Periodic Interruption Research Articles

Effects of low-pass filtering on intelligibility of periodically interrupted speech

The combined effect of low-pass filtering (cut-off frequencies between 500 and 3000 Hz) and periodic interruptions (1.5 and 10 Hz) on speech intelligibility was investigated. When combined, intelligibility was lower than each manipulation alone, even in some conditions where there was no effect from a single manipulation (such as the fast interruption rate of 10 Hz). By using young normal-hearing listeners, potential suprathreshold deficits and aging effects that may occur due to hearing impairment were eliminated. Thus, the results imply that reduced audibility of high-frequency speech components may partially explain the reduced intelligibility of interrupted speech in hearing impaired persons.

Transient Storage of Electrical Charge in Biofilms of Shewanella oneidensis MR-1 Growing in a Microbial Fuel Cell

Current output of microbial fuel cells (MFCs) depends on a number of engineering variables mainly related to the design of the fuel cell reactor and the materials used. In most cases the engineering of MFCs relies on the premise that for a constant biomass, current output correlates well with the metabolic activity of the cells. In this study we analyze to what extent, MFC output is also affected by the mode of operation, emphasizing how discontinuous operation can affect temporal patterns of current output. The experimental work has been carried out with Shewanella oneidensis MR-1, grown in conventional two-chamber MFCs subject to periodic interruptions of the external circuit. Our results indicate that after closure of the external circuit, current intensity shows a peak that decays back to basal values. The result suggests that the MFC has the ability to store charge during open circuit situations. Further studies using chronoamperometric analyses were carried out using isolated biofilms of Shewanella oneidensis MR-1 developed in a MFC and placed in an electrochemistry chamber in the presence of an electron donor. The results of these studies indicate that the amount of excess current over the basal level released by the biofilm after periods of circuit disconnection is proportional to the duration of the disconnection period up to a maximum of approximately 60 min. The results indicate that biofilms of Shewanella oneidensis MR-1 have the ability to store charge when oxidizing organic substrates in the absence of an external acceptor.

Growth mechanism of highly uniform InAs/GaAs quantum dot with periodic arsine interruption by metalorganic chemical vapor deposition

The mechanism for suppressing the formation of abnormally large islands during the conventional quantum dot (QD) growth was investigated. In comparison of the periodic arsine interruption method to the conventional method, InAs QDs grown on GaAs substrate by metal organic chemical vapor deposition has a higher density and aspect ratio without large islands. The formation of large islands was related to the inhomogeneity in the nucleation and growth process of QDs. The surface modification from As-stabilized to In-stabilized surfaces during arsine interruption modulated the surface energy and resulted in more homogeneous and simultaneous nucleation of QDs. The arsine interruption time was found to be a critical parameter for the homogeneous QD growth without abnormally large islands.

Mathematical modelling of the sorption dynamics of radionuclides by natural clinoptilolite in permeable reactive barriers

AbstractThe anthropogenic accidents in the world (including the underground emergency nuclear explosion at the site “Kraton-3” (Yakutiya) and also the recent Fukushima accident) resulted in significant environmental pollution by radionuclides, mainly long-lived 90Sr and 137Cs. One of the ways to solve this problem is the creation of “permeable reactive barriers” (PRBs). High selectivity of clinoptilolite-containing tuffs (CLT) towards Sr2+ and Cs+ radionuclides, together with their availability and reasonable cost, make possible their use as PRBs. The scales of the ion-exchange processes taking place on PRBs indicate the necessity of mathematical modelling. In this connection, Sr2+ and Cs+ ion-exchange sorption on Khonguruu CLT (Yakutiya) from solutions of various mineralizations was studied under equilibrium and non-equilibrium conditions. The physicochemical and mathematical models of the dynamic ion-exchange process and also the computer program considering both structural features of CLT (two-stage particle diffusion kinetics) and possible periodic interruptions of the process were developed. The breakthrough time of CLT as a geochemical barrier was calculated by such mathematical modelling.

