Piezotronics with capacity of constructing adaptive and seamless interactions between electronics/machines and human/ambient are of value in Internet of Things, artificial intelligence and biomedical ...engineering. Here, we report a kind of highly sensitive strain sensor based on piezotronic tunneling junction (Ag/HfO
/n-ZnO), which utilizes the strain-induced piezoelectric potential to control the tunneling barrier height and width in parallel, and hence to synergistically modulate the electrical transport process. The piezotronic tunneling strain sensor has a high on/off ratio of 478.4 and high gauge factor of 4.8 × 10
at the strain of 0.10%, which is more than 17.8 times larger than that of a conventional Schottky-barrier based strain sensor in control group as well as some existing ZnO nanowire or nanobelt based sensors. This work provides in-depth understanding for the basic mechanism of piezotronic modulation on tunneling junction, and realizes the highly sensitive strain sensor of piezotronic tunneling junction on device scale, which has great potential in advanced micro/nano-electromechanical devices and systems.
Interface engineering by local polarization using piezoelectric
, pyroelectric
and ferroelectric
effects has attracted considerable attention as a promising approach for tunable ...electronics/optoelectronics, human-machine interfacing and artificial intelligence. However, this approach has mainly been applied to non-centrosymmetric semiconductors, such as wurtzite-structured ZnO and GaN, limiting its practical applications. Here we demonstrate an electronic regulation mechanism, the flexoelectronics, which is applicable to any semiconductor type, expanding flexoelectricity
to conventional semiconductors such as Si, Ge and GaAs. The inner-crystal polarization potential generated by the flexoelectric field serving as a 'gate' can be used to modulate the metal-semiconductor interface Schottky barrier and further tune charge-carrier transport. We observe a giant flexoelectronic effect in bulk centrosymmetric semiconductors of Si, TiO
and Nb-SrTiO
with high strain sensitivity (>2,650), largely outperforming state-of-the-art Si-nanowire strain sensors and even piezoresistive, piezoelectric and ferroelectric nanodevices
. The effect can be used to mechanically switch the electronics in the nanoscale with fast response (<4 ms) and high resolution (~0.78 nm). This opens up the possibility of realizing strain-modulated electronics in centrosymmetric semiconductors, paving the way for local polarization field-controlled electronics and high-performance electromechanical applications.
Structures and gating mechanism of human TRPM2 Wang, Longfei; Fu, Tian-Min; Zhou, Yiming ...
Science (American Association for the Advancement of Science),
12/2018, Letnik:
362, Številka:
6421
Journal Article
Recenzirano
Odprti dostop
Transient receptor potential (TRP) melastatin 2 (TRPM2) is a cation channel associated with numerous diseases. It has a C-terminal NUDT9 homology (NUDT9H) domain responsible for binding adenosine ...diphosphate (ADP)-ribose (ADPR), and both ADPR and calcium (Ca
) are required for TRPM2 activation. Here we report cryo-electron microscopy structures of human TRPM2 alone, with ADPR, and with ADPR and Ca
NUDT9H forms both intra- and intersubunit interactions with the N-terminal TRPM homology region (MHR1/2/3) in the apo state but undergoes conformational changes upon ADPR binding, resulting in rotation of MHR1/2 and disruption of the intersubunit interaction. The binding of Ca
further engages transmembrane helices and the conserved TRP helix to cause conformational changes at the MHR arm and the lower gating pore to potentiate channel opening. These findings explain the molecular mechanism of concerted TRPM2 gating by ADPR and Ca
and provide insights into the gating mechanism of other TRP channels.
Ring Brazilian disc specimens are favored for determining the tensile strength and mixed mode fracture toughness. To further understand the fracture mechanism of ring Brazilian disc specimens, the ...phase field method is used to investigate the cracking process and peak load of ring Brazilian disc specimens. First, the numerical validity and accuracy of the phase field method is verified by a benchmark example. Then, the effect of aperture ratio and crack inclination angle on the failure process and peak load of ring Brazilian disc specimens is studied. Finally, by combining the phase field method and
J
-integral method, the influence of prefabricated crack inclination angle and aperture ratios on mode I and II fracture toughness of cracked ring Brazilian disc specimens is discussed.
Effective piezoelectric semiconductor based hybrid photocatalysts are successfully developed by assembling TiO2 nanoparticles on ZnO monocrystalline nanoplatelets. The piezopotential can be ...introduced and tuned by thermal stress on the piezoelectric material of ZnO monocrystalline nanoplatelets through cooling hybrid photocatalysts from high temperature to room temperature with different rates based on the mismatched thermal expansion coefficient of the two materials, which can be used to engineer the heterojunction band structure and significantly enhance the photocatalytic performance in a wide range by improving charge separation. It is proposed that the piezotronic effect enhanced photocatalyst will provide a strategy for high-performance photocatalysis applications.
