Intrinsic Period Research Articles

Modeling the evolutionary nexus between carbon dioxide emissions and economic growth

Given the fast-paced world economy, increasing carbon dioxide (CO2) emissions have caused serious concern regarding global warming. Many studies have examined the nexus between CO2 emissions and economic growth and inconsistent results are provided. Limited evidence suggests that different time periods under investigation could be a source of inconsistency, but there lacks of a thorough analysis. This paper systematically focuses on the evolutionary characteristics of the nexus to explore the influence of time periods. The panel data are reorganized by considering different time periods in various countries, and an intelligent data-driven approach, symbolic regression, is applied to discover models for each period without predefined structure and parameters. Three issues (Does the time period matter? What are the trends in different time periods? What are the applicable scopes of the models?) have been addressed in this paper. The results reveal the evolutionary nature of the nexus and it is verified that an intrinsic time period distinction does generate extrinsic inconsistency. The detailed dynamics of models indicate that the optimal models tend to be more complex as the time periods are extended. For countries with different locations and income levels, the applicable scopes of the four superior models (monotonically increasing, inverted U-shaped, inverted N-shaped, and M-shaped) vary in different time periods. The findings highlight that the effect of time periods cannot be ignored and the models should not be applied unconditionally when conducting empirical research. Finally, several policy implications are provided, which are critical for the balance of economic growth and CO2 emissions, particularly in some developing countries.

Dengue transmission: mathematical model with discrete time delays and estimation of the reproduction number

ABSTRACTIn this paper, we establish a mathematical model with two delays to reflect the intrinsic and extrinsic incubation periods of virus in dengue transmission. The basic reproduction number of the model is defined. It is proved that the disease-free equilibrium is stable when and the positive equilibrium is stable when . Next, we derive an estimation formula for the reproduction number when the human population is partially susceptible to dengue. As an application, the values of dengue transmission in Singapore in the years 2013–2015 are estimated. Our estimation method can be applied to estimating of other infectious diseases, especially when the human population is not completely susceptible to the disease.

Analyzing the control of dengue by releasing Wolbachia-infected male mosquitoes through a delay differential equation model.

To date, an innovative strategy to control dengue is to release Wolbachia-infected male mosquitoes into wild areas to sterilize wild female mosquito vectors by cytoplasmic incompatibility (CI). To investigate the efficacy of Wolbachia in blocking dengue virus transmission, we develop a deterministic mathematical model of human and mosquito populations in which one dengue serotype circulates. The delay differential equation model captures the respective extrinsic and intrinsic incu-bation periods (EIP and IIP) in the mosquito and human, as well as the maturation delay between mating and emergence of adult mosquitoes, which have received relatively little attention. We analyze the existence and stability of disease-free equilibria, and obtain a sufficient and necessary condition on the existence of the disease-endemic equilibrium. We also determine two threshold values of the release ratio $\theta$, denoted by $\theta_1^*$ and $\theta_2^*$ with $\theta_1^*>\theta_2^*$. When $\theta>\theta_1^*$, the mosquito population will be eradicated eventually. When $\theta_2^*<\theta < \theta_1^*$, a complete mosquito eradication becomes impossible, but virus eradication is ensured at the meantime. When $\theta<\theta_2^*$, the disease-endemic equilibrium emerges that allows dengue virus to circulate between humans and mosquitoes. We carry out sensitivity analysis of the threshold values in terms of the model parameters, and simulate several possible control strate-gies with different release ratios, which confirm the public awareness that reducing mosquito bites and killing adult mosquitoes are the most effective strategy to control the epidemic. Our model provides new insights on the effectiveness of Wolbachia in reducing dengue at a population level.

Heterogeneity of neuronal properties determines the collective behavior of the neurons in the suprachiasmatic nucleus.