Uptake of hydrogen from some carbon fibres examined by Secondary Ion Mass Spectrometry

The use of carbonaceous materials for hydrogen storage is not as simple as it may seem. Hydrogen atoms have different bonding energies and are incorporated into different types of these materials. Therefore, it is particularly important to distinguish between the surfacial atoms and those that are embedded in the bulk of the sample. SIMS spectrograph with periodical interruptions of the ion beam enables us to appreciate that at room temperature and in high vacuum, some outgassing of the surfacial hydrogen takes place.

Optical and structural properties of InGaN/GaN short-period superlattices for the active region of light- emitting diodes

The results of the study of structural and optical properties of short-period InGaN/GaN superlattices synthesized by MOCVD on sapphire substrates are presented. To form the superlattices, the method of periodic interruption of the growth of the InGaN layer with hydrogen supply into the reactor was used. It is shown that, with the use of the suggested method, an InGaN/GaN periodic structure with the developed interfaces and regions of joining the neighboring InGaN layers not correlated in a vertical direction is formed. The formation of such regions leads to a heavy dependence of the shape of the emission spectra of the super-lattices on the number of periods in the range of 400–470 nm.

Innovative responses for preventing HIV transmission: The protective value of population-wide interruptions of risk activity.

Concurrent partnering contributes to high HIV prevalence. This is in part due to the natural history of the virus. After transmission, an individual’s viral load spikes in a period of ‘acute infection’ during which they are highly infectious. Models estimate that around 10 - 45% of HIV acquisition arises from sex with an individual in the acute infection period.
 If everyone in a population abstained from high-risk sex for a given period of time, in theory the viral loads of all recent seroconverters should pass through the acute infection period. When risk behaviour resumed there would be almost no individuals in the high-viraemic phase, thereby reducing infectivity, and HIV incidence would fall. 
 Recurring population-wide shifts in risk behaviour are not unheard of. Many, in fact, occur as part of existing religious observances. The month of Ramadan in Muslim communities is perhaps one of the most obvious cases. Ramadan sees significant behaviour changes. In addition to fasting from sunrise to sunset, observant individuals abstain from coitus during daylight hours. There is anecdotal evidence that risky sexual behaviours are also significantly reduced over this period. In Indonesia, for instance, it was reported that research with sex workers was not possible during Ramadan because people ‘abstained from sex from one end of the month to the other … Many sex workers returned to home villages during this time.’ 
 This article argues that a population-wide interruption of risk behaviour for a set period of time could reduce HIV incidence and make a significant contribution to prevention efforts. It calls for mathematical modelling of periodic risk behaviour interruptions, as well as encouragement of policy interventions to develop campaigns of this nature. A policy response, such as a ‘safe sex/no sex’ campaign in a cohesive population, deserves serious consideration as an HIV prevention intervention. In some contexts, periods of abstinence from risk behaviour could also be linked to existing religious practices to provide policy options.

Creep damage characterization using non-linear ultrasonic techniques

Abstract This paper describes the use of non-linear ultrasonic techniques for the characterization of material degradation in 99.98% pure copper due to high-temperature creep. Flat dog-bone-shaped specimens were subjected to constant load creep testing at different stress and temperature levels. Creep damage progression was monitored by conducting continuous and interrupted mode creep tests. In the case of continuous loading non-linear ultrasonic (NLU) measurements were conducted after fracture at different locations along the gage length of the sample. For interrupted tests the NLU measurements were conducted on different creep life fractions, through periodic interruption of the creep test. In all cases a through transmission NLU measurement technique was employed. Three different non-linear measurements, namely static displacement, second harmonic and third harmonic, were taken and their responses compared. The NLU measurements were found to be significantly sensitive to the extent of creep damage (∼200–2500% of base level), while the linear ultrasonic measurements, representing the change in longitudinal velocities, were only in the range 10–30% for a comparable creep damage level. NLU measurements carried out on fractured samples suggest that the NLU response was locally high at locations where the creep damage was concentrated, compared with other locations, even within the gage length of the specimen. This was confirmed using micrograph observations. Of the three non-linear measurements, the third harmonic data was most sensitive to creep damage.

