Wurtzite AlGaAs Nanowires.

Semiconducting nanowires, unlike bulk, can be grown in both wurtzite and zincblende crystal phases. This unique feature allows for growth and investigation of technologically important and previously unexplored materials, such as wurtzite AlGaAs. Here we grow a series of wurtzite AlGaAs nanowires with Al content varying from 0.1 to 0.6, on silicon substrates and through a comparative structural and optical analysis we experimentally derive, for the first time, the formula for the bandgap of wurtzite AlGaAs. Moreover, bright emission and short lifetime of our nanowires suggest that wurtzite AlGaAs is a direct bandgap material.

Crystal Phase Quantum Well Emission with Digital Control.

One of the major challenges in the growth of quantum well and quantum dot heterostructures is the realization of atomically sharp interfaces. Nanowires provide a new opportunity to engineer the band structure as they facilitate the controlled switching of the crystal structure between the zinc-blende (ZB) and wurtzite (WZ) phases. Such a crystal phase switching results in the formation of crystal phase quantum wells (CPQWs) and quantum dots (CPQDs). For GaP CPQWs, the inherent electric fields due to the discontinuity of the spontaneous polarization at the WZ/ZB junctions lead to the confinement of both types of charge carriers at the opposite interfaces of the WZ/ZB/WZ structure. This confinement leads to a novel type of transition across a ZB flat plate barrier. Here, we show digital tuning of the visible emission of WZ/ZB/WZ CPQWs in a GaP nanowire by changing the thickness of the ZB barrier. The energy spacing between the sharp emission lines is uniform and is defined by the addition of single ZB monolayers. The controlled growth of identical quantum wells with atomically flat interfaces at predefined positions featuring digitally tunable discrete emission energies may provide a new route to further advance entangled photons in solid state quantum systems.

[Regulatory influence of hippocampus CA1 and CA3 areas on bulbar respiratory neurons under hypoxia].

We studied the influence of stimulation of the CA1 and CA3 areas of the hippocampus on the impulse activity of respiratory neurons (RN) of the medulla oblongata under normal and oxygen deficiency conditions. Under conditions of normal atmospheric pressure, the electrical stimulation of the CA1 and CA3 areas of the hippocampus had mainly an inhibiting influence. In the initial phase, at a 4-5-thousand meter altitude, activation of frequent discharge of neurons occurred. In this situation, stimulation of the CA1 and CA3 areas was more accentuated than under conditions of normoxia. In the second phase (an altitude of 7.5-8 thousand meters), on the reduction of the impulse activity of neurons, stimulation of the CA1 and CA3 areas of the hippocampus induced untypical responses of these neurons.

Crystal phase quantum dots.

In semiconducting nanowires, both zinc blende and wurtzite crystal structures can coexist. The band structure difference between the two structures can lead to charge confinement. Here we fabricate and study single quantum dot devices defined solely by crystal phase in a chemically homogeneous nanowire and observe single photon generation. More generally, our results show that this type of carrier confinement represents a novel degree of freedom in device design at the nanoscale.

[Determination of the role of the hypothalamic lateral mammilar nucleus in regulation of neurons in the respiratory center of rat's medulla during hypoxia].

The pulse activity of medullar respiration center neurons and rat's respiration as a function of excitation of the lateral mammillary (LM) nucleus of the hypothalamus were studied in differing hypoxic conditions. Electrical stimulation of the LM nucleus in normoxia had a predominantly activating effect. A moderate pO2 fall at the start of "ascent" to 4000-5000 m increased pulsation of the respiratory neurons. On this background the activating effect of LM nucleus stimulation was less pronounced as compared to normoxia although it still prevailed over inhibition. The alleviating effect of LM nucleus stimulation was particularly evident with a sharp inhibition of respiratory neurons caused by critical oxygen deficiency at the highest altitude (7500-8000 m). After the "descent" to the normal atmospheric pressure the spontaneous rhythmic activity of rat's neurons and reaction to stimulation gradually recovered baseline values.

[Reaction of respiration neurons in the medulla on locus coeruleus irritation by hypoxia].

