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Food insecurity is a chronic problem in Africa and is likely to worsen with climate change and population growth. It is largely due to poor yields of the cereal crops caused by factors including stemborer pests, striga weeds and degraded soils. A platform technology, ‘push–pull’, based on locally available companion plants, effectively addresses these constraints resulting in substantial grain yield increases. It involves intercropping cereal crops with a forage legume, desmodium, and planting Napier grass as a border crop. Desmodium repels stemborer moths (push), and attracts their natural enemies, while Napier grass attracts them (pull). Desmodium is very effective in suppressing striga weed while improving soil fertility through nitrogen fixation and improved organic matter content. Both companion plants provide high-value animal fodder, facilitating milk production and diversifying farmers’ income sources. To extend these benefits to drier areas and ensure long-term sustainability of the technology in view of climate change, drought-tolerant trap and intercrop plants are being identified. Studies show that the locally commercial brachiaria cv mulato (trap crop) and greenleaf desmodium (intercrop) can tolerate long droughts. New on-farm field trials show that using these two companion crops in adapted push–pull technology provides effective control of stemborers and striga weeds, resulting in significant grain yield increases. Effective multi-level partnerships have been established with national agricultural research and extension systems, non-governmental organizations and other stakeholders to enhance dissemination of the technology with a goal of reaching one million farm households in the region by 2020. These will be supported by an efficient desmodium seed production and distribution system in eastern Africa, relevant policies and stakeholder training and capacity development.

