A nucleolar-organizing B chromosome showing segregation–distortion in the grasshopper Dichroplus pratensis (Melanoplinae, Acrididae)

1986 ◽  
Vol 28 (1) ◽  
pp. 138-148 ◽  
Author(s):  
Claudio J. Bidau
Keyword(s):  
Segregation Distortion ◽  
Secondary Constriction ◽  
Low Frequency ◽  
B Chromosome ◽  
Early Prophase ◽  
Early Pachytene ◽  
Nucleolar Organizing Region ◽  
The Mean ◽  
Two Stages ◽  
Male Carrier

A nucleolar-organizing B chromosome occurs at low frequency in some populations of the grasshopper Dichroplus pratensis. This B chromosome is telocentric, mitotically stable, and has a proximal secondary constriction. Haematoxylin and silver staining both demonstrate that the constriction organizes a nucleolus in addition to the standard nucleolar organizing region present in the S8 bivalent. In the single 2B male carrier studied, both B's organized nucleoli. The analysis of the meiotic behaviour of 1B males revealed that the B and the X chromosome associate preferentially during early prophase I. At leptotene the B and the X are associated in approximately 50% of the nuclei, but by zygotene – early pachytene the mean frequency of association is 86 reaching 100% in one male. This difference in association frequency between the two stages is highly significant. Persistent X–B associations lead to both chromosomes moving to the same pole in approximately 60% of the first anaphases. In the 2B male, both B's are paired in all early pachytene nuclei, while X–B associations seem to be random and much less frequent than in 1B males. Both B's remain associated in 60% of the metaphase I meiocytes, although true chiasmata do not seem to be involved. Nevertheless the B bivalent disjoins regularly. In 2B cells where both B's are univalents their segregation is random with respect to the X.Key words: B chromosome, nucleolus, nucleolar-organizing region, segregation–distortion, grasshopper.

scholarly journals High Ripple-Density Resolution for Discriminating Between Rippled and Nonrippled Signals: Effect of Temporal Processing or Combination Products?

2021 ◽  
Vol 25 ◽  
pp. 233121652110101
Author(s):  
Dmitry I. Nechaev ◽  
Olga N. Milekhina ◽  
Marina S. Tomozova ◽  
Alexander Y. Supin
Keyword(s):  
Low Frequency ◽  
Noise Signal ◽  
Density Variation ◽  
Choice Procedure ◽  
Masker Level ◽  
Reference Signals ◽  
Forced Choice Procedure ◽  
The Mean ◽  
Density Resolution

The goal of the study was to investigate the role of combination products in the higher ripple-density resolution estimates obtained by discrimination between a spectrally rippled and a nonrippled noise signal than that obtained by discrimination between two rippled signals. To attain this goal, a noise band was used to mask the frequency band of expected low-frequency combination products. A three-alternative forced-choice procedure with adaptive ripple-density variation was used. The mean background (unmasked) ripple-density resolution was 9.8 ripples/oct for rippled reference signals and 21.8 ripples/oct for nonrippled reference signals. Low-frequency maskers reduced the ripple-density resolution. For masker levels from −10 to 10 dB re. signal, the ripple-density resolution for nonrippled reference signals was approximately twice as high as that for rippled reference signals. At a masker level as high as 20 dB re. signal, the ripple-density resolution decreased in both discrimination tasks. This result leads to the conclusion that low-frequency combination products are not responsible for the task-dependent difference in ripple-density resolution estimates.

scholarly journals Temporal Variations of the Turbulence Profiles at the Sayan Solar Observatory Site

Atmosphere ◽  
2019 ◽  
Vol 10 (9) ◽  
pp. 499 ◽  
Author(s):  
Artem Shikhovtsev ◽  
Pavel Kovadlo ◽  
Vladimir Lukin
Keyword(s):  
Atmospheric Turbulence ◽  
Temporal Variability ◽  
Low Frequency ◽  
Temporal Variations ◽  
Solar Observatory ◽  
Vertical Profiles ◽  
Spatial And Temporal Scales ◽  
Atmospheric Disturbances ◽  
Wide Range ◽  
The Mean

The paper focuses on the development of the method to estimate the mean characteristics of the atmospheric turbulence. Using an approach based on the shape of the energy spectrum of atmospheric turbulence over a wide range of spatial and temporal scales, the vertical profiles of optical turbulence are calculated. The temporal variability of the vertical profiles of turbulence under different low-frequency atmospheric disturbances is considered.

