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The formation of secondary ice in clouds, that is, ice particles that are created at temperatures above the limit for homogeneous freezing without the direct involvement of a heterogeneous ice nucleus, is one of the longest-standing puzzles in cloud physics. Here, we present comprehensive laboratory investigations on the formation of small ice particles upon the freezing of drizzle-sized cloud droplets levitated in an electrodynamic balance. Four different categories of secondary ice formation (bubble bursting, jetting, cracking, and breakup) could be detected, and their respective frequencies of occurrence as a function of temperature and droplet size are given. We find that bubble bursting occurs more often than droplet splitting. While we do not observe the shattering of droplets into many large fragments, we find that the average number of small secondary ice particles released during freezing is strongly dependent on droplet size and may well exceed unity for droplets larger than 300 μm in diameter. This leaves droplet fragmentation as an important secondary ice process effective at temperatures around −10°C in clouds where large drizzle droplets are present.

Because of the advent of discrete memristor, memristor effect in discrete map has become the important subject deserving discussion. To this end, this paper constructs a memristor-based neuron model considering magnetic induction by combining an existing map-based neuron model and a discrete memristor with absolute value memductance. Taking the coupling strength and initial state of the memristor as variables, complex mode transition behaviors induced by the introduced memristor are disclosed using numerical methods, including spiking-bursting behaviors, mode transition behaviors, and hyperchaotic spiking behaviors. In particular, all of these behaviors are greatly dependent on the memristor initial state, resulting in the existence of extreme multistability in the memristive neuron model. Therefore, this memristive neuron model can be used to effectively imitate the magnetic induction effects when complex mode transition behaviors appear in the neuronal action potential. Besides, a hardware platform based on FPGA is developed for implementing the memristive neuron model and various spiking-bursting sequences are experimentally captured therein. The results show that when biophysical memory effect is present, the memristive neuron model can better represent the firing activities of biological neurons than the original map-based neuron model.

The oceans represent a significant global source of atmospheric aerosols. Sea spray aerosol (SSA) particles comprise sea salts and organic species in varying proportions. In addition to size, the overall composition of SSA particles determines how effectively they can form cloud droplets and ice crystals. Thus, understanding the factors controlling SSA composition is critical to predicting aerosol impacts on clouds and climate. It is often assumed that submicrometer SSAs are mainly formed by film drops produced from bursting bubble-cap films, which become enriched with hydrophobic organic species contained within the sea surface microlayer. In contrast, jet drops formed from the base of bursting bubbles are postulated to mainly produce larger supermicrometer particles from bulk seawater, which comprises largely salts and water-soluble organic species. However, here we demonstrate that jet drops produce up to 43% of total submicrometer SSA number concentrations, and that the fraction of SSA produced by jet drops can be modulated by marine biological activity. We show that the chemical composition, organic volume fraction, and ice nucleating ability of submicrometer particles from jet drops differ from those formed from film drops. Thus, the chemical composition of a substantial fraction of submicrometer particles will not be controlled by the composition of the sea surface microlayer, a major assumption in previous studies. This finding has significant ramifications for understanding the factors controlling the mixing state of submicrometer SSA particles and must be taken into consideration when predicting SSA impacts on clouds and climate.

Microwave irradiation has been found efficient in weakening hard rocks through its heating effect. The fracturing and bursting mechanisms of water-bearing sandstones under microwave irradiation have not been well investigated. In this study, six types of sandstones were selected and subjected to microwave irradiation under scenarios of different saturations and power levels. After a comprehensive analysis of the test results, it was revealed that the fracturing and bursting was jointly governed by the thermal stress and steam pressure. The underlying mechanism was related to the interaction between the heating effect and water transfer behavior under microwave irradiation. Furthermore, a prediction model, including the bursting judgement coefficient BJC (determining the possibility of bursting) and the bursting capability index BCI (evaluating the ease or difficulty of bursting), was proposed with consideration of microwave power level, dielectric loss factor, water saturation, tensile strength, and permeability. The model was validated by comparing with experimental data and exhibited a high degree of reliability.HighlightsThe bursting mechanism of water-bearing sandstones under microwave irradiation was revealed.A bursting judgement coefficient (BJC) determining the possibility of sandstones bursting was proposed.A bursting capability index (BCI) evaluating the difficulty of sandstone bursting was introduced

