Cycle Oscillations Research Articles

Transitions between surface force- and inertia-dominant contact dynamics regimes in high-speed scanning probe microscopy

In contact mode scanning probe microscopy (SPM), the microcantilever probe’s dynamics are governed by the (short-range) surface interaction forces, where the tip is “always-in-contact” with the sample. In intermittent contact modes such as “tapping” or bimodal SPM, on the other hand, these are governed by the frequency of the microcantilever’s own external excitation. However, when contact mode is employed with high scan speeds (for “video-rate” SPM), we see intermittent transitions—within a single oscillation cycle—between the “always-in-contact” regime and another which is dominated by the microcantilever’s inertia. We find—through experiments and physical modeling—that the fast in-plane motion of the sample relative to the probe results in a high surface excitation frequency v/λ (and its harmonics), which excite the microcantilever’s out-of-plane eigenmodes and cause it to “break free” of the surface and “overshoot” and “parachute.” The impacts of the tip that consequently occur upon the sample inject energy over a wide frequency band into the higher eigenmodes, especially when operating in a low dissipation ambient environment. The microcantilever, then, exhibits phenomena such as eigenmode switching, sidebands, and fractional and combination resonances; such behavior is not seen in, say, tapping mode SPM, since, there, energy is injected at an externally-determined temporal rate. This article investigates the transition from the dynamics of the microcantilever at low speeds to that exhibited at high speeds. The model for dynamic contact loss is validated against the experiments and can be used to propose mitigation of such dynamics in order to achieve high-resolution imaging.

Interannual and decadal variations of the Kuroshio axis in the East China Sea

Much work has been focused on the variability and climatic effect of the Kuroshio Extension, but little focus on the Kuroshio variation in the East China Sea(ECS). This study, investigates the interannual and decadal migrations of Kuroshio axis(KA) in the ECS and its relationships to large-scale climate signals. On interannual timescale, variability of the KA in the ECS is closely related to El Niño-Southern Oscillation (ENSO) cycle. The shifting of the main axis in ECS presents a dipolar pattern with the offshore (onshore) shift of the south (north) part KA in ECS under the El Niño events and onshore (offshore) shift under the La Niña events. The interannual variation (IVAR) is modulated dominantly by wind stress curl (WSC) and surface relative vorticity advection associated with the ENSO. On the decadal timescale, the Pacific Decadal Oscillation (PDO) and North Pacific Gyre Oscillation (NPGO) could cause the WSC and relative vorticity (RV) anomalies, and in turn modulates the fluctuation of KA. The PDO is the main factor and the NPGO is secondary factor for the decadal variation (DVAR) of the KA in ECS.

Effects of different working gases on the heat transfer enhancement performance of a heating tube with spiral insert under oscillatory flow

The working gas type had an important effect on the heat transfer performance of the turbulence device in the heater of Stirling engine, but the related researches were scarce, especially under the oscillatory flow. This work investigated the effects of four working gases (i.e., H2, He, N2, and CO2) on the heat transfer characteristics of a heating tube with spiral insert compared with a smooth tube under oscillating flow for a Stirling engine. The transient physical fields under different phase angles in an oscillatory cycle were analyzed, and the Nusselt (Nu) number, pressure loss and outlet temperature of working gas were studied. The results show that the cycle average Nu number of the enhanced tube with H2, He, N2, and CO2 as working gas increased to 1.67, 1.62, 1.61 and 1.72 times when comparing with those of the smooth tube. The cycle average friction coefficient increased to 1.96, 2.37, 2.36 and 2.62 times, respectively. Moreover, the performance evaluation criterion (PEC) values of the enhanced tube using the four types of working gas were all greater than 1 (1.21∼1.33). This implies that the comprehensive heat transfer performance of the heating tube with spiral insert was all improved with the four types of working gas. Moreover, the heat transfer enhancement effect was best when hydrogen was used. While considering the thermodynamic performance and safety reliability, the helium was more recommended. The findings are beneficial to enhance the operating efficiency of a Stirling engine.

