Intermittent Type Research Articles

Waves and spatially localized structures in the turbulent flows of a viscous fluid: Calculation results

A direct numerical simulation was performed of intermittent and turbulent flows of viscous incompressible fluid in an infinite circular pipe. The Navier-Stokes equations were integrated at the Reynolds numbers of 1800 ≤ Re ≤ 4000 calculated from the mean velocity and a pipe diameter of D = 2R. The numerically obtained solutions belong to the class of mean streamwise periodic solutions with a very large period λmax = 16πR. The Fourier harmonic components of the velocity fluctuations corresponding to very low longitudinal wavenumbers are shown to be the most energetic. A detailed study was carried out of the structures of the calculated turbulent and intermittent flows. The accuracy and the very possibility of the approximation of the turbulent velocity field by the superposition of traveling and standing waves are analyzed. It is shown that the parameters of such a representation (wave amplitudes, phase velocities, and the position of the wave front) are strongly dependent on whether or not very low longitudinal wavenumbers are included in the mathematical model of the flow The numerical solutions at Re = 2200 and 2350 describe the intermittent type of the flow, for which the localized turbulent structures (turbulent puffs) propagate downstream while retaining their spatial dimensions. The space-time structure of the calculated turbulent puffs is compared with the available experimental data. The main statistical characteristics of the turbulence inside and outside the turbulent puff are calculated and the convective rate of the puffs downstream expansion is determined.

The Effect of Sodium Bicarbonate Ingestion on High-Intensity Intermittent Running and Subsequent Performance

The purpose of this study was to determine the effects of sodium bicarbonate (NaHCO3) ingestion on intermittent running and subsequent performance. Eight healthy men volunteered to take part in the study. One hour after the ingestion of either NaHCO(3) or placebo (sodium chloride; NaCl) participants undertook 20 x 24-second runs on a motorized treadmill at the velocity eliciting maximal oxygen uptake (100% v-VO(2)max). After sprint 20 participants performed a run to volitional exhaustion at 120% v-VO(2)max. Capillary blood samples for blood pH, bicarbonate ([HCO(3)]), and lactate ([Bla]) concentration were taken pre and postingestion, every fifth sprint and after the performance run. After ingestion of NaHCO(3), blood [HCO(3)] increased from resting values (p < 0.05), and the increase in pH approached significance. Blood [HCO(3)(-)] continually decreased throughout intermittent exercise (p < 0.05) and decreased further after performance in both trials (p < 0.05). [Bla] was similar in both trials throughout intermittent exercise but was greater at exhaustion for NaHCO(3) (main effect for trial; p < 0.05). There was no significant difference in performance of the group between trials (78 +/- 22 and 75 +/- 22 seconds for NaHCO(3) and NaCl, respectively). The intercept of the relationships between [Bla] and [HCO(3)(-)] and between [Bla] and pH was greater during NaHCO(3) (p < 0.05), whereas the relationship between pH and [HCO(3)(-)] was unchanged (p > 0.05). The results of this study suggest that the ingestion of NaHCO(3) before intermittent type exercise was sufficient to induce metabolic alkalosis but did not significantly affect performance. However, because significant individual variations in performance were observed, an individual approach to bicarbonate ingestion is recommended based on the intensity and duration of the required performance.

Complex nonlinear dynamics and controlling chaos in a Cournot duopoly economic model

