Effect of membrane thermal conductivity on ion current rectification in conical nanochannels under asymmetric temperature.

Nowadays, there have been extensively theoretical studies on the phenomenon of ion current rectification (ICR) induced by the asymmetric electrical double layer (EDL). As a key factor influencing the behavior of ion transport, temperature is given high priority by researchers. The thermal conductivity of the material commonly employed to prepare nanopores is 2-3 times higher than that of liquid solutions, which may affect ion transport within the nanochannel. However, it is often neglected in previous studies. Thus, we investigate the effect of membrane thermal conductivity on the ICR in conical nanochannels under asymmetric temperature. Based on the PNP-NS theoretical model, the ion current, the rectification ratio, as well as the temperature and ion concentration distributions along the nanochannel are calculated. It is found that the thermal conductivity of the solid membrane noticeably affects the temperature distribution across the nanochannel, altering the ion transport behavior. Larger membrane thermal conductivity tends to homogenize the temperature distribution in the nanochannel, leading to a decline of ionic thermal down-diffusion by a positive temperature difference and ionic thermal up-diffusion by a negative temperature difference, with the former promoting and the latter inhibiting ion current. As a result, the rectification ratio decreases under the positive temperature difference and increases under the negative temperature difference as the thermal conductivity of the membrane increases. These studies will be instructive for the design of nanofluidic diodes and biosensors.

Comparison of the response of microbial communities to region and rootstock disease differences in tobacco soils of southwestern China.

Introduction: Soil microorganisms are essential for crop growth and production as part of soil health. However, our current knowledge of microbial communities in tobacco soils and their impact factors is limited. Methods: In this study, we compared the characterization of bacterial and fungal communities in tobacco soils and their response to regional and rootstock disease differences. Results and discussion: The results showed that the diversity and composition of bacterial and fungal communities responded more strongly to regional differences than to rootstock diseases, while bacterial niche breadth was more sensitive than fungi to regional differences. Similarly, the core bacterial and fungal taxa shared by the three regions accounted for 21.73% and 20.62% of all OTUs, respectively, which was much lower than that shared by RD and NRD in each region, ranging from 44.87% to 62.14%. Meanwhile, the differences in topological characteristics, connectivity, and stability of microbial networks in different regions also verified the high responsiveness of microbial communities to regions. However, rootstock diseases had a more direct effect on fungal communities than regional differences. Conclusion: This provided insight into the interactions between microbial communities, regional differences, and rootstock diseases, with important implications for maintaining soil health and improving tobacco yield and quality.

An assessment of transmission dynamics via time-varying reproduction number of the second wave of the COVID-19 epidemic in Fiji.

This study involves the estimation of a key epidemiological parameter for evaluating and monitoring the transmissibility of a disease. The time-varying reproduction number is the index for quantifying the transmissibility of infectious diseases. Accurate and timely estimation of the time-varying reproduction number is essential for optimizing non-pharmacological interventions and movement control orders during epidemics. The time-varying reproduction number for the second wave of the pandemic in Fiji is estimated using the popular EpiEstim R package and the publicly available COVID-19 data from 19 April 2021 to 1 December 2021. Our findings show that the non-pharmacological interventions and movement control orders introduced and enforced by the Fijian Government had a significant impact in preventing the spread of COVID-19. Moreover, the results show that many restrictions were either relaxed or eased when the time-varying reproduction number was below the threshold value of 1. The results have provided some information on the second wave of the COVID-19 pandemic that could be used in the future as a guide for public health policymakers in Fiji. Estimation of time-varying reproduction numbers would be helpful for continuous monitoring of the effectiveness of the current public health policies that are being implemented in Fiji.

An application of the ensemble Kalman filter in epidemiological modelling.

Since the novel coronavirus (COVID-19) outbreak in China, and due to the open accessibility of COVID-19 data, several researchers and modellers revisited the classical epidemiological models to evaluate their practical applicability. While mathematical compartmental models can predict various contagious viruses' dynamics, their efficiency depends on the model parameters. Recently, several parameter estimation methods have been proposed for different models. In this study, we evaluated the Ensemble Kalman filter's performance (EnKF) in the estimation of time-varying model parameters with synthetic data and the real COVID-19 data of Hubei province, China. Contrary to the previous works, in the current study, the effect of damping factors on an augmented EnKF is studied. An augmented EnKF algorithm is provided, and we present how the filter performs in estimating models using uncertain observational (reported) data. Results obtained confirm that the augumented-EnKF approach can provide reliable model parameter estimates. Additionally, there was a good fit of profiles between model simulation and the reported COVID-19 data confirming the possibility of using the augmented-EnKF approach for reliable model parameter estimation.

Simultaneous Enhancement of Charge Separation and Hole Transportation in a TiO2 -SrTiO3 Core-Shell Nanowire Photoelectrochemical System.

Efficient charge separation and transportation are key factors that determine the photoelectrochemical (PEC) water-splitting efficiency. Here, a simultaneous enhancement of charge separation and hole transportation on the basis of ferroelectric polarization in TiO2 -SrTiO3 core-shell nanowires (NWs) is reported. The SrTiO3 shell with controllable thicknesses generates a considerable spontaneous polarization, which effectively tunes the electrical band bending of TiO2 . Combined with its intrinsically high charge mobility, the ferroelectric SrTiO3 thin shell significantly improves the charge-separation efficiency (ηseparation ) with minimized influence on the hole-migration property of TiO2 photoelectrodes, leading to a drastically increased photocurrent density ( Jph ). Specifically, the 10 nm-thick SrTiO3 shell yields the highest Jph and ηseparation of 1.43 mA cm-2 and 87.7% at 1.23 V versus reversible hydrogen electrode, respectively, corresponding to 83% and 79% improvements compared with those of pristine TiO2 NWs. The PEC performance can be further manipulated by thermal treatment, and the control of SrTiO3 film thicknesses and electric poling directions. This work suggests a material with combined ferroelectric and semiconducting features could be a promising solution for advancing PEC systems by concurrently promoting the charge-separation and hole-transportation properties.