Bubble bursting and subsequent collapse of the open cavity at free surfaces of contaminated liquids can generate aerosol droplets, facilitating pathogen transport. After film rupture, capillary waves focus at the cavity base, potentially generating fast Worthington jets that are responsible for ejecting the droplets away from the source. While extensively studied for Newtonian fluids, the influence of non-Newtonian rheology on this process remains poorly understood. Here, we employ direct numerical simulations to investigate the bubble cavity collapse in viscoelastic media, such as polymeric liquids. We find that the jet and drop formations are dictated by two dimensionless parameters: the elastocapillary number $Ec$ (the ratio of the elastic modulus and the Laplace pressure) and the Deborah number $De$ (the ratio of the relaxation time and the inertio-capillary time scale). We show that, for low values of $Ec$ and $De$ , the viscoelastic liquid adopts a Newtonian-like behaviour, where the dynamics is governed by the solvent Ohnesorge number $Oh_s$ (the ratio of visco-capillary and inertio-capillary time scales). In contrast, for large values $Ec$ and $De$ , the enhanced elastic stresses completely suppress the formation of the jet. For some cases with intermediate values of $Ec$ and $De$ , smaller droplets are produced compared with Newtonian fluids, potentially enhancing aerosol dispersal. By mapping the phase space spanned by $Ec$ , $De$ and $Oh_s$ , we reveal three distinct flow regimes: (i) jets forming droplets, (ii) jets without droplet formation and (iii) absence of jet formation. Our results elucidate the mechanisms underlying aerosol suppression versus fine spray formation in polymeric liquids, with implications for pathogen transmission and industrial processes involving viscoelastic fluids.

The design and analysis of a simple autonomous memristive chaotic circuit are important in theoretical, numerical, and experimental demonstrations of complex dynamics. In this paper, a simple autonomous memristive circuit is implemented, which only consists of an active second-order memristive diode bridge and a capacitor. Based on the available circuit, the mathematical model is established and its symmetry, dissipativity, and equilibrium stability are analyzed. Numerical simulations show that the proposed circuit exhibits complex behaviors of unipolar periodic and chaotic bursting oscillations along with coexisting attractors. It is worth noting that the circuit exhibits such a special bursting behavior previously unobserved in third-order autonomous memristive circuits. Moreover, spectral entropy complexities are calculated to provide an intuitive and effectual method for the circuit parameter configurations. The circuit simulations and hardware experiments verify the theoretical analyses and numerical simulations.

The bursting liability is very important to evaluate the risk of rock burst in coal mine. Conducting uniaxial compression test is the main method to study the bursting liability of rock (coal). To establish an accurate uniaxial constitutive model, the structure ensemble dynamics theory is adopted. The model of rock (coal) specimen compression by testing machine is simplified. Through dimensional analysis, the stress–strain relationship of the specimen is a power model. The mechanical properties of rock (coal) vary with different levels of deformation and can be divided into four stages. The different states can be considered as different ensembles. By using the analysis method of structural ensembles dynamics, one formula completely represents the four stages accurately. The parameters in the formula are physically meaningful and can be uniquely determined based on experimental data. A criterion for instability criterion of the system of the specimen and the testing machine is derived, and a theoretical explanation of instability failure related to uniaxial compressive strength is given. Parameters sensitivity analysis and verification are conducted on the theoretical results. The theoretical results are highly accurate and can effectively reflect the stress–strain relationship of rock (coal) under uniaxial compression. A bursting liability index which contains the information of the peak and post-peak of the stress–strain relationship is proposed. The new index is positively correlated with the compressive strength and the bursting energy index and a classification of bursting liability levels for the new index was determined based on them.HighlightsThe structure ensemble dynamics theory is used to establish a constitutive model.One formula completely represents the stress-stain relationship accurately.The parameters are physically meaningful and can be uniquely determined.A theoretical explanation of instability failure related to strength is given.A new bursting liability index based on the new constitutive model is proposed.

