Temporal Changes In Frequency Research Articles

Density spectrum array and difficult to diagnose seizure activity.

We present a case with non-convulsive status (NCSE) in which density spectrum array (DSA) illustrated "three little seizures." The conventional EEG was not useful. However, DSA revealed three seizures lasting for 30-40 seconds with a gradual decrease in frequency, along with the temporal frequency change. The present case highlights the usefulness of DSA in detecting NCSE, particularly in cases where there is no typical rhythmic and periodic pattern.

ARTEMIS Observations of Plasma Waves in Laminar and Perturbed Interplanetary Shocks

Abstract The “Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun” mission provides a unique opportunity to study the structure of interplanetary shocks and the associated generation of plasma waves with frequencies between ∼50 and 8000 Hz due to its long duration electric and magnetic field burst waveform captures. We compare wave properties and occurrence rates at 11 quasi-perpendicular interplanetary shocks with burst data within 10 minutes (∼3200 proton gyroradii upstream, ∼1900 downstream) of the shock ramp. A perturbed shock is defined as possessing a large amplitude whistler precursor in the quasi-static magnetic field with an amplitude greater than 1/3 the difference between the upstream and downstream average magnetic field magnitudes; laminar shocks lack these large precursors and have a smooth, step function-like transition. In addition to wave modes previously observed, including ion acoustic, whistler, and electrostatic solitary waves, waves in the ion acoustic frequency range that show rapid temporal frequency change are common. Three shocks had burst captures in the ramp; of these, the two laminar shocks contained a wide range of large amplitude wave modes in the ramp whereas the one perturbed shock contained no such waves. Thus, energy dissipation through wave–particle interactions is more prominent in these two laminar shocks than in the perturbed shock. Based on observations from all 11 shocks, the wave occurrence rates for laminar shocks are higher in the transition region, especially the ramp, than downstream. In contrast, perturbed shocks have approximately 2–3 times the wave occurrence rate downstream than laminar shocks.

Cross-frequency coupling during thermoacoustic oscillations in a pressurized aeronautical gas turbine model combustor

This paper demonstrates cross-frequency coupling between pressure, heat release rate, fuel spray and velocity oscillations in a model aeronautical gas turbine combustor operating at a pressure of approximately 10 atm. Heat release rate was characterized by 10 kHz chemiluminescence (CL) imaging of several species. Stereoscopic particle image velocimetry and laser Mie scattering from the fuel droplets were used to measure the gas velocity and spray dynamics, respectively, at 5 kHz. The pressure fluctuations were dominated by oscillations at a frequency f0, whereas the spray, CL and velocity oscillated at approximately 2f0. All oscillations were non-stationary, exhibiting temporal changes in frequency and amplitude. Comparing the time evolution of the dominant frequencies and amplitudes indicated a behaviour consistent with mutually coupled and unsynchronized self-oscillators; the observed dynamics are consistent with variations in reactive coupling strength. Specifically, increases in the frequency of the ca. 2f0 velocity oscillations away from the 1:2 harmonic ratio (increased frequency detuning) were correlated with decreases in the power of the f0 pressure oscillations. The corresponding nonreacting flow had a natural hydrodynamic mode at a frequency slightly greater than 2f0. Hence, the data are consistent with the f0 acoustic mode ‘pulling’ the hydrodynamic frequency towards the 1:2 harmonic ratio.

Temporal Change of Spectra and Lyapunov Exponent Volcanic Tremor at Raung Volcano, Indonesia

Spectral Analyses and estimation maximal lyapunov exponent (MLE) of volcanic tremor recorded at Raung Volcano were carried out to investigate dynamical systems regarding to their generating system. Their results of both analyses can explain the temporal change in frequency and deterministic processes of the dynamical system. Spectral analysis of volcanic tremor was estimated by the average periodogram method which includes division, Fast Fourier Transformation and averaging. MLE was estimated by graphing the relationship between Stretching Factor (S) and the number of points in the tractor (N) diagram. Content frequency of volcanic tremor Raung Volcano is range from 2.68 to 3.7 Hz. Temporally, there is no significant change, which means that there is no change in the geometry of the Raung volcanic tremor source. This is also shown by the maximal lyapunov exponent which is temporarily constant and positive. That shows that the source process of Raung volcano is chaotic

Gliadin genotypes worldwide for spring wheats (Triticum aestivum L.) 2. Strong differentiation of polymorphism between countries and regions of origin