Circadian rhythms have been observed in behavioral and physiological activities of living things exposed to the natural 24 h light-darkness cycle. Interestingly, even under constant darkness, living organisms maintain a robust endogenous circadian rhythm suggesting the existence of an endogenous clock. In mammals, the endogenous clock is located in the suprachiasmatic nucleus (SCN) which is composed of about 20,000 neuronal oscillators. These neuronal oscillators are heterogeneous in their properties, including the intrinsic period, intrinsic amplitude, light information sensitivity, cellular coupling strength, intrinsic amplitudes and the topological links. In this review, we introduce the influence of the heterogeneity of these properties on the two main functions of the SCN, i.e. the free running rhythm in constant darkness and entrainment to the external cycle, based on mathematical models where heterogeneous neuronal oscillators are coupled to form a network. Our findings show that the heterogeneities can alter the free running periods under constant darkness and the entrainment ability to the external cycle for the SCN by controlling a fine balance between flexibility and robustness of the clock. These findings can explain experimental observation, e.g., why the free running periods and entrainment abilities are different between species, and shed light on the heterogeneity of the SCN network.

Observation of Short‐Period Ionospheric Disturbances Using a Portable Digital Ionosonde at Sanya

AbstractA number of ionosondes have been operated in China to detect ionospheric disturbances for many years. These ionosondes, however, are not very suitable for the short‐period (&lt;15 min) disturbances due to their poor time resolutions (&gt;5 min). During recent years, the Institute of Geology and Geophysics, Chinese Academy of Sciences, together with the South Central University for Nationalities has been developing a portable digital ionosonde (PDI) equipped with the capability to detect and characterize small‐scale/short‐period ionospheric disturbances and to be quickly assembled and set up at temporary field stations for low‐latitude campaign coordinated observations. The PDI uses a set of technologies (e.g., code multiplexing and antenna/transmitter matching) that allow it to obtain quality Doppler ionograms at a good time resolution with small transmitting antennas. A preliminary analysis of observations by the PDI at Sanya (18.3°N, 109.6°E) shows the presence of ionospheric disturbances with periods ranging between several and tens of minutes. Interestingly, the disturbances (with different periods) were found to simultaneously occur at different F region altitudes, for example, with periods of ~5 and 20 min below and above ~180 km, respectively. The absence of shorter‐period disturbance at higher altitude is consistent with acoustic gravity waves through the region with intrinsic periods above the Brunt‐Väisälä period. The short‐period disturbances observed in F region bottomside are not evident in total electron content. The results demonstrate the capability of PDI to detect ionospheric disturbances with temporal scales down to a few minutes in routine ionogram mode. Future prospects of PDI are outlined.

Uncertainties in gravity wave parameters, momentum fluxes, and flux divergences estimated from multi-layer measurements of mesospheric nightglow layers

Measurements of dynamic parameters of atmospheric gravity waves, mainly the vertical wavelength, the momentum flux and the momentum flux divergence, are affected by large uncertainties crudely documented in the scientific literature. By using methods of error analysis, we have quantified these uncertainties for frequently observed temporal and spatial wave scales. The results show uncertainties of ∼10%, ∼35%, and ∼65%, at least, in the vertical wavelength, momentum flux, and flux divergence, respectively. The large uncertainties in the momentum flux and flux divergence are dominated by uncertainties in the Brunt-Väisälä frequency and in spatial separation of the nightglow layers, respectively. The measured uncertainties in fundamental wave parameters such as the wave amplitude, intrinsic period, horizontal wavelength, and wave orientation are ∼10% or less and estimated directly from our nightglow image data set. Other key environmental quantities such as the scale height and the Brunt-Väisälä frequency, frequently considered as constants in gravity wave parameter estimations schemes, are actually quite variable, presenting uncertainties of ∼4% and ∼9%, respectively, according to the several solar activity and seasonal atmosphere scenarios from the NRLMSISE-00 model simulated here.

