With their working mechanisms based on ion migration, the switching dynamics and electrical behaviour of memristive devices resemble those of synapses and neurons, making these devices promising ...candidates for brain-inspired computing. Built into large-scale crossbar arrays to form neural networks, they perform efficient in-memory computing with massive parallelism by directly using physical laws. The dynamical interactions between artificial synapses and neurons equip the networks with both supervised and unsupervised learning capabilities. Moreover, their ability to interface with analogue signals from sensors without analogue/digital conversions reduces the processing time and energy overhead. Although numerous simulations have indicated the potential of these networks for brain-inspired computing, experimental implementation of large-scale memristive arrays is still in its infancy. This Review looks at the progress, challenges and possible solutions for efficient brain-inspired computation with memristive implementations, both as accelerators for deep learning and as building blocks for spiking neural networks.
Abstract Ketamine exerts fast acting, robust, and lasting antidepressant effects in a sub-anesthetic dose, however, the underlying mechanisms are still not fully elucidated. Recent studies have ...suggested that ketamine's antidepressant effects are probably attributed to the activation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. The present study aimed to observe the effects of AMPA receptor modulators on mammalian target of rapamycin (mTOR) and brain-derived neurotrophic factor (BDNF) expression during the procedure of ketamine exerting antidepressant effects. Therefore, we pretreated rats with NBQX, an AMPA receptor antagonist, or CX546, an AMPA receptor agonist, and subsequently observed the immobility time during the forced swimming test (FST) and the hippocampal and prefrontal cortical levels of mTOR and BDNF. The results showed ketamine decreased the immobility time of rats during the FST and increased the hippocampal and prefrontal cortical mTOR and BDNF. NBQX pretreatment significantly increased the immobility time and decreased the levels of mTOR and BDNF when compared with vehicle 1 (DMSO) pretreatment. CX546 pretreatment significantly decreased the immobility time and increased the levels of mTOR and BDNF when compared with vehicle 2 (DMSO + ethanol) pretreatment. Our results suggest ketamine-induced antidepressant effects are associated with AMPA receptors-mediated upregulation of mTOR and BDNF in rat hippocampus and prefrontal cortex.
The present work investigates the influence of Mn on the electrochemical corrosion and passivation behaviors of CoFeNiMnCr high-entropy alloys in a 0.1 M H2SO4 solution. Potentiodynamic polarization ...and electrochemical impedance spectroscopy (EIS) results showed that the addition of Mn caused a marked difference in the active dissolution regions and active-passive transition regions. It was deduced from EIS and the potential decay results that the alloyed Mn suppressed the passivation processes and increased the chemical dissolution rate of the passive films. By contrast, the alloyed Mn did not affect the protective properties of the passive films of the alloys. Surface analysis indicated that Mn addition had little influence on the composition and thickness of the passive films. Thus the passivation current densities and transpassive potentials of the CoFeNiMnCr high-entropy alloy remained almost unchanged with the addition of Mn.
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•The addition of Mn degrades general corrosion resistance of CoFeNiMnCr high entropy alloys.•The detrimental effects of Mn were caused by suppression of adsorption of oxygen or OH− and degrade the film stability.•The alloyed Mn does not affect the protective properties of passive film.
Tough adhesives for diverse wet surfaces Li, J.; Celiz, A. D.; Yang, J. ...
Science (American Association for the Advancement of Science),
07/2017, Volume:
357, Issue:
6349
Journal Article
Peer reviewed
Open access
Adhesion to wet and dynamic surfaces, including biological tissues, is important in many fields but has proven to be extremely challenging. Existing adhesives are cytotoxic, adhere weakly to tissues, ...or cannot be used in wet environments. We report a bioinspired design for adhesives consisting of two layers: an adhesive surface and a dissipative matrix. The former adheres to the substrate by electrostatic interactions, covalent bonds, and physical interpenetration. The latter amplifies energy dissipation through hysteresis. The two layers synergistically lead to higher adhesion energies on wet surfaces as compared with those of existing adhesives. Adhesion occurs within minutes, independent of blood exposure and compatible with in vivo dynamic movements. This family of adhesives may be useful in many areas of application, including tissue adhesives, wound dressings, and tissue repair.
Pyruvate kinase isoform M2 (PKM2) is a glycolysis enzyme catalyzing conversion of phosphoenolpyruvate (PEP) to pyruvate by transferring a phosphate from PEP to ADP. We report here that PKM2 localizes ...to the cell nucleus. The levels of nuclear PKM2 correlate with cell proliferation. PKM2 activates transcription of MEK5 by phosphorylating stat3 at Y705. In vitro phosphorylation assays show that PKM2 is a protein kinase using PEP as a phosphate donor. ADP competes with the protein substrate binding, indicating that the substrate may bind to the ADP site of PKM2. Our experiments suggest that PKM2 dimer is an active protein kinase, while the tetramer is an active pyruvate kinase. Expression of a PKM2 mutant that exists as a dimer promotes cell proliferation, indicating that protein kinase activity of PKM2 plays a role in promoting cell proliferation. Our study reveals an important link between metabolism alteration and gene expression during tumor transformation and progression.