Plastic debris is ubiquitous in aquatic systems and has been proven vehicles for the transport of various pollutants including trace organic compounds. Nanoplastics have large specific surface area ...and hydrophobic characteristics and therefore are capable of adsorbing other organic or inorganic chemicals from the environment. Antibiotics, as another class of emerging contaminants, have raised significant research concern in recent years as they pose threats to the ecosytems and human health. Nevertheless, little information is available on the adsorption behaviors of antibiotics onto nano-sized plastics. The toxicity of combined nanoplastics and antibiotics is also largely unknown. In this study, the physicochemical and thermodynamic interactions between representative nanoplastics, which containing a carboxyl functional group of polystyrene nanoplastics (PS-COOH), and typical antibiotic, i.e., ciprofloxacin (CIP) were investigated in a batch adsorption experiment. The specific thermodynamic correlation function of PS-COOH combined with CIP was obtained through isothermal titration microcalorimetry (ITC) analysis. The adsorption kinetics and isotherm of CIP on PS-COOH closely fit the pseudo-second-order kinetic model (r2 = 0.99) and Freundlich isotherm (r2 = 0.99). The ITC results showed that the adsorption reaction of PS-COOH with CIP was a spontaneous exothermic reaction. The adsorption of antibiotics on nanoplastics may aggravate the negative impacts of these two pollutants on aqueous ecosystems, and we hypothesized that would be reflected in the survival rate of model organism of Caenorhabditis elegans when exposed to this combination. This work used a mechanistic approach to unravel the adsorption behavior of antibiotics on nanoplastics and shed light on their potential impact on aquatic ecosystems.
Display omitted
•Electrostatic interactions, hydrogen bonding, and hydrophobic interactions are critical mechanisms of CIP adsorption on PS-COOH.•Binding reaction between PS-COOH is an exothermic and thermodynamically favorable.•Toxicity of PS-COOH with adsorbed CIP to C. elegans was significantly higher than that of either CIP or PS-COOH.•Small size of PS-COOH caused more adverse effects on survival of C. elegans than that of larger size microplastics.
Objective:
The results from observation studies on the relationship between coffee intake and risk of depression and the relationship between caffeine consumption and depression remain controversial. ...We conducted a meta-analysis with a dose–response analysis to quantitatively summarize the evidence about the association between coffee and caffeine intakes and risk of depression.
Method:
Relevant articles were identified by researching PubMed, Web of Science, China National Knowledge Infrastructure and WANFANG DATA in English or Chinese from 1 January 1980 to 1 May 2015. Case-control, cohort or cross-sectional studies evaluating coffee or caffeine consumption and depression were included. A random-effects model was used to combine study-specific relative risk and 95% confidence interval. Dose–response relationship was assessed by restricted cubic spline functions.
Results:
Data were obtained from 11 observation articles; 330,677 participants from seven studies in seven articles were included in the coffee-depression analysis, while 38,223 participants from eight studies in seven articles were involved in the caffeine-depression analysis. Compared with the lowest level consumption, the pooled relative risk (95% confidence interval) for coffee-depression and caffeine-depression was 0.757 0.624, 0.917 and 0.721 0.522, 0.997, respectively. For dose–response analysis, evidence of a linear association was found between coffee consumption and depression, and the risk of depression decreased by 8% (relative risk = 0.92, 95% confidence interval = 0.87, 0.97, p = 0.002) for each cup/day increment in coffee intake; a nonlinear association was found between caffeine consumption and depression, the risk of depression decreased faster and the association became significant when the caffeine consumption was above 68 mg/day and below 509 mg/day.
Conclusions:
Coffee and caffeine consumption were significantly associated with decreased risk of depression.
The accuracy measurement of rock fracture toughness is one of the basic tasks of rock fracture mechanics. In order to study the influence of the width of the prefabricated crack on the fracture ...toughness of rock, the failure process of notched semi-circular bend (NSCB) specimens with four sizes and five different width of the prefabricated crack was studied by experimental and numerical methods. The influence of the width of the prefabricated crack on the peak load, crack initiation position, dimensionless stress intensity factor and fracture toughness is analyzed and discussed. The results show that the peak load and fracture toughness of NSCB increase with the increase of the width of the prefabricated crack, and the smaller the specimen size is, the larger the increase is. When the width of the prefabricated crack is less than 1.3 mm, the crack initiates at the dichotomy of the prefabricated crack tip; when the width of the prefabricated crack is greater than or equal to 1.3 mm, the crack initiates near the corner of the prefabricated crack tip. If NSCB specimen is adopted to determine the fracture toughness of limestone, it is recommended that the width of prefabricated crack should be less than 1.3 mm. The conclusions provide a reference for the fabrication of NSCB specimens and the accurate measurement of limestone fracture toughness.
An autapse is a special synapse that connects a neuron to itself. In this study, we investigated the effect of an autapse on the responses of a Hodgkin-Huxley neuron to different forms of external ...stimuli. When the neuron was subjected to a DC stimulus, the firing frequencies and the interspike interval distributions of the output spike trains showed periodic behaviors as the autaptic delay time increased. When the input was a synaptic pulse-like train with random interspike intervals, we observed low-pass and band-pass filtering behaviors. Moreover, the region over which the output ISIs are distributed and the mean firing frequency display periodic behaviors with increasing autaptic delay time. When specific autaptic parameters were chosen, most of the input ISIs could be filtered, and the response spike trains were nearly regular, even with a highly random input. The background mechanism of these observed dynamics has been analyzed based on the phase response curve method. We also found that the information entropy of the output spike train could be modified by the autapse. These results also suggest that the autapse can serve as a regulator of information response in the nervous system.
PDF
