scholarly journals Fine-scale position effects shape the distribution of inversion breakpoints in Drosophila melanogaster

2019 ◽  
Author(s):  
Jakob McBroome ◽  
David Liang ◽  
Russell Corbett-Detig
Keyword(s):  
High Frequency ◽  
Regulatory Networks ◽  
Genome Structure ◽  
Natural Populations ◽  
Low Frequency ◽  
Structure Evolution ◽  
Fine Scale ◽  
Position Effects ◽  
Wide Range ◽  
Inversion Breakpoints

AbstractChromosomal inversions are among the primary drivers of genome structure evolution in a wide range of natural populations. While there is an impressive array of theory and empirical analyses that has identified conditions under which inversions can be positively selected, comparatively little data is available on the fitness impacts of these genome structural rearrangements themselves. Because inversion breakpoints can interrupt functional elements and alter chromatin domains, each rearrangement may in itself have strong effects on fitness. Here, we compared the fine-scale distribution of low frequency inversion breakpoints with those of high frequency inversions and inversions that have fixed between Drosophila species. We identified important differences that may influence inversion fitness. In particular, proximity to insulator elements, large tandem duplications adjacent to the breakpoints, and minimal impacts on gene coding spans are more prevalent in high frequency and fixed inversions than in rare inversions. The data suggest that natural selection acts both to preserve both genes and larger cis-regulatory networks in the occurrence and spread of rearrangements. These factors may act to limit the availability of high fitness arrangements when suppressed recombination is favorable.

scholarly journals Fine-Scale Position Effects Shape the Distribution of Inversion Breakpoints in Drosophila melanogaster

2020 ◽  
Vol 12 (8) ◽  
pp. 1378-1391 ◽  
Author(s):  
Jakob McBroome ◽  
David Liang ◽  
Russell Corbett-Detig
Keyword(s):  
High Frequency ◽  
Regulatory Networks ◽  
Genome Structure ◽  
Natural Populations ◽  
Low Frequency ◽  
Structure Evolution ◽  
Fine Scale ◽  
Position Effects ◽  
Wide Range ◽  
Inversion Breakpoints

Abstract Chromosomal inversions are among the primary drivers of genome structure evolution in a wide range of natural populations. Although there is an impressive array of theory and empirical analyses that have identified conditions under which inversions can be positively selected, comparatively little data are available on the fitness impacts of these genome structural rearrangements themselves. Because inversion breakpoints can disrupt functional elements and alter chromatin domains, the precise positioning of an inversion’s breakpoints can strongly affect its fitness. Here, we compared the fine-scale distribution of low-frequency inversion breakpoints with those of high-frequency inversions and inversions that have gone to fixation between Drosophila species. We identified a number of differences among frequency classes that may influence inversion fitness. In particular, breakpoints that are proximal to insulator elements, generate large tandem duplications, and minimize impacts on gene coding spans which are more prevalent in high-frequency and fixed inversions than in rare inversions. The data suggest that natural selection acts to preserve both genes and larger cis-regulatory networks in the occurrence and spread of rearrangements. These factors may act to limit the availability of high-fitness arrangements when suppressed recombination is favorable.

A Geometric Parametric Analysis of a Magnetorheological Engine Mount

2010 ◽  
Author(s):  
Walter Anderson ◽  
Constantine Ciocanel ◽  
Mohammad Elahinia
Keyword(s):  
High Frequency ◽  
New Technology ◽  
Low Frequency ◽  
Variable Stiffness ◽  
Small Displacement ◽  
Element Analysis ◽  
Mr Fluid ◽  
Wide Range ◽  
Engine Mount ◽  
Vehicle Technology

Engine vibration has caused a great deal of research for isolation to be performed. Traditionally, isolation was achieved through the use of pure elastomeric (rubber) mounts. However, with advances in vehicle technology, these types of mounts have become inadequate. The inadequacy stems from the vibration profile associated with the engine, i.e. high displacement at low frequency and small displacement at high frequency. Ideal isolation would be achieved through a stiff mount for low frequency and a soft mount for high frequency. This is contradictory to the performance of the elastomeric mounts. Hydraulic mounts were then developed to address this problem. A hydraulic mount has variable stiffness and damping due to the use of a decoupler and an inertia track. However, further advances in vehicle technology have rendered these mounts inadequate as well. Examples of these advances are hybridization (electric and hydraulic) and cylinder on demand (VCM, MDS & ACC). With these technologies, the vibration excitation has a significantly different profile, occurs over a wide range of frequencies, and calls for a new technology that can address this need. Magnetorheological (MR) fluid is a smart material that is able to change viscosity in the presence of a magnetic field. With the use of MR fluid, variable damping and stiffness can be achieved. An MR mount has been developed and tested. The performance of the mount depends on the geometry of the rubber part as well as the behavior of the MR fluid. The rubber top of the mount is the topic of this study due to its major impact on the isolation characteristics of the MR mount. To develop a design methodology to address the isolation needs of different hybrid vehicles, a geometric parametric finite element analysis has been completed and presented in this paper.

