Non-monotonic Response Research Articles

3D printing of soft and porous composite pressure sensor with monotonic and positive resistance response

Recently, 3D printing as a facile and customized technology has been employed to fabricate soft pressure sensors. However, the soft pressure sensors developed to date often suffer from nonmonotonic or negative resistance response, thus limiting their performance and applications. Herein, a new class of printable ternary inks with suitable rheological characteristics by the combination of conductive fillers (carbon nanotubes (CNTs)) and rheological modifiers (insulating microspheres) is developed unprecedentedly and enables the 3D printed composite pressure sensors with excellent mechanical elasticity and monotonic and positive resistance response. Firstly, the rheological behaviors of the as-prepared inks as well as relevant printing parameters are investigated in detail, and a printable phase diagram is proposed to select proper relevant printing parameters. Subsequently, the pressure sensing properties of the as-printed composite pressure sensor are demonstrated and it shows a monotonic and positive resistance response characteristic with a maximum gauge factor (GF) of 280 over a large range of 80% compression strain, exhibiting an outstanding balance between sensitivity and working range when compared with other previously printed pressure sensors. Furthermore, finite-element analysis (FEA) is conducted and a theoretical model for the resistance response is developed to clarify the response mechanisms of the as-printed pressure sensor. The excellent sensing performance suggests that the as-printed pressure sensor has great application potentials in the field of robotic perception and motion monitoring as demonstrated.

Low amplitude strain accumulation model for natural soft clays below railways

An improved constitutive model for strain accumulation of natural clays under undrained cyclic loading is presented. The proposed model includes a formulation for the non-linear small-strain stiffness in the overconsolidated regime, along with a modified hardening law for cyclic accumulation to improve the tracking of strain accumulation at small stress amplitudes. To calibrate and validate the proposed model, a series of laboratory tests were conducted to study the cyclic response of natural Swedish clays, the effect of loading amplitude and pre-shearing history. Good agreement between predicted and measured accumulated axial strains and excess pore water pressures was obtained with different loading amplitudes. The findings reveal that the undrained pre-shearing has a substantial impact on the rate of accumulated strain, with pre-sheared samples exhibiting lower resistance values. The proposed and validated model opens up possibilities to study the monotonic and non-monotonic quasi-static response of soft clays below railway embankments over the lifetime of the structure, i.e. including the effects of construction, operation and decommissioning.

Corona Phase Molecular Recognition of the Interleukin-6 (IL-6) Family of Cytokines Using nIR Fluorescent Single-Walled Carbon Nanotubes

The Interleukin-6 (IL-6) family of cytokines regulates inflammation and plays important roles in numerous biochemical pathways. Typically, cytokine levels are measured using enzyme-linked immunosorbent assay (ELISA) or western blot. However, these techniques usually require substantial processing time, cost, machinery, and specialist training. Understanding the fundamental molecular recognition mechanism of cytokines with synthetic substrates is key to developing new biomedical technologies such as assays, sensors, and therapeutics that overcome the above limitations. Herein, we use the corona phase molecular recognition (CoPhMoRe) approach to engineer new carbon nanotube constructs and study their binding to the inflammatory cytokines: IL-6, interleukin-11 (IL-11), ciliary neurotrophic factor (CNTF), and leukemia inhibitory factor (LIF). Library screening identified two polymer-based CoPhMoRe constructs consisting of single-walled carbon nanotubes complexed with p(AA68-rand-BA16-rand-CD16) polymer (MK2) or p(SS80-rand-BS20) polymer (P14) corona phases. The resulting dissociation constants (KD) were 8.38 ng/mL and 16.7 μg/mL, respectively, compared to that of the natural IL-6 receptor at ∼0.32 ng/mL. In addition, the MK2 constructs showed a nonmonotonic response function upon binding with IL-6. Comparative binding experiments suggest that both constructs appear to recognize the axially aligned α-helical structures present in the Interleukin-6 family. The findings from this study elucidate how nanoparticle interfaces, such as those produced by CoPhMoRe, can be designed to lock onto specific protein features. We find that the α-helical structure of the IL-6 family of cytokines can enable facile molecular recognition, opening the door to new types of label-free, low-cost sensing technologies.