Gas exchange alteration caused by water deficit during the bean reproductive stage

The purpose of the present study was to analyze gas exchanges in leaves and the parameters of productivity of beans (Phaseolus vulgaris, L.) submitted to two water deficiency periods during which three water regimes were employed: W1 (1,0 ETo during the entire plant cycle); W2 (1,0 ETo up to the flowering period and irrigation interruption from the 37 to the 51st day following sowing, and W3 (in addition to the reproductive phase, water deficit was also applied during the vegetative stage). Photosynthesis was one of the main physiological factors affected by water deficit. This was not only caused by the stomata closure, but also by carboxilation reduction due to metabolic damage. This effect was, however, offset 24 h after rehydration. During flowering, the water deficit caused crop productivity to drop significantly, reducing the number of pods and the number of seeds per pod, independently of the water deficit during the vegetative stage. The weight of 100 seeds however, was the same regardless of treatment. These results suggest that the water deficit caused the reduction of photo-assimilates, which affected grain productivity. Nevertheless, once properly formed, seeds developed totally; a strategy of the plant to produce less seeds under stress, but viable to perpetuate the species.

Effect of Orthognathic Surgery for Correction of Class III Facial Deformities in the Development of Obstructive Sleep Apnea

Obstructive sleep apnea is recognized as a major respiratory disorder in adults, characterized by a sharp decline or periodic interruption of airflow during sleep. The exact cause of this condition is uncertain and apparently multifactorial. Prognathic (Class III) cases are generally subject to the procedures of mandibular retrusion through sagittal ramus osteotomies that change the characteristics of the oropharynx, causing reduction of the airway space. The aim of this paper is to review the literature on the influence of orthognathic surgery for the correction of prognathism in the development of postoperative respiratory disorders such as obstructive sleep apnea.

Growth patterns of fossil vertebrates as deduced from bone microstructure: case studies from India

Bone microstructure is affected by ontogeny, phylogeny, biomechanics and environments. These aspects of life history of an extinct animal, especially its growth patterns, may be assessed as fossil bone generally maintains its histological integrity. Recent studies on the bone histology of fossil vertebrates from India encompass different types of temnospondyls and dicynodonts from different Permian and Triassic horizons. The examined taxa show that they had distinct bone histology and varied growth patterns. The Early Triassic trematosaurids had an overall fast growth, which contrasts with that of the Middle and Late Triassic temnospondyl taxa examined. The dicynodonts on the other hand, were characterized by an overall fast growth with periodic interruptions, variable growth rates dependent on ontogeny and indeterminate growth strategy. A comparative study encompassing several neotherapsid genera including the dicynodonts shows signifi cant evolutionary trends towards determinate growth strategy and reduced developmental plasticity.

Speech with Gaps: Effects of Periodic Interruptions on Speech Intelligibility

Objective: This study examined the role of central auditory completion in speech understanding. The perception of periodically interrupted speech was investigated. For this purpose, gaps were inserted into speech signals by silencing out defined intervals. The main hypothesis was that word recognition increases with shorter gaps and is less influenced by the total amount of gaps. Patients and Methods: Seventeen normal-hearing young adults took part in this study. Phrases from the German HSM speech recognition test were used as speech material. The examination comprised 220 modulated sentences presented binaurally at 65 dB. Intervals with durations ranging from 50 to 700 ms were taken to silence out 50, 65 and 80% of each sentence, respectively. Results: Mean speech perception values were in the range of 65–92%, 35–92% and 35–95% correct answers for gap ratios of 50, 65 and 80%, respectively. When comparing the same interval duration, word recognition was better for smaller gap ratios. Both, gap ratio and gap duration had a significant influence on identification performance. Conclusions: Speech can be understood even when very large proportions are blanked out. A significant decrease in perception can be observed when gap duration exceeds more than half of the syllable length.