CLASSICAL-LIKE RESONANCE INDUCED BY NOISE IN A FITZHUGH–NAGUMO NEURON MODEL

1999 ◽  
Vol 09 (12) ◽  
pp. 2295-2303 ◽  
Author(s):  
S. RIPOLL MASSANÉS ◽  
C. J. PÉREZ VICENTE
Keyword(s):  
High Frequency ◽  
Interspike Interval ◽  
Low Frequency ◽  
Resonance Phenomenon ◽  
Characteristic Time Scale ◽  
Wide Range ◽  
External Stimuli ◽  
Interspike Interval Distribution ◽  
Stochastic Resonance Phenomenon ◽  
Interval Distribution

We have studied the stochastic behavior of Fitzhugh–Nagumo neuron-like model (FN) induced by subthreshold external stimuli. Our analysis based on three standard measures: the power spectrum, interspike interval distribution (ISI) and autocorrelation function shows that it is possible to define a characteristic time scale which can be identified in the response of the system for a wide range of frequencies. In contrast to previous studies we have focused our attention on high frequency signals which could be of interest for real systems such as nervous fibers in the auditory system. We report behaviors which resemble those of classical deterministic oscillators but never the stochastic resonance phenomenon typical of low frequency signals.

Effects of Response Range in Frequency Judgments of Common versus Uncommon Events

1996 ◽  
Vol 82 (3_suppl) ◽  
pp. 1371-1376 ◽  
Author(s):  
Kimihiko Yamagishi
Keyword(s):  
Cognitive Processes ◽  
High Frequency ◽  
Narrow Range ◽  
Frequency Estimation ◽  
Low Frequency ◽  
Social Facts ◽  
Frequency Judgments ◽  
Response Range ◽  
Wide Range ◽  
Wide Condition

Frequency estimation of social facts was compared between two methods of response elicitation. In the “narrow range” method, respondents answered questions like: “Out of 100 instances, how many instances belong to category X?”. In the “wide range” method, the same question was asked regarding “Out of 10,000.” A previous study in 1994 showed that judged frequencies were proportionally greater in the narrow condition than in the wide condition when subjects estimated the occurrence of low-frequency events. These results were interpreted to reflect cognitive processes of anchoring, wherein judged frequencies he close to small numbers within particular response ranges. The current work extends this argument to high-frequency events. In such cases, judgments about high-frequency events would be reached by similar cognitive processes operating toward the opposite direction. Hence, I predicted that judged frequencies for high-frequency events would be proportionally greater in the wide than in the narrow condition. Results were mostly consistent with these predictions. The relation to previous research is discussed.

Spatial Scale Interactions and Visual-Tracking Performance

Perception ◽  
1997 ◽  
Vol 26 (8) ◽  
pp. 1047-1058 ◽  
Author(s):  
Howard C Hughes ◽  
David M Aronchick ◽  
Michael D Nelson
Keyword(s):  
Spatial Frequency ◽  
High Frequency ◽  
Visual Information ◽  
Low Frequency ◽  
High Spatial Frequency ◽  
Performance Measure ◽  
High Frequency Component ◽  
Stimulus Velocity ◽  
Spatial Frequencies ◽  
Wide Range

It has previously been observed that low spatial frequencies (≤ 1.0 cycles deg−1) tend to dominate high spatial frequencies (≥ 5.0 cycles deg−1) in several types of visual-information-processing tasks. This earlier work employed reaction times as the primary performance measure and the present experiments address the possibility of low-frequency dominance by evaluating visually guided performance of a completely different response system: the control of slow-pursuit eye movements. Slow-pursuit gains (eye velocity/stimulus velocity) were obtained while observers attempted to track the motion of a sine-wave grating. The drifting gratings were presented on three types of background: a uniform background, a background consisting of a stationary grating, or a flickering background. Low-frequency dominance was evident over a wide range of velocities, in that a stationary high-frequency component produced little disruption in the pursuit of a drifting low spatial frequency, but a stationary low frequency interfered substantially with the tracking of a moving high spatial frequency. Pursuit was unaffected by temporal modulation of the background, suggesting that these effects are due to the spatial characteristics of the stationary grating. Similar asymmetries were observed with respect to the stability of fixation: active fixation was less stable in the presence of a drifting low frequency than in the presence of a drifting high frequency.

