SnSe is a promising thermoelectric material with record-breaking figure of merit. However, to date a comprehensive understanding of the electronic structure and most critically, the self-hole-doping ...mechanism in SnSe is still absent. Here we report the highly anisotropic electronic structure of SnSe investigated by angle-resolved photoemission spectroscopy, in which a unique pudding-mould-shaped valence band with quasi-linear energy dispersion is revealed. We prove that p-type doping in SnSe is extrinsically controlled by local phase segregation of SnSe
microdomains via interfacial charge transferring. The multivalley nature of the pudding-mould band is manifested in quantum transport by crystallographic axis-dependent weak localisation and exotic non-saturating negative magnetoresistance. Strikingly, quantum oscillations also reveal 3D Fermi surface with unusual interlayer coupling strength in p-SnSe, in which individual monolayers are interwoven by peculiar point dislocation defects. Our results suggest that defect engineering may provide versatile routes in improving the thermoelectric performance of the SnSe family.
In this study, we discuss the role of the linear heating term and nonlinear terms associated with a non-linear feedback loop in the energy cycle of the three-dimensional (X-Y-Z) non-dissipative ...Lorenz model (3D-NLM), where (X, Y, Z) represent the solutions in the phase space. Using trigonometric functions, we first present the closed-form solution of the nonlinear equation
without the heating term (i.e. rX), (where τ is a non-dimensional time and r is the normalized Rayleigh number), a solution that has not been previously documented. Since the solution of the simplified 3D-NLM is oscillatory (wave-like) and since the nonlinear term (X
3
) is associated with the nonlinear feedback loop, here, we suggest that the nonlinear feedback loop may act as a restoring force. When the heating term is considered, the system yields three critical points. A linear analysis suggests that the origin (i.e. the trivial critical point) is a saddle point and that the other two non-trivial critical points (i.e. centers) are stable. Here, we provide an analysis for three types of solutions that are associated with these critical points. Two of the solutions represent closed curves that travel around one non-trivial critical point or all three critical points. The third type of solution, appearing to connect the stable and unstable manifolds of the saddle point, is called the homoclinic orbit. Using the solution that encloses one non-trivial critical point, here, we show that the competing impact of the nonlinear restoring force and the linear (heating) force determines the partition of the average available potential energy from the Y and Z modes. Based on the energy analysis, an energy cycle with four different regimes is identified. The cycle is only half of a 'large' cycle, displaying the wing pattern of a glass-winged butterfly. The other half cycle is anti-symmetric with respect to the origin. The two types of oscillatory solutions with either a small cycle or a large cycle are orbitally stable. As compared to the oscillatory solutions, the homoclinic orbit is not periodic because it "takes forever" to reach the origin. Two trajectories with starting points near the homoclinic orbit may be diverged because one moves with a small cycle and the other moves with a large cycle. Therefore, the homoclinic orbit is not orbitally stable. In a future study, dissipation and/or additional nonlinear terms will be further examined in order to determine how their interactions with the original nonlinear feedback loop and the heating term may change the periodic orbits (as well as homoclinic orbits) to become quasi-periodic orbits and chaotic solutions.
A Li-ion capacitor (LIC), typically composed of a pre-lithiated negative electrode and an activated-carbon positive electrode, can provide high energy and power density. In this work, we compare the ...electrochemical performances of pre-lithiated graphene nanosheets and conventional graphite as negative electrode materials for LICs. The LICs employing pre-lithiated graphene nanosheets show a specific capacitance of 168.5 F g−1 with 74% capacitance retention at 400 mA g−1 after 300 cycles. Moreover, the capacitors deliver a maximum power density of 222.2 W kg−1 at an energy density of 61.7 Wh kg−1, operated in the voltage range of 2.0–4.0 V. Therefore, pre-lithiated graphene nanosheets are promising negative electrode materials for high power LICs.
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•Pre-lithiated graphene nanosheets are explored for Li-ion capacitors.•The Li-ion capacitors exhibit high energy and power density at high voltages.•Pre-lithiated graphene nanosheets are promising for high power Li-ion capacitors.