Quantum formalism to describe binocular rivalry

On the basis of the general character and operation of the process of perception, a formalism is sought to mathematically describe the subjective or abstract/mental process of perception. It is shown that the formalism of orthodox quantum theory of measurement, where the observer plays a key role, is a broader mathematical foundation which can be adopted to describe the dynamics of the subjective experience. The mathematical formalism describes the psychophysical dynamics of the subjective or cognitive experience as communicated to us by the subject. Subsequently, the formalism is used to describe simple perception processes and, in particular, to describe the probability distribution of dominance duration obtained from the testimony of subjects experiencing binocular rivalry. Using this theory and parameters based on known values of neuronal oscillation frequencies and firing rates, the calculated probability distribution of dominance duration of rival states in binocular rivalry under various conditions is found to be in good agreement with available experimental data. This theory naturally explains an observed marked increase in dominance duration in binocular rivalry upon periodic interruption of stimulus and yields testable predictions for the distribution of perceptual alteration in time.

Growth behaviour of InGaN/GaN self‐assembled quantum dots with different growth conditions in horizontal MOCVD

AbstractInGaN/GaN self‐assembled quantum dots (QDs) were grown on (0001) sapphire substrates by low pressure metalorganic chemical vapor deposition. The growth behavior of the InGaN/GaN QDs was examined under different experimental conditions. The InGaN/GaN QDs were formed in Stranski‐Krastanow growth mode by the continuous supply of metalorganic (MO) sources, whereas they were formed in the Volmer‐Weber growth mode by the periodic interruption of the MO sources. In addition, a quantum ring (QRs) structure was confirmed during the formation of InGaN QDs. The In content in the InGaN QDs appeared to increase with decreasing temperature. The photoluminescence spectrum (PL) showed peaks for the GaN buffer layer and the InGaN QDs layer at 362.2 nm (3.41 eV) and between 420–460 nm (2.96–2.70 eV), respectively. The composition of InGaN QDs was estimated from the PL peak position to be In0.12‐0.15Ga0.88‐0.85N. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Enhancement of optical properties of InAs quantum dots grown by using periodic arsine interruption

We investigated the morphological and optical properties of InAs quantum dots (QDs) grown by using periodic arsine interruption (PAI) and compared them with QDs grown conventionally. In the conventional growth, the formation of large islands was observed, which suppresses the nucleation and growth of QDs. Furthermore, the growth of capping layers was significantly degraded by these large islands. On the other hand, in the PAI growth, the formation of large islands was completely suppressed, resulting in the increase of the density and aspect ratio of QDs and the uniform growth of capping layers. As a result of photoluminescence (PL) measurements, we found that the emission efficiency was enhanced and the full-width-half-maximum was reduced to 32 meV. The temperature dependence of these optical properties also revealed the enhancement of the uniformity of QDs grown by the PAI method.

An efficient method-of-lines simulation procedure for organic semiconductor devices

We describe an adaptive grid method-of-lines (MOL) solution procedure for modelling charge transport and recombination in organic semiconductor devices. The procedure we describe offers an efficient, robust and versatile means of simulating semiconductor devices that allows for much simpler coding of the underlying equations than alternative simulation procedures. The MOL technique is especially well-suited to modelling the extremely stiff (and hence difficult to solve) equations that arise during the simulation of organic-and some inorganic-semiconductor devices. It also has wider applications in other areas, including reaction kinetics, combustion and aero- and fluid dynamics, where its ease of implementation also makes it an attractive choice. The MOL procedure we use converts the underlying semiconductor equations into a series of coupled ordinary differential equations (ODEs) that can be integrated forward in time using an appropriate ODE solver. The time integration is periodically interrupted, the numerical solution is interpolated onto a new grid that is better matched to the solution profile, and the time integration is then resumed on the new grid. The efficacy of the simulation procedure is assessed by considering a single layer device structure, for which exact analytical solutions are available for the electric potential, the charge distributions and the current-voltage characteristics. Two separate state-of-the-art ODE solvers are tested: the single-step Runge-Kutta solver Radau5 and the multi-step solver ODE15s, which is included as part of the Matlab ODE suite. In both cases, the numerical solutions show excellent agreement with the exact analytical solutions, yielding results that are accurate to one part in 1 x 10(4). The single-step Radau5 solver, however, is found to provide faster convergence since its efficiency is not compromised by the periodic interruption of the time integration when the grid is updated.