► Pyruvate kinase M2 is also a protein kinase ► The tetramer PKM2 is a pyruvate kinase, while the dimer is a protein kinase ► PKM2 regulates gene transcriptions by direct phosphorylation of transcription activators ► The protein kinase activity of PKM2 is important for cell proliferation
The control of domain walls or spin textures is crucial for spintronic applications of antiferromagnets. Despite many efforts, it has been challenging to directly visualize antiferromagnetic domains ...or domain walls with nanoscale resolution, especially in magnetic field. Here, we report magnetic imaging of domain walls in several uniaxial antiferromagnets, the topological insulator MnBi2Te4 family, using cryogenic magnetic force microscopy (MFM). Our MFM results reveal higher magnetic susceptibility inside the domain walls than in domains. Domain walls in these antiferromagnets form randomly with strong thermal and magnetic field dependence. The direct visualization of these domain walls and domain structures in the magnetic field will not only facilitate the exploration of intrinsic topological phenomena in antiferromagnetic topological insulators but will also open a new path toward control and manipulation of domain walls or spin textures in functional antiferromagnets.
Abstract
Front-line epidermal growth factor receptor tyrosine kinase inhibitor (EGFR TKI) therapy is the standard of care for lung cancer patients with sensitising EGFR mutations (exon 19 deletion or ...L858R mutation). Several phase III studies have demonstrated the superiority of gefitinib, erlotinib (first generation of TKIs) or afatinib (second generation) to chemotherapy in progression-free survival and response rates. Drug-related toxicities, such as diarrhoea, acneiform skin rash, mucositis, and paronychia, are frequently encountered in patients who receive EGFR TKIs. Other rare side-effects, such as hepatic impairment and interstitial lung disease, should be identified early and managed carefully. Patients with uncommon EGFR mutations, such as G719X, S768I, and L861Q, may require special selection of EGFR TKIs. The combination of erlotinib plus bevacizumab has been accepted in certain parts of the world as an alternative front-line treatment. This review article summarizes the studies leading to the establishment of EGFR TKIs in EGFR-mutant lung cancer patients. The side-effect profiles of the current EGFR TKIs in these large trials are listed, and the management of uncommon EGFR mutations is discussed. Finally, the potential role of combination front-line treatment is discussed.
•We reviewed common statistical methods for DSSAT model calibration and evaluation.•OLS regression was not suggested for model evaluation if data violate assumptions.•R2 was insensitive to additive ...and proportional differences.•The deviation statistics were suggested for model calibration and evaluation.•Co-variability analysis was carried out using ten field experiments & DSSAT model.
Calibration and evaluation are two important steps prior to the application of a crop simulation model. The objective of this paper was to review common statistical methods that are being used for crop model calibration and evaluation. A group of deviation statistics were reviewed, including root mean squired error (RMSE), normalize-RMSE (nRMSE), mean absolute error (MAE), mean error (E), paired-t, index of agreement (d), modified index of agreement (d1), revised index of agreement (d1′), modeling efficiency (EF) and revised modeling efficiency (EF1). A case study of the statistical evaluation was conducted for the DSSAT Cropping System Model (CSM) using 10 experimental datasets for maize, peanut, soybean, wheat and potato from Brazil, China, Ghana, and the USA. The results indicated that R2 was not a good statistic for model evaluation because it is insensitive to regression coefficients (α and β) of the linear model y=α+βx+ε. However, linear regression can be used for model evaluation (test H0: α=0, β=1) if auto-correlation, normality and heteroskedasticaity of the error term (ε) are tested or the proper data transfers are made. The results also illustrated that statistical evaluation of total dataset across treatments might be insufficient. Hence the evaluation of each treatment is necessary to make the right conclusion, especially when evaluating soil water content under different planting date treatments and soil mineral N under different N treatments. Co-variability analysis among dimensionless statistics (d, d1, d1′, EF and EF1) recommended that d and EF are inflated by the sum of squares-based deviations, i.e., the larger deviations contribute more weight on the statistic than the smaller deviation due to the squared term. However, EF had a larger range and a clear physical meaning at EF=0, making it superior to d. Values of d=0.75 were obtained from regression with all positive values of EF (EF⩾0), indicating that values of d⩾0.75 and EF⩾0 should be the minimum values for plant growth evaluation. Values of d⩾0.60 and EF⩾−1.0 should be the minimum values for soil outputs evaluation combined with t-test due to the fact that the soil parameters in the DSSAT SOIL module are difficult to calibrate compared with plant growth parameters because of no sufficient observed soil dataset. Due to the statistical nature, no single statistic is more robust over others but some statistics are highly correlated. Therefore, several statistics may be used from each of the following correlated groups (RMSE, MAE), (E, t-test), (d, d1, d1′) and (EF, EF1) in one assessment of model evaluation so that a representative statistical conclusion can be obtained with respect to model performance.
Memristive devices are promising candidates to emulate biological computing. However, the typical switching voltages (0.2-2 V) in previously described devices are much higher than the amplitude in ...biological counterparts. Here we demonstrate a type of diffusive memristor, fabricated from the protein nanowires harvested from the bacterium Geobacter sulfurreducens, that functions at the biological voltages of 40-100 mV. Memristive function at biological voltages is possible because the protein nanowires catalyze metallization. Artificial neurons built from these memristors not only function at biological action potentials (e.g., 100 mV, 1 ms) but also exhibit temporal integration close to that in biological neurons. The potential of using the memristor to directly process biosensing signals is also demonstrated.
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