Complex nonlinear economic dynamics in a Cournot duopoly model proposed by M. Kopel is studied in detail in this work. By utilizing the topological horseshoe theory proposed by Yang XS, the authors detect the topological horseshoe chaotic dynamics in the Cournot duopoly model for the first time, and also give the rigorous computer-assisted verification for the existence of horseshoe. In the process of the proof, the topological entropy of the Cournot duopoly model is estimated to be bigger than zero, which implies that this economic system definitely exhibits chaos. In particular, the authors observe two different types of economic intermittencies, including the Pomeau–Manneville Type-I intermittency arising near a saddle-node bifurcation, and the crisis-induced attractor widening intermittency caused by the interior crisis, which lead to the appearance of intermittency chaos. The authors also observe the transient chaos phenomenon which leads to the destruction of chaotic attractors. All these intermittency phenomena will help us to understand the similar dynamics observed in the practical stock market and the foreign exchange market. Besides, the Nash-equilibrium profits and the chaotic long-run average profits are analyzed. It is numerically demonstrated that both firms can have higher profits than the Nash-equilibrium profits, that is to say, both of the duopolists could be beneficial from a chaotic market. The controlled Cournot duopoly model can make one firm get more profit and reduce the profit of the other firm, and control the system to converge to an equilibrious state, where the two duopolists share the market equally.

Analysis of the intermittent behavior in a low-temperature discharge plasma by recurrence plot quantification

The paper presents applications of the recurrence plot quantification to the analysis of type 1 intermittency observed in a discharge plasma. The main measures of recurrence plot analysis considered are the laminarity and the determinism. First, it is demonstrated that the laminarity measure can be related to the average time between chaotic bursts in this type of intermittency. Second, it is shown that the determinism measure introduced by the recurrence plot quantification depends on the control parameter as a decreasing exponential. The test of the results is performed by analyzing the determinism measure for type 1 intermittency observed in the logistic map. It is also shown that the role of the intrinsic noise of the plasma can easily be identified by this technique.

A BRIEF REVIEW ON NUCLEAR FRAGMENTATION

In this article a brief review on nuclear fragmentation has been presented on both theoretical and experimental ground. On the theoretical aspects discussion on different models has been done. On experimental overview the multiplicity distribution, angular distribution, correlation and intermittent type of fluctuations have been discussed for black and grey particles is presented. An experimental review on projectile fragments is also given.

Is This a Philosophic Issue?

Brugada syndrome (BS) has an intermittent or concealed type, which can be unmasked by the sodium (Na(+))-channel-blocker challenge test. The appropriate risk stratification of patients with a drug-induced Brugada-type electrocardiographic (ECG), especially those without a history of syncope or aborted sudden cardiac death, remains unclear. The prognosis of patients with BS depends on the clinical type, cardiac arrest, syncope or if asymptomatic. The ratio of the asymptomatic group varies from 56.9% to 63.6% and, furthermore, their annual cardiac event rate is relatively lower at 0.24-3.6% compared with the cardiac arrest group. Patients with a drug-induced Brugada-type ECG have a poor prognosis if they had a history of ventricular fibrillation (VF) or aborted sudden cardiac death, because their risk becomes similar to that of patients with spontaneous Brugada-type ECG. They have the disturbance of the Na(+)-channel and the electrophysiologic substrate of VF, proven by the high inducibility of VF by stimulation test even in patients without spontaneous VF. Spontaneous VF will never occur if there is no VF substrate. Implantable cardioverter-defibrillators will certainly protect them, so patients with a drug-induced Brugada-type ECG, even without a history of VF or aborted sudden cardiac death, should be considered to have a poor prognosis.

Biologia populacional de Corydoras flaveolus (Siluriformes, Callichthyidae) no Rio Passa Cinco, sub-bacia do Rio Corumbataí, São Paulo, Brasil

O objetivo desse trabalho foi caracterizar a população de Corydoras flaveolus do Rio Passa Cinco com relação à estrutura em comprimento, proporção sexual e aspectos reprodutivos de acordo com os períodos de seca e cheia, bem como analisar sua condição corporal. Seis amostragens foram realizadas em cinco pontos distintos no Rio Passa Cinco (contemplando trechos de ordem dois, três, quatro, cinco e seis) com o uso de peneira, pesca elétrica e covos. Foram capturados 70 indivíduos, sendo 35 machos e 35 fêmeas. Não houve variação significativa nos graus de repleção e de gordura acumulada na cavidade visceral dos exemplares analisados entre os períodos considerados. O período reprodutivo de C. flaveolus foi extenso, sendo mais intenso na cheia, visto a maior porcentagem de indivíduos com gônadas maduras e o maior valor da relação gonadossomática durante esse período. A fecundidade absoluta média foi de 137 ovócitos, sendo a desova do tipo intermitente. As fêmeas foram maiores e relativamente mais pesadas do que os machos. Não houve diferença significativa na condição corporal de ambos os sexos entre os períodos considerados.