Evidence of a Third Body and Photometric Solutions of a High Temperature Marginal Contact Binary CW Aqr

Marginal contact binary systems are an important class of binary systems in exploited by astronomers to understand various astrophysical phenomena as they bridge both semi-detached and overcontact stages. We studied the photometric data of CW Aqr using the JCB 1.3 m telescope (JCBT), Kepler, and TESS to understand the period variations and constrain the light curve solutions. We noted that the period of CW Aqr is increasing with a mass transfer rate of = 7.53 × 10−8 M ⊙ yr−1 from the secondary to the primary component. We also ascertained cyclic deviations along with a parabolic trend in the O − C diagram. The residuals displayed a sinusoidal trend which was fitted with an LTTE, indicating the presence of a third body with an orbital period of P 3 ∼10 yr and e = 0.10. We fitted the JCBT, Kepler, and TESS photometric normalized light curves and noted the mass ratio to be q ∼ 0.32 for both contact and semi-detached configurations. We identified a temperature difference between the primary and secondary components of ∼2500 K. No activity signatures were found in the observed light curves which were also evident from the Hα line studies where the filled-in effect was not seen. Overall our study suggests that CW Aqr is a marginal contact binary with a low mass ratio evolving toward a semi-detached configuration. However, it may merge if the period increases due to ongoing mass transfer accompanied by a lowering in the mass ratio and later oscillate back to the period-decreasing trend due to angular momentum loss over a few cycles of thermal relaxation oscillations followed by instability.

The drainage of glacier and ice sheet surface lakes

Supraglacial lakes play a central role in storing melt water, enhancing surface melt and ultimately in driving ice flow and ice shelf melt through injecting water into the subglacial environment and through facilitating fracturing. Here, we develop a model for the drainage of supraglacial lakes through the dissipation-driven incision of a surface channel. The model consists of the St Venant equations for flow in the channel, fed by an upstream lake reservoir, coupled with an equation for the evolution of channel elevation due to advection, uplift and downward melting. After reduction to a ‘stream power’-type hyperbolic model, we show that lake drainage occurs above a critical rate of water supply to the lake due to the backward migration of a shock that incises the lake seal. The critical water supply rate depends on advection velocity and uplift (or more precisely, drawdown downstream of the lake) as well as model parameters such as channel wall roughness and the parameters defining the relationship between channel cross-section and wetted perimeter. Once lake drainage does occur, it can either continue until the lake is empty, or terminate early, leading to oscillatory cycles of lake filling and draining, with the latter favoured by large lake volumes and relatively small water supply rates.

On symmetric and alternating-symmetric patterns in the wake of a cylinder undergoing vortex-induced vibrations in the inline or close to the inline direction

We provide a quantitative study of two types of vortex-shedding patterns that are observed within the first response range of a flexibly-mounted cylinder allowed to oscillate only in the direction of flow (the inline direction) or directions close to the inline, and undergoing Vortex-Induced Vibration (VIV). We had recently shown that within this range, two types of shedding patterns are observed: a symmetric shedding, where two vortices of the same size are shed from the two sides of the cylinder simultaneously, and an alternating-symmetric pattern, where two vortices are still shed simultaneously, but with different sizes, and their sizes alternate in each cycle of oscillations. Here, we use bubble image velocimetry (BIV) results to quantitatively study these two types of wakes. We introduce a novel method of representing the wakes that we refer to as the “Vortex Arm” representation, which makes it possible to observe the differences between the two types of shedding very clearly. We discuss the paths of these vortices in the wake and observe that while the two vortices in a symmetric shedding do not interact, the large and small vortices shed in an alternating-symmetric pattern interact, resulting in deviations from their straight downstream paths and even upstream movements of the smaller vortex. We show how the symmetric and alternating-symmetric patterns are influenced when the direction of oscillations makes an angle with respect to the direction of the incoming flow.

