Nanogap Device: Fabrication and Applications

A nanogap device as a platform for nanoscale electronic devices is presented. Integrated nanostructures on the platform have been used to functionalize the nanogap for biosensor and molecular electronics. Nanogap devices have great potential as a tool for investigating physical phenomena at the nanoscale in nanotechnology. In this dissertation, a laterally self-aligned nanogap device is presented and its feasibility is demonstrated with a nano ZnO dot light emitting diode (LED) and the growth of a metallic sharp tip forming a subnanometer gap suitable for single molecule attachment. For realizing a nanoscale device, a resolution of patterning is critical, and many studies have been performed to overcome this limitation. The creation of a sub nanoscale device is still a challenge. To surmount the challenge, novel processes including double layer etch mask and crystallographic axis alignment have been developed. The processes provide an effective way for making a suspended nanogap device consisting of two self-aligned sharp tips with conventional lithography and 3-D micromachining using anisotropic wet chemical Si etching. As conventional lithography is employed, the nanogap device is fabricated in a wafer scale and the processes assure the productivity and the repeatability. The anisotropic Si etching determines a final size of the nanogap, which is independent of the critical dimension of the lithography used. A nanoscale light emitting device is investigated. A nano ZnO dot is directly integrated on a silicon nanogap device by Zn thermal oxidation followed by Ni and Zn blanket evaporation instead of complex and time consuming processes for integrating nanostructure. The electrical properties of the fabricated LED device are analyzed for its current-voltage characteristic and metal-semiconductor-metal model. Furthermore, the electroluminescence spectrum of the emitted light is measured with a monochromator implemented with a CCD camera to understand the optical properties. The atomically sharp metallic tips are grown by metal ion migration induced by high electric field across a nanogap. To investigate the growth mechanism, in-situ TEM is conducted and the growing is monitored. The grown dendrite nanostructures show less than 1nm curvature of radius. These nanostructures may be compatible for studying the electrical properties of single molecule

Rampant exchange of the structure and function of extramembrane domains between membrane and water soluble proteins.

Of the membrane proteins of known structure, we found that a remarkable 67% of the water soluble domains are structurally similar to water soluble proteins of known structure. Moreover, 41% of known water soluble protein structures share a domain with an already known membrane protein structure. We also found that functional residues are frequently conserved between extramembrane domains of membrane and soluble proteins that share structural similarity. These results suggest membrane and soluble proteins readily exchange domains and their attendant functionalities. The exchanges between membrane and soluble proteins are particularly frequent in eukaryotes, indicating that this is an important mechanism for increasing functional complexity. The high level of structural overlap between the two classes of proteins provides an opportunity to employ the extensive information on soluble proteins to illuminate membrane protein structure and function, for which much less is known. To this end, we employed structure guided sequence alignment to elucidate the functions of membrane proteins in the human genome. Our results bridge the gap of fold space between membrane and water soluble proteins and provide a resource for the prediction of membrane protein function. A database of predicted structural and functional relationships for proteins in the human genome is provided at sbi.postech.ac.kr/emdmp

Prediction of monthly Arctic sea ice concentrations using satellite and reanalysis data based on convolutional neural networks

Changes in Arctic sea ice affect atmospheric circulation, ocean current, and polar ecosystems. There have been unprecedented decreases in the amount of Arctic sea ice due to global warming. In this study, a novel 1-month sea ice concentration (SIC) prediction model is proposed, with eight predictors using a deep-learning approach, convolutional neural networks (CNNs). This monthly SIC prediction model based on CNNs is shown to perform better predictions (mean absolute error - MAE - of 2.28 %, anomaly correlation coefficient - ACC - of 0.98, root-mean-square error - RMSE - of 5.76 %, normalized RMSE - nRMSE - of 16.15 %, and NSE - Nash-Sutcliffe efficiency - of 0.97) than a random-forest-based (RF-based) model (MAE of 2.45 %, ACC of 0.98, RMSE of 6.61 %, nRMSE of 18.64 %, and NSE of 0.96) and the persistence model based on the monthly trend (MAE of 4.31 %, ACC of 0.95, RMSE of 10.54 %, nRMSE of 29.17 %, and NSE of 0.89) through hindcast validations. The spatio-temporal analysis also confirmed the superiority of the CNN model. The CNN model showed good SIC prediction results in extreme cases that recorded unforeseen sea ice plummets in 2007 and 2012 with RMSEs of less than 5.0 %. This study also examined the importance of the input variables through a sensitivity analysis. In both the CNN and RF models, the variables of past SICs were identified as the most sensitive factor in predicting SICs. For both models, the SIC-related variables generally contributed more to predict SICs over ice-covered areas, while other meteorological and oceanographic variables were more sensitive to the prediction of SICs in marginal ice zones. The proposed 1-month SIC prediction model provides valuable information which can be used in various applications, such as Arctic shipping-route planning, management of the fishing industry, and long-term sea ice forecasting and dynamics

6.4 GHz Acoustic Sensor for In-situ Monitoring of AFM Tip Wear

This paper demonstrates an acoustic sensor that can resolve atomic force microscopy (AFM) tip blunting with a frequency sensitivity of 0.007%. The AFM tip is fabricated on a thin film piezoelectric aluminum nitride (AlN) membrane that is excited as a film bulk acoustic resonator (FBAR). We demonstrate that cutting 0.98 μm off of the tip apex results in a resonance frequency change of 0.4MHz at 6.387GHz. This work demonstrates the potential for in-situ monitoring of AFM tip wear