scholarly journals A reassessment of frequency and vocabulary size in L2 vocabulary teaching

2012 ◽  
Vol 47 (4) ◽  
pp. 484-503 ◽  
Author(s):  
Norbert Schmitt ◽  
Diane Schmitt
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Lexical Resources ◽  
Vocabulary Size ◽  
Authentic Texts ◽  
Word Families ◽  
Wide Range ◽  
English Usage ◽  
Graded Readers ◽  
L2 Vocabulary

The high-frequency vocabulary of English has traditionally been thought to consist of the 2,000 most frequent word families, and low-frequency vocabulary as that beyond the 10,000 frequency level. This paper argues that these boundaries should be reassessed on pedagogic grounds. Based on a number of perspectives (including frequency and acquisition studies, the amount of vocabulary necessary for English usage, the range of graded readers, and dictionary defining vocabulary), we argue that high-frequency English vocabulary should include the most frequent 3,000 word families. We also propose that the low-frequency vocabulary boundary should be lowered to the 9,000 level, on the basis that 8–9,000 word families are sufficient to provide the lexical resources necessary to be able to read a wide range of authentic texts (Nation 2006). We label the vocabulary between high-frequency (3,000) and low-frequency (9,000+) as mid-frequency vocabulary. We illustrate the necessity of mid-frequency vocabulary for proficient language use, and make some initial suggestions for research addressing the pedagogical challenge raised by mid-frequency vocabulary.

scholarly journals Investigation of Flow Around a Slender Body at High Angles of Attack

2019 ◽  
Vol 30 (1) ◽  
pp. 51-61
Author(s):  
Ibraheem AlQadi Ibraheem AlQadi
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
The Body ◽  
Slender Body ◽  
Frequency Mode ◽  
Dynamic Mode ◽  
High Frequency Mode ◽  
Wide Range ◽  
Low Frequency Mode ◽  
High Angles Of Attack

A numerical investigation of flow around a slender body at high angles of attack is presented. Large eddy simulation of the flow around an ogive-cylinder body at high angles of attack is carried out. Asymmetric vortex flow was observed at angles of attack of α = 55◦ and 65◦ . The results showed that the phenomenon is present in the absence of artificial geometrical or flow perturbation. Contrary to the accepted notion that flow asymmetry is due to a convective instability, the development of vortex asymmetry in the absence of perturbations indicates the existence of absolute instability. An investigation of the unsteady flow field was carried out using dynamic mode decomposition. The analysis identified two distinct unsteady modes; high-frequency mode and low-frequency mode. At angle of attack 45◦ the high-frequency mode is dominant in the frontal part of the body and the low-frequency mode is dominant at the rear part. At α = 55◦ , the highfrequency mode is dominant downstream of vortex breakdown. At α = 65◦ , the spectrum shows a wide range of modes. Reconstruction of the dynamical modes shows that the low-frequency mode is associated with the unsteady wake and the high-frequency mode is associated with unsteady shear layer.

scholarly journals MEMS energy harvesters with a wide bandwidth for low frequency vibrations

2015 ◽  
Author(s):  
◽  
Nuh Sadi Yuksek
Keyword(s):  
Resonance Frequency ◽  
High Frequency ◽  
Maximum Output Power ◽  
Low Frequency ◽  
Maximum Output ◽  
Wide Bandwidth ◽  
Electromagnetic Power ◽  
Wide Range ◽  
Macro Scale ◽  
Load Resistor