152 Caudate and Dorsolateral Prefrontal Cortex Beta Bursts During Working Memory Encoding Correlate with Memory Impairment in Parkinson’s Disease

INTRODUCTION: Cognitive dysfunction is a common nonmotor symptom of Parkinson’s disease (PD), with memory impairment being a primary cause of disability. Decreased dopamine in PD elevates beta power in cortico-striato-thalamo-cortico (CSTC) motor circuits and is the basis of closed-loop deep brain stimulation (DBS) strategies. Analogous dysfunction of parallel CSTC cognitive circuitry including caudate and dorsolateral prefrontal cortex (DLPFC) may mediate PD cognitive impairment and be a neuromodulation target for cognitive symptoms. We have previously shown caudate and DLPFC beta power contributes to working memory updating, and suppression of prefrontal cortex beta bursts during working memory encoding has been linked with improved performance. However, how PD affects beta bursting in relation to memory function remains unknown. METHODS: Fourteen PD patients undergoing awake DBS surgery with electrode trajectories traversing the caudate, DLPFC, or both participated in this study. Subjects completed a 2-back working memory task where they identified whether a presented word matched the word presented two trials prior. Bursts were defined as epochs where power exceeded a Z-score of two for at least three oscillatory cycles. We correlated change in caudate and DLPFC beta burst rates during working memory encoding with subjects’ composite memory scores, which were calculated from preoperative neuropsychological assessments. RESULTS: Caudate and DLPFC beta burst rates decreased significantly during working memory encoding for correct trials. In both structures, change in beta burst rate was significantly correlated with subjects’ composite memory scores, with greater decreases in beta bursting corresponding with better memory function. CONCLUSIONS: Beta bursts are suppressed in caudate and DLPFC during working memory encoding. Reduced beta burst suppression during encoding correlated with greater memory impairment in PD patients, indicating that altered caudate and DLPFC beta bursting dynamics may contribute to PD memory impairment.

New Photometric Investigations of G-type Contact Binary TU Boo

Two sets of CCD photometric observations for contact binary TU Boo were obtained in 2020 and 2021. Different from its asymmetric light curves published from the literature, our BVR c I c -band curves show that the heights of maximum are almost equal. These distortions of light curves possibly indicate that the components were active in past 25 yr, but they were stable in the last two years. For total-eclipse binary TU Boo, due to some star-spots on the surface of the components, the physical structure obtained by many investigators are different. Therefore, the symmetric multi-color light curves in 2020, 2021 are important for understanding configuration and evolution of this system. By using the Wilson–Devinney program, it is confirmed that TU Boo is an A-type shallow-contact binary with the temperature difference of ΔT = 152 K and fill-out of f = 14.67%. In the O−C diagram of orbital period analysis, a cyclic oscillation superimposed on a continuous decrease was determined. The long-term decreasing is often explained by the mass transfer from the more massive star to less massive one, this system will evolve into a deeper contact binary with time. The cyclic oscillations computed from much more CCD times of light minimum maybe result from the light-travel time effect via the presence of a third body. These characters of structure, evolution and ternary belong to typical A-type W UMa binaries with spectral G.

Long-term trends and sensitivities of PM2.5 pH and aerosol liquid water to chemical composition changes and meteorological parameters in Hong Kong, South China: Insights from 10-year records from three urban sites