Effects of locus coeruleus (LC) stimulation on the impulse activity of bulbar respiration neurons in rats were studied on a background of varying hypoxia. Different levels of hypoxia were used as an experiment model for ensuing summation of the LC effect. At the normal atmospheric pressure, LC electrical stimulation had an alleviating and also inhibiting effect on the impulse activity of these medulla neurons; however, the former effect was dominant. During the initial hypoxia simulating the altitude of 4000-5000 m, LC stimulation had a weak alleviating effect. On this level of hypoxia such effect is highly important, as unchecked strengthening of respiration activating mechanisms may result in excessive hyperventilation and consequent respiration slowing down to standstill because of low blood content of carbonic acid. During heavy hypoxia simulating the altitude of 7500-8000 m LC electrical stimulation had an intrinsic to this structure activating effect on markedly inhibited respiratory neurons. In the event of acute hypoxia the highly sensitive cortical component lose their inhibitory effect on the bulbar respiratory center and suprabulbary formations. However, this favours startup of the activating systems and enhancement of the respiration ventilatory function.

[Efficiency of an arbitrary respiratory rhythm reducing method in students of special medical physical educational groups].

Three-month decreased voluntary optimum respiration rate (DVORR) trainings during therapeutic exercises in students with various abnormalities caused increases in vital capacity and chest circumference amplitude. DVORR also affected cardiovascular performance. During exercises, heart rate decreased and pulse pressure increased, suggesting economized cardiac performance and better myocardial function. The use of this method in the students reduces morbidity, improves health, and increases physical fitness and progress in studies.

[Influence of cholinergic and adrenergic agents of the electric activity of the brain and the heart under hypoxia].

Injection of adrenergic and cholinergic agents to animals in the normal athmospheric conditions did not tigger drastic changes on the electric activity of the brain and heart. Acutehipoxia demands high adaptability from the body. In such conditions stimulation of reticular formation and hypothalamus produces different changes in the EEG and ECG activity whith injecting adrenergic and cholinergic agents. It was determined that cholinergic influence are effective in the regulation of electrical brain activity while adrenergics are more important for the realization of descending influences of the truncus cerebri vegetative centers and are less active in the modulation of the cerebral cortex activity.

Entangled photon pairs from semiconductor quantum dots.

Tomographic analysis demonstrates that the polarization state of pairs of photons emitted from a biexciton decay cascade becomes entangled when spectral filtering is applied. The measured density matrix of the photon pair satisfies the Peres criterion for entanglement by more than 3 standard deviations of the experimental uncertainty and violates Bell's inequality. We show that the spectral filtering erases the "which path" information contained in the photons' color and that the remanent information in the quantum dot degrees of freedom is negligible.

[Effects of adrenergic substances on the cardiac rhythm and electrical activity of the brain in rabbits during hypoxia].

The paper reports the effects of alpha and beta-adrenergic substances on the cardiac rhythm and electrical activity of the brain under the hypoxic conditions. beta-adrenergic substances were shown to have a stronger influence on these parameters as compared with alpha-adrenergic. The neoepinephrine effects were pronounced before "lifting", while the propranolol effects increased "at the altitude". Neopinephrine was found to have a stimulating effect on the cerebral cortex under the conditions of hypoxia.

[The limbical mechanisms of regulations of respiratory neurons in hypoxia conditions]. / Vliianie limbicheskikh struktur na dykhanie v usloviiakh gipoksii.

The structures of limbic system have great integration in vegetative reactions. In the oxygen deficiency conditions we studied influence of irritation of limbical cortex, orbitofrontal cortes, hipotalamys, septum and hippocampus (CA1 and CA3 areas) on the impulse activity of respiratory neurons. Phases of hypoxia were the model of experiment. Irritation some of this structures on normoxia and 4-5 thousand meters higher, we discover inhibiting influense on respiratory neurons; some structures irritation had activating influence. In difficult conditions of hypoxia (7.5-8 thousand meters) on the reduction of the impulse activity of neurons, stimulation induced uncharacteristic reactions. Those different reactions of irritation limbic structures have regulation sense on respitatory neurons.

[Response of respiratory neurons of the medulla oblongata to the septum stimulation in hypoxia]. / Reaktsiia dykhatel'nykh neironov prodolgovatogo mozga na razdrazhenie iader peregorodki pri gipoksii.

