Tip-Enhanced Raman Scattering Imaging of Two-Dimensional Tungsten Disulfide with Optimized Tip Fabrication Process

We successfully achieve the tip-enhanced nano Raman scattering images of a tungsten disulfide monolayer with optimizing a fabrication method of gold nanotip by controlling the concentration of etchant in an electrochemical etching process. By applying a square-wave voltage supplied from an arbitrary waveform generator to a gold wire, which is immersed in a hydrochloric acid solution diluted with ethanol at various ratios, we find that both the conical angle and radius of curvature of the tip apex can be varied by changing the ratio of hydrochloric acid and ethanol. We also suggest a model to explain the origin of these variations in the tip shape. From the systematic study, we find an optimal condition for achieving the yield of similar to 60% with the radius of similar to 34 nm and the cone angle of similar to 35 degrees. Using representative tips fabricated under the optimal etching condition, we demonstrate the tip-enhanced Raman scattering experiment of tungsten disulfide monolayer grown by a chemical vapor deposition method with a spatial resolution of similar to 40 nm and a Raman enhancement factor of similar to 4,760. © The Author(s) 2017

Pt/Ti/Al2O3/Al tunnel junctions showing electroforming-free bipolar resistive switching behavior

We investigated electroforming-free bipolar resistive switching behavior in Pt/Ti/Al2O3/Al tunnel junctions where the Al2O3 tunnel barrier was naturally formed on Al in air. Various compliance current values for the junction's set switching successfully lead to various resistance values in its low resistance state, suggesting the possibility for multi-level-operation. A mechanism for the bipolar switching is qualitatively discussed in terms of the modulation of the tunnel barrier by the reactive Ti layer on top of the barrier

Training Spiking Neural Networks Using Lessons From Deep Learning

The brain is the perfect place to look for inspiration to develop more efficient neural networks. The inner workings of our synapses and neurons provide a glimpse at what the future of deep learning might look like. This paper serves as a tutorial and perspective showing how to apply the lessons learnt from several decades of research in deep learning, gradient descent, backpropagation and neuroscience to biologically plausible spiking neural neural networks. We also explore the delicate interplay between encoding data as spikes and the learning process; the challenges and solutions of applying gradient-based learning to spiking neural networks; the subtle link between temporal backpropagation and spike timing dependent plasticity, and how deep learning might move towards biologically plausible online learning. Some ideas are well accepted and commonly used amongst the neuromorphic engineering community, while others are presented or justified for the first time here. A series of companion interactive tutorials complementary to this paper using our Python package, snnTorch, are also made available: https://snntorch.readthedocs.io/en/latest/tutorials/index.htm

Association between baseline smoking status and clinical outcomes following myocardial infarction

BackgroundWhether the effect of smoking on clinical outcomes following an acute myocardial infarction (AMI) is beneficial or detrimental remains inconclusive. We invesetigated the effect of smoking on the clinical outcomes in patients following an AMI.MethodsAmong 13,104 patients between November 2011 and June 2015 from a nationwide Korean AMI registry, a total of 10,193 participants were extracted then classified into two groups according to their smoking habit: (1) smoking group (n = 6,261) and (2) non-smoking group (n = 3,932). The participants who smoked were further subclassified according to their smoking intensity quantified by pack years (PYs): (1) <20 PYs (n = 1,695); (2) 20–40 PYs (n = 3,018); and (3) ≥40 PYs (n = 2,048). Each group was compared to each other according to treatment outcomes. The primary outcome was the incidence of major adverse cardiac and cerebrovascular events (MACCEs), which is a composite of all-cause mortality, non-fatal MI (NFMI), any revascularization, cerebrovascular accident, rehospitalization, and stent thrombosis. Secondary outcomes included the individual components of MACCEs. The Cox proportional hazard regression method was used to evaluate associations between baseline smoking and clinical outcomes following an AMI. Two propensity score weighting methods were performed to adjust for confounders, including propensity score matching and inverse probability of treatment weighting.ResultsWhile the incidence of all clinical outcomes, except for stent thrombosis, was lower in the smoking group than in the non-smoking group in the unadjusted data, the covariates-adjusted data showed statistical attenuation of these differences but a higher all-cause mortality in the smoking group. For smokers, the incidence of MACCEs, all-cause mortality, cardiac and non-cardiac death, and rehospitalization was significantly different between the groups, with the highest rates of MACCE, all-cause mortality, non-cardiac death, and rehospitalization in the group with the highest smoking intensity. These differences were statistically attenuated in the covariates-adjusted data, except for MACCEs, all-cause mortality, and non-cardiac death, which had the highest incidence in the group with ≥40 PYs.ConclusionSmoking had no beneficial effect on the clinical outcomes following an AMI. Moreover, for those who smoked, clinical outcomes tended to deteriorate as smoking intensity increased