Slip flow of diverse liquids on robust superomniphobic surfaces.

Water slips exist over superhydrophobic solid surfaces, but the slip flow of diverse liquids on a single surface has not been deliberately studied to date. Here, we report the slip flow behavior of a variety of liquids with different surface tensions and viscosities on a robust omniphobic surface. This surface displayed a dramatic slippage effect and thus a high drag reduction efficiency of approximately 10-20% for all liquids, depending on both liquid viscosity and surface energy. The observed liquid slip was attributed to the surface dual micro/nanostructure and the low-surface-energy coating.

Wormlike micelles formed by sodium erucate in the presence of a tetraalkylammonium hydrotrope.

Anionic wormlike micelles, particularly those formed by long-chain carboxylate surfactants, are relatively less documented though their cationic or zwitterionic counterparts are frequently reported. In this study, the wormlike micelles of sodium erucate (NaOEr), a C22-tailed anionic surfactant with a monounsaturated tail, in the presence of a tetraalkylammonium hydrotrope were investigated for the first time. The different effects of two hydrotropes, benzyl trimethyl ammonium bromide (BTAB) and tetramethyl ammonium bromide (TMAB), on the phase behavior and rheological behaviors were compared, and the influences of surfactant concentration and temperature on the rheological properties of NaOEr solutions were also examined. Both organic salts can lower the Krafft temperature of NaOEr solutions and thus improve its water solubility, but BTAB can make T(K) drop more sharply. At a fixed NaOEr concentration, less BTAB is demanded to induce the formation of viscoelastic solution and to obtain the maximum viscosity of NaOEr solution; at a constant salt concentration, with increasing NaOEr content, the NaOEr-BTAB system shows a larger zero-shear viscosity (η(0)), relaxation time, and plateau modulus but lower overlapping concentration than those of the NaOEr-TMAB system. The occurrence of maximum η(0) with increasing salt content for the NaOEr-BTAB system results from the formation of vesicles and L(3) phases, which were verified by cryo-TEM observations. η(0) shows an exponential decrease with increasing temperature; nevertheless it still remains above 10(3) mPa·s even at 90 °C.

Wettability of a quartz surface in the presence of four cationic surfactants.

Advancing contact angle (θ) measurements were carried out for aqueous solutions of four cationic surfactants, hexadecanol glycidyl ether ammonium chloride (C(16)PC), guerbet alcohol hexadecyl glycidyl ether ammonium chloride (C(16)GPC), hexadecanol polyoxyethylene(3) glycidyl ether ammonium chloride (C(16)(EO)(3)PC), and guerbet alcohol hexadecyl polyoxyethylene(3) glycidyl ether ammonium chloride (C(16)G(EO)(3)PC), on the quartz surface using the sessile drop analysis. The influences of surfactant type and bulk concentration on contact angle were expounded, and the changes in adhesional tension and adhesion work were discussed. The contact angle increases up to a maximum with the increasing concentration for all cationic surfactants. Surfactants with branched chain have more hydrophobic group density on the quartz surface, which results in higher values of maxima in contact angle curves. When ethylene oxide groups CH(2)CH(2)O were incorporated in the hydrophobic group, the decrease in contact angle maximum was observed for C(16)(EO)(3)PC and C(16)G(EO)(3)PC. Moreover, an increase in quartz-water interfacial free energy (γ(SL)) has been observed due to the adsorption of four cationic surfactants. The four cationic surfactants can form a monolayer with alignment structure on the quartz surface through electrostatic interaction and then form the bilayer with increasing bulk concentration. In contrast with literature, the maximal contact angles may not necessarily correspond to the beginning of the formation of bilayer for cationic surfactants at the quartz-water interface. Moreover, the concentrations corresponding to maximal contact angles for C(16)PC and C(16)(EO)(3)PC were much lower than their CMC. The contact angle passes through a maximum at a concentration obviously higher than CMC for C(16)G(EO)(3)PC.

Effect of divalent cationic ions on the adsorption behavior of zwitterionic surfactant at silica/solution interface.

The adsorption behavior of zwitterionic surfactant dodecyl sulfobetaine (DBS) on a silica/solution interface with Ca(2+), Mg(2+) existing in aqueous solution is explored by atomistic molecular simulations. The interaction energy contribution of van der Waals and electrostatic potentials in the surfactants/water/silica system are respectively calculated, from which the electrical interaction can be found to play a decisive role in the adsorption tendency of DBS on the silica surface with or without inorganic ions, despite different mechanisms. The distinct decrease of energy has been found to be derived from electrical interaction when DBS adsorb on the silica surface covered by Ca(2+) or Mg(2+). Therefore, it can be predicted that the cationic ions combined on the negatively charged silica surface in a mineral water medium might decrease the adsorption trend of DBS on the silica surface, which has been experimentally proven by TOC measurement. Structural information of the close interface layer and the distribution of water molecules are analyzed after the complete molecular dynamics simulation using a ternary model. Ca(2+) and Mg(2+) combined on the silica surface can reduce the adsorption amount of DBS by preventing the direct interaction between DBS and surface, and bringing about the orientation reversal of DBS molecules to break the order of adsorption interface layer. Furthermore, changes in the status of the water spreading on the silica surface caused by the complexation of cations are also an important reason in the adsorption reduction.