Genotypes of 290 cultivars from ten countries (four continents) of spring wheat Triticum aestivum, were analyzed through the identification of alleles at the gliadin-encoding (Gli) loci. The group of cultivars bred in one country during the 20th century might be characterized by its level of genetic diversity (H) and a specific set of alleles. Strong differences between genotypes of cultivars bred in different countries were confirmed by cluster analysis of genetic distances. Genotypes of cultivars bred in regions of the same country might differ, but they always composed a single cluster and strongly differed from genotypes from other countries or regions. Therefore, world polymorphism of spring wheat germplasm of the 20th century is highly structured and differentiated between countries and their regions. This differentiation seems to be mainly a result of natural selection acting in different ways in different eco-climatic conditions of breeding and propagation. At a regional scale, statistically significant temporal changes in frequency of some gliadin alleles and a tendency to temporal decrease of overall genetic diversity were discovered in cultivars bred in each of seven regions studied in Australia, Canada and the former USSR. In regions of Canada (provinces of Manitoba and Ontario) and of the former USSR (Saratov), a statistically significant decay of the genetic diversity of cultivars bred during the 20th century was discovered. However, the influence of breeders' selection for end-use wheat quality on the wheat genetic diversity was the least, if any.

Temporal changes in frequency of severe hypoglycemia treated by emergency medical services in types 1 and 2 diabetes: a population-based data-linkage cohort study

BackgroundAlmost 20 years ago, the frequencies of severe hypoglycemia requiring emergency medical treatment were reported in people with types 1 and 2 diabetes in the Tayside region of Scotland. With subsequent improvements in the treatment of diabetes, concurrent with changes in the provision of emergency medical care, a decline in the frequency of severe hypoglycemia could be anticipated. The present population-based data-linkage cohort study aimed to ascertain whether a temporal change has occurred in the incidence rates of hypoglycemia requiring emergency medical services in people with types 1 and 2 diabetes.MethodsThe study population comprised all people with diabetes in Tayside, Scotland over the period 1 January 2011 to 31 December 2012. Patients’ data from different healthcare sources were linked anonymously to measure the incidence rates of hypoglycemia requiring emergency medical services that include treatment by ambulance staff and in hospital emergency departments, and necessitated hospital admission. These were compared with data recorded in 1997–1998 in the same region.ResultsIn January 2011 to December 2012, 2029 people in Tayside had type 1 diabetes and 21,734 had type 2 diabetes, compared to 977 and 7678, respectively, in June 1997 to May 1998. In people with type 2 diabetes, the proportion treated with sulfonylureas had declined from 36.8 to 22.4% (p < 0.001), while insulin-treatment had increased from 11.7 to 18.7% (p < 0.001). The incidence rate of hypoglycemia requiring emergency medical treatment had significantly fallen from 0.115 (95% CI: 0.094–0.136) to 0.082 (0.073–0.092) events per person per year in type 1 diabetes (p < 0.001), and from 0.118 (0.095–0.141) to 0.037 (0.003–0.041) in insulin-treated type 2 diabetes (p = 0.008). However, the absolute annual number of hypoglycemia events requiring emergency treatment was 1.4-fold higher.ConclusionsAlthough from 1998 to 2012 the incidences of hypoglycemia requiring emergency medical services appeared to have declined by a third in type 1 diabetes and by two thirds in insulin-treated type 2 diabetes, because the prevalence of diabetes was higher (2.7 fold), the number of severe hypoglycemia events requiring emergency medical treatment was greater.

A few words on differentiating magno- and parvocellular contributions to vision on the basis of temporal frequency

A number of authors have proposed that changes in temporal frequency within the range of 0–30Hz may be used to differentiate contributions from the magno- and parvocellular systems. The present analyses estimate the percentage of active magnocellular cells as a function of frequency based on published cut-off values for magno- and parvocellular cells. These analyses indicate that varying the temporal frequency over the range of 0–30Hz has little effect upon the percentage of active magnocellular cells. The analyses were also carried out for a series of hypothetical cut-off frequencies and standard deviations of these frequencies for magnocellular cells. The results of these simulations indicate that even large alterations in these values do not alter the above conclusion to a noteworthy extent.