Aerosol pH and aerosol liquid water (ALW) play key roles in regulating many atmospheric processes. In many countries, large reductions in SO2 and NOx emissions as a result of air pollution regulatory policies have led to improved air quality and significant changes in aerosol mass and chemical composition. Understanding the long-term trends and sensitivities of aerosol pH and ALW to changes in meteorological conditions and chemical composition is useful for predicting how atmospheric processes that depend on aerosol acidity and/or ALW will evolve as air pollutant emissions change over time. At present, long-term monitoring records of aerosol pH and ALW are limited in most parts of China and elsewhere in Asia due to the scarcity of long-term aerosol chemical speciation measurements acquired through regular sampling schedules and consistent analysis protocols in this region. We used a 10-year dataset (2011–2020) from three long-term monitoring sites to investigate the long-term trends of PM2.5 pH and ALW concentrations, identify key factors that drive the variations of PM2.5 pH and ALW concentrations, and investigate the sensitivities of PM2.5 pH and ALW concentrations to chemical composition changes during different seasons in Hong Kong, a highly populated urbanized city located in South China that has experienced improved air quality as a result of various effective air pollution regulatory policies. Despite the substantial decreases in PM2.5 concentrations and changes in chemical composition in this 10-year period, PM2.5 pH showed little change. The rates at which PM2.5 pH and ALW concentration changed ranged from −0.007 to −0.001 pH units/year and from −1.45 to −0.53 μg m−3/year, respectively. Clear and consistent seasonal oscillatory cycles were observed for both PM2.5 pH (∼2–∼4) and ALW concentrations (∼5–∼40 μg m−3) at the three sites during this 10-year period. PM2.5 was the most acidic in the fall, and was the least acidic in winter. ALW concentrations were the lowest in summer, and the highest in winter/spring. Sensitivity tests revealed that chemical composition, especially particulate sulfate concentrations, plays a major role in driving the variations in aerosol pH and ALW concentration during each season. However, the magnitudes to which aerosol pH and ALW concentration respond to changes in chemical composition depend strongly on the meteorological conditions in each season. Given that many urbanized cities in South China share similar air quality and meteorological characteristics as Hong Kong, the results presented here are useful for advancing our understanding of how air pollution regulatory policies can alter aerosol pH and ALW concentrations, and consequently aqueous aerosol chemistry, in other South China cities.

Locus coeruleus noradrenergic neurons phase-lock to prefrontal and hippocampal infra-slow rhythms that synchronize to behavioral events.

The locus coeruleus (LC) is the primary source of noradrenergic projections to the forebrain, and, in prefrontal cortex, is implicated in decision-making and executive function. LC neurons phase-lock to cortical infra-slow wave oscillations during sleep. Such infra-slow rhythms are rarely reported in awake states, despite their interest, since they correspond to the time scale of behavior. Thus, we investigated LC neuronal synchrony with infra-slow rhythms in awake rats performing an attentional set-shifting task. Local field potential (LFP) oscillation cycles in prefrontal cortex and hippocampus on the order of 0.4 Hz phase-locked to task events at crucial maze locations. Indeed, successive cycles of the infra-slow rhythms showed different wavelengths, as if they are periodic oscillations that can reset phase relative to salient events. Simultaneously recorded infra-slow rhythms in prefrontal cortex and hippocampus could show different cycle durations as well, suggesting independent control. Most LC neurons (including optogenetically identified noradrenergic neurons) recorded here were phase-locked to these infra-slow rhythms, as were hippocampal and prefrontal units recorded on the LFP probes. The infra-slow oscillations also phase-modulated gamma amplitude, linking these rhythms at the time scale of behavior to those coordinating neuronal synchrony. This would provide a potential mechanism where noradrenaline, released by LC neurons in concert with the infra-slow rhythm, would facilitate synchronization or reset of these brain networks, underlying behavioral adaptation.

Oscillatory and transient dynamics of a slow–fast predator–prey system with fear and its carry-over effect

In almost every ecological system, growth of various interacting species evolve in different time scales and the implementation of this time scale difference in the corresponding mathematical model exhibits some rich and complex oscillatory dynamics. In this article, we consider a predator–prey model with Beddington–DeAngelis functional response in which the prey reproduction is affected by the predation induced fear and its carry-over effect. Considering the growth of prey species occurs on a faster time scale than that of predator, the proposed system reduces to a ‘slow–fast predator–prey’ system. Using the geometric singular perturbation theory and asymptotic expansion technique, we investigate the system both analytically and numerically, and observe a wide range of rich and complex dynamics such as canard cycles (with or without head) near the singular Hopf-bifurcation threshold and relaxation oscillation cycles. The system experiences a canard explosion through which a rapid transition from small amplitude limit cycle to large amplitude limit cycle occurs in a tiny parametric interval. These types of complex oscillatory dynamics are absent in non slow–fast systems. Furthermore, it is shown that the interplay between fear and its carry-over effect, and the variation of time scale parameter may lead to a regime shift of the oscillatory dynamics. We also study the impact of fear and its carry-over effect on the properties of long transient dynamics. Thus our study provides some valuable biological insights of a slow–fast predator–prey system which will aid in understanding the interplay between fear and its carry-over effect.