Effect of non-parallel mean flow on the Green’s function for predicting the low-frequency sound from turbulent air jets

2012 ◽  
Vol 695 ◽  
pp. 199-234 ◽  
Author(s):  
M. E. Goldstein ◽  
Adrian Sescu ◽  
M. Z. Afsar
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Low Frequency ◽  
Source Location ◽  
Parallel Flow ◽  
Numerical Calculations ◽  
Mean Flow ◽  
Frequency Sound ◽  
The Mean ◽  
Radiated Sound

AbstractIt is now well-known that there is an exact formula relating the far-field jet noise spectrum to the convolution product of a propagator (that accounts for the mean flow interactions) and a generalized Reynolds stress autocovariance tensor (that accounts for the turbulence fluctuations). The propagator depends only on the mean flow and an adjoint vector Green’s function for a particular form of the linearized Euler equations. Recent numerical calculations of Karabasov, Bogey & Hynes (AIAA Paper 2011-2929) for a Mach 0.9 jet show use of the true non-parallel flow Green’s function rather than the more conventional locally parallel flow result leads to a significant increase in the predicted low-frequency sound radiation at observation angles close to the downstream jet axis. But the non-parallel flow appears to have little effect on the sound radiated at $9{0}^{\ensuremath{\circ} } $ to the downstream axis. The present paper is concerned with the effects of non-parallel mean flows on the adjoint vector Green’s function. We obtain a low-frequency asymptotic solution for that function by solving a very simple second-order hyperbolic equation for a composite dependent variable (which is directly proportional to a pressure-like component of this Green’s function and roughly corresponds to the strength of a monopole source within the jet). Our numerical calculations show that this quantity remains fairly close to the corresponding parallel flow result at low Mach numbers and that, as expected, it converges to that result when an appropriately scaled frequency parameter is increased. But the convergence occurs at progressively higher frequencies as the Mach number increases and the supersonic solution never actually converges to the parallel flow result in the vicinity of a critical- layer singularity that occurs in that solution. The dominant contribution to the propagator comes from the radial derivative of a certain component of the adjoint vector Green’s function. The non-parallel flow has a large effect on this quantity, causing it (and, therefore, the radiated sound) to increase at subsonic speeds and decrease at supersonic speeds. The effects of acoustic source location can be visualized by plotting the magnitude of this quantity, as function of position. These ‘altitude plots’ (which represent the intensity of the radiated sound as a function of source location) show that while the parallel flow solutions exhibit a single peak at subsonic speeds (when the source point is centred on the initial shear layer), the non-parallel solutions exhibit a double peak structure, with the second peak occurring about two potential core lengths downstream of the nozzle. These results are qualitatively consistent with the numerical calculations reported in Karabasov et al. (2011).

scholarly journals Diffraction Measurements and Equilibrium Parameters

2011 ◽  
Vol 2011 ◽  
pp. 1-14 ◽  
Author(s):  
Victor A. Sipachev
Keyword(s):  
Low Frequency ◽  
Mean Square ◽  
Structural Studies ◽  
Free Rotation ◽  
Theory Analysis ◽  
First Order ◽  
Internuclear Distances ◽  
The Mean ◽  
Asymmetry Parameters ◽  
First Order Perturbation

Structural studies are largely performed without taking into account vibrational effects or with incorrectly taking them into account. The paper presents a first-order perturbation theory analysis of the problem. It is shown that vibrational effects introduce errors on the order of 0.02 Å or larger (sometimes, up to 0.1-0.2 Å) into the results of diffraction measurements. Methods for calculating the mean rotational constants, mean-square vibrational amplitudes, vibrational corrections to internuclear distances, and asymmetry parameters are described. Problems related to low-frequency motions, including torsional motions that transform into free rotation at low excitation levels, are discussed. The algorithms described are implemented in the program available from the author (free).

scholarly journals Analysis of stimulus-related activity in rat auditory cortex using complex spectral coefficients

2013 ◽  
Vol 110 (3) ◽  
pp. 621-639 ◽  
Author(s):  
Bryan M. Krause ◽  
Matthew I. Banks
Keyword(s):  
Low Frequency ◽  
Phase Changes ◽  
Induced Response ◽  
Top Down ◽  
Time Frequency ◽  
State Dependent ◽  
Spectral Coefficients ◽  
The Mean ◽  
Sensory Responses ◽  
Mean Variance

The neural mechanisms of sensory responses recorded from the scalp or cortical surface remain controversial. Evoked vs. induced response components (i.e., changes in mean vs. variance) are associated with bottom-up vs. top-down processing, but trial-by-trial response variability can confound this interpretation. Phase reset of ongoing oscillations has also been postulated to contribute to sensory responses. In this article, we present evidence that responses under passive listening conditions are dominated by variable evoked response components. We measured the mean, variance, and phase of complex time-frequency coefficients of epidurally recorded responses to acoustic stimuli in rats. During the stimulus, changes in mean, variance, and phase tended to co-occur. After the stimulus, there was a small, low-frequency offset response in the mean and modest, prolonged desynchronization in the alpha band. Simulations showed that trial-by-trial variability in the mean can account for most of the variance and phase changes observed during the stimulus. This variability was state dependent, with smallest variability during periods of greatest arousal. Our data suggest that cortical responses to auditory stimuli reflect variable inputs to the cortical network. These analyses suggest that caution should be exercised when interpreting variance and phase changes in terms of top-down cortical processing.