Strategies of search behaviuor in trematode Cercariae

On the base of analysis of original and literature data four basic strategies were distinguished in host-search behaviour of trematode cercariae. There are active search (1), passive waiting (2), active waiting (3) and prey mimetism (4). Many of the Xiphidiocercaria, cercariae of some Echinostomatidae, Psilostomatidae, Acanthocolpidae and Lepocreadiidae as well as cercariae of Fasciolidae, Haploporidae, Notocotylidae, Pronocephalidae, Gladorchiidae and some Haplosplanchnidae encysting on surface of underwater substrates follow the first strategy. These cercariae demonstrate a continuous swimming and photo-, geo- and sometimes chemoreactivity. The second strategy is characteristic for cercariae of Microcerca group with ambuscade behaviour. These cercariae exhibit pronounced oscilloreactions whereas other orienting reactions are feebly marked or even absent. Cercariae of Bucephalidae and Hemiuroidea which float passively in the water column also follow the strategy of passive waiting. The strategy of active waiting is characteristic of cercariae (Furcocercaria, Pleurolophocerca, Parapleurolophocerca, etc.) with an intermittent type of locomotion, where periods of active movement alternate regularly with periods of repose. These cercariae demonstrate a wide range of orienting reactions. The pray mimetism strategy exhibit cercariae of some trematodes (Azygiidae, Bivesiculidae, some Echinostomatidae, Heterophyidae, Lepocreadiidae, Gyliauchinidae, etc.) infecting their hosts passively per os. The active searching cercariae (strategy 1) usually infect sedentary animals or mobile ones but during periods of their minimal locomotory activity. The cercariae exploiting strategies 2–4 predominantly infect mobile animals. It was emphasized that the model of foraging strategies produced by Schoener (1971) and Huey and Pianka (1981) for free-living animals could be applied to analysis of cercarial hostsearch behaviour.

A novel type of intermittency in a non-linear dynamo in a compressible flow

The transition to intermittent mean--field dynamos is studied using numerical simulations of isotropic magnetohydrodynamic turbulence driven by a helical flow. The low-Prandtl number regime is investigated by keeping the kinematic viscosity fixed while the magnetic diffusivity is varied. Just below the critical parameter value for the onset of dynamo action, a transient mean--field with low magnetic energy is observed. After the transition to a sustained dynamo, the system is shown to evolve through different types of intermittency until a large--scale coherent field with small--scale turbulent fluctuations is formed. Prior to this coherent field stage, a new type of intermittency is detected, where the magnetic field randomly alternates between phases of coherent and incoherent large--scale spatial structures. The relevance of these findings to the understanding of the physics of mean--field dynamo and the physical mechanisms behind intermittent behavior observed in stellar magnetic field variability are discussed.

On–off intermittent synchronization between two bidirectionally coupled double scroll circuits

In this report the intermittent route from full synchronization to full desynchronization, of two bidirectionally coupled, double-scroll circuits, was experimentally studied. Coupling resistance, between the two circuits, served as the bifurcation parameter, controlling the synchronization. It was shown that the synchronization–desynchronization transition was realized through a regime of incomplete synchronization of the on–off intermittency type.

