scholarly journals Polyrhythmic foraging and competitive coexistence

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Akihiko Mougi
Keyword(s):  
Environmental Changes ◽  
Biological Rhythms ◽  
Activity Cycle ◽  
Coexistence Region ◽  
Annual Cycles ◽  
Coexistence Theory ◽  
Competitive Coexistence ◽  
Niche Shifts ◽  
Activity Cycles ◽  
Predator Foraging

AbstractThe current ecological understanding still does not fully explain how biodiversity is maintained. One strategy to address this issue is to contrast theoretical prediction with real competitive communities where diverse species share limited resources. I present, in this study, a new competitive coexistence theory-diversity of biological rhythms. I show that diversity in activity cycles plays a key role in coexistence of competing species, using a two predator-one prey system with diel, monthly, and annual cycles for predator foraging. Competitive exclusion always occurs without activity cycles. Activity cycles do, however, allow for coexistence. Furthermore, each activity cycle plays a different role in coexistence, and coupling of activity cycles can synergistically broaden the coexistence region. Thus, with all activity cycles, the coexistence region is maximal. The present results suggest that polyrhythmic changes in biological activity in response to the earth’s rotation and revolution are key to competitive coexistence. Also, temporal niche shifts caused by environmental changes can easily eliminate competitive coexistence.

scholarly journals Diversity of biological rhythm and food web stability

2021 ◽  
Vol 17 (2) ◽  
Author(s):  
Akihiko Mougi
Keyword(s):  
Food Web ◽  
Weak Interactions ◽  
Biological Activities ◽  
Biological Rhythms ◽  
Biological Rhythm ◽  
Annual Cycles ◽  
Biological Communities ◽  
Key Factor ◽  
Activity Cycles ◽  
Food Web Complexity

How ecosystem biodiversity is maintained remains a persistent question in the field of ecology. Here, I present a new coexistence theory, i.e. diversity of biological rhythm. Circadian, circalunar and circannual rhythms, which control short- and long-term activities, are identified as universal phenomena in organisms. Analysis of a theoretical food web with diel, monthly and annual cycles in foraging activity for each organism shows that diverse biological cycles play key roles in maintaining complex communities. Each biological rhythm does not have a strong stabilizing effect independently but enhances community persistence when combined with other rhythms. Biological rhythms also mitigate inherent destabilization tendencies caused by food web complexity. Temporal weak interactions due to hybridity of multiple activity cycles play a key role toward coexistence. Polyrhythmic changes in biological activities in response to the Earth's rotation may be a key factor in maintaining biological communities.

scholarly journals Discovery of short-term activity cycles in F-type stars

2019 ◽  
Vol 621 ◽  
pp. A136 ◽  
Author(s):  
M. Mittag ◽  
J. H. M. M. Schmitt ◽  
A. Hempelmann ◽  
K.-P. Schröder
Keyword(s):  
Activity Cycle ◽  
Total Activity ◽  
Short Term ◽  
Cyclic Activity ◽  
Solar Type ◽  
Cyclic Variations ◽  
Activity Cycles ◽  
F Stars ◽  
One Year ◽  
Index Time Series

Previous studies have revealed a 120 day activity cycle in the F-type star τ Boo, which represents the shortest activity cycle discovered until now. The question arises as to whether or not short-term activity cycles are a common phenomenon in F-type stars. To address this question, we analyse S-index time series of F-type stars taken with the TIGRE telescope to search for periodic variations with a maximal length of 2 years using the generalised Lomb-Scargle periodogram method. In our sample, we find four F-type stars showing periodic variations shorter than one year. However, the amplitude of these variations in our sample of F-star type stars appears to be smaller than that of solar-type stars with well-developed cyclic activity, and apparently represents only a part of the total activity. We conclude that among F-stars, the time-behaviour of activity differs from that of the Sun and cooler main sequence stars, as short-term cyclic variations with shallow amplitude of the cycle seem to prevail, rather than cycles with 10+ years periods and a larger cycle amplitude.