In the oxygen deficiency conditions, we studied influence of irritation of ventral (BNST), lateral (LSN) and medial (MSN) nuclei of the septum on the impulse activity of the bulbar respiratory neurons and on respiration. Phases of hypoxia were the model of experiment. In conditions of normal atmospheric pressure, the electrical stimulation of BNST, LSN and MSN nuclei of the septum exerted inhibiting as well as activating influence with the inhibiting influence prevailing. In difficult conditions of hypoxia (7.5-8 thousand meters) on the reduction of the impulse activity of neurons, stimulation of septum nucleuses induced uncharacteristic reactions of those neurons.

[Pathological types of breathing during acute hypoxia]. / Patologicheskie tipy dykhaniia pri vozdeistvii ostroi gipoksii.

Different breathing pathologies (apneusis, gasping, Cheyne-Stokes breathing and Kussmaul breathing) were observed in anaesthetized rabbits and rats exposed to hypoxia at the altitude of 7500-8000 meters. Dominance of the high-voltage slow EKG activity (the delta-wave type) suggested deterioration of the brain functioning. Registration of impulse activities of the inspiration and expiration breathing neurons in medulla oblongata revealed a higher tolerance of the inspiration neurons to severe hypoxia which is attributed to the metabolic specifics and functional heterogeneity of these neurons. Character of the neuron impulsation is indicative of the reflectory effects of hemo- and mechanoreceptors, and the direct effects of different humoral substances resulting in impairment of the central control of pacemakers and breathing pathologies. It appears that various breathing pathologies in altitude chambers and mountains are triggered by the hypoxic factor. However, no dependence was established either between the initial breathing rhythm (before "ascent") and various types of breathing at the "altitude" or these types of breathing and magnitude of hypoxia.

[Effect of insulin on the composition of chromatin phospholipid in rat liver cells]. / Deistvie insulina na sostav fosfolipidov khromatina kletok pecheni krys.

In vivo the action of insulin on rat liver chromatin phospholipid composition was investigated. It was shown that the hormone led to reliable increase (nearly 20%) of total phospholipid content. The same phenomenon was shown also in the fraction of active chromatin while the phospholipids content of non-active chromatin didn't changed. It was also shown that the content of three from six phospholipid fractions altered under the insulin action. The content of sphingomyelin and phosphatidilethanolamine increased and the quantity of phosphatidylinositol decreased under the hormone action. The decrease of monophosphoinositides content was accompanied by the reliable increase of triphosphoinositides amount. It was suggested that the fractions of chromatin polyphosphoinositides were redistributed under the action of insulin.

[Effect of mediodorsal thalamic nucleus on the respiratory neurons from medulla oblongata and the rat respiration during hypoxia]. / Vliianie mediodorsal'nogo iadra talamusa na dykhatel'nye neirony prodolgovatogo mozga i dykhanie krys v usloviiakh gipoksii.

In the normal as well as in the oxygen deficiency conditions the research has been conducted to study the influence of associative mediodorsal (MD) nucleus of thalamus on impulsive activity of respiratory neurons of medulla oblongata of respiration. In conditions of normal atmospheric pressure, before the uplift of the animals, the electrical stimulation of MD of nucleus of thalamus has had mainly inhibiting influence. In the initial phase, on 4-5 thousand meter altitude, activation of frequent discharge of neurons occurred, the respiration has become frequent as well. In this situation the inhibiting influence of stimulation of MD nucleus of thalamus was more accentuated than in conditions of normoxia. In the second phase, 7.5-8 thousand meters, the opposite occurred, i.e. reduction of respiratory center activity of medulla oblongata and thalamus. In this difficult conditions of hypoxia, a reduction of impulsive activity of neurons has been observed; the respiration was becoming slower and surface. Meanwhile, the inhibiting influence of thalamus was not significant.

[Involvement of central and peripheral cholinergic structures in regulation of cerebral electric activity and cardiac function in rabbits during hypoxia]. / Rol' tsentral'nykh i perifericheskikh kholinérgicheskikh struktur v reguliatsii élektricheskoi aktivnosti mozga i serdechnoi deiatel'nosti krolikov v usloviiak gipoksii.