Detection of the type of intermittency using characteristic patterns in recurrence plots

One of the common routes to chaos is intermittency. Identification of the intermittency type is usually made using the properties of the probability distribution of laminar phases and of the average length of the laminar phases. Both have a statistical character and to obtain them a long time series has to be examined. Here, we present a recurrence plot method applicable to the analysis of short time series and through which the type of intermittency may be identified. The three types of intermittency introduced by Pomeau and Manneville and a chaos-chaos intermittency induced by interior crisis were examined. The identification of the type of intermittency is equivalent to the identification of the bifurcation associated with it. Our result seems particularly interesting as our method allows the analysis of short time series. The effect of the measurement noise on the effectiveness of the method is also discussed. An application of the method to the detection of type I intermittency in measured heart rate variability data is discussed.

Protein phosphatase 2Cm is a critical regulator of branched-chain amino acid catabolism in mice and cultured cells

The branched-chain amino acids (BCAA) are essential amino acids required for protein homeostasis, energy balance, and nutrient signaling. In individuals with deficiencies in BCAA, these amino acids can be preserved through inhibition of the branched-chain-alpha-ketoacid dehydrogenase (BCKD) complex, the rate-limiting step in their metabolism. BCKD is inhibited by phosphorylation of its E1alpha subunit at Ser293, which is catalyzed by BCKD kinase. During BCAA excess, phosphorylated Ser293 (pSer293) becomes dephosphorylated through the concerted inhibition of BCKD kinase and the activity of an unknown intramitochondrial phosphatase. Using unbiased, proteomic approaches, we have found that a mitochondrial-targeted phosphatase, PP2Cm, specifically binds the BCKD complex and induces dephosphorylation of Ser293 in the presence of BCKD substrates. Loss of PP2Cm completely abolished substrate-induced E1alpha dephosphorylation both in vitro and in vivo. PP2Cm-deficient mice exhibited BCAA catabolic defects and a metabolic phenotype similar to the intermittent or intermediate types of human maple syrup urine disease (MSUD), a hereditary disorder caused by defects in BCKD activity. These results indicate that PP2Cm is the endogenous BCKD phosphatase required for nutrient-mediated regulation of BCKD activity and suggest that defects in PP2Cm may be responsible for a subset of human MSUD.

Bronchogenic Cyst of the Interatrial Septum Presenting as Atrioventricular Block

Bronchogenic cysts are congenital lesions that are a remnant from abnormal budding of the embryonic foregut. These cysts are usually single; most cases are either asymptomatic or present with respiratory symptoms. A 43-year-old woman presented with intermittent type II atrioventricular block during cholecystectomy. The cardiac evaluation including transthoracic and transesophageal echocardiography and magnetic resonance imaging revealed a cystic homogeneous mass within the interatrial septum. The patient underwent surgical resection of the mass and closure of the septal defect. Histopathology identified ciliated columnar epithelium, consistent with the diagnosis of a bronchogenic cyst.

Circuit implementation and multiform intermittency in a hyper-chaotic model extended from the Lorenz system

This paper presents a non-autonomous hyper-chaotic system, which is formed by adding a periodic driving signal to a four-dimensional chaotic model extended from the Lorenz system. The resulting non-autonomous hyper-chaotic system can display any dynamic behaviour among the periodic orbits, intermittency, chaos and hyper-chaos by controlling the frequency of the periodic signal. The phenomenon has been well demonstrated by numerical simulations, bifurcation analysis and electronic circuit realization. Moreover, the system is concrete evidence for the presence of Pomeau–Manneville Type-I intermittency and crisis-induced intermittency. The emergence of a different type of intermittency is similarly subjected to the frequency of periodic forcing. By statistical analysis, power scaling laws consisting in different intermittency are obtained for the lifetime in the laminar state between burst states.

Pacemaker Syndrome During Managed Ventricular Pacing Mode: What is the Mechanism?