A comparative study of chlorine and bromine species addition on the explosion limits of hydrogen-oxygen mixtures

In this work, we investigate the effects of chlorine (Cl) and bromine (Br) containing species additions on the pressure-temperature explosion limits of hydrogen-oxygen (H2-O2) mixtures computationally. It is shown that, with the addition of HCl, Cl2, HBr and Br2, the explosion limit evolves from being a non-monotonic Z-shaped curve to monotonic or maintains its non-monotonic response depending on the different types of additives. Specifically, with the addition of HCl to the mixtures, the limit always maintains the non-monotonic structure, while with the addition of around 18% of Cl2, it loses its Z-shaped structure. Compared with HCl and Cl2, more sensitive responses were found for HBr and Br2. With the addition of around 1% of HBr and 0.7% of Br2 to the H2-O2 mixtures, the limit's non-monotonic feature disappears rapidly, and becomes a monotonic curve. Further detailed kinetics analysis explains that after the addition of the halogen species, the radical competitions are different at the low- (P = 1.0 × 102 Pa), intermediate- (P = 1.0 × 104 Pa) and high- (P = 1.0 × 106 Pa) pressures respectively, resulting in the change of the dominant reactions. These findings enhance the understanding of Cl and Br containing species sensitization for the explosion limits of the H2-O2 mixtures and help to understand the kinetic interaction between the H2-O2 system and halogen.

Paternal genetic effects of cadmium exposure during pregnancy on hormone synthesis disorders in ovarian granulosa cells of offspring

The aim of this study was to investigate the paternal genetic intergenerational and transgenerational genetic effects of cadmium (Cd) exposure during pregnancy on estradiol (E2) and progesterone (Pg) synthesis in the ovarian granulosa cells (GCs) of offspring. Pregnant SD rats were intragastrically exposed to CdCl2 (0, 0.5, 2.0, 8.0 mg/kg) from days 1 to 20 to produce the F1 generation, F1 males were mated with newly purchased females to produce the F2 generation, and the F3 generation was obtained in the same way. Using this model, Cd-induced hormone synthesis disorders in GCs of F1 have been observed [8]. In this study, altered serum E2 and Pg levels in both F2 and F3 generations showed a nonmonotonic dose‒response relationship. In addition, hormone synthesis-related genes (Star, Cyp11a1, Cyp17a1, Cyp19a1, Sf-1) and miRNAs were observed to be altered in both F2 and F3. No differential changes in DNA methylation modifications of hormone synthesis-related genes were observed, and only the Adcy7 was hypomethylated. In summary, paternal genetic intergenerational and transgenerational effects exist in ovarian GCs E2 and Pg synthesis disorders induced by Cd during pregnancy. In F2, the upregulation of StAR and CYP11A1, and changes in the miR-27a-3p, miR-27b-3p, and miR-146 families may be important, while changes in the miR-10b-5p and miR-146 families in F3 may be important.

Terahertz third harmonic generation in c -axis La1.85Sr0.15CuO4

Terahertz nonlinear optics is a viable method to interrogate collective phenomena in quantum materials spanning ferroelectrics, charge-density waves, and superconductivity. In superconductors this includes the Higgs amplitude and Josephson phase modes. We have investigated the nonlinear $c$-axis response of optimally doped ${\mathrm{La}}_{1.85}{\mathrm{Sr}}_{0.15}\mathrm{Cu}{\mathrm{O}}_{4}$ using high-field THz time domain spectroscopy at field strengths up to $\ensuremath{\sim}80$ kV/cm. With increasing field, we observe a distinct redshift of the Josephson plasma edge and enhanced reflectivity (above the plasma edge) arising from third harmonic generation. The nonmonotonic temperature-dependent response is consistent with nonlinear drive of the Josephson plasma mode (JPM) as verified with comparison to theoretical expectations. Our results add to the understanding that, using THz light, the JPM (in addition to the Higgs mode) provides a route to interrogate and control superconducting properties.

