Given the widespread use and application of the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas gene editing system across many fields, a major focus has been the development, ...engineering and discovery of molecular means to precisely control and regulate the enzymatic function of the Cas9 nuclease. To date, a variety of Cas9 variants and fusion assemblies have been proposed to provide temporally inducible and spatially controlled editing functions. The discovery of a new class of 'anti-CRISPR' proteins, evolved from bacteriophage in response to the prokaryotic nuclease-based immune system, provides a new platform for control over genomic editing. One Cas9-based application of interest to the field of population control is that of the 'gene drive'. Here, we demonstrate use of the AcrIIA2 and AcrIIA4 proteins to inhibit active gene drive systems in budding yeast. Furthermore, an unbiased mutational scan reveals that titration of Cas9 inhibition may be possible by modification of the anti-CRISPR primary sequence.
A smooth fault-tolerant control (FTC) of induction motor drives with sensor failures is presented in this paper. The drive uses concurrently active direct torque control (DTC), indirect ...field-oriented control (IFOC), and volts-per-hertz ( V / f ) controllers as replacements of each other in the case of sensor failure or recovery. Speed encoder, current, and voltage sensors are considered. The DTC and IFOC controllers are properly modified and integrated with the V / f controller in synchronous frame, which allows switching between dc-type voltage commands of different controllers. Therefore, difficult synchronization of different controllers is avoided, and a simple rate limiter is able to achieve smooth handoff transition of different controllers. Details of the DTC, IFOC, and V / f controllers, as well as their integration are presented. Simulation and experimental verification of the proposed FTC are given, where normal abc -frame switching and the proposed synchronous-frame switching of controllers are compared with different switching schemes and at different machine operation conditions. Simulation and experimental results show significantly smoother handoff transients.
In some cases, LC filters are installed between the inverters and motors to suppress the adverse effects of pulse width modulation. However, some techniques should be modified, because the ...mathematical model of the drive system is changed by the LC filter and the sensors on the inverter output cannot measure some necessary variables. In this study, a multi-purpose proportional-integral (PI) observer is proposed at first. The type of observer depends on whether the position sensor is equipped. A sliding mode controller for the LC filter based on the observer is presented, therefore improving the dynamic performance. Furthermore, if the position sensor of the rotor is equipped, an open-switch fault diagnostic method is realised by means of the PI observer; if the position sensor is not equipped, the sensorless estimation is realized. The proposed strategies were realised without any additional current/voltage sensors. Experimental results verified the effectiveness of the proposed strategies.
Invasive rodents are a major cause of environmental damage and biodiversity loss, particularly on islands. Unlike insects, genetic biocontrol strategies including population-suppressing gene drives ...with biased inheritance have not been developed in mice. Here, we demonstrate a gene drive strategy (
) that leverages super-Mendelian transmission of the
haplotype to spread inactivating mutations in a haplosufficient female fertility gene (
). Using spatially explicit individual-based in silico modeling, we show that
can eradicate island populations under a range of realistic field-based parameter values. We also engineer transgenic
mice that, crucially, exhibit biased transmission of the modified
haplotype and
mutations at levels our modeling predicts would be sufficient for eradication. This is an example of a feasible gene drive system for invasive alien rodent population control.
Recent advances in research on gene drives have produced genetic constructs that could theoretically spread a desired gene (payload) into all populations of a species, with a single release in one ...place. This attribute has advantages, but also comes with risks and ethical concerns. There has been a call for research on gene drive systems that are spatially and/or temporally self‐limiting. Here, we use a population genetics model to compare the expected characteristics of three spatially self‐limiting gene drive systems: one‐locus underdominance, two‐locus underdominance and daisy‐chain drives. We find large differences between these gene drives in the minimum release size required for successfully driving a payload into a population. The daisy‐chain system is the most efficient, requiring the smallest release, followed by the two‐locus underdominance system, and then the one‐locus underdominance system. However, when the target population exchanges migrants with a nontarget population, the gene drives requiring smaller releases suffer from higher risks of unintended spread. For payloads that incur relatively low fitness costs (up to 30%), a simple daisy‐chain drive is practically incapable of remaining localized, even with migration rates as low as 0.5% per generation. The two‐locus underdominance system can achieve localized spread under a broader range of migration rates and of payload fitness costs, while the one‐locus underdominance system largely remains localized. We also find differences in the extent of population alteration and in the permanence of the alteration achieved by the three gene drives. The two‐locus underdominance system does not always spread the payload to fixation, even after successful drive, while the daisy‐chain system can, for a small set of parameter values, achieve a temporally limited spread of the payload. These differences could affect the suitability of each gene drive for specific applications.
