Existence and Uniqueness of Nontrivial Periodic Solutions to a Discrete Switching Model

To control the spread of mosquito-borne diseases, one goal of the World Mosquito Program’s Wolbachia release method is to replace wild vector mosquitoes with Wolbachia-infected ones, whose capability of transmitting diseases has been greatly reduced owing to the Wolbachia infection. In this paper, we propose a discrete switching model which characterizes a release strategy including an impulsive and periodic release, where Wolbachia-infected males are released with the release ratio α1 during the first N generations, and the release ratio is α2 from the (N+1)-th generation to the T-th generation. Sufficient conditions on the release ratios α1 and α2 are obtained to guarantee the existence and uniqueness of nontrivial periodic solutions to the discrete switching model. We aim to provide new methods to count the exact numbers of periodic solutions to discrete switching models.

Discrete scattering and meta-arrest of locally resonant elastic wave metamaterials with a semi-infinite crack

Previous investigations on wave scattering and crack propagation in the discrete periodic structure are concentrated on the conditional mass–spring model, in which the internal mass is not included. In this work, elastic wave metamaterials with local resonators are studied to show the scattering of elastic waves by a semi-infinite crack and the arrest behaviour. The influences of internal mass–spring structure are analysed and the discrete Wiener–Hopf method is used to obtain the displacement solution. Numerical calculations are performed to show that the dynamic negative effective mass and band gaps can be observed owing to the local resonance of the internal mass. Therefore, the scattering of an elastic wave with a specific frequency by a semi-infinite crack can be avoided by tuning the structural parameters. Moreover, the energy release ratio which characterizes the splitting resistance is presented and the meta-arrest performance is found. It is expected that this study will increase understanding of how to control the scattering characteristics of elastic waves by a semi-infinite crack in locally resonant metamaterials and also help to improve their fracture resistance.

Existence and uniqueness of periodic orbits in a discrete model on Wolbachia infection frequency

In this paper, we study a discrete model on Wolbachia infection frequency. Assume that a periodic and impulsive release strategy is implemented, where infected males are released during the first N generations with the release ratio α, and the release is terminated from (N + 1)-th generation to T-th generation. We find a release ratio threshold denoted by α *(N, T), and prove the existence of a T-periodic solution for the model when α ∈ (0, α *(N, T)). For the special case when N = 1 and T = 2, we prove that the model has a unique T-periodic solution which is unstable when α ∈ (0, α *(N, T)). While α ≥ α *(N, T), no periodic phenomenon occurs and the Wolbachia fixation equilibrium is globally asymptotically stable. Numerical simulations are also provided to illustrate our theoretical results. One main contribution of this work is to offer a new method to determine the exact number of periodic orbits to discrete models.

The concomitant effects of self-limiting insect releases and behavioural interference on patterns of coexistence and exclusion of competing mosquitoes

Aedes aegypti is the dominant vector of dengue, a potentially fatal virus whose incidence has increased eightfold in the last two decades. As dengue has no widely available vaccine, vector control is key to reducing the global public health burden. A promising method is the release of self-limiting Ae. aegypti , which mate with wild Ae. aegypti and produce non-viable offspring. The resultant decrease in Ae. aegypti population size may impact coexistence with Ae. albopictus , another vector of dengue. A behavioural mechanism influencing coexistence between these species is reproductive interference, where incomplete species recognition results in heterospecifics engaging in mating activities. We develop a theoretical framework to investigate the interaction between self-limiting Ae. aegypti releases and reproductive interference between Ae. aegypti and Ae. albopictus on patterns of coexistence. In the absence of self-limiting Ae. aegypti release, coexistence can occur when the strength of reproductive interference experienced by both species is low. Results show that substantial overflooding with self-limiting Ae. aegypti prevents coexistence. For lower release ratios, as the release ratio increases, coexistence can occur when the strength of reproductive interference is increasingly high for Ae. albopictus and increasingly low for Ae. aegypti . This emphasizes the importance of including behavioural ecological processes into population models to evaluate the efficacy of vector control.

Selenium in wastewater can be adsorbed by modified natural zeolite and reused in vegetable growth

Modified natural zeolites (MNZ) are widely used in pollutant removal, but how to address these MNZ that have adsorbed pollutants must be considered. Selenium is an essential trace element for metabolism and is also a water pollutant. Selenium is adsorbed in the water by MNZ in this study first. Then the Brassica chinensis L. was planted in the soil which contains the MNZ loaded with selenium (MNZ-Se) to explore selenium uptake. MNZ-Se release tests in water and soil were also considered. The results showed the following: (1) The maximum adsorption capacity of MNZ for selenium is 46.90 mg/g. (2) Water release experiments of MNZ-Se showed that regardless of how the pH of the aqueous solution changes, the trend of the release of selenium from MNZ-Se in aqueous solution is not affected and first decreases before stabilizing. (3) Soil release experiments of MNZ-Se showed that the selenium content in the soil increased and reached the concentration in the standard of selenium-rich soil. Addition amount and soil pH value will affect the release ratio. The release ratio of MNZ-Se in the water was higher than that in the soil. (4) With an increase in the soil MNZ-Se content, the selenium content in the soil and B. c increases. Above all, MZN can be a good medium for water pollutant removal and soil improvement.