Value Discount of Business Groups Surrounding the Asia Financial Crisis: Evidence from Korean Chaebols

Asian Financial Crisis, Business Group, Chaebol, Diversification, Firm Value

A Suspended Nanogap Formed by Field-Induced Atomically Sharp Tips

A sub-nanometer scale suspended gap (nanogap) defined by electric field-induced atomically sharp metallic tips is presented. A strong local electric field (\u3e109 V=m) across micro/nanomachined tips facing each other causes the metal ion migration in the form of dendrite-like growth at the cathode. The nanogap is fully isolated from the substrate eliminating growth mechanisms that involve substrate interactions. The proposed mechanism of ion transportation is verified using real-time imaging of the metal ion transportation using an in situ biasing in transmission electron microscope (TEM). The configuration of the micro/nanomachined suspended tips allows nanostructure growth of a wide variety of materials including metals, metal-oxides, and polymers. VC 2012 American Institute of Physics

A Novel Batch-Processing Method for Accurate Crystallographic Axis Alignment

A new method for the accurate alignment of lithographically-defined patterns to the crystallographic axes of substrates is presented. We provide a lower (worst-case) limit of the achievable high aspect ratio using anisotropic wet chemical silicon etch for deep trenches. The method uses the fact that the intensity of light reflected from two sets of gratings, one on the photomask and the other on the substrate, is a sharp function of their relative angular misalignment. By using pre-etched gratings on the substrate formed by wet anisotropic etching, alignment accuracies better than 50 millidegrees with respect to silicon crystallographic axes have been demonstrated. Two types of microstructures—trenches with an aspect ratio \u3e90:1 and silicon nanowires with widthsfacets—have been fabricated using i-line lithography to illustrate some applications of this alignment method. This all-optical method is readily applicable to industry-standard optical lithography and avoids the need for any individualized process steps, enabling cost-effective micro/nanostructure manufacturing

Nano-electromechanical Zero-dimensional Freestanding Nanogap Actuator

Micromachined free standing nanogap with metal electrodes is presented. The gap size is as small as 17 nm, and can be reduced further with electrostatic or piezoelectric actuation. The nanoscale gap is fabricated by industrial standard optical lithography and anisotropic wet chemical Si etching. Electron transport between the metal electrodes with optical stimulus enhancing photon-electron coupling (plasmon) is presented

Conservative Management of Spontaneous Isolated Dissection of the Superior Mesenteric Artery

Purpose. We report the clinical outcomes of patients with spontaneous isolated dissection of the superior mesenteric artery (SIDSMA) who were treated conservatively. Materials and Methods. A retrospective review was performed in 14 patients from 2006 to 2016 with SIDSMA. Their clinical features and computed tomographic angiography (CTA) characteristics, treatment methods, and clinical outcomes were analyzed. The mean age was 53.6 (range, 41–73) years, and the mean follow-up duration was 20.6 (range, 1–54) months. Conservative management was the primary treatment if no bowel ischemia or arterial rupture was noted. Results. The mean initial abdominal visual analog pain score was 7 (range, 5–9) in seven patients. The mean total duration of abdominal pain was 10.2 days (range, 2–42 days) in 10 patients. The mean percentage stenosis of the dissected SMA at the initial presentation was 78.8% in 14 patients. Complete obstruction of the SMA at the initial presentation was evident in 4 of the 14 patients (28.6%). Conservative management was successful in all 14 patients. None of the 14 patients developed bowel ischemia or an infarction. Abdominal pain did not recur in any patient during follow-up (mean, 20.6 months; range, 1–54 months). Conclusion. Conservative management was successful for all SIDSMA patients, even those with severe compression of the true lumen or complete obstruction of the dissected SMA

PPM1A Controls Diabetic Gene Programming through Directly Dephosphorylating PPAR?? at Ser273

Peroxisome proliferator-activated receptor gamma (PPAR gamma) is a master regulator of adipose tissue biology. In obesity, phosphorylation of PPAR gamma at Ser273 (pSer273) by cyclin-dependent kinase 5 (CDK5)/extracellular signal-regulated kinase (ERK) orchestrates diabetic gene reprogramming via dysregulation of specific gene expression. Although many recent studies have focused on the development of non-classical agonist drugs that inhibit the phosphorylation of PPAR gamma at Ser273, the molecular mechanism of PPAR gamma dephosphorylation at Ser273 is not well characterized. Here, we report that protein phosphatase Mg2+/Mn2+-dependent 1A (PPM1A) is a novel PPAR gamma phosphatase that directly dephosphorylates Ser273 and restores diabetic gene expression which is dysregulated by pSer273. The expression of PPM1A significantly decreases in two models of insulin resistance: diet-induced obese (DIO) mice and db/db mice, in which it negatively correlates with pSer273. Transcriptomic analysis using microarray and genotype-tissue expression (GTEx) data in humans shows positive correlations between PPM1A and most of the genes that are dysregulated by pSer273. These findings suggest that PPM1A dephosphorylates PPAR gamma at Ser273 and represents a potential target for the treatment of obesity-linked metabolic disorders