The Excitation of Secondary Gravity Waves From Local Body Forces: Theory and Observation

AbstractWe examine the characteristics of secondary gravity waves (GWs) excited by a localized (in space) and intermittent (in time) body force in the atmosphere. This force is a horizontal acceleration of the background flow created when primary GWs dissipate and deposit their momentum on spatial and temporal scales of the wave packet. A broad spectrum of secondary GWs is excited with horizontal scales much larger than that of the primary GW. The polarization relations cause the temperature spectrum of the secondary GWs generally to peak at larger intrinsic periods τIr and horizontal wavelengths λH than the vertical velocity spectrum. We find that the one‐dimensional spectra (with regard to frequency or wave number) follow lognormal distributions. We show that secondary GWs can be identified by a horizontally displaced observer as “fishbone” or “&gt;” structures in z − t plots whereby the positive and negative GW phase lines meet at the “knee,” zknee, which is the altitude of the force center. We present two wintertime cases of lidar temperature measurements at McMurdo, Antarctica (166.69°E, 77.84°S) whereby fishbone structures are seen with zknee=43 and 52 km. We determine the GW parameters and density‐weighted amplitudes for each. We show that these parameters are similar below and above zknee. We verify that the GWs with upward (downward) phase progression are downward (upward) propagating via use of model background winds. We conclude that these GWs are likely secondary GWs having ground‐based periods τr=6–10 hr and vertical wavelengths λz=6–14 km, and that they likely propagate primarily southward.

A Reaction–Diffusion Model of Vector-Borne Disease with Periodic Delays

A vector-borne disease is caused by a range of pathogens and transmitted to hosts through vectors. To investigate the multiple effects of the spatial heterogeneity, the temperature sensitivity of extrinsic incubation period and intrinsic incubation period, and the seasonality on disease transmission, we propose a nonlocal reaction–diffusion model of vector-borne disease with periodic delays. We introduce the basic reproduction number $$\mathfrak {R}_0$$ for this model and then establish a threshold-type result on its global dynamics in terms of $$\mathfrak {R}_0$$ . In the case where all the coefficients are constants, we also prove the global attractivity of the positive constant steady state when $$\mathfrak {R}_0>1$$ . Numerically, we study the malaria transmission in Maputo Province, Mozambique.

Observation of Kelvin–Helmholtz instabilities and gravity waves in the summer mesopause above Andenes in Northern Norway

Abstract. We present observations obtained with the Middle Atmosphere Alomar Radar System (MAARSY) to investigate short-period wave-like features using polar mesospheric summer echoes (PMSEs) as a tracer for the neutral dynamics. We conducted a multibeam experiment including 67 different beam directions during a 9-day campaign in June 2013. We identified two Kelvin–Helmholtz instability (KHI) events from the signal morphology of PMSE. The MAARSY observations are complemented by collocated meteor radar wind data to determine the mesoscale gravity wave activity and the vertical structure of the wind field above the PMSE. The KHIs occurred in a strong shear flow with Richardson numbers Ri &lt; 0.25. In addition, we observed 15 wave-like events in our MAARSY multibeam observations applying a sophisticated decomposition of the radial velocity measurements using volume velocity processing. We retrieved the horizontal wavelength, intrinsic frequency, propagation direction, and phase speed from the horizontally resolved wind variability for 15 events. These events showed horizontal wavelengths between 20 and 40 km, vertical wavelengths between 5 and 10 km, and rather high intrinsic phase speeds between 45 and 85 m s−1 with intrinsic periods of 5–10 min.

0167 Determinants Of Irregular Sleep On Different Work Schedules Using Mathematical Modeling

Even on the same work schedule (regular or rotating), two individuals can differ in the regularity of their sleep patterns. Recent studies have reported a relationship between low day-to-day sleep regularity and a late circadian phase or late chronotype based on two novel metrics: Sleep Regularity Index (SRI) and Composite Phase Deviation (CPD). We aimed to identify possible mechanisms that underlie this relationship using a validated mathematical model of human sleep-wake regulation. Sleep-wake patterns were generated under realistic constraints on sleep timing for a range of circadian periods from short (τ = 23.8 h) to long (τ = 24.4 h). We simulated schedules of weekly daytime work and rotating shift-work by enforcing wakefulness during work times ± commute time. Light exposure was set to 800 lux during the day, 40 lux in the evening, and 0 lux during sleep. Sleep regularity was assessed by calculating two metrics: SRI (similarity of sleep-wake patterns between consecutive 24-h time intervals) and CPD (difference in midsleep timing between consecutive days and relative to chronotype). Work start times and intrinsic circadian period τ were varied to investigate the impact of exogenous vs. endogenous model factors on SRI and CPD. Longer τ-values resulted in later chronotypes independent of work schedule type and start times. Sleep regularity was lower (lower SRI, higher CPD) in most scenarios for longer τ-values and later chronotypes, particularly in the day-work schedule for early start times (before 7:00). It was possible to reverse this relationship (i.e., lower regularity for shorter τ-values and earlier chronotypes) in the rotational shift schedule by advancing shift times; such a schedule forces the earliest chronotypes to be awake at times when the latest chronotypes had to be awake at under standard shift times. Our findings suggest that irregular sleep patterns are the result of the interaction between external, environmental characteristics (i.e., imposed work schedules, self-selected light exposure) and individual, endogenous traits (i.e., circadian period), and are not only a characteristic of late chronotypes. R00HL119618, K24HL105664, R01HL114088, R01GM105018, R01HL128538, P01AG009975.