A 51-year-old woman underwent implantation of a dual chamber pacemaker 10 years ago, for symptomatic intermittent second-degree type II AV block. She remained free of symptoms during follow-up. Recently, she underwent pacemaker replacement because of battery depletion (Adapta ADDR01, Medtronic Inc., Minneapolis, MN, USA). Given intact AV conduction at the time of intervention, the Managed Ventricular Pacing mode algorithm (MVP, Medtronic), which provides AAI(R) pacing with ventricular monitoring and backup DDD/R pacing as needed, was programmed with a lower rate limit of 60 ppm and an upper rate limit of 130 ppm. Ten days after the procedure, the patient complained of asthenia, dyspnea, and presyncope. ECG at pacemaker interrogation revealed sinus tachycardia with second-degree type II AV block (Fig. 1). Atrial pacing artifacts with atrial capture are seen dissociated from the native QRS complexes. Pacemaker interrogation revealed pacing and sensing thresholds as well as impedances within normal range. In our patient, the repetitive atrial pacing during ventricular systole led to pacemaker syndrome and symptoms resolved by reprogramming the device to AV sequential pacing without MVP. What is the mechanism of atrial stimulation dissociated from the native QRS complexes?

Efeito do ácido indolbutírico e épocas de estaqueamento sobre o enraizamento de estacas herbáceas de figueira (&lt;em&gt;Ficus carica L.&lt;/em&gt;)

This work had as objective to verify the effect of six concentrations of indolbutiric acid (IBA) in the rooting of herbaceous cuttings of fig (Ficus carica L.) under intermittent mist irrigation, at three different times. The assays were installed in May, September and January, where in each time the used experimental design was entirely randomized, with six concentrations of IBA (0, 500, 1,000; 1,500;, 2,000; 2,500 and 3,000 mg L-1). The cuttings were collected at the Experimental Station of Unesp, located in the municipal district of Selvíria, Mato Grosso do Sul, Brazil, standardized at 10 cm long and two leaves. After the cutting preparation, they were immersed in Metiltiofan solution for one minute, and later immersed in IBA solutions for 10 minutes. Next, they were planted in flower boxes containing vermiculite. They were transported to a greenhouse, with 50% light reduction, with overhead irrigation of the intermittent mist type. The analyzed variables were: percentage of surviving cutting and taken root, number of roots and mass, maximum length of the root system and dry matter of the root. In the conditions in which the study work was conducted, it can be concluded that: the herbaceous propagation of fig is viable; there was an effect of IBA in May only, where the best concentration was 1,000 mg L-1; the best times for herbaceous cutting of fig are in September and January, without the use of IBA, in which the best results were obtained for the percentage of rooted cuttings.

Model Based Optimization of Nitrogen Removal in a Full Scale Activated Sludge Plant

This paper evaluates model-based upgrading of an activated sludge plant treating wastewaters of leather tanning industrial district with an average capacity of 13,000 m3/d. Significant impact of temperature changes on biochemical processes, such as nitrification and denitrification were quantified and used in setting the aeration control for process optimization in terms of total nitrogen removal. Model evaluation based upon kinetic and stoichiometric parameters specifically determined for the tannery wastewater, indicated that an intermittent aeration type of an operation strategy was suitable for achieving the required effluent total nitrogen level of 100 mgN/L under all operating conditions at the process temperature range of 21°–C35°C. The simulation study also showed that the nitrification performance of the plant was improved by increasing the aeration intensity. The application of intermittent aeration provided a competitive advantage in meeting the total nitrogen standards, improving the total nitrogen removal to around 60%.

A single center study of clinical and paraclinical aspects in Iranian patients with allergic rhinitis.