The speed control effect of highway tunnel sidewall markings based on color and temporal frequency

SummaryThe low‐luminance monotonous environment in the middle section of highway tunnels offers few reference points and is prone to cause severe visual illusion. Thus, drivers tend to underestimate their driving speed, which can induce speeding behaviors that result in rear‐end collisions. Therefore, discovering low‐cost methods of traffic engineering that reduce this visual illusion and ensure a steady driving speed is an important challenge for current highway tunnel operations. This study analyzes the effects of sidewall markings in typical highway tunnels, specifically observing how their colors and temporal frequencies affect the driver's speed perception in a low‐luminance condition. A three‐dimensional model of the middle section of highway tunnels was built in a driving simulator. Psychophysical tests of speed perception were carried out by the method of limits. The precision of the simulation model was then checked by comparing the results to field test data. The simulation tests studied the stimulus of subjectively equal speed and reaction time in relation to sidewall markings in different colors (red–white combined, yellow–white combined, and blue–white combined). Furthermore, based on the optimal color, the effects of sidewall marking with different temporal frequencies (0.4, 0.8, 1.2, 2, 4, 8, 12, 16, and 32 Hz) on the speed perception of drivers were also analyzed. The test results reveal that the color and temporal frequency of sidewall marking have a significant impact on the driver's stimulus of subjectively equal speed and reaction time. The subjects have the highest speed overestimation and an easy speed judgment with the red–white combined sidewall marking. Within the temporal frequency range of 4.45–7.01 Hz, the subjects have a certain degree of speed overestimation (less than 20%), and the speed perception is sensitive to the temporal frequency changes. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Use of an attenuated live Salmonella Typhimurium vaccine on three breeding pig units: A longitudinal observational field study.

The study examined the effects of a licensed live Salmonella Typhimurium vaccine, administered to sows and gilts on three commercial pig units experiencing clinical salmonellosis associated with S. Typhimurium or its monophasic variant. After vaccination, clinical salmonellosis resolved and shedding of S. Typhimurium declined markedly and persistently on all breeding or breeding-finishing units, during the one- to two-year monitoring period. On two finishing units supplied in part by one of the vaccinated herds, pigs from the vaccinated herd were less likely to shed Salmonella than those from non-vaccinating herds, and Salmonella counts in faeces were also lower from the vaccine-linked animals. Non-Typhimurium Salmonella serovars were isolated typically in fewer than 10% of samples, and showed no clear temporal changes in frequency. Vaccination of dams alone with S. Typhimurium was associated with reduced shedding of closely-related serovars among all age groups in this commercial setting.

A generative inference framework for analysing patterns of cultural change in sparse population data with evidence for fashion trends in LBK culture.

Cultural change can be quantified by temporal changes in frequency of different cultural artefacts and it is a central question to identify what underlying cultural transmission processes could have caused the observed frequency changes. Observed changes, however, often describe the dynamics in samples of the population of artefacts, whereas transmission processes act on the whole population. Here we develop a modelling framework aimed at addressing this inference problem. To do so, we firstly generate population structures from which the observed sample could have been drawn randomly and then determine theoretical samples at a later time t2 produced under the assumption that changes in frequencies are caused by a specific transmission process. Thereby we also account for the potential effect of time-averaging processes in the generation of the observed sample. Subsequent statistical comparisons (e.g. using Bayesian inference) of the theoretical and observed samples at t2 can establish which processes could have produced the observed frequency data. In this way, we infer underlying transmission processes directly from available data without any equilibrium assumption. We apply this framework to a dataset describing pottery from settlements of some of the first farmers in Europe (the LBK culture) and conclude that the observed frequency dynamic of different types of decorated pottery is consistent with age-dependent selection, a preference for 'young' pottery types which is potentially indicative of fashion trends.

Photodissociation of D2 (+) induced by linearly chirped laser pulses.

Recently, it has been revealed that so-called light-induced conical intersections (LICIs) can be formed both by standing or by running laser waves even in diatomic molecules. Due to the strong nonadiabatic couplings, the existence of such LICIs has significant impact on the dynamical properties of a molecular system. In our former studies, the photodissociation process of the D2 (+) molecule was studied initiating the nuclear dynamics both from individual vibrational levels and from the superposition of all the vibrational states produced by ionizing D2. In the present work, linearly chirped laser pulses were used for initiating the dissociation dynamics of D2 (+). In contrast to the constant frequency (transform limited) laser fields, the chirped pulses give rise to LICIs with a varying position according to the temporal frequency change. To demonstrate the impact of these LICIs on the dynamical properties of diatomics, the kinetic energy release spectra, the total dissociation probabilities, and the angular distributions of the D2 (+) photofragments were calculated and discussed.

How temporal frequency affects global form coherence in Glass patterns

Glass patterns are textural moirés from random dots. Sequential presentation of Glass patterns induces a sense of illusory motion. We evaluated how changes in temporal frequency affected the detection of global form in Glass patterns. We found linear improvement in coherence thresholds with increasing temporal frequency (Experiment 1), particularly in stimuli with large dot-pair separations (Experiment 2). These results support the notion that temporal and orientation information sum to boost sensitivity to visually obscure objects, and are discussed within the framework of "motion streak" detectors.