Synchronization of the circadian clock to the environment tracked in real time

The circadian system of the cyanobacterium Synechococcus elongatus PCC 7942 relies on a three-protein nanomachine (KaiA, KaiB, and KaiC) that undergoes an oscillatory phosphorylation cycle with a period of ~24 h. This core oscillator can be reconstituted invitro and is used to study the molecular mechanisms of circadian timekeeping and entrainment. Previous studies showed that two key metabolic changes that occur in cells during the transition into darkness, changes in the ATP/ADP ratio and redox status of the quinone pool, are cues that entrain the circadian clock. By changing the ATP/ADP ratio or adding oxidized quinone, one can shift the phase of the phosphorylation cycle of the core oscillator invitro. However, the invitro oscillator cannot explain gene expression patterns because the simple mixture lacks the output components that connect the clock to genes. Recently, a high-throughput invitro system termed the invitro clock (IVC) that contains both the core oscillator and the output components was developed. Here, we used IVC reactions and performed massively parallel experiments to study entrainment, the synchronization of the clock with the environment, in the presence of output components. Our results indicate that the IVC better explains the invivo clock-resetting phenotypes of wild-type and mutant strains and that the output components are deeply engaged with the core oscillator, affecting the way input signals entrain the core pacemaker. These findings blur the line between input and output pathways and support our previous demonstration that key output components are fundamental parts of the clock.

La Niña conditions influence interannual call detections of pygmy blue whales in the eastern Indian Ocean

Oceans across the globe are warming rapidly and marine ecosystems are changing as a result. However, there is a lack of information regarding how blue whales are responding to these changing environments, especially in the Southern Hemisphere. This is because long term data are needed to determine whether blue whales respond to variability in environmental conditions. Using over 16 years of passive acoustic data recorded at Cape Leeuwin, we investigated whether oceanic environmental drivers are correlated with the migration patterns of eastern Indian Ocean (EIO) pygmy blue whales off Western Australia. To determine which environmental variables may influence migration patterns, we modelled the number of acoustic call detections of EIO pygmy blue whale calls with broad and fine scale environmental variables. We found a positive correlation between total annual whale call detections and El Niño Southern Oscillation (ENSO) cycles and the Indian Ocean Dipole (IOD), with more whale calls detected during La Niña years. We also found that monthly whale call detections correlated with sea surface height around the hydrophone and chlorophyll-a concentration at a prominent blue whale feeding aggregation area (Bonney Upwelling) where whales feed during the summer before migrating up the west Australian coast. At the interannual scale, ENSO had a stronger relationship with call detections than IOD. During La Niña years, up to ten times more EIO pygmy blue whale calls were detected than in neutral or El Niño years. This is likely linked to changes in productivity in the feeding areas of the Great Australian Bight and Indian Ocean. We propose that in lower productivity years whales either skipped migration or altered their habitat use and moved further offshore from the hydrophones and therefore were not detected. The frequency and intensity of ENSO events are predicted to increase with climate change, which is likely to impact the productivity of the areas used by blue whales. These changes in productivity may affect the physical condition and reproductive success of individual whales. A reduction in reproductive success could have a significant impact on blue whale recovery from historical whaling and their ability to adapt to a changing environment.