Effect of periodic interruption of the atmospheric-pressure MOVPE growth of InAs/GaAs quantum dots on their morphology and optoelectronic spectra

A modified regime of growing InAs/GaAs quantum dots (QDs) by metalorganic vapor phase epitaxy (MOVPE) at atmospheric pressure is described. In contrast to the standard growth regime, the time of periodic interruption of the supply of trimethylindium and arsin to the reactor was increased and varied from 4 to 18 s. It is shown that optimization of the interruption time leads to the formation of dense, homogeneous (with respect to dimensions) QD arrays and to a decrease in the concentration of coarse relaxed clusters without using additional treatments (e.g., doping with surfactants, chemical etching). In particular, the surface concentration of QDs increases up to 6 × 1010 cm−2, that is, by almost an order of magnitude as compared to the standard growth regime. QD structures grown using the modified MOVPE method are characterized by high thermal stability and ensure high intensity of room-temperature electroluminescence of the related edge-emitting Schottky diodes.

The effects of periodic interruptions of physical activities on the physical capacities of adult active women

Physical activity programs adapted to the elderly have been proposed with the purpose of minimizing the alterations provoked by aging. These programs usually present break periods of more than 30 days, at least once a year. The aim of this study was to verify if 30-day interruptions cause alterations in the acquisition of physical capacities for senescent women. The study was longitudinal in design, 125 senescent women completed a physical activity program consisting of stretching, aerobic resistance, strength, power and resistance exercises; coordination, agility and flexibility activities; respiratory and relaxation exercises during almost 2 years. Two periods were selected, containing four evaluations with two activities’ interruption periods in between the measurements. The main outcome measures were manual pressing strength, flexibility, dynamic balance and physical conditioning (VO2max). During the program there was an increasing tendency for the muscular strength and the VO2max. A significant improvement in flexibility was noted (p<0.0001), but there was no significant difference between the 3rd and the 4th, and the 7th and the 8th measurements. During the program, the dynamic balance showed significant difference (p<0.0001), but there was no significant difference in the interruption periods. It was possible to observe that 30 days of interruption of physical activities in both studied periods were not enough to significantly alter the values of physical capacities of senescent active women.

Growth Behavior of InGaN/GaN Quantum Dots Structure ViaMetal-organic Chemical Vapor Deposition

Growth behavior of InGaN/GaN self-assembled quantum dots (QDs) was investigated with respect to different growth parameters in low pressure metalorganic chemical vapor deposition. Locally formed examples of three dimensional InGaN islands were confirmed from the surface observation image with increasing indium source ratio and growth time. The InGaN/GaN QDs were formed in Stranski-Krastanow (SK) growth mode by the continuous supply of metalorganic (MO) sources, whereas they were formed in the Volmer-Weber (V-W) growth mode by the periodic interruption of the MO sources. High density InGaN QDs with 1~2nm height and 40~50nm diameter were formed by the S-K growth mode. Dome shape InGaN dots with 200~400nm diameter were formed by the V-W growth mode. InN content in InGaN QDs was estimated to be reduced with the increase of growth temperature. A strong peak between 420-460 nm (2.96-2.70 eV) was observed for the InGaN QDs grown by S-K growth mode in photoluminescence spectrum together with the GaN buffer layer peak at 362.2 nm (3.41 eV).

LOTKA–VOLTERRA TWO-SPECIES SYSTEM WITH PERIODIC INTERRUPTION OF COMPETITION

We consider the two-species Lotka–Volterra competition system with a temporally periodic interruption of competition coefficient. We assume that the competition coefficient is constant in a time interval of fixed length τ+, while it is zero in the other time interval of length τ-. The temporal variation of the competition coefficient is rigorously periodic with period τ+ + τ-, in which the competition coefficient becomes a given positive constant and zero by turns, the other parameters being constant in time. We analyze the system analytically and numerically, and derive the condition for the permanence of the whole system, the coexistence of two competing species, and the change of the species-dominance in terms of the competition. We discuss some interesting natures of our system, distinguished from the original two-species Lotka–Volterra competition system with constant competition coefficients. The temporal interruption of competition could cause the change of the destiny of competing species.