Here we provide a theoretical framework revealing that the radius$R_{d}$of the top droplet ejected from a bursting bubble of radius$R_{b}$and$Bo\\leqslant 0.05$can be expressed as$R_{d}/R_{b}=K_{b}(1-(Oh/Oh_{c}^{\\prime })^{1/2})$for$Oh\\lesssim Oh_{c}^{\\prime }$or as$R_{d}\\approx 18\\,\\unicode[STIX]{x1D707}_{l}^{2}/(\\unicode[STIX]{x1D70C}_{l}\\unicode[STIX]{x1D70E})$for$Oh\\gtrsim Oh_{c}^{\\prime }$, with the numerically fitted constants$K_{b}\\approx 0.2$,$Oh_{c}^{\\prime }\\approx 0.03$,$Oh=\\unicode[STIX]{x1D707}_{l}/\\sqrt{\\unicode[STIX]{x1D70C}_{l}\\,R_{b}\\,\\unicode[STIX]{x1D70E}}\\ll 1$the Ohnesorge number,$Bo=\\unicode[STIX]{x1D70C}_{l}\\,g\\,R_{b}^{2}/\\unicode[STIX]{x1D70E}$the Bond number, and$\\unicode[STIX]{x1D70C}_{l}$,$\\unicode[STIX]{x1D707}_{l}$and$\\unicode[STIX]{x1D70E}$indicating the liquid density, dynamic viscosity and interfacial tension coefficient, respectively. These predictions, which do not only have solid theoretical roots but are also much more accurate than the usual 10 % rule used in the context of marine spray generation via whitecaps for$R_{b}\\lesssim 1$mm, agree very well with both experimental data and numerical simulations for the values of$Oh$and$Bo$investigated. Moreover, making use of a criterion which reveals the mechanism that controls the growth rate of capillary instabilities, we also explain here why no droplets are ejected from the tip of the fast Worthington jet for$Oh\\gtrsim 0.04$. In addition, our results predict the generation of submicron-sized aerosol particles with diameters below 100 nm and velocities${\\sim}\\unicode[STIX]{x1D70E}/\\unicode[STIX]{x1D707}_{l}$for bubble radii$10~\\unicode[STIX]{x03BC}\\text{m}\\lesssim R_{b}\\lesssim 20~\\unicode[STIX]{x03BC}\\text{m}$, within the range found in natural conditions and in good agreement with experiments – a fact suggesting that our study could be applied in the modelling of sea spray aerosol production.

Bursting is a diverse and common phenomenon in neuronal activation patterns and it indicates that fast action voltage spiking periods are followed by resting periods. The interspike interval (ISI) is the time between successive action voltage spikes of neuron and it is a key indicator used to characterize the bursting. Recently, a three-dimensional memristive Hindmarsh-Rose (mHR) neuron model was constructed to generate hidden chaotic bursting. However, the properties of the discrete mHR neuron model have not been investigated, yet. In this article, we first construct a discrete mHR neuron model and then acquire different hidden chaotic bursting sequences under four typical sets of parameters. To make these sequences more suitable for the application, we further encode these hidden chaotic sequences using their ISIs and the performance comparative results show that the ISI-encoded chaotic sequences have much more complex chaos properties than the original sequences. In addition, we apply these ISI-encoded chaotic sequences to the application of image encryption. The image encryption scheme has a symmetric key structure and contains plain-text permutation and bidirectional diffusion processes. Experimental results and security analyses prove that it has excellent robustness against various possible attacks.

Many mammalian genes are transcribed during short bursts of variable frequencies and sizes that substantially contribute to cell-to-cell variability. However, which molecular mechanisms determine bursting properties remains unclear. To probe putative mechanisms, we combined temporal analysis of transcription along the circadian cycle with multiple genomic reporter integrations, using both short-lived luciferase live microscopy and single-molecule RNA-FISH. Using the Bmal1 circadian promoter as our model, we observed that rhythmic transcription resulted predominantly from variations in burst frequency, while the genomic position changed the burst size. Thus, burst frequency and size independently modulated Bmal1 transcription. We then found that promoter histone-acetylation level covaried with burst frequency, being greatest at peak expression and lowest at trough expression, while remaining unaffected by the genomic location. In addition, specific deletions of ROR-responsive elements led to constitutively elevated histone acetylation and burst frequency. We then investigated the suggested link between histone acetylation and burst frequency by dCas9p300-targeted modulation of histone acetylation, revealing that acetylation levels influence burst frequency more than burst size. The correlation between acetylation levels at the promoter and burst frequency was also observed in endogenous circadian genes and in embryonic stem cell fate genes. Thus, our data suggest that histone acetylation-mediated control of transcription burst frequency is a common mechanism to control mammalian gene expression.