Analysis of flame instability in low-emission tower-type gas turbine combustor with multi-stage methane injection

A low-emission tower-type coaxial-staged combustor with a pilot stage, first main stage and second main stage is simulated in this study. The flow field, flame structure, vortex-mixing interaction, and flame instabilities are predicted with large eddy simulation and partially stirred reactor model. Heat radiation is not considered in the simulations. The results show that the maximum of the averaged length and width of the inner recirculation zone are approximately 249.8 and 71.3 mm, respectively. The distributions of the fuel from various stages in the combustor are analyzed based on the respective mixture fractions. The pressure and heat release rate (HRR) in the combustor fluctuate periodically with a frequency of about 373 Hz. Both HRR and pressure fluctuations increase and then decrease with time, and there is a phase difference of 46.1° between them. Due to the combustion instabilities, the flame structures change periodically, including attached flame and lifted V-shaped flame, in one HRR oscillation cycle. Moreover, the swirling flame length also varies periodically with time. As the pilot stage and first main stages are turned-off, the frequency of HRR fluctuations and pressure fluctuations, as well as the flame root dynamics, are significantly affected. It is also found that the effects of the fuel ratio of the first and second main stages have a significant influence on the flame root dynamics, e.g., different degrees of flashback observed in different cases.

Dynamic modeling and residual vibration suppression of electrostatically driven soft dielectric elastomer minimum energy structures

Dielectric elastomers (DEs), a special class of soft electro-active polymers that undergo finite deformation under external electrical stimuli, offer a wide range of applications that include but are not limited to soft actuators, soft robots, and energy harvesters. Among the various configurations of dielectric elastomer-based soft mechanisms, DE-based minimum energy structures (DEMES) are elite due to their several advantageous characteristics, such as lightweight, an easy fabrication process, the ability to achieve a desirable complex 3-D shape, the capability of undergoing large out-of-plane actuation despite planar fabrication, fast response, and controllability. However, when a DEMES actuator is driven by an input voltage signal consisting of different Heaviside steps, the intrinsic residual vibrations exhibited by the actuator may restrict the motion precision required in real-world applications. In this work, a nonlinear dynamic model of the DEMES actuator is devised using the Euler–Lagrange equation of motion, and the neo-Hookean material model is utilized to describe the material behavior of the DE membrane. A feedforward control technique is developed to suppress the inherent residual vibrations exhibited by the DEMES actuator. The control technique relies on the balance of the electro-mechanical forces at the minimum point, characterized by zero velocity and minimum bending angle in an oscillation cycle. The capability of the proposed feedforward control technique is demonstrated by controlling the DEMES actuator to different desired positions without residual vibrations. A parametric study is performed to explore the dependence of the proposed control technique on several parameters, such as frame bending stiffness, pre-stretch of the membrane, and membrane damping. The feedforward control technique and the inferences obtained from the current research can be implemented effectively in the design and development of open loop controllers for electrostatically driven soft electro-active devices.

Strength training as a dynamical model of motor learning

ABSTRACT This paper outlines a framework for strength training as a dynamical model of perceptual-motor learning. We show, with emphasis on fixed-point attractor dynamics, that strength training can be mapped to the general dynamical principles of motor learning that arise from the constraints on action, including the distribution of practice/training. The time scales of the respective dynamics of performance change (increment and decrement) in discrete strength training and motor learning tasks reveal superposition of exponential functions in fixed-point dynamics, but distinctive attractor and parameter dynamics in oscillatory limit cycle and more continuous tasks, together with unique timescales to process influences (including practice, learning, strength, fitness, fatigue, warm-up decrement). Increments and decrements of strength can be viewed within a dynamical model of change in motor performance that reflects the integration of practice and training processes at multiple levels of learning and skill development.

Dynamic measurement of gas flow using acoustic resonance tracking.