Determination of the Installation Time of Secondary Liner during Excavation of Large Cross-Section Double-Arch Tunnels

Double-arch tunnel construction involves in high risk due to its large span and special structural shape. In order to explore the proper installation time for the secondary liner during the excavation of large cross-sectional double-arch tunnels supported by three layers of the liner, this paper optimizes the distribution of the stress release ratio based on the analysis of surrounding rock deformation and structural stress. Proper installation time for the secondary liner is determined according to the optimization results and regressive analysis of monitoring data of initial support crown settlement. The results show that the reasonable distribution of stress release ratio is 30% during tunnel excavation, 30% after initial support installation, and 40% after secondary liner installation. After installing the initial support, the total crown settlement at three monitored sections is 51.5, 52.0, and 49.8 mm, respectively. When the initial support crown settlement reaches 65–75% of the final value, the secondary liner should be installed, and the crown settlement is 14.4–19.5 mm, 15.3–20.5 mm, and 14.4–19.4 mm, respectively, at three monitored sections. Findings from this paper can provide reference for design and construction of similar projects.

Spatial variations in terrestrial net ecosystem productivity and its local indicators

Multiple lines of evidence have demonstrated the persistence of global land carbon (C) sink during the past several decades. However, both annual net ecosystem productivity (NEP) and its inter-annual variation (IAVNEP) keep varying over space. Thus, identifying local indicators for the spatially varying NEP and IAVNEP is critical for locating the major and sustainable C sinks on land. Here, based on daily NEP observations from FLUXNET sites and large-scale estimates from an atmospheric-inversion product, we found a robust logarithmic correlation between annual NEP and seasonal carbon uptake–release ratio (i.e. U ∕ R). The cross-site variation in mean annual NEP could be logarithmically indicated by U ∕ R, while the spatial distribution of IAVNEP was associated with the slope (i.e. β) of the logarithmic correlation between annual NEP and U ∕ R. Among biomes, for example, forests and croplands had the largest U ∕ R ratio (1.06 ± 0.83) and β (473 ± 112 g C m−2 yr−1), indicating the highest NEP and IAVNEP in forests and croplands, respectively. We further showed that these two simple indicators could directly infer the spatial variations in NEP and IAVNEP in global gridded NEP products. Overall, this study provides two simple local indicators for the intricate spatial variations in the strength and stability of land C sinks. These indicators could be helpful for locating the persistent terrestrial C sinks and provide valuable constraints for improving the simulation of land–atmospheric C exchanges.

Effect of a real-time feedback smartphone application (TCPRLink) on the quality of telephone-assisted CPR performed by trained laypeople in China: a manikin-based randomised controlled study

ObjectivesTo determine the effect of a free smartphone application (TCPRLink) that provides real-time monitoring and audiovisual feedback on chest compressions (CC) on trained layperson telephone-assisted cardiopulmonary resuscitation (T-CPR) performance.DesignA manikin-based randomised controlled study.SettingThis study was conducted at a multidisciplinary university and a community centre in China.ParticipantsOne hundred and eighty-six adult participants (age 18–65 years) with T-CPR training experience were randomly assigned to the TCPRLink (n=94) and T-CPR (n=92) groups with age stratification.InterventionsWe compared the participants’ performance for 6 min of CC in a simulated T-CPR scenario both at the baseline and after 3 months.Primary and secondary outcome measuresThe primary outcomes were the CC rate and proportion of adequate CC rate (100–120 min−1). The secondary outcomes included the proportion of participants counting the CC rhythm, time to first CC, CC depth, hands-off time and CC full-release ratio.ResultsParticipants in the TCPRLink feedback group more consistently performed CC with higher rate, both initially and 3 months later (median 111 (IQR 109–113) vs 108 (103–112) min−1, p=0.002 and 111 (109–113) vs 108 (105–112) min−1, p<0.001, respectively), with less need to count the rhythm (21.3% vs 41.3%, p=0.003% and 7% vs 22.6%, p=0.004, respectively) compared with the T-CPR group. There were no significant differences in time to the first CC, hands-off time or CC full-release ratio. Among 55–65 year group, the CC depth was deeper in the TCPRLink group than in the TCPR group (47.1±9.6 vs 38.5±8.7 mm, p=0.001 and 44.7±10.1 vs 39.3±10.8 mm, p=0.07, respectively).ConclusionsThe TCPRLink application improved T-CPR quality in trained laypersons to provide more effective CCs and lighten the load of counting out the CC with the dispatcher in a simulated T-CPR scenario. Further investigations are required to confirm this effectiveness in real-life resuscitation attempts.