scholarly journals Word Roots in English: Learning English Words through Form and Meaning Similarity

2021 ◽  
Author(s):  
◽  
Zheng Wei
Keyword(s):  
High Frequency ◽  
English Language ◽  
Vocabulary Learning ◽  
Data Gathering ◽  
Low Frequency ◽  
Word List ◽  
Word Families ◽  
Frequency Criterion ◽  
Etymological Dictionary ◽  
Two Stages

<p>The research first proposes a vocabulary learning technique: the word part technique, and then tests its effectiveness in aiding vocabulary learning and retention. The first part of the thesis centers around the idea that the knowledge of the first 2000 words language learners already possess may give them easier access to words of other frequency levels because the root parts of the low frequency new words share form and meaning similarities with the high frequency known words. The research addresses the issue at two stages: to quantify the information concerning the number of words able to be accessed through the analysis of the word roots, and to analyze the pedagogical usefulness of the accessible words. A Comprehensive Etymological Dictionary of the English Language (Klein, 1966) was used as the source to show the possible formal and meaning connections among words. All the words in the first 2000 word list were first looked up individually and all the cognates provided under each of these words were collected and placed under each of the high frequency words if they meet the requirement that their roots share more than one letter and/or more than one phoneme with the roots of the first 2000 known words. After the data was roughly gathered, three criteria were applied to filter the data, namely, the frequency criterion, the meaning criterion and form criterion. In applying the frequency criterion, words with frequency levels lower than the tenth thousand were removed from the data. In applying the meaning criterion, hints were given to show the semantic relations between the higher frequency words and the first 2000 thousand words. The hints were then rated on the scale for measuring meaning transparency. Words that were rated at level 5 on the scale were considered inaccessible; words that were rated at levels 1, 2a, 2b, 2c, and 3a were considered easy to access. In applying the form criterion, calculations were done for each semantically accessible word to show their phonological similarity and orthographic similarity in relation to the known word. The words whose phonological or orthographical similarity scores were larger than 0.5 were considered to be phonologically or orthographically easy to access. Finally the "find" function of Microsoft Word was used to check the data by picking up any words that might have been missed in the first round of data gathering. The above procedures resulted in 2156 word families that are able to be accessed through the meaning and form relations with the first 2000 words in their root parts. Among the 2156 word families, 739 can be accessed easily and are therefore more pedagogically useful and 259 can be accessed, but with difficulty. 21 pedagogically useful form constants were selected because they can give access to more unknown lower frequency words than other form constants. In the second part of the thesis, an experiment was conducted to test the effectiveness of the word part technique in comparison with the keyword technique and self-strategy learning. The results show that with the experienced Chinese EFL learners, the keyword technique is slightly inferior to the word part technique and the self-strategy learning.</p>

Fluctuating boundary layer on a magnetized plate

1967 ◽  
Vol 63 (2) ◽  
pp. 513-525 ◽  
Author(s):  
Sahib Singh Chawla
Keyword(s):  
Boundary Layer ◽  
Low Frequency ◽  
Surface Current ◽  
Frequency Range ◽  
Mean Flow ◽  
Wave Type ◽  
High Frequencies ◽  
Phase Lead ◽  
The Mean ◽  
The Magnetic Field

The laminar boundary layer on a magnetized plate, when the magnetic field oscillates in magnitude about a constant non-zero mean, is analysed. For low-frequency fluctuations the solution is obtained by a series expansion in terms of a frequency parameter, while for high frequencies the flow pattern is of the ‘skin-wave’ type unaffected by the mean flow. In the low-frequency range, the phase lead and the amplitude of the skin-friction oscillations increase at first and then decrease to their respective ‘skin-wave’ values. On the other hand the phase angle of the surface current decreases from 90° to 45° and its amplitude increases with frequency.

Abstract P200: The Circadian Pattern of Cardiac Autonomic Modulation and its Correlates in Adolescents- Penn State Child Cohort (PSCC) Study

Circulation ◽  
2014 ◽  
Vol 129 (suppl_1) ◽  
Author(s):  
Sol M Rodriguez-Colon ◽  
Fan He ◽  
Edward O Bixler ◽  
Julio Fernandez-Mendoza ◽  
Susan Calhoun ◽  
...  
Keyword(s):  
Heart Rate ◽  
Low Frequency ◽  
Population Based ◽  
Autonomic Modulation ◽  
Circadian Pattern ◽  
Late Afternoon ◽  
Cardiac Autonomic Modulation ◽  
Penn State ◽  
State Child ◽  
The Mean