scholarly journals Global evolution of solar magnetic fields and prediction of activity cycles

2019 ◽  
Vol 15 (S354) ◽  
pp. 147-156
Author(s):  
Irina N. Kitiashvili
Keyword(s):  
Solar Activity ◽  
Magnetic Fields ◽  
Activity Cycle ◽  
Dynamo Model ◽  
Solar Magnetic Fields ◽  
Solar Cycles ◽  
Multiscale Dynamics ◽  
Activity Cycles ◽  
Solar Dynamics ◽  
Solar Activity Cycles

AbstractPrediction of solar activity cycles is challenging because physical processes inside the Sun involve a broad range of multiscale dynamics that no model can reproduce and because the available observations are highly limited and cover mostly surface layers. Helioseismology makes it possible to probe solar dynamics in the convective zone, but variations in differential rotation and meridional circulation are currently available for only two solar activity cycles. It has been demonstrated that sunspot observations, which cover over 400 years, can be used to calibrate the Parker-Kleeorin-Ruzmaikin dynamo model, and that the Ensemble Kalman Filter (EnKF) method can be used to link the modeled magnetic fields to sunspot observations and make reliable predictions of a following activity cycle. However, for more accurate predictions, it is necessary to use actual observations of the solar magnetic fields, which are available only for the last four solar cycles. In this paper I briefly discuss the influence of the limited number of available observations on the accuracy of EnKF estimates of solar cycle parameters, the criteria to evaluate the predictions, and application of synoptic magnetograms to the prediction of solar activity.

Physical and Technical Demands of Rugby League 9s Tournament Match Play: A Preliminary Study

2015 ◽  
Vol 10 (6) ◽  
pp. 774-779 ◽  
Author(s):  
Thomas Kempton ◽  
Aaron J. Coutts
Keyword(s):  
High Speed ◽  
Activity Cycle ◽  
Rugby League ◽  
Performance Data ◽  
Match Play ◽  
Technical Performance ◽  
Cycle Lengths ◽  
System Data ◽  
Average Activity ◽  
Activity Cycles

Purpose:To describe the physical and technical demands of rugby league 9s (RL9s) match play for positional groups.Methods:Global positioning system data were collected during 4 games from 16 players from a team competing in the Auckland RL9s tournament. Players were classified into positional groups (pivots, outside backs, and forwards). Absolute and relative physical-performance data were classified as total high-speed running (HSR; >14.4 km/h), very-high-speed running (VHSR; >19.0 km/h), and sprint (>23.0 km/h) distances. Technical-performance data were obtained from a commercial statistics provider. Activity cycles were coded by an experienced video analyst.Results:Forwards (1088 m, 264 m) most likely completed less overall and high-speed distances than pivots (1529 m, 371 m) and outside backs (1328 m, 312 m). The number of sprint efforts likely varied between positions, although differences in accelerations were unclear. There were no clear differences in relative total (115.6−121.3 m/min) and HSR (27.8−29.8 m/min) intensities, but forwards likely performed less VHSR (7.7 m/min) and sprint distance (1.3 m/min) per minute than other positions (10.2−11.8 m/min, 3.7−4.8 m/min). The average activity and recovery cycle lengths were ~50 and ~27 s, respectively. The average longest activity cycle was ~133 s, while the average minimum recovery time was ~5 s. Technical involvements including tackles missed, runs, tackles received, total collisions, errors, off-loads, line breaks, and involvements differed between positions.Conclusions:Positional differences exist for both physical and technical measures, and preparation for RL9s play should incorporate these differences.

scholarly journals The Relationship between Fatigue and Actigraphy-Derived Sleep and Rest-Activity Patterns in Cancer Survivors