Cable-connected motor winding insulation is prone to failures owing to reflected wave (RFW) overvoltages (OV). RFW is caused by the impedance mismatch between source and load and impacted by the ...impedance interactions of the motor drive system and pulse width and risetime of the excitation source. According to the literature, the OV across the motor winding is less detrimental in an integrated motor drive due to the absence of cable. However, in this paper, two scenarios are shown which can cause detrimental voltage stress across the winding in an integrated wide band gap (WBG)-based drive system. First, WBG-based motor drive generates short risetime and short pulse width that excites the higher frequency resonance network of the integrated motor winding. So, it brings higher OV amplitude across the motor winding. Second, voltage stress across motor winding is shown to worsen when the antiresonance of the winding (least impedance) coincides with OV resonance frequency across it, termed as antiresonance phenomenon (ARP). Due to the absence of cable, the ARP is bound to happen in an integrated drive system. Experimental results are given to validate the claims.
Population suppression is an effective way for controlling insect pests and disease vectors, which cause significant damage to crop and spread contagious diseases to plants, animals and humans. Gene ...drive systems provide innovative opportunities for the insect pests population suppression by driving genes that impart fitness costs on populations of pests or disease vectors. Different gene-drive systems have been developed in insects and applied for their population suppression. Here, different categories of gene drives such as meiotic drive (MD), under-dominance (UD), homing endonuclease-based gene drive (HEGD) and especially the CRISPR/Cas9-based gene drive (CCGD) were reviewed, including the history, types, process and mechanisms. Furthermore, the advantages and limitations of applying different gene-drive systems to suppress the insect population were also summarized. This review provides a foundation for developing a specific gene-drive system for insect population suppression.
Four-switch three-phase inverter (FSTPI) is widely applied as a fault-tolerant topology of six-switch three-phase inverter (SSTPI) with an open-phase fault or as a cost-effective topology due to the ...reduced semiconductor power switches. However, conventional single-vector-based predictive torque control (SV-PTC) for FSTPI-fed induction motor (IM) presents poor steady-state performance and requires high sampling frequency. To address these issues, a dual-vector-based PTC (DV-PTC) for FSTPI-fed IM with adaptive switching instant is proposed in this article. Therein, two optimal voltage vectors are determined in each sampling period, and a simplification strategy for selecting the optimal voltage vectors is established. A switching instant adaptation scheme is developed to improve the steady-state performance of machine control. An optimized overmodulation strategy is proposed to improve the transient-state performance of machine control and reduce the computational burden in digital implementation. Extensive experimental studies validate the effectiveness and superiority of the proposed DV-PTC scheme.
Insects play important roles as predators, prey, pollinators, recyclers, hosts, parasitoids, and sources of economically important products. They can also destroy crops; wound animals; and serve as ...vectors for plant, animal, and human diseases. Gene drive-a process by which genes, gene complexes, or chromosomes encoding specific traits are made to spread through wild populations, even if these traits result in a fitness cost to carriers-provides new opportunities for altering populations to benefit humanity and the environment in ways that are species specific and sustainable. Gene drive can be used to alter the genetic composition of an existing population, referred to as population modification or replacement, or to bring about population suppression or elimination. We describe technologies under consideration, progress that has been made, and remaining technological hurdles, particularly with respect to evolutionary stability and our ability to control the spread and ultimate fate of genes introduced into populations.
PDF