THE VALUES’ DETERMINATION OF THE OSCILLATIONS’ INTRINSIC PERIOD OF THE RUBBER-METAL SUPPORTED SPAN STRUCTURE BY APPROXIMATE METHODS

The natural vibration frequencies’ calculation of the pedestrian bridges’ span structures is still practically valued. Such factors as dynamic effects, elements’ structural features, the neglection of which is the norm in the classical hinge-rod model of the span structure, provide a significant influence on the dynamic characteristics of the longitudinal girders. Not taking into account the real conditions of the span structure supporting leads to the appearance in them of the vertical oscillations’ period in an unacceptable interval of 0.45 ... 0.60 s (in accordance with SP35.13330.2011). The appropriate preliminary calculations in engineering practice are based on approximate methods. However, the existing methods for determining the values of the oscillations’ intrinsic period of the span structures, which are based on the simplifications and the assumptions, have the significant calculation error. The research suggests the approximate method for determining the values of the intrinsic oscillations’ period of the span supported structures with the rubber-metal support parts. The proposed method is based on the work [1], the calculation scheme is also defined, the most accurate analytical expressions are also obtained on the differential equation solution basis. The longitudinal beams of the flyover along the M-60 «Ussuri» highway, in Khabarovsk-Vladivostok section 747- 750 km of the PK 156 + 132 are calculated as an example in the research.

An investigation into the characteristics of inertia gravity waves in the upper troposphere/lower stratosphere using a 205 MHz wind profiling radar

ABSTRACTA stratosphere-troposphere (ST) wind profiler at 205 MHz is operational at the Advanced Centre for Atmospheric Radar Research (10.04N; 76.33E), Cochin University of Science and Technology, India. This profiler provides accurate three-dimensional wind profiles for an altitude range of 315 m to 20 km. In this paper, we present the characteristics of inertia-gravity waves (IGWs) observed in the upper troposphere/lower stratosphere from uninterrupted observations of wind profiles taken from 22–27 October 2016. The propagation properties of the waves were derived using hodograph analysis. The intrinsic period of the IGWs is found to be 28.75 hours, and the vertical and horizontal wavelengths of the wave are 3.74 and 1221 km, respectively. The hodograph shows a clockwise rotation of the ellipse, which indicates an upward propagation of energy from the upper troposphere to the lower stratosphere. These waves were observed in conjunction with a persistent deep depression over the Bay of Bengal.

PSR J2322−2650 – a low-luminosity millisecond pulsar with a planetary-mass companion

We present the discovery of a binary millisecond pulsar (MSP), PSR J2322$-$2650, found in the Southern section of the High Time Resolution Universe survey. This system contains a 3.5-ms pulsar with a $\sim10^{-3}$ M$_{\odot}$ companion in a 7.75-hour circular orbit. Follow-up observations at the Parkes and Lovell telescopes have led to precise measurements of the astrometric and spin parameters, including the period derivative, timing parallax, and proper motion. PSR J2322$-$2650 has a parallax of $4.4\pm1.2$ mas, and is thus at an inferred distance of $230^{+90}_{-50}$ pc, making this system a candidate for optical studies. We have detected a source of $R\approx26.4$ mag at the radio position in a single $R$-band observation with the Keck Telescope, and this is consistent with the blackbody temperature we would expect from the companion if it fills its Roche lobe. The intrinsic period derivative of PSR J2322$-$2650 is among the lowest known, $4.4(4)\times10^{-22}$ s s$^{-1}$, implying a low surface magnetic field strength, $4.0(4)\times10^7$ G. Its mean radio flux density of 160 $\mu$Jy combined with the distance implies that its radio luminosity is the lowest ever measured, $0.008(5)$ mJy kpc$^2$. The inferred population of these systems in the Galaxy may be very significant, suggesting that this is a common MSP evolutionary path.

