Entanglement of qubits via a nonlinear resonator.

Coherent coupling of two qubits mediated by a nonlinear resonator is studied. It is shown that the amount of entanglement accessible in the evolution depends on both the strength of nonlinearity in the Hamiltonian of the resonator and on the initial preparation of the system. The created entanglement survives in the presence of decoherence.

Entanglement of distant flux qubits mediated by non-classical electromagnetic field.

The mechanism for entanglement of two flux qubits each interacting with a single mode electromagnetic field is discussed. By performing a Bell state measurement (BSM) on photons we find the two qubits in an entangled state depending on the system parameters. We discuss the results for two initial states and take into consideration the influence of decoherence.

Reflex reversal of apnoeic episodes by electrical stimulation of upper airway in cats.

Respiratory effects of electrical stimulation of the upper airways (UAW) before and during apnoeic episodes induced by nitrogen inhalation were studied in 9 anaesthetized cats. In eupnoeic animals these electrically-evoked reflexes comprise rapid and powerful inspiratory efforts characterized by strong maximal airway occlusion pressures (Pmax = 635 +/- 39 mm H2O) and rapid peak inspiratory flow rates (PIF = 536 +/- 36 ml.sec-1) similar to the sniff-like aspiration reflex elicited mechanically. Electrical stimulation of the UAW mucosa can elicit reflex inspirations and sniff-like aspiration reflexes even during reversible hypoxic apnoea but their intensity and reproducibility are transiently reduced. When repeated adequately, the electrically-induced reflexes can increase the reactivity of respiratory centre and interrupt or terminate apnoeic episodes as do other types of UAW stimulation. Reflex mechanisms and respiratory centre activations seem to be involved in these effects. The results suggest that electrical stimulation of UAW could be useful for testing the respiratory centre reactivity as well as for reflex reversal of apnoeic episodes and restoration of normal breathing in animal experiments and clinico-physiological studies. Such investigation of the role of UAW reflexes in the pathogenesis and therapy of apnoeic syndromes might also be possible by using a cardiostimulator adapted as respiratory pacemaker.

Sniff-like aspiration reflex evoked by pressure pulses from the upper airways in cats.

Respiratory effects of single positive and negative pressure pulses (PPP, NPP) applied to the functionally isolated upper airways (UA) were studied in 11 anaesthetized cats breathing spontaneously through a tracheal tube. The UA pressure and the changes of tracheal airflow were recorded and the blood pressure and electrocardiogram were occasionally monitored. Sniff-like aspiration reflexes comprising powerful spasmodic inspirations could be elicited by PPP or NPP of 20 to 110 cm H2O or -14 to -140 cm H2O. The responses to NPP but also to PPP characterized by high peak inspiratory flow, mean inspiratory flow and tidal volume (PIF = 312.5 +/- 64.3 and 231.1 +/- 21.7 ml.sec-1; VTI = 178.3 +/- 46.7 and 110.1 +/- 14.4 ml.sec-1; VT = 40.9 +/- 8.3 and 22.5 +/- 1.7 ml) resembled closely the aspiration reflex elicited by mechanical stimulation of the pharyngeal wall. Occasionally, sneezing, minor modifications of breathing pattern and solitary forced inspirations could be induced by lower pressures. The results indicate that sudden pressure stimulation of the UA evokes vigorous respiratory responses including the aspiration reflex. These reflexes and their alterations may contribute to development or release of both UA obstruction and apnoea, at least in cats.

[Computer evaluation of respiratory changes during acute hypoxia in an experimental model]. / Pocítacové hodnotenie zmien dýchania pocas akútnej hypoxie v modelovom pokuse.

Experiences are presented concerning the use of a computer system in analyzing the dynamics of respiratory changes during reversible respiratory failure induced by inhalation of nitrogen in anesthetized cats. The main focus is on semiautomatic evaluation of the air flow signal during experimentally induced hypoxia in model experiment. On the basis of experience with computer aided evaluation of respiratory changes in over 40 animals and regarding the analysis of actual data obtained from 29 hypoxic episodes leading to reversible respiratory failure in 9 cats, advantages and pitfalls of evaluating respiration parameters by the breath-by-breath method are highlighted. Besides demonstrating the applied computer processing of data, the paper evaluates the most important of the 30 respiratory parameters studied, i.e. tidal volume (VT), minute ventilation (VE), inspiratory time (TI), and the ratios VI/TI and TI/TTOT. The results allow to quantify well the dynamics of development of changes of the respiratory model particularly during the first phase of acute hypoxic hypoxia. (Tab. 1, Fig. 5, Ref. 21).

Comparison of inspiratory effort in sniff-like aspiration reflex, gasping and normal breathing in cats.

The changes in airway occlusion pressure and airflow, occurring during two spasmodic breathing patterns, were studied and compared with normal breathing pattern in 12 anaesthetized cats. The inspiratory effort developed during the sniff-like aspiration reflex elicited by mechanical stimulation of the nasopharynx under control conditions proved to be very similar in character and intensity to the activity observed during gasping which occurred on resuscitation, of the same cats, from hypoxic apnoea. The starting (P50) and maximum (Pmax) airway occlusion pressure developed in these two spasmodic breathing patterns were very high. Extremely rapid rates of contraction and relaxation were detected by computer-assisted measurements of dynamic changes in both the pressure values and the slopes of pressure curves. The results suggest common effector mechanisms, reflecting similar forceful inspiratory drives, for the aspiration reflex and gasping. These two spasmodic processes differ substantially from normal breathing. Nevertheless, the aspiration reflex differs from gasping in that it can be elicited by activation of upper airway afferents during eupnea. Moreover, as yet, there is no definitive evidence that the brainstem mechanisms responsible for generating the aspiration reflex are the same as those of the gasp. The main benefits of this reflex are its rather easy elicitability under various conditions and its capability to induce important cardiorespiratory effects (e.g.) reversal of central apnoea) owing to its powerful activity.