Design and synthesis of basic functional circuits are the fundamental tasks of synthetic biologists. Before it is possible to engineer higher‐order genetic networks that can perform complex functions, a toolkit of basic devices must be developed. Among those devices, sequential logic circuits are expected to be the foundation of the genetic information‐processing systems. In this study, we report the design and construction of a genetic sequential logic circuit in Escherichia coli . It can generate different outputs in response to the same input signal on the basis of its internal state, and ‘memorize’ the output. The circuit is composed of two parts: (1) a bistable switch memory module and (2) a double‐repressed promoter NOR gate module. The two modules were individually rationally designed, and they were coupled together by fine‐tuning the interconnecting parts through directed evolution. After fine‐tuning, the circuit could be repeatedly, alternatively triggered by the same input signal; it functions as a push‐on push‐off switch. Synopsis Design and synthesis of basic functional circuits are the fundamental tasks of synthetic biologists. Before it is possible to engineer higher‐order genetic networks that can perform complex functions, a toolkit of basic devices must be developed. Among those devices, sequential logic circuits are expected to be the foundation of genetic information‐processing systems. As in electronics, combinational and sequential logic circuits are two kinds of fundamental processors in cells. In a combinational logic circuit, the output depends only on the present inputs, whereas in a sequential logic circuit, the output also depends on the history of the input due to its own memory. If we can successfully construct the two kinds of basic logic circuits in a cell, they can serve as building blocks to be assembled into high‐order genetic circuits and implement more sophisticated computation. Construction of genetic combinational logic circuits (GSLCs), such as AND, OR, and NOR gates, has been frequently reported in the last decade (Guet et al , 2002 ; Dueber et al , 2003 ; Anderson et al , 2007 ; Win and Smolke, 2008 ). Meanwhile toggle switches, which can function as memory modules, have been implemented in prokaryotic and eukaryotic cells (Becskei et al , 2001 ; Kramer et al , 2004 ; Ajo‐Franklin et al , 2007 ). Here, we constructed a novel GSLC that functions as a push‐on push‐off switch by coupling a combinational logic module with a bistable switch module (Figure 1A ). When the internal state of the memory is in the ‘ON’ state, the external UV input makes the circuit's output promoter P NOR generate an ‘OFF’ pulse signal and register the ‘OFF’ state into the memory; when the internal state is in the ‘OFF’ state, the same external UV input induces the circuit's output promoter P NOR to generate an ‘ON’ pulse signal and register the ‘ON’ state into the memory. In our design, the combinatorial logic gate is a NOR gate and the switch module is a clearable bistable switch (Figure 1C ). Two interconnecting parts are designed to connect the NOR gate and the bistable switch (Figure 1D ). UV irradiation was used as both an external input signal and a reset signal for the clearable bistable switch (Figure 1B ). Before implementing the experimental construction, we used a set of ordinary differential equations to simulate the dynamic process. With a set of reasonable parameters, the simulation results showed that the circuit could function as a push‐on push‐off switch (Figure 1E ). Then the bistable switch module and NOR gate module were rationally designed and constructed. Our experimental results showed that the corresponding functions were implemented very well. After the construction of the memory and the NOR gate module, we coupled the two modules together by fine‐tuning the expression of two interconnecting parts lacI and cI ind − . The two libraries for the ribosome‐binding sites (RBSs) of lacI and cI ind − were simultaneously transformed into Escherichia coli cells harboring the memory module plasmid. After growth on agar plates with appropriate antibiotics, colonies containing all three plasmids were selected. With efficient mutation libraries, we developed a new screening method to select the functional circuits. The experimental process is described in Figure 4A . It consists of two rounds of selection. In the first round of selection, approximatelybout 300 mutants out of 1000 were chosen. In the second round, only three mutants were selected. As shown in Figure 4B , if the initial state was ‘OFF’ with green color, the fraction of green cells in the population was near 100% before UV stimulus, whereas less than 10% of cells remained in the green ‘OFF’ state after UV stimulus (Figure 4B ). This result indicates that the switch from ‘OFF’ to ‘ON’ is quite complete. Unfortunately, the switch from ‘ON’ to ‘OFF’ was not as efficient: only about one‐third of the population switched to the ‘OFF’ state after UV triggering (Figure 4C ). Nonetheless, the switch is still significant compared with that of the population not exposed to UV irradiation (Figure 4B and C ). These results show that the fine‐tuned GSLC can generate different output signals under the same input on the basis of the internal state of its memory, and register the output signal into its memory as the new internal state. To show that decoupled circuits cannot achieve the sequential logic function, we also constructed three control circuits. The bistable switch module and the NOR gate module were decoupled by removing either or both of the interconnecting parts. In the first control circuit, LacI was removed; without LacI, LexA becomes the only effective input for the NOR gate. As a consequence, upon UV stimulus, promoter P NOR always generates a high output signal, and the ‘ON’ state (high CI and low CI434) is latched in the memory with the help of CI ind− . Correspondingly, the color of the cells will change to red. In the other two control circuits, CI ind− or both LacI and CI ind− were removed. Owing to the lack of the feedback part CI ind− , when the output of the promoter P NOR is ‘ON’, no output signal can be registered into the memory. In this case, the memory module will spontaneously enter into the low CI/high CI434 state after UV stimulus. All experimental results are consistent with the above expectation. Finally, to show the property of the push‐on push‐off switch of the circuit, we sequentially stimulated a homogeneous population of cells with the same dose of UV signal multiple times. The first UV stimulus caused the fraction of green cells in the population to decrease from 99.3% to 8.4%, so that more than 90% of the population switched from the ‘OFF’ to the ‘ON’ state. The second UV stimulus resulted in the fraction of green cells increasing from 8.4% to 34.5%. Therefore, only 26.1% of the population switched back to the ‘OFF’ state. These results are comparable to the results of switching efficiency measurement shown in Figure 4B and C . With repeated exposure to UV irradiation, the population increasingly appeared like a mixture of the two states, the ratio of which gradually reached a steady state. The push‐on–push‐off function of the circuit was thus lost at the population level. In summary, we successfully assembled a bistable switch module and a combinatorial NOR gate module into a functional sequential logic circuit. We combined rational design with directed evolution to generate the desired system behavior. In this work, we showed that simultaneous mutation of multiple RBS targets, followed by directed evolution, is a powerful tool to search the in vivo parameter space to generate functional circuits from multiple rationally designed synthetic device modules. We anticipate that this approach will lend itself well to the next step in synthetic biology, combining multiple circuits, each composed of several device modules, to create useful synthetic systems that perform sophisticated computation. We designed and constructed a genetic sequential logic circuit that can function as a push‐on push‐off switch. The circuit consists of a bistable switch module and a NOR gate module. The bistable switch module and NOR gate module were rationally designed and constructed. The two above modules were coupled by two interconnecting parts, cIind‐ and lacI. When optimizing the defined function, we fine‐tuned the expression of the two interconnecting parts by directed evolution. Three control circuits were constructed to show the interconnecting parts are essential for achieving the defined function.