2019 ◽  
Author(s):  
Tristan Martin ◽  
Rosemary Twomey ◽  
Mary E Medysky ◽  
John Temesi ◽  
S. Nicole Culos-Reed ◽  
...  
Keyword(s):  
Cancer Survivors ◽  
Activity Patterns ◽  
Sleep Onset ◽  
Activity Cycle ◽  
Objective Measures ◽  
Sleep Onset Latency ◽  
Cancer Related Fatigue ◽  
Wrist Actigraphy ◽  
Activity Cycles ◽  
Rest Activity

Background: Cancer-related fatigue can continue long after curative cancer treatment. The aim of this study was to investigate sleep and rest-activity cycles in fatigued and non-fatigued cancer survivors. We hypothesized that sleep and rest-activity cycles would be more disturbed in people experiencing clinically-relevant fatigue, and that objective measures of sleep would be associated with the severity of fatigue in cancer survivors.Methods: Cancer survivors (n=87) completed a 14-day wrist actigraphy measurement for the estimation of sleep and rest-activity cycles. Fatigue was measured using the Functional Assessment of Chronic Illness Therapy-Fatigue Scale (FACIT-F). Participants were dichotomised into two groups using a previously validated score (fatigued n=51 and non-fatigued n=36). Perception of sleep was measured using the Insomnia Severity Index (ISI).Results: FACIT-F score was correlated with wake after sleep onset (r =-0.28; p = 0.010), sleep efficiency (r=0.26; p=0.016), sleep onset latency (r=-0.31; p=0.044) and ISI score (r=-0.56; p <0.001). The relative amplitude of the rest-activity cycles was lower in the fatigued vs. non-fatigued group (p=0.017; d=0.58). Conclusions: After treatment for cancer, the severity of cancer-related fatigue is correlated with specific objective measures of sleep, and there is evidence of rest-activity cycle disruption in people experiencing clinically-relevant fatigue.

scholarly journals Transition from spot to faculae domination

2018 ◽  
Vol 621 ◽  
pp. A21 ◽  
Author(s):  
Timo Reinhold ◽  
Keaton J. Bell ◽  
James Kuszlewicz ◽  
Saskia Hekker ◽  
Alexander I. Shapiro
Keyword(s):  
Time Series ◽  
Phase Difference ◽  
Process Model ◽  
Activity Cycle ◽  
Magnetic Activity ◽  
Cycle Period ◽  
Stellar Activity ◽  
Rotation Periods ◽  
Active Stars ◽  
Activity Cycles

Context. The study of stellar activity cycles is crucial to understand the underlying dynamo and how it causes magnetic activity signatures such as dark spots and bright faculae. Having knowledge about the dominant source of surface activity might allow us to draw conclusions about the stellar age and magnetic field topology, and to put the solar cycle in context. Aims. We investigate the underlying process that causes magnetic activity by studying the appearance of activity signatures in contemporaneous photometric and chromospheric time series. Methods. Lomb-Scargle periodograms are used to search for cycle periods present in the photometric and chromospheric time series. To emphasize the signature of the activity cycle we account for rotation-induced scatter in both data sets by fitting a quasi-periodic Gaussian process model to each observing season. After subtracting the rotational variability, cycle amplitudes and the phase difference between the two time series are obtained by fitting both time series simultaneously using the same cycle period. Results. We find cycle periods in 27 of the 30 stars in our sample. The phase difference between the two time series reveals that the variability in fast-rotating active stars is usually in anti-phase, while the variability of slowly rotating inactive stars is in phase. The photometric cycle amplitudes are on average six times larger for the active stars. The phase and amplitude information demonstrates that active stars are dominated by dark spots, whereas less-active stars are dominated by bright faculae. We find the transition from spot to faculae domination to be at the Vaughan–Preston gap, and around a Rossby number equal to one. Conclusions. We conclude that faculae are the dominant ingredient of stellar activity cycles at ages ≳2.55 Gyr. The data further suggest that the Vaughan–Preston gap cannot explain the previously detected dearth of Kepler rotation periods between 15 and 25 days. Nevertheless, our results led us to propose an explanation for the lack of rotation periods to be due to the non-detection of periodicity caused by the cancelation of dark spots and bright faculae at ∼800 Myr.