The National Institute of Standards and Technology measured gas flows exiting large, unthermostated, gas-filled, pressure vessels by tracking the time-dependent pressure P(t) and resonance frequency fN(t) of an acoustic mode N of the gas remaining in each vessel. This is a proof-of-principle demonstration of a gas flow standard that uses P(t), fN(t), and known values of the gas's speed of sound w(p,T) to determine a mode-weighted average temperature ⟨T⟩φ of the gas remaining in a pressure vessel while the vessel acts as a calibrated source of gas flow. To track fN(t) while flow work rapidly changed the gas's temperature, we sustained the gas's oscillations using positive feedback. Feedback oscillations tracked ⟨T⟩φ with a response time of order 1/fN. In contrast, driving the gas's oscillations with an external frequency generator yielded much slower response times of order Q/fN. (For our pressure vessels, Q ∼ 103-104, where Q is the ratio of the energy stored to the energy lost in one cycle of oscillation.) We tracked fN(t) of radial modes in a spherical vessel (1.85m3) and of longitudinal modes of a cylindrical vessel (0.3m3) during gas flows ranging from 0.24 to 12.4 g/s to determine the mass flows with an uncertainty of 0.51 % (95 % confidence level). We discuss the challenges in tracking fN(t) and ways to reduce the uncertainties.

Pulsating Turbulent Flows through a Square Pipe

Pulsating turbulent flows in a square pipe are studied numerically. The flow dominance regime in which the fluid flow rate remains positive in all phases of the oscillatory cycle is considered. The flows are studied at several oscillation frequencies. The results are compared with oscillating laminar flows and a steady turbulent flow in a square pipe, as well as with pulsating turbulent flows in a round pipe. The integral and fluctuating characteristics of turbulence and their dependence on the oscillation frequency are determined. In particular, it is found that at the considered Reynolds number Re = 2200 the friction coefficient in pulsating flows turns out to be lower than that in the stationary flows. The drag reduction increases with growth of the oscillation period and reaches 14.7%. A distinctive feature of turbulent flows in pipes of rectangular cross-section is the occurrence of secondary flows of Prandtl’s 2nd kind. The details of secondary flows under the pulsating flow conditions are studied at length.

Intermittent hypoxia treatments cause cellular priming in human microglia.

Obstructive sleep apnoea syndrome (OSAS) is a sleep-disordered breathing characterized by nocturnal collapses of the upper airway resulting in cycles of blood oxygen partial pressure oscillations, which lead to tissue and cell damage due to intermittent hypoxia (IH) episodes. Since OSAS-derived IH may lead to cognitive impairment through not fully cleared mechanisms, herein we developed a new in vitro model mimicking IH conditions to shed light on its molecular effects on microglial cells, with particular attention to the inflammatory response. The in vitro model was set-up and validated by measuring the hypoxic state, HIF-1α levels, oxidative stress by ROS production and mitochondrial activity by MTS assay. Then, the mRNA and protein levels of certain inflammatory markers (NF-κB and interleukin 6 (IL-6)) after different IH treatment protocols were investigated. The IH treatments followed by a normoxic period were not able to produce a high inflammatory state in human microglial cells. Nevertheless, microglia appeared to be in a state characterized by increased expression of NF-κB and markers related to a primed phenotype. The microglia exposed to IH cycles and stimulated with exogenous IL-1β resulted in an exaggerated inflammatory response with increased NF-κB and IL-6 expression, suggesting a role for primed microglia in OSAS-driven neuroinflammation.

Comparing Growth Models with Other Investment Methods

Abstract This article introduces five growth models as an investment method. These are conventional logistic growth, Gompertz growth, generalized charged capacitor growth, combined logistic and charged capacitor growth, and combined Gompertz and charged capacitor growth. This article demonstrates how to apply the growth models in investing while taking oscillation and lengthening cycles into consideration. The growth models applied as an investment method are compared with 15 other common investment methods. The growth models can be used to predict the prices of various types of assets, including derivatives, stocks, bonds, real estate, and cryptocurrencies. Other phenomena involving growth and fluctuations can also be analyzed. This article provides insights for researchers and investors for how to predict when investing. JEL classification numbers: C5, G11. Keywords: Growth models, Investment methods, Price prediction, Oscillatory growth, Lengthening cycle, Differential equation.