Enhanced efficiency of crystalline Si solar cells based on kerfless-thin wafers with nanohole arrays

Several techniques have been proposed for kerfless wafering of thin Si wafers, which is one of the most essential techniques for reducing Si material loss in conventional wafering methods to lower cell cost. Proton induced exfoliation is one of promising kerfless techniques due to the simplicity of the process of implantation and cleaving. However, for application to high efficiency solar cells, it is necessary to cope with some problems such as implantation damage removal and texturing of (111) oriented wafers. This study analyzes the end-of-range defects at both kerfless and donor wafers and ion cutting sites. Thermal treatment and isotropic etching processes allow nearly complete removal of implantation damages in the cleaved-thin wafers. Combining laser interference lithography and a reactive ion etch process, a facile nanoscale texturing process for the kerfless thin wafers of a (111) crystal orientation has been developed. We demonstrate that the introduction of nanohole array textures with an optimal design and complete damage removal lead to an improved efficiency of 15.2% based on the kerfless wafer of a 48 mu m thickness using the standard architecture of the Al back surface field

Comparison of short-term clinical outcomes between Resolute Onyx zotarolimus-eluting stents and everolimus-eluting stent in patients with acute myocardial infarction: Results from the Korea Acute Myocardial infarction Registry (KAMIR)

Background: There are few studies which compare the efficacy and safety of the Resolute Onyx zotarolimus-eluting stent (O-ZES) and everolimus-eluting stent (EES) in patients with acute myocardial infarction (AMI). Therefore, the present study aimed to compare clinical outcomes of O-ZES and EES in patients with AMI undergoing successful percutaneous coronary intervention (PCI). Methods: From January 2016 to December 2016, the Korea Acute Myocardial Infarction Registry (KAMIR) enrolled 3,364 consecutive patients. Among them, O-ZES was used in 402 patients and EES was used in 1,084 patients. The primary endpoint was target lesion failure (TLF), as defined by composite of cardiac death, target vessel myocardial infarction (TV-MI), and ischemic driven-target lesion revascularization (ID-TLR) at 6 month clinical follow-up. Results: At 6 months, the incidence of TLF was not significantly different between O-ZES and EES group (4.0% vs. 3.9%, adjusted hazard ratio [HR] 1.17, 95% confidential interval [CI] 0.58–2.35, p = 0.665). O-ZES also showed similar results of cardiac death (3.7% vs. 3.4%, adjusted HR 1.25, 95% CI 0.59–2.63, p = 0.560), TV-MI (0.2% vs. 0.6%, adjusted HR 0.56, 95% CI 0.07–4.85, p = 0.600), ID-TLR (0.0% vs. 0.3%, p = 0.524), and definite or probable stent thrombosis (0.2% vs. 0.3%, adjusted HR 0.63, 95% CI 0.06–6.41, p = 0.696) when compared with EES. Conclusions: The present study shows that implantation of O-ZES or EES provided similar clinical outcomes with similar risk at 6-month of TLF and definite/probable ST in patients with AMI undergoing successful PCI