Abstract Previous data demonstrate that traumatic brain injury (TBI) activates autophagy, and increases microtubule-associated protein 1 light chain 3 (LC3) immunostaining mainly in neurons. However, ...the role of autophagy in traumatic brain damage remains elusive. The aim of the present study was to investigate the autophagic mechanisms participating in traumatic brain injury. The autophagy inhibitors 3-methyladenine (3-MA) and bafliomycin A1 (BFA) were administered with a single i.c.v. injection before TBI. We first examined the protein levels of Beclin-1 and LC3 II, which have been found to promote autophagy previously. Immunoblotting analysis showed that 3-MA pretreatment reduced post-TBI Beclin-1 and LC3-II levels, and maintained p62/SQSTM1 (p62) levels. In addition, double immunolabeling showed that the increased punctate LC3-II dots colocalizing with Propidium Iodide (PI)-stained nuclei at 24 h after injury, were partially inhibited by 3-MA pretreatment. Furthermore, inhibition of autophagy could reduce TBI-induced cell injury assessed with i.p. injection of PI and lesion volume, and attenuate behavioral outcome evaluated by motor test and Morris water maze. The neuroprotective effects were associated with an inhibition on TBI-induced up-regulation of LC3, Beclin-1, cathepsin B, caspase-3 and the Beclin-1/Bcl-2 ratio. Taken together, these data imply that the autophagy pathway is involved in the pathophysiologic responses after TBI, and inhibition of this pathway may help attenuate traumatic damage and functional outcome deficits.
Earthquakes induced during hydraulic fracturing operations have occurred in a number of locales. However, in situ studies aimed to discern the triggering mechanism remain exclusively statistical in ...their nature. Here we calculate the fault slip tendencies of 11 hydraulic fracturing induced earthquakes in a historically aseismic area using a recently constructed quantitative model for the in‐situ stresses. It is shown that the ambient pore pressures of the nearby Duvernay unconventional reservoirs can provide enough ΔPf triggering fault movement. The local fluid pressures acting on the fault could readily be increased above the critical value if hydraulic connection exists between the fault and a propagating hydraulic fracture. The critical pressures necessary to induce slip are estimated using a probabilistic model that incorporates uncertainties of stress and fault's mechanical properties. These critical pressures are greater than the expected hydrostatic pressure but less the pore pressures of nearby unconventional reservoirs.
Plain Language Summary
Hydraulic fracturing operations within the Duvernay Formation, a major hydrocarbon source rock in the Western Canada Sedimentary Basin, have been linked to induced earthquakes primarily on the basis of statistical analysis. Here we attempt to examine whether faults in the area are prone to slip, causing earthquakes, using well‐constrained values for the state of stress in the Earth's crust at the locations of the induced earthquakes. Perhaps most interestingly, the fault planes, along which slip occurred, could not have remained immobile if the fluid pressures directly acting on the faults are the same as the anomalously high pore fluid pressures measured within the Duvernay Formation itself. However, the faults have been historically quiescent and this suggests that the fluid pressures acting on them must be lower. This might be accomplished if pressures are relieved by fluid migration to overlying hydrocarbon reservoirs. Further, this suggests that the earthquakes are triggered by elevated fluid pressures communicated to the preexisting faults.
Key Points
The slip tendency along the fault planes is determined using a quantitative model for the stress tensors at the epicentral locations
The faults cannot be stable at the ambient high pore fluid pressures within the Duvernay Formation
Triggered planes of weakness need not be perfectly optimally oriented to the stress field
We describe a computationally designed enzyme, formolase (FLS), which catalyzes the carboligation of three one-carbon formaldehyde molecules into one three-carbon dihydroxyacetone molecule. The ...existence of FLS enables the design of a new carbon fixation pathway, the formolase pathway, consisting of a small number of thermodynamically favorable chemical transformations that convert formate into a three-carbon sugar in central metabolism. The formolase pathway is predicted to use carbon more efficiently and with less backward flux than any naturally occurring one-carbon assimilation pathway. When supplemented with enzymes carrying out the other steps in the pathway, FLS converts formate into dihydroxyacetone phosphate and other central metabolites in vitro. These results demonstrate how modern protein engineering and design tools can facilitate the construction of a completely new biosynthetic pathway.
Significance This paper describes the development of a computationally designed enzyme that is the cornerstone of a novel metabolic pathway. This enzyme, formolase, performs a carboligation reaction, directly fixing one-carbon units into three-carbon units that feed into central metabolism. By combining formolase with several naturally occurring enzymes, we created a new carbon fixation pathway, the formolase pathway, which assimilates one-carbon units via formate. Unlike native carbon fixation pathways, this pathway is linear, not oxygen sensitive, and consists of a small number of thermodynamically favorable steps. We demonstrate in vitro pathway function as a proof of principle of how protein design in a pathway context can lead to new efficient metabolic pathways.