scholarly journals Multi-wavelength variability of the young solar analog ι Horologii

2019 ◽  
Vol 631 ◽  
pp. A45 ◽  
Author(s):  
J. Sanz-Forcada ◽  
B. Stelzer ◽  
M. Coffaro ◽  
S. Raetz ◽  
J. D. Alvarado-Gómez
Keyword(s):  
Light Curve ◽  
Thermal Structure ◽  
Rotation Period ◽  
Activity Cycle ◽  
X Rays ◽  
X Ray ◽  
Multi Wavelength ◽  
Activity Cycles ◽  
Irregular Behavior

Context. Chromospheric activity cycles are common in late-type stars; however, only a handful of coronal activity cycles have been discovered. ι Hor is the most active and youngest star with known coronal cycles. It is also a young solar analog, and we are likely facing the earliest cycles in the evolution of solar-like stars, at an age (~600 Myr) when life appeared on Earth. Aims. Our aim is to confirm the ~1.6 yr coronal cycle and characterize its stability over time. We use X-ray observations of ι Hor to study the corona of a star representing the solar past through variability, thermal structure, and coronal abundances. Methods. We analyzed multi-wavelength observations of ι Hor using XMM-Newton, TESS, and HST data. We monitored ι Hor throughout almost seven years in X-rays and in two UV bands. The summed RGS and STIS spectra were used for a detailed thermal structure model, and the determination of coronal abundances. We studied rotation and flares in the TESS light curve. Results. We find a stable coronal cycle along four complete periods, more than covered in the Sun. There is no evidence for a second longer X-ray cycle. Coronal abundances are consistent with photospheric values, discarding any effects related to the first ionization potential. From the TESS light curve we derived the first photometric measurement of the rotation period (8.2 d). No flares were detected in the TESS light curve of ι Hor. We estimate the probability of having detected zero flares with TESS to be ~2%. Conclusions. We corroborate the presence of an activity cycle of ~1.6 yr in ι Hor in X-rays, more regular than its Ca II H&K counterpart. A decoupling of the activity between the northern and southern hemispheres of the star might explain the disagreement. The inclination of the system would result in an irregular behavior in the chromospheric indicators. The more extended coronal material would be less sensitive to this effect.

SLEEP CYCLE CHARACTERISTICS IN INFANTS

PEDIATRICS ◽  
1969 ◽  
Vol 43 (1) ◽  
pp. 65-70
Author(s):  
Evelyn Stern ◽  
Arthur H. Parmelee ◽  
Yoshio Akiyama ◽  
Marvin A. Schultz ◽  
Waldemar H. Wenner
Keyword(s):  
Cycle Length ◽  
Activity Cycle ◽  
Sleep Cycle ◽  
Normal Brain ◽  
Active Sleep ◽  
Quiet Sleep ◽  
Activity Cycles ◽  
Significant Measure ◽  
Polygraphic Recording ◽  
Rest Activity

Within the sleep of adults and infants there are cyclic fluctuations between quiet and active sleep. These fluctuations may also persist during wakefulness as rest-activity cycles but are less readily detected. They constitute a fundamental biological rhythm on which other daily rhythms are superimposed. In adults the rest-activity cycle is 90 minutes in duration. The quiet-active sleep cycles of term, 3-, and 8-month-old infants were determined by polygraphic recording of eye and body movements, respirations, and electroencephalogram. The cycle length at term was 47 minutes and 49 and 50 minutes at 3 and 8 months. The increase in cycle length with maturation was not significant, but there was a significant change in the proportion of quiet to active sleep within a cycle. At term they were equal, while at 8 months quiet sleep was twice as long as active sleep. Quiet sleep is a highly controlled state requiring complex feedback mechanisms. The increasing proportion of quiet sleep may be a significant measure of normal brain development.