In the normoxic conditions, prior to the "ascent" of rabbits, the i.v. injection of M-choline blocking benactyzine slowed down the ECG rhythm already within the next few minutes. Irritation of the reticular formation against this background did not initiate the reaction of activation; yet, heart rate was essentially unaltered by benactyzine. This was ascribed to low effectiveness of the benactyzine M-cholinergic mediation with respect to the cardiac function in contrast to the electric activity of the brain cortex due to, apparently, the abundance of M-choline receptors in this structure. The effect of N-cholinolytic ganglerone on the spontaneous and induced cortical activities was weak and, as compared with benactyzine, more expressed upon the heart rate. These choline blockers combined with hypoxia and the benactyzine-produced slow ECG waves on the initial phase (4000-5000 m) brought about neither spontaneous nor induced by the reticular formation irritation activation of ECG. At the maximal "altitude" (8500-9000 m) the benactyzine-synchronized ECG rhythm tended to become deeper assuming the low delta-type activity observed at the same "altitude" without i.v. benactyzine. With this ECG, irritation of Dieters' formation was impotent to trigger the reaction of activation.

[Effect of hydrocortisone on composition of polyphosphoinositides in liver cell nuclear membrane and rat brain]. / Deistvie gidrokortizona na sostav polifosfoinozitidov iadernykh membran kletok pecheni i golovnogo mozga krys.

The action of hydrocortisone in vivo was shown to cause changes both in the total amount of phospholipids and polyphosphoinositides of rat liver and brain nuclear membranes. The hormone increased the content of five from seven phospholipid fractions including the fraction of monophosphoinositide when acting in concentration and exposition leading to activation of biosynthetic processes. The increasing of monophosphoinositides amount was accompanied by the decreasing of triphosphoinositides content which indicated the redistribution among the phosphoinositides fractions under the steroid hormone action in both cell types.

[Effect of estradiol on phosphoinositide composition of nuclear membranes of rat brain cells]. / Deistvie éstradiola na sostav fosfoinozitidov iadernykh membran kletok golovnogo mozga krys.

The effect of estradiol on phospholipids and particularly on phosphoinositides of nuclear membranes of rat brain cells at different stages of hormone action was investigated. It was shown that hormone leads to the elevation of phospholipids total amount at the primary and early stages of its action (1 and 4 h after estradiol injection, correspondingly). The increase of content of almost all individual fractions of phospholipids as well as phosphatidylinositol (i.e. monophosphoinositide) was detected. It is remarkable that the monophosphoinositides elevation takes place mainly due to the decrease of di- and especially of triphosphoinositide. The ratio of triphosphoinositide/monophosphoinositide decreases more than twice. It was concluded that the ratio of triphosphoinositide to monophosphoinositide may be a peculiar indicator of the status of nuclear membranes for the functioning of triphosphoinositide regulatory system.

[Diprivan as a component of the anesthesia in emergency surgical interventions in children]. / Diprivan kak komponent anestezii pri ékstrennykh operativnykh vmeshatel'stvakh u detei.

Sixty-seven children aged 5-15 years were induced to narcosis and narcotized with diprivan. The patients were operated on for appendicitis, peritonitis, osteomyelitis, phlegmons of different localization, and craniocerebral injuries. For induction, diprivan was intravenously injected in a dose of 3-4 mg/kg. During the main narcosis (central analgesia with fentanyl in a total dose of 0.008 mg/kg/h) diprivan was infused by microjets in a dose of 6-9 mg/kg/h in combination with nitrogen oxide and oxygen in 1:1 ratio. Control group consisted of similar age-matched patients, to whom central analgesia without diprivan was administered. Respiration rate, heart rate, systolic and diastolic arterial pressure, mean arterial pressure (MAP), SaO2, and clinical course of anesthesia were examined at different stages of analgesia and surgery. During induction anesthesia the respiratory rate decreased by 27% and SaO2 decreased to 92.75 +/- 1.2% due to the specific effect of diprivan. MAP decreased by 4.8%. During the traumatic moment of surgery, respiratory rate increased by 20.1%, SaO2 was 98.25 +/- 0.24%, and heart rate increased by 22.6%. In the controls this period of surgery was associated with a more expressed reaction of the cardiovascular system, presenting as tachycardia (114.5 +/- 3.6) and increase of MAP by 10.1%. After anesthesia pain sensitivity returned earlier, due to which tachycardia and negligible hypertension were observed.