Investigation of different anaerobic respiratory pathways and their impacts on the release ratio of DIC/alkalinity at selected North Sea regions

&lt;p&gt;&lt;strong&gt;Investigation of different anaerobic respiratory pathways and their impacts on the release ratio of DIC/alkalinity at selected North Sea regions&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;Tentative authors: Nele Treblin&lt;sup&gt;1,2&lt;/sup&gt;, Michael E. B&amp;#246;ttcher&lt;sup&gt;3&lt;/sup&gt;, Tristan Zimmermann&lt;sup&gt;1&lt;/sup&gt;, Daniel Pr&amp;#246;frock&lt;sup&gt;1&lt;/sup&gt;, Mona Norbisrath&lt;sup&gt;1&lt;/sup&gt;, Bryce van Dam&lt;sup&gt;1&lt;/sup&gt;, Helmuth Thomas&lt;sup&gt;1&lt;/sup&gt;&lt;/p&gt;&lt;p&gt;&lt;sup&gt;1&lt;/sup&gt;Institute for Coastal Research, Helmholtz Center Geesthacht&lt;/p&gt;&lt;p&gt;&lt;sup&gt;2&lt;/sup&gt;Alfred-Wegener-Institute Helmholtz Center for Polar and Marine Research&lt;/p&gt;&lt;p&gt;&lt;sup&gt;3&lt;/sup&gt;Leibniz Institute for Baltic Sea Research Warnem&amp;#252;nde&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Coastal sediments play a crucial role in carbon metabolism, which decreases with increasing distance from the shoreline. The North Sea, a NW European shelf sea, represents a relatively shallow, well-ventilated (on annual timescales) system, connected to the Baltic Sea and the North Atlantic. Especially the southern part of the North Sea receives a large amount of organic matter (OM), both from riverine input and internal North Sea sources. After the depletion of oxygen due to aerobic OM respiration, anaerobic metabolic activities become dominant in the sediment. In the absence of oxygen, electron acceptors, such as NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;, Fe&lt;sup&gt;3+&lt;/sup&gt;, Mn&lt;sup&gt;4+&lt;/sup&gt; and SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2-&lt;/sup&gt;, facilitate not only the release of respired CO&lt;sub&gt;2&lt;/sub&gt;, but also of alkalinity, furthermore enhanced by potential dissolution of sedimentary carbonates. Therefore, under these conditions, benthic-pelagic coupling may impact on the potential to absorb CO&lt;sub&gt;2&lt;/sub&gt; from the atmosphere.&lt;/p&gt;&lt;p&gt;To investigate the described processes, porewater and sediment samples, collected from six different stations in the German Bight (North Sea) during the RV Heincke cruise HE541 in September 2019, have been analyzed for their vertical concentration profiles of nutrients, various trace metals, sulfur, DIC and alkalinity.&lt;/p&gt;&lt;p&gt;Benthic oxic and anoxic zones have been identified based on the vertical concentration gradients. Furthermore, alkalinity and DIC are set in relation to anaerobic metabolic activities. Finally, active reworking and ventilation becomes pivotal in areas such as the North Sea. Thus, the influence of bioturbation on anaerobic respiration is also considered.&lt;/p&gt;

Numerical Simulation of Sulfur Deposit with Particle Release

Sulfur deposition commonly occurs during the development of a high-sulfur gas reservoirs. Due to the high gas flow velocity near the wellbore, some of the deposited sulfur particles re-enter the pores and continue to migrate driven by the high-speed gas flow. The current mathematical model for sulfur deposition ignores the viscosity between particles, rising flow caused by turbulence, and the corresponding research on the release ratio of particles. In order to solve the above problems, firstly, the viscous force and rising force caused by turbulence disturbance are introduced, and the critical release velocity of sulfur particles is derived. Then, a release model of sulfur particles that consider the critical release velocity and release ratio is proposed by combining the probability theory with the hydrodynamics theory. Notably, based on the experimental data, the deposition ratio of sulfur particles and the damage coefficient in the sulfur damage model are determined. Finally, a comprehensive particle migration model considering the deposition and release of sulfur particles is established. The model is then applied to the actual gas wells with visible sulfur deposition that target the Da-wan gas reservoir, and the results show that the model correctly reflects flow transport during the process of sulfur deposition in porous media. In addition, through the numerical simulation experiments, it was found that considering the release of sulfur particles reduces the saturation of sulfur particles within a specific range around the well and improve the reservoir permeability in this range. From the perspective of gas production rate, the release of sulfur particles has a limited effect on the gas production rate, which is mainly due to the sulfur particle release being limited, having only a 5 m range near the wellbore area, and thus the amount of gas flow from the unaffected area is basically unchanged.