Associations between per- and polyfluoroalkyl substances (PFAS) and diabetes in two population-based cohort studies from Sweden

BackgroundPer- and polyfluoroalkyl substances (PFAS) have been suggested to contribute to the development of metabolic diseases such as obesity, diabetes and non-alcoholic fatty liver disease (NAFLD). However, evidence from epidemiological studies remain divergent. The aim of the present study was to evaluate associations between PFAS exposure and prevalent diabetes in a cross-sectional analysis and fasting glucose in a longitudinal analysis.MethodsIn 2373 subjects aged 45–75 years from the EpiHealth study, three PFAS; perfluorohexanesulfonic acid (PFHxS), perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) were analyzed in plasma together with information on prevalent diabetes. Participants in the PIVUS study (n = 1016 at baseline, all aged 70 years) were followed over 10 years regarding changes in plasma levels of six PFAS; PFHxS, PFOA, PFOS, perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), and perfluoroundecanoic acid (PFUnDA), and changes in plasma levels of fasting glucose.ResultsIn the EpiHealth study, no overall associations could be observed between the levels of PFOA, PFOS or PFHxS and prevalent diabetes. However, there was a significant sex-interaction for PFOA (p = 0.02), and an inverse association could be seen between PFOA (on a SD-scale) and prevalent diabetes in women only (OR: 0.71, 95% CI: 0.52, 0.96, p-value: 0.02). This association showed a non-monotonic dose-response curve. In the PIVUS study, inverse relationships could be observed between the changes in levels (ln-transformed) of PFOA and PFUnDA vs the change in fasting glucose levels (ln-transformed) over 10 years (p = 0.04 and p = 0.02, respectively). As in EpiHealth, these inverse associations were significant only in women (PFOA: β: −0.03, p = 0.02, PFUnDA: β: −0.03, p = 0.03).ImpactExposure to per- and polyfluoroalkyl substances (PFAS) has been linked to unfavorable human health, including metabolic disorders such as obesity, diabetes and non-alcoholic fatty liver disease. However, results from in vivo, in vitro and epidemiological studies are incoherent. The aim of the present study was therefore to investigate associations between PFAS and diabetes in a cross-sectional study and glucose levels in a longitudinal study. Results show inverse associations in women only. Results also display non-monotonic dose response curves (i.e., that only low levels of PFOA are related to higher probability of prevalent diabetes). This suggests that sex differences and complex molecular mechanisms may underlie the observed findings. A better understanding of the factors and molecular mechanisms contributing to such differences is recognized as an important direction for future research.ConclusionsPFOA was found to be inversely related to both prevalent diabetes and changes in plasma glucose levels among women only. Thus, our findings suggest there are sex differences in the inverse relationship of PFOA and type 2 diabetes and glucose levels.

Continuum modeling of soft glassy materials under shear

Soft Glassy Materials (SGM) consist in dense amorphous assemblies of colloidal particles of multiple shapes, elasticity, and interactions, which confer upon them solid-like properties at rest. They are ubiquitously encountered in modern engineering, including additive manufacturing, semi-solid flow cells, dip coating, adhesive locomotion, where they are subjected to complex mechanical histories. Such processes often include a solid-to-liquid transition induced by large enough shear, which results in complex transient phenomena such as non-monotonic stress responses, i.e., stress overshoot, and spatially heterogeneous flows, e.g., shear banding or brittle failure. In the present article, we propose a pedagogical introduction to a continuum model based on a spatially resolved fluidity approach that we recently introduced to rationalize shear-induced yielding in SGMs. Our model, which relies upon non-local effects, quantitatively captures salient features associated with such complex flows, including the rate dependence of the stress overshoot, as well as transient shear-banded flows together with non-trivial scaling laws for fluidization times. This approach offers a versatile framework to account for subtle effects, such as avalanche-like phenomena, or the impact of boundary conditions, which we illustrate by including in our model the elasto-hydrodynamic slippage of soft particles compressed against solid surfaces.