Allergic rhinitis (AR) is a common form of allergic disorder in Iran and rest of the world. This study was conducted to investigate the symptoms and paraclinical aspects of this allergy among Iranian patients. A total of 206 patients (51.5%: male), with one of the specific symptoms of AR, from March 2005 to March 2007 were enrolled in the study. A written questionnaire was completed for each patient. Furthermore, paraclinical evaluations including CBC, serum total IgE, spirometry and skin prick test (SPT) with common allergens were done for the patients. The ages of our patients ranged from 2 to 62 years of age (mean age of 18 - /+11.8 years). Mean age of onset of symptoms was 11.6 -/+ 9.9 years. In 82% of cases histories of other allergic diseases were seen in patients or their family members. Rhinorrhea was the most common symptom in our patients (77.9%). Frequencies of mild persistent, moderate - severe persistent, mild intermittent and moderate -severe intermittent types of AR were 20.5%, 41%, 21% and 17.5%, respectively. Frequencies of positive SPTs in all cases, patients with persistent and intermittent allergic rhinitis were 86.7%, 88.2% and 84.1%, respectively. The most common allergens in positive SPTs, were trees, weeds, grasses and Dermatophagoides pteronysinus. About 55.5 % of patients showed elevated total IgE levels (> or = 100 IU/ML). Abnormal spirometry results were seen in 33.5% of cases. The present study showed that among paraclinical investigations for AR, positive SPTs with aeroallergens, are more consistent with clinical findings. Regarding high ferequency of abnormal spirometry, we recommend that clinical suspicion about hyperreactive airway disease in AR patients is mandatory and performing spirometry for these cases is necessary whenever possible.

Analysis of complex intermittency in Boost converter from a bifurcation control viewpoint

Due to undesirable interference via unintended coupling paths, switching converters may exhibit complex intermittency, which appears as a form of bifurcation undergoing regular operation, subharmonics, and chaos orderly and repeatedly for a long period of time. Such intermittent operation, being an unwanted operating state, should normally be avoided in power converters. This paper expounds the mechanism and conditions for the emergence of intermittency in a common current-mode controlled Boost converter. It is found that interference at frequencies near the switching frequency or its rational multiples may induce intermittent operation. The strengths and frequencies of the interfering signals determine the type and period of intermittency. The problem is analyzed by transforming the time-bifurcation analysis to a conventional parameter-bifurcation analysis. Based on this transformation, intermittency can be investigated from the bifurcation control viewpoint. Furthermore, the critical circuit parameter conditions for the emergence of intermittency can be predicted and compared with those from circuit simulation.

Geology of a submarine volcanic caldera in the Tonga Arc: Dive results

A submersible dive conducted on Volcano #1 located near 21° 09′S–175° 45′W on the Tonga Arc showed that the volcanic edifice with a caldera floor area of 30 km 2 located at and 450 m deep (b.s.l.=below sea level) was constructed recently during episodic volcanism. The sequential volcanic events are recorded along a faulted terrain formed in response to the collapse of the caldera wall. The post-caldera events are marked by occasional eruptions that have built scoriaceous cones associated with low-temperature hydrothermal venting and localized small-scale collapse features. The stratigraphy of the caldera wall indicates that the volcano was built by explosive volcanism alternating with quieter eruptive events. The repeated, violent explosive events formed ≤ 20 m thick sequences composed of alternating fine-grained ash beds and sand- to boulder-sized pyroclastic layers. During quieter volcanic events, dykes and massive flows intruded and/or accompanied the eruption of the volcaniclastic deposits throughout the sections of the wall explored. Massive columnar-jointed flows consist of viscous, silica-rich lavas forming tabular and giant radial-jointed (GRJ) flows formed in large (> 8 m in diameter) conduits and extruded onto the sea floor. In addition, massive lava flows forming sill-like complexes were observed underneath and near the giant radial-jointed columnar flows. Also, an intermittent quiet type of eruption produced vesicular lava flows, which are interbedded within the pyroclastic layered deposits. The massive and vesicular lavas consist of andesites and dacites with Ca-depleted (pigeonite) and Ca-enriched (salite) pyroxene, and intermediate (andesine-labradorite) to calcic (bytownite) plagioclase. They are depleted in total alkalis (Na 2O + K 2O < 3%), K 2O (< 1%), Zr/Y (< 1.8), Nb/Zr (< 0.01) and light Rare Earth Elements. We interpret that these andesite–dacite series were erupted after undergoing crystal-liquid fractionation in a magma chamber located underneath the caldera floor.