Dispersion of the intrinsic neuronal periods affects the relationship of the entrainment range to the coupling strength in the suprachiasmatic nucleus.

Living beings on the Earth are subjected to and entrained (synchronized) to the natural 24-h light-dark cycle. Interestingly, they can also be entrained to an external artificial cycle of non-24-h periods. The range of these periods is called the entrainment range and it differs among species. In mammals, the entrainment range is regulated by a main clock located in the suprachiasmatic nucleus (SCN) which is composed of 10000 neurons in the brain. Previous works have found that the entrainment range depends on the cellular coupling strength in the SCN. In particular, the entrainment range decreases with the increase of the cellular coupling strength, provided that all the neuronal oscillators are identical. However, the SCN neurons differ in the intrinsic periods that follow a normal distribution in a range from 22 to 28 h. In the present study, taking the dispersion of the intrinsic neuronal periods into account, we examined the relationship between the entrainment range and the coupling strength. Results from numerical simulations and theoretical analyses both show that the relationship is altered to be paraboliclike if the intrinsic neuronal periods are nonidentical, and the maximal entrainment range is obtained with a suitable coupling strength. Our results shed light on the role of the cellular coupling in the entrainment ability of the SCN network.

Time-delayed feedback control of coherence resonance chimeras.

Using the model of a FitzHugh-Nagumo system in the excitable regime, we investigate the influence of time-delayed feedback on noise-induced chimera states in a network with nonlocal coupling, i.e., coherence resonance chimeras. It is shown that time-delayed feedback allows for the control of the range of parameter values where these chimera states occur. Moreover, for the feedback delay close to the intrinsic period of the system, we find a novel regime which we call period-two coherence resonance chimera.

The Influence of Circadian Timing on Olfactory Sensitivity.

Olfactory sensitivity has traditionally been viewed as a trait that varies according to individual differences but is not expected to change with one's momentary state. Recent research has begun to challenge this position and time of day has been shown to alter detection levels. Links between obesity and the timing of food intake further raise the issue of whether odor detection may vary as a function of circadian processes. To investigate this question, 37 (21 male) adolescents (M age = 13.7 years) took part in a 28-h forced desynchrony (FD) protocol with 17.5 h awake and 10.5 h of sleep, for 7 FD cycles. Odor threshold was measured using Sniffin' Sticks 6 times for each FD cycle (total threshold tests = 42). Circadian phase was determined by intrinsic period derived from dim light melatonin onsets. Odor threshold showed a significant effect of circadian phase, with lowest threshold occurring on average slightly after the onset of melatonin production, or about 1.5○ (approximately 21:08 h). Considerable individual variability was observed, however, peak olfactory acuity never occurred between 80.5○ and 197.5○ (~02:22-10:10 h). These data are the first to show that odor threshold is differentially and consistently influenced by circadian timing, and is not a stable trait. Potential biological relevance for connections between circadian phase and olfactory sensitivity are discussed.

Case study of inclined sporadic E layers in the Earth’s ionosphere observed by CHAMP/GPS radio occultations: Coupling between the tilted plasma layers and internal waves

We have used the radio occultation (RO) satellite data CHAMP/GPS (Challenging Minisatellite Payload/Global Positioning System) for studying the ionosphere of the Earth. A method for deriving the parameters of ionospheric structures is based upon an analysis of the RO signal variations in the phase path and intensity. This method allows one to estimate the spatial displacement of a plasma layer with respect to the ray perigee, and to determine the layer inclination and height correction values. In this paper, we focus on the case study of inclined sporadic E (Es) layers in the high-latitude ionosphere based on available CHAMP RO data. Assuming that the internal gravity waves (IGWs) with the phase-fronts parallel to the ionization layer surfaces are responsible for the tilt angles of sporadic plasma layers, we have developed a new technique for determining the parameters of IGWs linked with the inclined Es structures. A small-scale internal wave may be modulating initially horizontal Es layer in height and causing a direction of the plasma density gradient to be rotated and aligned with that of the wave propagation vector k. The results of determination of the intrinsic wave frequency and period, vertical and horizontal wavelengths, intrinsic vertical and horizontal phase speeds, and other characteristics of IGWs under study are presented and discussed.