We have designed and built macro-scale wideband electrostatic and electromagnetic power harvesters for low frequency vibration. Initially, MEMS capacitive plates for power harvesting have been designed, modeled and fabricated, and characterized. It was designed with a 2 x 2 mm2 movable metallic plate with a thickness of 10 [mu]m suspended by four straight beams above a fixed electrode with a gap of 10 [mu]m to form a variable capacitor. The suspension beams are made with a width, thickness and total length of 20 [mu]m, 10 [mu]m and 1500 [mu]m, respectively. It was found that the single cavity device can harvest almost 180 nW peak power across a 100 k[omega] load resistor at 5g. The harvested power was dependent on excitation amplitude and supplied DC voltage. The MEMS capacitive energy harvester was integrated with two impact oscillators at 18 Hz and 25 Hz for transferring energy from low frequency structural vibration with varying mechanical spectra to high frequency vibration of a high resonance frequency cantilever at 605 Hz. The results demonstrate that the device was able to harvest power on a wide range from 14 to 39 Hz at 1g excitation. The harvested power was 96 nW on a 100 k[omega] load resistor. We also studied a macro-scale electromagnetic power harvester with multi-impact oscillations to achieve a broad bandwidth at low frequency vibrations. The device consists of three low frequency cantilever designed to resonate at 12 Hz, 19 Hz and 40 Hz, a high frequency cantilever with resonance frequency of 210 Hz and a pick-up coil fixed at the tip of the high frequency cantilever. This results in a wide bandwidth response from 11-62 Hz at 1 g. A maximum output power of 23.5 [mu]W can be harvested at 1 g acceleration on an optimum load resistor of 22 [omega].

Evaluation of Surface Vibrations in the Low and High Frequency Domain

1995 ◽  
Author(s):  
Peter Fischer ◽  
Helmut J. Pradlwarter ◽  
Gerhart I. Schuëller
Keyword(s):  
Frequency Domain ◽  
High Frequency ◽  
Flow Characteristics ◽  
Low Frequency ◽  
Structural Response ◽  
Short Wave ◽  
Fe Model ◽  
Special Cases ◽  
Wide Range ◽  
Surface Vibrations

Abstract The frequency domain of many problems in structural dynamics encompasses a wide range, covering nearly static behavior up to vibration flow characteristics similar to heat transfer. This work presents an uniform approach for low and high frequency vibration analysis, which is based on Finite Element modeling of the structure. Vibrations in the low frequency range are determined by an efficient superposition technique of complex modes, which accounts accurately for any linear damping effect. The modal method is extended to the high frequency domain by applying different levels of averaging to the response and eigenfrequencies and by the introduction of random properties of modeshapes. The high frequency domain is defined by the size of the Finite Elements, i.e. short wave lengths of high frequency modeshapes cannot be represented by the FE-model. The response computation of isolated structures is extended to substructures of complex systems by prescribing stochastic multi-support base excitation at the substructure boundaries. It may be noted, that the presented approach of stochastic high frequency dynamics contains, as special cases, the expressions of the structural response of Statistical Energy Analysis, Bolotin’s integral method and the results of Asymptotic Modal Analysis.

scholarly journals Response of Seed Carrot to Various Water Regimes. II. Reproductive Development, Seed Yield, and Seed Quality

1990 ◽  
Vol 115 (5) ◽  
pp. 722-727 ◽  
Author(s):  
J.J. Steiner ◽  
R.B. Hutmacher ◽  
A.B. Mantel ◽  
J.E. Ayars ◽  
S.S. Vail
Keyword(s):  
Water Deficit ◽  
Seed Yield ◽  
High Frequency ◽  
Seed Quality ◽  
Low Frequency ◽  
Reproductive Development ◽  
Germination Percentage ◽  
Water Application ◽  
Water Deficits ◽  
Wide Range

Seed yield and quality of carrot (Daucus carota var. sativa DC.) were influenced by a wide range of water application regimes and levels. Irrigation treatments were imposed beginning at the time of extension of the primary umbel and extending throughout the reproductive development period. The three application regimes used were: 1) a high-frequency, low water deficit treatment [100% of daily accumulated crop evapotranspiration (ETc)]; 2) a series of five low-frequency (irrigated after 30 mm of accumulated ET,) application treatments with a range of water deficits from moderate to minimal (40% to 120% of ETc applied); and 3) a series of three treatments that had rapidly developing water deficits applied by terminating irrigation at 7, 5, and 2 weeks before harvest after being grown under low-stress conditions. Pure live seed (PLS) yield was optimized by different treatments within each of the three application regimes. Maximum yields were achieved with short-term (2-week) rapidly developing water deficits near harvest, moderate deficit irrigation with 60% to 80% of ETc applied after 30 mm of ETc, or with a low water deficit, high-frequency application. Seed germination percentage decreased as the amount of applied water increased. This effect was more pronounced in the later-developing umbel orders. However, seed quality measured as seedling root length was improved with increasing water application.

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