Understanding multi-regime detonation development for hydrogen and syngas fuels

Autoignition and detonation development are foundational events in the combustion community and are fundamentally relevant to engine knocking and detonation propulsion. Autoignition-induced reaction front propagation modes have been extensively investigated, addressing the role of thermal and concentration inhomogeneities. In this work, we have further investigated the nonmonotonic response of detonation development to temperature gradients for low-carbon fuels (hydrogen and syngas) and have found additional detonation regimes, which can depict the panorama of reaction front propagation modes. Results show that separate detonation regimes can be observed when hotspot sizes are below some critical thresholds, with the first corresponding to the known “Bradley detonation peninsula” and the second newly identified featuring broader detonation regions. Despite this, distinct combustion characteristics are observed in the demarcation of detonation regimes between hydrogen and syngas fuels. Specifically, the upper branch of the first detonation regimes for hydrogen is sensitive to temperature gradients at various hotspot sizes, while it exhibits similar behaviors in the lower branch of the second one for syngas, which results in narrower detonation regions. Meanwhile, hydrogen possesses a larger critical hotspot size compared to syngas, and the underlying mechanism is ascribed to the chemical reactivity when hotspot autoignition and the difference of energy density between hotspot interior and exterior. Finally, various detonation regimes are summarized in dimensionless detonation diagrams, in which hydrogen and syngas show similar distributions of detonation peninsula. Despite this, those distinctions in the detonation characteristics between hydrogen and syngas can still be manifested quantitatively. The current work can provide useful insights into knocking inhabitation and detonation promotion.

Capital ideas: optimal capital accumulation strategies for a bank and its regulator

We formulate a continuous-time model of a deposit taking bank, operating subject to capital adequacy regulation, and where the bank's loans are exposed to default risk. The bank maximises its market value of equity by appropriately controlling loan and equity issuance, dividend payments, and endogenous closure. Of interest to regulators, we show how the bank responds to the span of capital adequacy requirements and to changes in default variance. We find a nonmonotonic response of bank lending to increased capital requirements (initially increasing and then decreasing). We also find that the probability of early closure (through either insolvency or endogenous closure) can be minimised for a well-chosen capital adequacy ratio. Moreover, the level of capital requirement that minimises the probability of early closure and maximises lending is fairly robust to changes in the bank's default variance/risk; contributing to the ongoing discussion on optimal bank capital.

Glassy magnetism of Tm2Cu2In in elevated pressures

Tm2Cu2In belonging to the family of R2T2X intermetallics is a ferromagnet with glassy features. This work describes results of high-pressure studies of its magnetic behavior. While TC exhibits only a weak and non-monotonous response to hydrostatic pressure, the pressure impact on frequency dependence of AC susceptibility can be interpreted as due to gradual increase of relaxation time and decrease of the activation energy barrier. Since the magnetic behavior is strongly related to the details of crystal structure, the temperature and pressure effects on the lattice are presented, as well. First principles calculations based on the density functional theory provide a background information.

Woven ceramic matrix composite surrogate model based on physics-informed recurrent neural network

• Recurrent neural network-based surrogate model for nonlinear, non-monotonic CMC constitutive response presented. • Physics-informed constraints employed through regularization to enforce requisite physics. • Surrogate model accurately represents non-monotonic, included reversed loading, behavior of multiple textile CMC material systems. • Efficiency over multiscale numerical approach improved several orders of magnitude. A recurrent neural network (RNN) based surrogate model is developed to emulate the nonlinear constitutive behavior of woven ceramic matrix composites (CMCs) driven by matrix damage at multiple length scales. Physics-informed constraints are introduced into the surrogate model through regularization to ground the prediction in physics and improve its predictive capabilities. Training data is generated using the multiscale generalized method of cells (MSGMC) approach coupled with a matrix damage model. This coupling permits simulating the nonlinear behavior of woven CMCs based on constituent response at the micro-, meso-, and macroscales. The multiscale repeating unit cell is loaded under non-monotonic conditions including multiple load / unload cycles and tension / compression. The fiber volume fraction as well as the intra- and intertow void volume fractions are also varied in the generation of training data. Therefore, the RNN-based surrogate model is tasked with predicting, as a function of variable input strain sequence and fiber and void volume fractions, the resulting stress versus strain response while satisfying physical constraints such as positive semi-definiteness of the tangent stiffness matrix and linear elastic unloading. The trained surrogate model effectively matches the stress versus strain response and successfully predicts the tangent modulus throughout the loading regime. Neural network based surrogate models can offer efficient alternatives to running computationally intensive multiscale material models to simulate the nonlinear response of large structural models. Therefore the presented work provides evidence towards the feasibility of developing, training, and running such models for CMCs with complex architectures, nonlinear multiaxial material response, and under non-monotonic loading conditions.