A Model-Based Approach to Optimizing Ultradian Forced Desynchrony Protocols for Human Circadian Research.

The human circadian system regulates internal 24-h rhythmicity and plays an important role in many aspects of human health and behavior. To investigate properties of the human circadian pacemaker such as intrinsic period and light sensitivity, experimental researchers have developed forced desynchrony (FD) protocols in which manipulations of the light-dark (LD) cycle are used to desynchronize the intrinsic circadian rhythm from the rest-activity cycle. FD protocols have typically been based on exposure to long LD cycles, but recently, ultradian FD protocols with short LD cycles have been proposed as a new methodology for assessing intrinsic circadian period. However, the effects of ultradian FD protocol design, including light intensity or study duration, on estimates of intrinsic circadian period have not, to our knowledge, been systematically studied. To address this gap, we applied a light-sensitive, dynamic mathematical model of the human circadian pacemaker to simulate ultradian FD protocols and analyze the effects of protocol design on estimates of intrinsic circadian period. We found that optimal estimates were obtained using protocols with low light intensities, at least 10 d of exposure to ultradian cycling, and a 7-h LD cycle duration that facilitated uniform light exposure across all circadian phases. Our results establish a theoretical framework for ultradian FD protocols that can be used to provide insights into data obtained under existing protocols and to optimize protocols for future experiments.

Differences in intrinsic amplitudes of neuronal oscillators improve synchronization in the suprachiasmatic nucleus.

In mammals, a main clock located in the suprachiasmatic nucleus (SCN) regulates the ∼24 h rhythms of behavioral and physiological activities exposed to a natural 24 light-dark cycle or even under constant darkness. The rhythms originate from self-sustained oscillations of the SCN neurons, which differ in both intrinsic periods and intrinsic amplitudes. The intrinsic periods and the intrinsic amplitudes were found to be bound to specific regions in the previous experiments. In particular, neurons of smaller amplitudes and larger periods are located in a ventrolateral part, and neurons of larger amplitudes and smaller periods are in a dorsomedial part. In the present study, we examined the effects of the differences in the intrinsic frequencies and the differences in the intrinsic amplitudes of neuronal oscillators on the synchronization, respectively. We found that the differences in the intrinsic frequencies weaken the synchronization, whereas the differences in the intrinsic amplitudes strengthen the synchronization. Our finding may shed light on the effects of the heterogenous properties of individual neurons on the collective behaviors of the SCN network and provide a way to enhance the synchronization.

A simple method using ex vivo culture of hair follicle tissue to investigate intrinsic circadian characteristics in humans

Almost all organisms maintain a circadian clock from birth to death to synchronize their own physiology and behavior with the earth’s rotation. Because the in vivo evaluation of human circadian characteristics is labor-intensive, in vitro or ex vivo approaches could provide advantages. In this study, to enable the simple and non-invasive evaluation of autonomous circadian oscillation, we established a method for monitoring clock gene expression by performing ex vivo culture of whole hair root tissue. This method is extremely simple and imposes little burden on subjects. Results obtained using Cryptochrome-deficient mice support that circadian period length in hair tissue correlates with intrinsic period length observed in physiology and behavior. We then applied this method to old-old subjects with severe dementia, who showed abnormal circadian behavior, and found that their peripheral clocks autonomously oscillated in a manner similar to those of healthy or younger subjects, indicating that the effect of cellular senescence on the autonomous clock oscillator is limited at least in some cell types. Although further validation may be required, the hair tissue-based culture assay would be a tool to investigate intrinsic circadian characteristics in humans.