scholarly journals HD 38858: a solar-type star with an activity cycle of ∼10.8 yr

2018 ◽  
Vol 620 ◽  
pp. A34 ◽  
Author(s):  
M. Flores ◽  
J. F. González ◽  
M. Jaque Arancibia ◽  
C. Saffe ◽  
A. Buccino ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Activity Cycle ◽  
Earth Planet ◽  
Stellar Activity ◽  
Balmer Lines ◽  
Solar Type ◽  
Activity Cycles ◽  
Novel Strategy ◽  
Solar Type Star

Context. The detection of chromospheric activity cycles in solar-analogue and twin stars can be used to place the solar cycle in a wider context. However, relatively few of these stars with activity cycles have been detected. It is well known that the cores of the Ca II H&K lines are modulated by stellar activity. The behaviour of the Balmer and other optical lines with stellar activity is not yet completely understood. Aims. We search for variations in the Ca II H&K, Balmer, and Fe II lines modulated by stellar activity. In particular, we apply a novel strategy to detect possible shape variations in the Hα line. Methods. We analysed activity signatures in HD 38858 using HARPS and CASLEO spectra obtained between 2003 and 2017. We calculated the Mount Wilson index (SMW), log(R′HK), and the statistical moments of the Ca II H&K, Balmer, and other optical lines. We searched for periodicities using the generalized Lomb-Scargle periodogram. Results. We detect a long-term activity cycle of 10.8 yr in Ca II H&K and Hα in the solar-analogue star HD 38858. In contrast, this cycle is marginally detected in the Fe II lines. We also detect a noticeable variation in radial velocity that seems to be produced by stellar activity. Conclusions. HD 38858 is the second solar-analogue star where we find a clear activity cycle that is replicated in the Balmer lines. Spectral indexes based on the shape of Hα line seem to be more reliable than the fluxes in the same line for detecting activity variations. The cyclic modulation we detected gives place to a variation in radial velocity that previously has been associated with a super-Earth planet. Finally, due to the similarity of HD 38858 with the Sun, we recommend to continue monitoring this star.

Reduced ground beetle activity following ice damage in maple stands of southwestern Quebec

2001 ◽  
Vol 77 (4) ◽  
pp. 651-656 ◽  
Author(s):  
Michel Saint-Germain ◽  
Yves Mauffette
Keyword(s):  
Sugar Maple ◽  
Environmental Changes ◽  
Deciduous Forest ◽  
Ground Beetle ◽  
Activity Cycle ◽  
Pitfall Traps ◽  
Ice Storm ◽  
Forest Species ◽  
Tree Crown ◽  
Provincial Park

The 1998 ice storm led to significant tree crown loss in the deciduous forests of southwestern Quebec. Increased irradiation in the understory may alter edaphic parameters of affected forests, such as temperature and humidity. We examined effects such a disturbance might have on the epigeal fauna of sugar maple stands during the summers of 1998 and 1999. Dry pitfall traps were set in the deciduous forest of Mont-Saint-Bruno Provincial Park, 20 km southeast of Montreal, Quebec under three different post-ice storm conditions (light tree crown loss, severe loss, and gaps) from mid-July to mid-August. We captured significantly fewer total Coleoptera and Carabidae at sites damaged by the ice storm. Species diversity of Coleoptera was also lower at damaged sites. However, the daily activity cycle of the insects did not change following heavy crown loss. Synhuchus impunctatus (Say), the dominant forest species, proved to be very sensitive to the disturbance. Observed decreases in insect abundance may be related to environmental changes resulting from heavy crown loss; these effects were probably both direct (on metabolism) and indirect (on nutritional resources). Key words: Carabidae, crown loss, disturbance, ice storm, maple stands, Synuchus impunctatus

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