The androgen receptor as a potential regulator of prostate cancer contractility.

Prostate cancer (PCa) is a common health hazard for men that displays androgen-dependent growth at early stages through signalling mediated by the Androgen Receptor (AR). This has inspired androgen deprivation therapy (ADT) to be the gold standard treatment; however, in later stages, PCa displays a transition to androgen-independence and loss of AR, accompanied by a drastic increase in invasiveness. Critically, both the loss of AR and ADT have been shown to induce PCa invasiveness by promoting the epithelial-to-mesenchymal transition (EMT) which has been associated with biophysical changes in other cell models. Indeed, during metastasis cancers cells change their biophysical properties (reduced cell stiffness, increased contractility) facilitating migration through crowded microenvironments. Given AR's essential role in mediating PCa progression, we suspect that AR signalling may also regulate mechanical transitions required for PC metastasis and directed cell migration. In this study we characterize PCa biophysics in response to changes in AR signalling and expression. First, we applied Traction Force Microscopy on the metastatic PCa cell line LNCaP (AR-positive) to quantify contractile changes from androgen deprivation and supplementation, observing a non-monotonic contractile response with increasing androgen dose. These results suggest that the androgen-induced biophysical response shifts depending on the androgen availability, a finding consistent with past reports demonstrating that distinct pathways depend on both androgen concentration and AR expression. Regarding the latter, we then evaluated how AR expression and activity (nuclear localization) affects PCa biophysics by quantifying the contractility of highly metastatic PC3 cells with and without AR expression under varying androgen concentrations. We find that cell contractility is positively correlated with AR nuclear localization in androgen-containing media, yet negatively correlated in androgen-deprived media. These results complement emerging trends suggesting AR may have an important mechanobiological role in PCa migration and metastasis.

Unraveling context-specific mechanisms governing calcium-YAP/TAZ distinct relationships through computational modeling.

Yes-associated protein (YAP) and its homolog TAZ are transducers of several biochemical and biomechanical signals, serving to integrate multiplexed inputs from the microenvironment into higher level cellular functions such as proliferation, differentiation, apoptosis, migration, and hemostasis. Emerging evidence suggests that calcium is a key second messenger that closely connects microenvironmental input signals and YAP/TAZ regulation. However, studies that directly modulate Ca2+ have reported contradictory YAP/TAZ responses: In some studies, a reduction in Ca2+ influx increases the activity of YAP/TAZ, while in others an increase in Ca2+ influx activates YAP/TAZ. Importantly, Ca2+ and YAP/TAZ exhibit distinct spatiotemporal dynamics, making it difficult to unravel their connections from a purely experimental approach. In this study, we developed a network model of Ca2+-mediated YAP/TAZ signaling to investigate how temporal dynamics and crosstalk of signaling pathways interacting with calcium can alter YAP/TAZ response. By including six signaling modules (e.g., GPCR, IP3- Ca2+, Kinases, RhoA, F-actin, and Hippo-YAP/TAZ) that interact with calcium, we investigated both transient and steady-state cell response to Angiotensin II, Thapsigargin, and ECM stiffness stimuli. The model predicts a context-dependent relationship between calcium signaling and YAP/TAZ activation primarily mediated by PKC, DAG, CaMKII, and F-actin. Model results illustrate the role of calcium dynamics and CaMKII bistable response in switching the direction of changes in Ca2+-induced YAP/TAZ activity. Frequency-dependent YAP/TAZ response revealed the competition between upstream regulators of LATS1/2, leading to the YAP/TAZ non-monotonic response to periodic GPCR stimulation. We also identified key roles of Ca2+ and CaMKII dynamics in shaping the nonlinear relationship between cell size and YAP/TAZ activity. The model predicts Ca2+-YAP/TAZ distinct relationships in different settings consistent with experiments. The model predictions provide new insights into the underlying mechanisms responsible for the controversial Ca2+-YAP/TAZ relationship observed in experiments.