Objective: To examine the circadian pattern of cardiac autonomic modulation (CAM) and its correlates in a population-based sample of adolescents. Methods: We used the data from 400 adolescents who completed the follow up exam in the PSCC study. CAM was assessed by heart rate variability (HRV) analysis of beat-to-beat normal R-R intervals from a 24-hour (7:00 PM to 7:00 PM) ECG, on a 30-minute basis (48 segments/person). The HRV indices included frequency domain: [high and low frequency powers (HF, LF), and LF/HF ratio] and time domain: [standard deviation of normal RRs (SDNN), and the square root of the mean squared difference of successive normal RRs (RMSSD), and heart rate (HR)]. We used a cosine periodic model to estimate each participant’s circadian parameters: mean (M), amplitude (Â), and crescent time (θ). We then used mixed-effects models to calculate group level circadian pattern as the overall M, Â of the oscillation, and θ of the highest oscillation. Results: The mean age was 16.9 yrs (SD=2.2), with 54% male and 77% white. The mean BMI percentile is 61, with 16% were obese (BMI percentile ≥ 95). Overall, the parasympathetic modulation gradually increases from late afternoon throughout the evening, and reaches the peak amplitude around 3:00 AM, at which it gradually decrease throughout most of the daytime until late afternoon. The age, sex and race showed varying differences on the CAM circadian parameters. In contrast, obesity in adolescents had adverse effects on all three circadian parameters. Using HF (a reliable index of parasympathetic modulation) as an example, the circadian pattern of the entire sample, and stratified by obesity are shown in Figure 1. Conclusion: Circadian pattern of CAM can be quantified by three cosine parameters (M, Â, and θ). Obesity in adolescents is already associated with a CAM profile indicative of sympathetic overflow and reduced parasympathetic modulation, at all levels of the CAM circadian rhythm.

NUMERICAL INVESTIGATION OF UNSTEADY COMBUSTOR TURBINE INTERACTION FOR FLEXIBLE POWER GENERATION

2021 ◽  
pp. 1-22
Author(s):  
Federico Lo Presti ◽  
Marwick Sembritzky ◽  
Benjamin Winhart ◽  
Pascal Post ◽  
Francesca di Mare ◽  
...  
Keyword(s):  
Low Frequency ◽  
Temperature Fluctuations ◽  
Two Dimensional ◽  
Periodic Load ◽  
Migration Patterns ◽  
Solution Approach ◽  
Periodic Disturbances ◽  
Turbine Inlet ◽  
The Mean ◽  
Industrial Gas Turbine

Abstract In the present study low-frequency disturbances introduced by a periodic load variation have been simulated and superimposed to the inhomogeneous, unsteady flow entering a 3-stage, high-pressure industrial gas turbine fed by a can-type combustion chamber comprising 6 silo-burners. The effects of the unsteadiness realized at the combustor exit have been investigated by means of Detached Eddy Simulations, whereby a density-based solution approach with detailed thermodynamics has been employed. The periodic disturbances at the turbine inlet have been obtained by means of an artificially generated, unsteady field, resulting from a two-dimensional snapshot of the flow field at the combustor exit. Also, a combustor failure has been mimicked by reducing (respectively increasing) the mean temperature in some of the turbine inlet regions corresponding to the outlet of two burners. The propagation and amplitude changes of temperature fluctuations have been analyzed in the frequency domain. Tracking of the temperature fluctuations' maxima at the lowest frequencies revealed characteristic migration patterns indicating that the corresponding fluctuations persist with a non-negligible amplitude up to the last rows. A distinct footprint could also be observed at the same locations when a combustor failure was simulated, showing that, in principle, the early detection of combustor failures is indeed possible.

Contribution of the Torsional Modes to the Equilibrium Distribution of Vibrational States and to the Specific Heat of a Chain Molecule

1983 ◽  
Vol 38 (12) ◽  
pp. 1285-1292 ◽  
Author(s):  
J. A. Borges da Costa ◽  
C. Scherer ◽  
A. Holz ◽  
J. Naghizadeh
Keyword(s):  
Specific Heat ◽  
Equilibrium Distribution ◽  
Spatial Configuration ◽  
Low Frequency ◽  
Chain Molecule ◽  
Vibrational States ◽  
Polymer Molecules ◽  
The Mean ◽  
A Chain ◽  
Increasing Temperature

Abstract The torsional modes of a chain molecule were studied recently under the assumption that it has a well defined spatial configuration at any time. Here we show how the averages over the possible configurations, for a distribution in thermal equilibrium, should be performed in the calculation of the thermodynamical properties. Our results show that the mean density of torsional states increases in the low frequency region with increasing temperature. The specific heat behaviour shows a considerable difference from the result obtained in the previous paper, where only the lowest energetic configuration was considered. The consequences of this result with respect to the configurational properties of polymer molecules near the θ temperature are discussed.

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