Inherited retinal disease (IRD) affects about 1 in 3000 to 1 in 5000 individuals and is now believed to be the most common cause of blindness registration in developed countries. Until recently, the ...management of such conditions had been exclusively supportive. However, advances in molecular biology and medical engineering have now seen the rise of a variety of approaches to restore vision in patients with IRDs. Optogenetic approaches are primarily aimed at rendering secondary and tertiary neurons of the retina light-sensitive in order to replace degenerate or dysfunctional photoreceptors. Such approaches are attractive because they provide a “causative gene-independent” strategy, which may prove suitable for a variety of patients with IRD. We discuss theoretical and practical considerations in the selection of optogenetic molecules, vectors, surgical approaches and review previous trials of optogenetics for vision restoration. Optogenetic approaches to vision restoration have yielded promising results in pre-clinical trials and a phase I/II clinical trial is currently underway (ClinicalTrials.gov NCT02556736). Despite the significant inroads made in recent years, the ideal optogenetic molecule, vector and surgical approach have yet to be established.
•Optogenetic approaches to vision restoration seek to restore vision to patients with inherited retinal diseases by rendering secondary and tertiary neurones of the retina light-sensitive.•Two principal classes of molecule can be used: Type 1 (microbial) opsins or Type 2 (animal) opsins.•Pre-clinical trials of optogenetic approaches in animal models suggest that the technique may restore vision in previously blind animals, with the threshold for activation being within 1-2 log units of the threshold for cone activation.
Wind energy has been receiving more acceptance as a reproducible, resourceful and clean energy source since last decade. Wind power is not constant and may fluctuate below the rated wind power when ...the wind speed is lower than the rated speed. This fact affects the stability of the power system, to which the wind generators are connected. This is becoming more significant with the increasing penetration of wind energy systems. Pitch angle control has been one of the most common methods for smoothing output power fluctuations during below rated wind incidents. A fuzzy logic pitch angle controller is proposed in this paper for smoothing wind power fluctuations during below rated wind incidents beside traditional power regulations during above rated wind incidents. Two smoothing methods have been presented: the determination of the command output power based on the exponential moving average with a proper selection of correction factor by fuzzy reasoning and the dynamic selection of target output power according to the wind incident. Simulation results show the effectiveness of the proposed fuzzy logic pitch angle controller in smoothing output power fluctuations with significantly small drop of output power.
► Regulated power during above rated wind using fuzzy logic systems. ► Smoothed power fluctuations during below rated wind using two fuzzy logic methods. ► Performance of both methods were compared with conventional method. ► Method 1 performed partial smoothing with 4.7% more of power drop. ► Method 2 performed complete smoothing with 8.28% more of power drop.
Prime editing (PE) is a versatile genome editing technology, but design of the required guide RNAs is more complex than for standard CRISPR-based nucleases or base editors. Here we describe ...PrimeDesign, a user-friendly, end-to-end web application and command-line tool for the design of PE experiments. PrimeDesign can be used for single and combination editing applications, as well as genome-wide and saturation mutagenesis screens. Using PrimeDesign, we construct PrimeVar, a comprehensive and searchable database that includes candidate prime editing guide RNA (pegRNA) and nicking sgRNA (ngRNA) combinations for installing or correcting >68,500 pathogenic human genetic variants from the ClinVar database. Finally, we use PrimeDesign to design pegRNAs/ngRNAs to install a variety of human pathogenic variants in human cells.
The cast-grown monocrystalline-like silicon (mono-like Si) technology has been reactivated recently for the manufacture of high-efficiency solar cells at low cost. In this paper, we have provided a ...progressive research, both experimentally and theoretically, to improve the efficiency of mono-like Si passivated emitter and rear cells (PERCs) through production lines. By employing rear surface passivation of AlOx/triple-SiNx:H layers, the average efficiency has increased to 21.87% with a champion efficiency of 22.32% from the standard mono-like Si PERCs of 21.72% efficiency with AlOx capped with double-SiNx:H layers. We have further optimized the rear electrode contact patterns and introduced the selective emitter (SE) technology, yielding an absolute efficiency improvement of 0.19% and 0.26%, respectively. Integrating all approaches of the triple-SiNx:H, rear contact pattern optimization and SE technology, we have demonstrated that the mono-like Si PERCs can reach the average efficiency of 22.2% with a maximum efficiency of 22.5%, similar to the current Czochralski monocrystalline Si counterparts.
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