Strain-Sensing Composite Nanofiber Filament and Regulation Mechanism of Shoulder Peaks Based on Carbon Nanomaterial Dispersion.

Conductive polymer composite-based strain sensors are essential components of flexible wearable devices. However, nonmonotonic responses with shoulder peaks limit their practical application. Herein, we innovatively optimized the shoulder-peak phenomenon in a strain-sensing composite nanofiber filament by regulating carbon nanomaterial dispersion. Further, the preparation methods, characteristics, and performances of the filament strain sensors were systematically introduced. On this basis, transmission electron microscopy, finite element analysis, and mathematic and structural evolution models were used to explore the origin of shoulder peaks and explain the sensing mechanism of conductive networks. Results confirmed that the beacon tower-shaped conductive network designed by constructing nanofiller agglomerates could cause strain concentration and resist the Poisson transverse contraction of nanofibers, considerably improving the monotonicity and sensitivity of the sensor. The strain-sensing performance was optimal when the nanofillers were dispersed using 2.5 wt % of an anionic dispersant. The sensor exhibited a maximum detective strain of 120%, an ultralow detection limit of 0.01%, and high sensitivity and linearity of 9.66 and 0.996 within 20% strain, respectively. Moreover, it showed the advantages of a fast response time (120 ms), excellent durability (3000 cycles), anti-interference, washability, and antibacterial capability. Finally, a smart Kinesio tape was developed for protecting/treating the human body and detecting joint/muscle movement via simple sewing.

Subsurface Ocean Temperature Responses to the Anthropogenic Aerosol Forcing in the North Pacific

AbstractSeparating the climate response to external forcing from internal climate variability is a key challenge. While most previous studies have focused on surface responses, here we examine zonal‐mean patterns of North Pacific subsurface temperature responses. In particular, the changes since 1950 driven by anthropogenic aerosol emissions are found by using a pattern recognition method. Based on the single‐forcing large‐ensemble simulations from two models, we show that aerosol forcing caused a nonmonotonic temporal response and a characteristic zonal‐mean pattern within North Pacific, which is distinct from the pattern associated with internal variability. The aerosol‐forced pattern with the nonmonotonic temporal feature shows a substantial temperature change in subpolar regions and a reversed change on the southern flank of the subtropical gyre. A similar characteristic pattern and nonmonotonic time evolution are extracted from the subsurface observations, which likely reflect the subsurface responses to the aerosol forcing, although differences exist with the simulated responses.

Mechanisms underlying divergent relationships between Ca2+ and YAP/TAZ signalling.