Exploring large vegetation databases to detect temporal trends in species occurrences

Question: Can vegetation releve databases be used to analyse species losses and gains in specific vegetation types in Germany over time? Does the type of response (increase or decline in relative frequency) conform to observed large-scale environmental trends in the last decades? Location: Germany. Exploring the German Vegetation Reference Database Halle (GVRD) that was established for forest and grassland vegetation within the framework of German Biodiversity Exploratories. Methods: Use of generalized linear models (GLMs) for testing changes in temporal frequency of plant taxa in a semi-dry grassland data set (Mesobromion) and a beech forest data set (Fagion). Data were either aggregated by year, decade or by a balanced re-sampling approach. Interpretation of the observed changes was based on species traits. Results: In both data sets significant temporal changes were observed, although the frequency of the majority of species remained unchanged. In both data sets, species with a temporal increase in frequency had higher Ellenberg N and F indicator values, compared to species that decreased, thus indicating effects of widespread atmospheric nitrogen deposition. In the forest data set, the observed increase in recruitment of deciduous trees pointed to a change in management, while trends in the grassland data set suggested use abandonment, as seen in an increased frequency of woody species. Conclusion: We demonstrate that vegetation databases represent very valuable resources for analysis of temporal changes in species frequencies. GLMs proved their value in detecting these trends, as also shown by the interpretability of model results with species traits. In contrast, the method of aggregation or re-sampling had little influence on the general outcome of analyses.

Octopaminergic modulation of temporal frequency coding in an identified optic flow-processing interneuron.

Flying generates predictably different patterns of optic flow compared with other locomotor states. A sensorimotor system tuned to rapid responses and a high bandwidth of optic flow would help the animal to avoid wasting energy through imprecise motor action. However, neural processing that covers a higher input bandwidth itself comes at higher energetic costs which would be a poor investment when the animal was not flying. How does the blowfly adjust the dynamic range of its optic flow-processing neurons to the locomotor state? Octopamine (OA) is a biogenic amine central to the initiation and maintenance of flight in insects. We used an OA agonist chlordimeform (CDM) to simulate the widespread OA release during flight and recorded the effects on the temporal frequency coding of the H2 cell. This cell is a visual interneuron known to be involved in flight stabilization reflexes. The application of CDM resulted in (i) an increase in the cell's spontaneous activity, expanding the inhibitory signaling range (ii) an initial response gain to moving gratings (20–60 ms post-stimulus) that depended on the temporal frequency of the grating and (iii) a reduction in the rate and magnitude of motion adaptation that was also temporal frequency-dependent. To our knowledge, this is the first demonstration that the application of a neuromodulator can induce velocity-dependent alterations in the gain of a wide-field optic flow-processing neuron. The observed changes in the cell's response properties resulted in a 33% increase of the cell's information rate when encoding random changes in temporal frequency of the stimulus. The increased signaling range and more rapid, longer lasting responses employed more spikes to encode each bit, and so consumed a greater amount of energy. It appears that for the fly investing more energy in sensory processing during flight is more efficient than wasting energy on under-performing motor control.

Language impairment is reflected in auditory evoked fields

Specific language impairment (SLI) is diagnosed when a child has problems in producing or understanding language despite having a normal IQ and there being no other obvious explanation. There can be several associated problems, and no single underlying cause has yet been identified. Some theories propose problems in auditory processing, specifically in the discrimination of sound frequency or rapid temporal frequency changes. We compared automatic cortical speech–sound processing and discrimination between a group of children with SLI and control children with normal language development (mean age: 6.6 years; range: 5–7 years). We measured auditory evoked magnetic fields using two sets of CV syllables, one with a changing consonant /da/ba/ga/ and another one with a changing vowel /su/so/sy/ in an oddball paradigm. The P1m responses for onsets of repetitive stimuli were weaker in the SLI group whereas no significant group differences were found in the mismatch responses. The results indicate that the SLI group, having weaker responses to the onsets of sounds, might have slightly depressed sensory encoding.

