ЕМКОСТЬ СРЕДЫ КАК ПРЕДПОСЫЛКА ДЛЯ УПРАВЛЕНИЯ СОСТОЯНИЕМ ПОПУЛЯЦИЙ

We study the possibility of using the carrying capacity for the state control of species populations important for human. The populations can have multiple states of equilibrium caused by the cumulative effects of the factors. Therefore, it is necessary to appreciate adequately the possible equilibrium states and the reasons for the transition between them. Management arrangements should be divided into two groups: «rise» (improvement of population status) and «decline» (its deterioration). Both groups effects on the organism at the same time. In the course of cognitive modeling it was revealed the existence of the natural restrictions of increasing of the Ring-necked pheasant population in the grounds: neither the hunting ban, nor conducted biotechnical measures do not allow to achieve the increasing of number. Ix the case of cessation of annual releases of this kind in the land, its number will come down to a minimum, and in some areas it will completely disappear. In the bounds of the biotic community of each ecosystem a certain additive summation of carrying capacities of environment of certain types takes place – an integrated capacity is formed. The attempts to increase the carrying capacity of the medium to separate the desired types to integrated capacity may promote degradation of all biological systems.

Graded and dynamic reflex summation of myelinated and unmyelinated rat aortic baroreceptors

Unmyelinated (C) and myelinated (A) baroreceptor (BR) axons are present in rat aortic depressor nerve (ADN). With graded ADN electrical activation and anodal conduction blockade, reflex responses in anesthetized rats were assessed as changes in mean arterial pressure (MAP) and heart rate (HR). We tested the hypothesis that C-type BR inputs are effective at low frequencies because they outnumber A-type. Anodal current ( I an) reversibly eliminated all MAP and HR responses to A-selective stimuli. High intensities activated all ADN axons (A+C) and decreased MAP at lower frequencies (<10 Hz) than were effective with A-selective stimulation. I anreduced only MAP responses to >10-Hz ADN stimulation. Burst patterns significantly augmented A- but not C-selective reflex responses despite identical numbers of shocks per second. A-selective stimuli failed to evoke significant bradycardia even at 200 Hz. Maximum intensity stimuli plus I an (C selective) evoked less bradycardia than without I an (A+C), indicating supra-additive summation unlike the occlusive summation for MAP responses. However, activation of reduced numbers of C-type BRs with all A-type BRs suggests a strong A to C interaction in reflex bradycardia responses. Surprisingly, I an block of A-type conduction eliminated all reflex bradycardia at such submaximal intensities despite C conduction and depressor responses. A- and C-type BRs act synergistically, and A-type activity is absolutely required in cardiac but not in depressor pathways. Thus greater numbers do not appear to account for C-type BR efficacy, and critical interactions between these two sensory subtypes appear to occur differentially across cardiac and systemic baroreflex effector pathways.

THE CASIMIR FORCE BETWEEN PLATES WITH SMALL DEVIATIONS FROM PLANE PARALLEL GEOMETRY

We present a general calculation of the corrections to the Casimir force between plates with small deviations from plane parallel geometry of the arbitrary type. These corrections are considered up to the fourth order with respect to the relative amplitudes of the deviations. The developed formalism is applied to the cases of nonparallel plates and of large scale as well as short scale deformations of the surfaces of different types. A number of particular examples are explicitly calculated. The method used is the previously developed method of additive summation of the Casimir force potentials with a subsequent renormalization. The results obtained by this method are tested by comparison with the results from the Green function method. A special investigation is performed into the role of mixed terms in the expansion with respect to the deviation amplitudes resulting from different plates. It is shown that such contributions are present already in the first nonvanishing correction to the Casimir force, so that this correction is nonadditive.

Summation of sinoaortic baroreflexes depends on size of input signals

We studied sinoaortic baroreflex summation in seven anesthetized rabbits by paying special attention to the sigmoidal nature of the open-loop characteristic curve of the two reflexes. Carotid sinuses were isolated to control carotid sinus pressure (CSP). Aortic nerves were cut, and the left aortic nerve was electrically stimulated. Initially, CSP was set between 75 and 95 mmHg, and the parameters for aortic nerve stimulation (ANS) were chosen so that mean arterial pressure (MAP) was between 80 and 100 mmHg. We then increased CSP and ANS mildly so that MAP would fall by 10-20 mmHg in each case. Comparison of the sum of these decreases with the decrease caused by simultaneous increases in CSP and ANS showed no statistical difference, indicating a simply additive summation. With mild decreases in CSP and ANS, a similar additive summation was observed in the reflex increases in MAP. When we input slightly larger changes in CSP and ANS so that MAP fell by 20-30 mmHg for each stimulus, comparison of the sum of the separate effects with the combined effect on MAP indicated a mildly inhibitory summation. By analyzing the total peripheral resistance calculated from aortic flow data, we found this inhibitory summation occurred in the reflex controls of the total peripheral resistance. We conclude that the summation of the sinoaortic reflex controls of arterial pressure can be regarded as simply additive when small input signals are given in the physiological range of both reflexes, but the summation is mildly to moderately inhibitory when moderately larger input signals are given.

Sinovagal interaction in arterial pressure restoration after 10% hemorrhage

The summation between the carotid sinus baroreceptor reflex system (CS system) and the vagally mediated reflex system (V system) was studied as they restore mean arterial pressure (MAP) after 10% quick hemorrhage in splenectomized conscious dogs chronically instrumented with catheters for pressure measurement and hemorrhage. The experiment was repeated under nerve-intact condition (intact), with cold block of the vagi ([V]), after carotid sinus denervation (CS), and CS plus [V] situations. MAP falls at 1.5 min after the hemorrhage were 7.2 in intact, 24.7 in [V], 36.0 in CS, and 67.6 in CS + [V] mmHg. When we calculated the open-loop gains of CS and V systems assuming a simply additive summation between them a self-contradiction occurred. To avoid this contradiction, it was necessary to assume that CS and V systems interact in a facilitatory manner. Mean open-loop gains calculated under this assumption were 1.64 for the CS system alone, 0.89 for the V system alone, and 6.59 for the interacting component between them. These intriguing results warrant further analysis of the summation between the two reflex systems.