With their high storage capacity and energy efficiency as well as the compatibilities with renewable energy sources, high‐temperature aquifer thermal energy storage (HT‐ATES) systems are frequently the target today in the design of temporally and spatially balanced and continuous energy supply systems. The inherent density‐driven buoyancy flow is of greater importance with HT‐ATES, which may lead to a lower thermal recovery efficiency than conventional low‐temperature ATES. In this study, the governing equations for HT‐ATES considering buoyancy flow are nondimensionalized, and four key dimensionless parameters regarding thermal recovery efficiency are determined. Then, using numerical simulations, recovery efficiency for a sweep of the key dimensionless parameters for multiple cycles and storage volumes is examined. Ranges of the key dimensionless parameters for the three displacement regimes, that is, a buoyancy‐dominated regime, a conduction‐dominated regime, and a transition regime, are identified. In the buoyancy‐dominated regime, recovery efficiency is mainly correlated to the ratio between the Rayleigh number and the Peclet number. In the conduction‐dominated regime, recovery efficiency is mainly correlated to the product of a material‐related parameter and the Peclet number. Multivariable regression functions are provided to estimate recovery efficiency using the dimensionless parameters. The recovery efficiency estimated by the regression function shows good agreement with the simulation results. Additionally, well screen designs for optimizing recovery efficiency at various degrees of intensity of buoyancy flow are investigated. The findings of this study can be used for a quick assessment and characterization of the potential HT‐ATES systems based on the geological and operational parameters. Key Points Four key dimensionless parameters for the high‐temperature aquifer thermal energy storage systems are identified The displacement processes are classified into a buoyancy‐dominated regime, a conduction‐dominated regime, and a transition regime Multivariable regression functions are demonstrated for the estimation of thermal recovery efficiency

More than 244 million international migrants were estimated to live in a foreign country in 2015, leaving apart the massive number of people that have been relocated in their own country. Furthermore, a substantial proportion of international migrants from southern countries do not reach western nations but resettle in neighbouring low-income countries in the same geographical area. Migration is a complex phenomenon, where 'macro'-, 'meso'- and 'micro'-factors act together to inform the final individual decision to migrate, integrating the simpler previous push-pull theory.Among the 'macro-factors', the political, demographic, socio-economic and environmental situations are major contributors to migration. These are the main drivers of forced migration, either international or internal, and largely out of individuals' control.Among the 'meso-factors', communication technology, land grabbing and diasporic links play an important role. In particular, social media attract people out of their origin countries by raising awareness of living conditions in the affluent world, albeit often grossly exaggerated, with the diaspora link also acting as an attractor. However, 'micro-factors' such as education, religion, marital status and personal attitude to migration also have a key role in making the final decision to migrate an individual choice. The stereotype of the illiterate, poor and rural migrant reaching the borders of affluent countries has to be abandoned. The poorest people simply do not have the means to escape war and poverty and remain trapped in their country or in the neighbouring one.Once in the destination country, migrants have to undergo a difficult and often conflictive integration process in the hosting community. From the health standpoint, newly arrived migrants are mostly healthy (healthy migrant effect), but they may harbour latent infections that need appropriate screening policies. Cultural barriers may sometimes hamper the relation between the migrant patient and the health care provider. The acquisition of western lifestyles is leading to an increase of non-communicable chronic diseases that require attention.Destination countries have to reconsider the positive medium/long-term potential of migration and need to be prepared to receive migrants for the benefit of the migrants themselves and their native population.

At a former uranium mill site where tailings have been removed, prior work has determined several potential ongoing secondary uranium sources. These include locations with uranium sorbed to organic carbon, uranium in the unsaturated zone, and uranium associated with the presence of gypsum. To better understand uranium mobility controls at the site, four single-well push–pull tests (with a drift phase) were completed with the goal of deriving aquifer flow and contaminant transport parameters for inclusion in a future sitewide reactive transport model. This goes beyond the traditional use of a constant sorption distribution coefficient (Kd) and allows for the evaluation of alternative remedial injection fluids, which can produce variable Kd values. Dispersion was first removed from the resulting data to determine possible reactions before conducting reactive transport simulations. These initial analyses indicated the potential need to include cation exchange, uranium sorption, and gypsum dissolution. A reactive transport model using multiple layers to account for partially penetrating wells was completed using the PHT-USG reactive transport modeling code and calibrated using PEST. The model results quantify the hydraulic conductivity and dispersion parameters using the injected tracer concentrations. Uranium sorption, cation exchange, and gypsum dissolution parameters were quantified by comparing the simulated versus observed geochemistry. All simulations required some cation exchange and calcite equilibrium, and one simulation required gypsum dissolution to improve the model fit for calcium and sulfate. Uranium sorption parameters were not strongly influenced by the other parameter values but were highly influenced by uranium concentrations during the drift phase, with possible kinetic rate limitations. Thus, a future recommendation for such push–pull tests is to collect more geochemical data during the drift phase. The final uranium sorption parameters were within the range of values determined from prior column testing. The flow and transport parameters derived from these single-well push–pull tests will provide initial parameters for any future sitewide reactive transport model.

