A homing suppression gene drive with multiplexed gRNAs maintains high drive conversion efficiency and avoids functional resistance alleles

Gene drives are engineered alleles that can bias inheritance in their favor, allowing them to spread throughout a population. They could potentially be used to modify or suppress pest populations, such as mosquitoes that spread diseases. CRISPR/Cas9 homing drives, which copy themselves by homology-directed repair in drive/wild-type heterozygotes, are a powerful form of gene drive, but they are vulnerable to resistance alleles that preserve the function of their target gene. Such resistance alleles can prevent successful population suppression. Here, we constructed a homing suppression drive in Drosophila melanogaster that utilized multiplexed gRNAs to inhibit the formation of functional resistance alleles in its female fertility target gene. The gRNA target sites were placed close together, preventing reduction in drive conversion efficiency. The construct reached a moderate equilibrium frequency in cage populations without apparent formation of resistance alleles. However, a moderate fitness cost prevented suppression of the cage population. Nevertheless, our results experimentally demonstrate the viability of the multiplexed gRNAs strategy in homing type suppression gene drives.

Design and Investigation of Gate Stacked Vertical TFET with N+ SiGe Pocket Doped Heterojunction for Performance Enhancement

In this paper, a novel delta-doped N + Silicon-Germanium Gate Stacked Triple Metal Gate Vertical TFET (Delta doped N + GS TMG VTFET) is proposed and investigated using the Silvaco TCAD simulation tool. Four different combinations were presented and compared with and without the gate stacking method and Si0.2Ge0.8 N + pocket delta-doped layer to render the optimized results. Among all, Delta doped N + GS TMG VTFET structure comes out with a very steep sub-threshold slope (9.75 mV/dec), 40 % lower than the first configuration of TMG VTFET. The inclusion of the N + delta-doped layer between the source and channel and gate will enhance the ON-state drive current performance by reducing the OFF-state leakage current. This happens due to the lower bandgap of the N + delta-doped layer cause narrow BTBT, which results in a high drive current. The Triple metal gate is designed to mitigate the ambipolar conduction by modulating the optimized wok function at 4.15, 4.3, and 4.15 eV. The distribution of the source channel in the vertical structure will enhance the device's scalability due to the electron tunneling moves in the vertical electric field direction. The optimally constructed structure demonstrates improved performance, such as a high ION/IOFF current ratio (~ 1013) and sub-threshold voltage (0.33 V). The results obtained from the proposed device make it suitable for the ultra-low-power device application.

Ultrahigh drive current and large selectivity in GeS selector

Selector devices are indispensable components of large-scale nonvolatile memory and neuromorphic array systems. Besides the conventional silicon transistor, two-terminal ovonic threshold switching device with much higher scalability is currently the most industrially favored selector technology. However, current ovonic threshold switching devices rely heavily on intricate control of material stoichiometry and generally suffer from toxic and complex dopants. Here, we report on a selector with a large drive current density of 34 MA cm−2 and a ~106 high nonlinearity, realized in an environment-friendly and earth-abundant sulfide binary semiconductor, GeS. Both experiments and first-principles calculations reveal Ge pyramid-dominated network and high density of near-valence band trap states in amorphous GeS. The high-drive current capacity is associated with the strong Ge-S covalency and the high nonlinearity could arise from the synergy of the mid-gap traps assisted electronic transition and local Ge-Ge chain growth as well as locally enhanced bond alignment under high electric field.