresholds were lower, on average, than unilateral thresholds when the latter were categorized in terms of left and right nares. However, the bilateral thresholds did not differ significantly from those of the side of the nose with the lower threshold. Overall smell ability, as measured by the University of Pennsylvania Smell Identification Test, did not interact with any of the test measures. These data imply that (i) the left and right sides of the nose do not systematically differ in detection threshold sensitivity for either dextrals or sinistrals and (ii) if central integration of left:right olfactory threshold sensitivity occurs, its effects do not exceed the function of the better side of the nose.   相似文献   
182.
Ophioglossum yongrenense Ching ex Z. R. He et W. M. Chu, sp. nov.Species nova aspectu inter O. kawamuram Tagawa et O. parvum Nishida et Kurita Japonicae, differt a priore frondibus pro parte laminis sterilibus praeditis (in illa frondibus omnino laminis sterilibus non praeditis), a posteriore frondibus pro parte laminis sterilibus non praeditis (in O. parvo Nishida et Kurita frondibus omino laminis sterilibus praeditis).……  相似文献   
183.
In this paper we propose a new model of an isolated beating heart. The model is described by a one-dimensional non-linear discrete dynamical system which depends on several parameters. Applying stability analysis we investigate the dynamic properties of the non-linear system. We find those domains in the parameter space in which the equilibrium point of the system (the fixed point) and the periodic orbits are attractors and in which they are unstable. These domains correspond to a normal and abnormal beating heart, i.e. when the end diastolic volumes are stable time invariant and time variant, respectively. On transition between these domains there is a bifurcation which gives rise to a pair of attracting points of period 2. This case corresponds to the simplest type of period doubling behavior of an abnormal beating heart, called mechanical alternans. Our results provide qualitative and quantitative predictions which can be used for comprehensive experimental design.  相似文献   
184.
Death in normobaric hyperoxia was related in the past to pulmonary insufficiency of the edematous lung. However, high arterial O2 tension on final collapse led to the suggestion that the heart and not the lung is the first organ that fails. We measured aortic flow, coronary flow, left ventricular pressure, affluent and effluent PO2, PCO2, and pH in the working heart excised from control and normobaric O2-exposed rats (51-63 h). The oxygen consumption (VO2) of experimental hearts was not different from control, but mechanical power output (PVAP) (calculated from pressure-volume area) was reduced as a function of O2 exposure time. Myocardial contractility indexes, maximal elastance and maximal time derivative of pressure, increased as a function of O2 exposure time, being below control values after 50 h and above control values after 60 h. The individual slopes for the regression of VO2 vs. PVAP rose as a function of exposure time from values below control after 50 h exposure to values above control after 60 h. Energetic efficiency (PVAP/VO2) decreased as a function of O2 exposure time and points to possible heart failure in the intact animal. After 50 h O2 exposure the heart was energetically more efficient than the control. Possible changes in the heart are discussed.  相似文献   
185.
Chest wall mechanics: effects of acute and chronic lung disease   总被引:1,自引:0,他引:1  
Data from the literature show that lung tissue properties affect the chest wall compliance, Ccw, which is the change in lung volume, Vl, with respect to the pleural pressure, Ppl. to analyze the difference between acute and chronic lung tissue changes, we used a mathematical model that describes the static, nonlinear mechanics of the ventilatory system in terms of its major elements: rib cage; abdomen; diaphragm and lung. With this model we derived the relationship between chest wall, rib-cage and diaphragm compliances. Although the Vl-Ppl relation is independent of lung mechanics, the volume operating point (FRC) of the ventilatory system depends on lung tissue properties. This accounts for the effect of acute lung abnormalities. In the presence of chronic lung abnormalities, the properties of the rib-cage are changed which shifts the entire Vl-Ppl curve. In general, valid comparisons of (extra-pulmonary) chest wall mechanics can only be made using the entire Vl-Ppl relation, or at least a sufficiently large part of the relation about FRC. Differentiation of the rib-cage and diaphragm mechanics requires additional measurements of the rib-cage A-P distance and the relative position of the diaphragm.  相似文献   
186.
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