This paper conducts a static study on the internal reeds of a broadband coaxial switch. A model of the reed unit is established, and simulation analysis is performed by using the finite element ANSYS-Workbench software to clarify the stress state of the reeds and identify critical stress locations. The results show that the maximum stress in the short reed occurs at the contact area between the reed and the push rod, with a theoretical calculation value of 202.7 MPa and a finite element simulation value of 287.57 MPa. The maximum stress in the long reed occurs at the same location as in the short reed, with a theoretical calculation value of 194.65 MPa and a finite element simulation value of 261.05 MPa. The yield strength of beryllium bronze is 1035 MPa, indicating that neither reed will yield under these conditions.

Accurate modeling of heat transport behavior near the test well is essential for the efficient operation and management of aquifer thermal energy storage (ATES) systems. Existing models typically assume a linear relationship between thermal dispersion and velocity, whereas previous controlled experiments have revealed that this relationship is nonlinear. We present a finite element model for thermal single‐well push‐pull (SWPP) tests in ATES systems, incorporating both nonlinear velocity‐dependent thermal dispersion and wellbore mixing effects. Morris global sensitivity analysis shows that heat transport is most affected by nonlinear velocity‐dependent thermal dispersion, followed by injection and extraction rates. A higher exponent of nonlinear velocity‐dependent thermal dispersion leads to a smaller thermal breakthrough curve at the wellbore and a shorter heat transport distance, while thermal dispersivity has the opposite effect. Also, neglecting nonlinear velocity‐dependent thermal dispersion significantly underestimates both effective thermal diffusivity and thermal recovery efficiency in the SWPP tests, where the former is potentially underestimated by four orders of magnitude in the thermal dispersivity range of 1.478–1,000 s. Moreover, the proposed model is used to analyze the relationship between thermal recovery efficiency and the injection‐extraction rate ratio, suggesting that keeping the ratio below one ensures that efficiency exceeds 60%. The capabilities of new model are further demonstrated through two in situ thermal SWPP tests on different time scales (1,000 min and 3 months), highlighting that incorporating nonlinear velocity‐dependent thermal dispersion into models significantly enhances their ability to interpret observations, and the thermal dispersion potentially connected to the test duration.

Through the research and analysis of the existing gantry crane and cantilever crane to unload and transport goods, at the same time the application of the characteristics of triangular stability, a combination of the advantages of the three; A triangular omnidirectional cantilever crane is designed and developed by using electric push rod instead of rope lifting and the most basic triangular body.

Conventional design method of the downhole tractor is based on cementing casing, which is only suitable for the smooth wellbore. For the open hole well, the conventional downhole tractor has poor adaptability and even cannot work normally. In order to improve the obstacle surmounting performance of the wheeled downhole tractor (WDR) and expand the application range of the WDR, a double push rod-double spring support adjustment mechanism (DPRDSSAM) is proposed in this paper. Meanwhile, the proposed DPRDSSAM also needs to increase the traction force and the stability of the WDR in the open hole well. Kinematic simulation numerical models of both conventional support adjustment mechanism and the DPRDSSAM are established. The two models comprehensively considere the influence of different obstacle forms and sizes on the obstacle surmounting performance of the tractor. The influence of different obstacle forms on the obstacle surmounting performance of DPRDSSAM and single push rod support adjustment mechanism (SPRSAM) is analyzed. Results show that the DPRDSSAM has better obstacle surmounting performance than the SPRSAM. The DPRDSSAM can effectively promote further research and application of the tractor in the open hole well.