Detection sensitivity of frequency modulated (FM) and constant frequency (CF) signals in temporal masking conditions in the Mongolian gerbils

The auditory systems would be sensitive to temporal changes in frequency of sounds. We hypothesized that frequency modulation would play an important role in perception. And in this study, the difference in detection sensitivity between frequency-modulated signals (FM) and constant frequency signals (CF) in temporal masking conditions was examined in three Mongolian gerbils (Meriones unguiculatus) by GO-NOGO procedure. We focused on their detection sensitivity of three types of signals; upward FM, downward FM, and CF. The frequency range of each FM was from 4 to 7 kHz, and CF was 6 kHz. We set S+ that signals were presented between white noise bursts (BW: 0 to 17.5 kHz), and then signals were temporally masked by white noise. In contrast, we set S− in which silence was presented instead of signals. Subjects were trained to detect whether signals were presented or not. After subjects reached criterion (80%), each stimulus was presented randomly and attenuated in amplitude. We investigated their response rate to each S+. Result showed that their detection sensitivity to FM was higher than that of CF. It suggests that FM is superior to CF in recognition for subjects. [Research was supported with financial assistance from MEXT.]

Rapid temporal change in frequency of infanticide in a passerine bird associated with change in population density and body condition

Sexually selected infanticide, whereby unmated males obtain a mate by killing the dependent offspring of an already mated female, is a common alternative reproductive strategy in many animals. I estimated the frequency of infanticide in a population of barn swallows, Hirundo rustica, during the period 1977–2002. Population size decreased by more than a factor 10 during this period, and this decrease was associated with an increase in mortality, selecting for adults with better body condition. Densitydependent effects acted on infanticide through the relationship between the relative number of unmated males and population size. Because males in prime condition are better able to defend their nests against infanticidal males, the frequency of infanticide decreased as mean tail length and mean body condition of males increased during the study period. Therefore, a rapid decrease in population size, a decrease in the abundance of unmated males, and a concomitant increase in body condition have changed the importance of infanticide from being a major cause of mortality accounting for more than 25% of all nestling mortality to being almost completely absent during a period of 25 years. Key words: alternative reproductive strategy, condition dependence, density dependence, Hirundo rustica, unmated males. [Behav Ecol 15:462–468 (2004)]

Dose-Dependent Morphological Changes of Intercellular Canaliculi during Stimulation with Carbachol and Isoproterenol in the Isolated Rat Submandibular Gland

Intercellular canaliculi (IC) form a primary mixing reservoir for transcellularly and paracellularly secreted saliva whose composition depends on the degree of elevation of cytosolic Ca2+ and of cytosolic cyclic AMP concentrations caused by the secretagogues employed. In perfused rat submandibular gland (SMG), appearance of exocytosis on IC reflected the quantity of secreted mucin. Morphological observations were carried out by HR-SEM using a modified osmium maceration method on specimens treated with CCh and/or ISP. Mild secretory stimulation revealed that exocytosis did not occur simultaneously, even along the same intercellular canaliculus. Higher doses did not alter the spatial distribution of exocytosis along intercellular canaliculi but increased its temporal frequency, dose dependently. These findings lead us to conclude that, under low levels of secretory stimulation, exocytosis does not show a dose-dependent change, but that its spatial and temporal frequency changes in a dose-dependent manner.

Time and frequency information processing in the midbrain: Evidence found in the gerbil inferior colliculus

We have investigated the firing pattern of neurons in the central nucleus of the inferior colliculus (ICc) in time-frequency coordinate. The ICc is the major nucleus in the auditory midbrain. Single-unit recordings were made from ICc contralateral to the monaurally stimulated ear in anesthetized gerbils. We could classify firing patterns into four groups, except the simple ON neurons. Three out of four groups of neurons (53.8%) demonstrated that firing distribution changed depending on time and frequency, which was not shown previously. One group (37.6%) exhibited a frequency response range that changed little with time. The remainder (8.6%) belonged to none of the above. The time-frequency sensitive neuron in ICc may be a good candidate to code communication sounds, which comprise complex temporal change in frequency. [Research supported by Special Coordination Funds from the Science and Technology Agency and a grant to RCAST at Doshisha University from the Ministry of Education and Science of Japan.]

Time–frequency distribution of neuronal activity in the gerbil inferior colliculus responding to auditory stimuli

We classified the firing pattern of neurons in the central nucleus of the inferior colliculus (ICc) in a time–frequency coordinate, except for simple phasic onset responses, into four groups using tone bursts with a wide frequency range. The ICc is the major nucleus in the auditory midbrain. Single-unit recordings were made from ICc contralateral to the monaurally stimulated ear in anesthetized gerbils. Neurons of three out of the four groups (53.8%) demonstrated that the firing distribution changed depending on time and frequency, which was not shown previously. Neurons of one group (37.6%) exhibited a frequency response range that changed little with time. The remaining neurons (8.6%) belonged to none of the above classifications. The time–frequency-sensitive neurons in ICc may be good candidates for coding communication sounds, which comprise complex temporal changes in frequency.