Yes-associated protein (YAP) and its homologue TAZ are transducers of several biochemical and biomechanical signals, integrating multiplexed inputs from the microenvironment into higher level cellular functions such as proliferation, differentiation and migration. Emerging evidence suggests that Ca2+ is a key second messenger that connects microenvironmental input signals and YAP/TAZ regulation. However, studies that directly modulate Ca2+ have reported contradictory YAP/TAZ responses: in some studies, a reduction in Ca2+ influx increases the activity of YAP/TAZ, while in others, an increase in Ca2+ influx activates YAP/TAZ. Importantly, Ca2+ and YAP/TAZ exhibit distinct spatiotemporal dynamics, making it difficult to unravel their connections from a purely experimental approach. In this study, we developed a network model of Ca2+ -mediated YAP/TAZ signalling to investigate how temporal dynamics and crosstalk of signalling pathways interacting with Ca2+ can alter the YAP/TAZ response, as observed in experiments. By including six signalling modules (e.g. GPCR, IP3-Ca2+ , kinases, RhoA, F-actin and Hippo-YAP/TAZ) that interact with Ca2+ , we investigated both transient and steady-state cell response to angiotensin II and thapsigargin stimuli. The model predicts that stimuli, Ca2+ transients and frequency-dependent relationships between Ca2+ and YAP/TAZ are primarily mediated by cPKC, DAG, CaMKII and F-actin. Simulation results illustrate the role of Ca2+ dynamics and CaMKII bistable response in switching the direction of changes in Ca2+ -induced YAP/TAZ activity. A frequency-dependent YAP/TAZ response revealed the competition between upstream regulators of LATS1/2, leading to the YAP/TAZ non-monotonic response to periodic GPCR stimulation. This study provides new insights into underlying mechanisms responsible for the controversial Ca2+ -YAP/TAZ relationship observed in experiments. KEY POINTS: YAP/TAZ integrates biochemical and biomechanical inputs to regulate cellular functions, and Ca2+ acts as a key second messenger linking cellular inputs to YAP/TAZ. Studies have reported contradictory Ca2+ -YAP/TAZ relationships for different cell types and stimuli. A network model of Ca2+ -mediated YAP/TAZ signalling was developed to investigate the underlying mechanisms of divergent Ca2+ -YAP/TAZ relationships. The model predicts context-dependent Ca2+ transient, CaMKII bistable response and frequency-dependent activation of LATS1/2 upstream regulators as mechanisms governing the Ca2+ -YAP/TAZ relationship. This study provides new insights into the underlying mechanisms of the controversial Ca2+ -YAP/TAZ relationship to better understand the dynamics of cellular functions controlled by YAP/TAZ activity.

Response of one-dimensional ionised layer to oscillatory electric fields

To provide fundamental insights into the response of laminar flames to alternating current (AC) electric fields, a simplified one-dimensional model using an ionised layer model is formulated with the conservation equations for the ion species with ionisation, recombination, and transport due to molecular diffusion and electric mobility. A parametric study is conducted to investigate the response of the ion layer at different voltages and oscillation frequencies, and the results are examined mainly in terms of the net current–voltage (I–V) characteristics. As the oscillation frequency is increased, a nonmonotonic response in the I–V curve is seen such that the current may exceed the saturation condition corresponding to the steady DC condition. In general the current reaches a peak as the unsteady time scale becomes comparable to the ion transport time scale, which is dictated by the mobility, and eventually becomes attenuated at higher frequencies to behave like a low-pass filter. The extent of the peak current rise and the cut-off frequency are found to depend on the characteristic time scales of the ion chemistry and mobility-induced transport. The simplified model serves as a framework to characterise the behaviour of complex flames in terms of the dominant ionisation and transport processes. The current overshoot behaviour may also imply that the overall effect of the electric field may be further magnified under the AC conditions, motivating further studies of multi-dimensional flames for the ionic wind effects.

Qualitative structure of a discrete predator-prey model with nonmonotonic functional response

<p style='text-indent:20px;'>In this paper, we study the qualitative structure of a discrete predator-prey model with nonmonotonic functional response near a degenerate fixed point whose eigenvalues are <inline-formula><tex-math id="M2">\begin{document}$ \pm1 $\end{document}</tex-math></inline-formula>. Firstly, the model is transformed into an ordinary differential system by using the normal form theory and the Takens's theorem. Then, the qualitative properties of this ordinary differential system near the degenerate equilibrium are analyzed with the blowing-up method. Finally, according to the conjugacy between the discrete model and the time-one mapping of the vector field, the qualitative structure of this discrete model is obtained. Numerical simulations are also given.</p>

BIFURCATION AND CHAOS ANALYSIS OF A TWO-DIMENSIONAL DISCRETE-TIME PREDATOR–PREY MODEL

The dynamical behavior of a discrete predator-prey system with a nonmonotonic functional response is investigated in this work. We study the local asymptotic stability of the positive equilibrium of the system by examining the characteristic equation of the linearized system corresponding to the model. By choosing the growth rate as a bifurcation parameter, the existence of Neimark-Sacker and period-doubling bifurcations at the positive equilibrium is established. Furthermore, the effects of perturbations on the system dynamics are investigated. Finally, examples are presented to illustrate our main results.