[Show abstract][Hide abstract] ABSTRACT: While the recent theory of compressed sensing or compressive sampling (CS)
provides an opportunity to overcome the Nyquist limit in recovering sparse
signals, a recovery algorithm usually takes the form of penalized least squares
or constraint optimization framework that is different from classical signal
sampling theory. In this paper, we provide a drastically different compressive
sampling framework that can exploit all the benefits of the CS, but can be
still implemented in a classical sampling framework using a digital correction
filter. The main idea is originated from the fundamental duality between the
sparsity in the primary space and the low-rankness of a structured matrix in
the reciprocal spaces, which demonstrates that the low-rank interpolator as a
digital correction filter can enjoy all the optimality of the standard CS. We
show that the idea can be generalised to recover signals in large class of
signals such as piece-wise polynomial, and spline representations. Moreover, by
restricting signal class as cardinal splines, the proposed low-rank
interpolation approach can achieve inherent regularization to improve the noise
robustness. Using the powerful dual certificates and golfing scheme by Gross,
we show that the new framework still achieves the near-optimal sampling rate
for signal recovery. Numerical results using various type of signals confirmed
that the proposed scheme has significant better phase transition than the
conventional CS approaches.
[Show abstract][Hide abstract] ABSTRACT: In our earlier paper dealing with dispersion retrieval from ultra-deep, reactive-ion-etched, slow-wave circuits on silicon substrates, it was proposed that splitting high-aspect-ratio circuits into multilevels enabled precise characterization in sub-terahertz frequency regime. This achievement prompted us to investigate beam-wave interaction through a vacuum-sealed integration with a 15-kV, 85-mA, thermionic, electron gun. Our experimental study demonstrates sub-terahertz, backward-wave amplification driven by an external oscillator. The measured output shows a frequency downshift, as well as power amplification, from beam loading even with low beam perveance. This offers a promising opportunity for the development of terahertz radiation sources, based on silicon technologies.
No preview · Article · Nov 2015 · Applied Physics Letters
[Show abstract][Hide abstract] ABSTRACT: Drug-eluting stents, which are widely used in percutaneous coronary intervention, are fabricated with various considerations, such as drugs, design, polymers, and coating techniques. The aim of this study was to compare tacrolimus-eluting stents (TES), sirolimus-eluting stents (SES) and everolimus-eluting stents (EES) under identical conditions. Poly(lactic-co-glycolic acid) (PLGA) biodegradable polymer was used to coat bare metal stents (Chonnam National University Hospital Stent, CNUH Stent) with the drugs in all fabricating procedures with an ultrasonic stent-coating machine. Surface morphologies of the stents were investigated by scanning electron microscopy. The effect of drugs released from stents on rat smooth muscle and human umbilical vein endothelial cells was examined by MTT assay. The stents were implanted in rabbit iliac arteries randomly, with either TES (n=10), SES (n=10), or EES (n=10). After six weeks of implantation, the stents were isolated and subjected to histopathological analysis. Cell viability decreased in a dose-dependent manner. The surface morphologies of the stents showed a smooth and uniform shape. The release patterns of the stents showed similar profiles over 30 days. There were no significant differences in the injury score, internal elastic lamina, lumenal area, neointimal area, percent area stenosis, and inflammation score among the three groups. However, there was a significant difference in the fibrin score (0.6±0.44 in the TES, vs. 0.8±0.48 in the SES, vs. 0.8±0.61 in the EES, n=10, p<0.05). This study showed that tacrolimus was not inferior to sirolimus (SRL) and everolimus (EVL). Moreover, tacrolimus (TCL) is more effective in decreasing the fibrin score. Therefore, tacrolimus can be a useful alternative drug for fabricating drug-eluting stents.
No preview · Article · Oct 2015 · Macromolecular Research
[Show abstract][Hide abstract] ABSTRACT: Although precisely controlled microdomains of block copolymers (BCP) provide an excellent guiding matrix for multiple nanoparticles (NPs) to be controllably segregated into a desired polymer block, localization and positioning of individual NPs have not been demonstrated. Here, we report a unique one-to-one positioning phenomenon of guest Au NPs in the host BCP microdomains; each of polystyrene-functionalized Au NPs is embedded within the perforation domain of hexagonally perforated lamellar (HPL) morphology of poly(dimethylsiloxane-b-styrene) BCP. The local minimization of free energy achieved by the placement of Au NPs into the center of the perforation domain is theoretically supported by the self-consistent field theory (SCFT) simulation. We propose a novel design principle for more precisely controllable nanocomposites by developing a new route of NP arrangement within a polymer matrix.
[Show abstract][Hide abstract] ABSTRACT: In this paper, we report the effects of O2-plasma treatment on the reliability and electrical properties of indium tin zinc oxide (ITZO) films. Excellent electrical properties, including a saturation mobility (μ sat) of ∼20.2 cm2/V · s, a threshold voltage (V TH) of ∼−6.8 V, a sub-threshold swing (S.S) of ∼0.956 V/decade, and an on/off current ratio (I ON/OFF) of ∼105 can be found with a molarity of 0.4 M and ratio of In:Zn:Sn = 2:1:2. Following O2-plasma treatment, it was confirmed that the electrical properties of the ITZO films are improved when compared to the untreated films. The devices showed a decreased S.S of ∼0.51 V/decade, while the V TH and I ON/OFF tended to increase. To determine the reliability of a-ITZO TFTs, we analyzed the electrical characteristics according to gate bias stress, VG, stress = 10 V for 4000 s. Improved reliability was confirmed when compared with the variation in threshold voltage prior to O2-plasma treatment, most likely stemming from a smooth surface on the active layer as a result of O2-plasma treatment. We were able to obtain a solution a-ITZO film transmittance of 92% in the visible light region (400∼700 nm). These results show that a-ITZO TFTs fabricated via solution process with optimized molar ratio exhibit good electrical properties. a-ITZO films fabricated via spin-coating are a visible alternative to those fabricated via high-cost sputtering methods, and are applicable in flexible and transparent electronics.
No preview · Article · Oct 2015 · Journal of Nanoscience and Nanotechnology
[Show abstract][Hide abstract] ABSTRACT: Background:
Anti-Gal is a major antibody induced in non-human primates (NHPs) after xenotransplantation. To understand the mechanism of graft rejection, we investigated the association between anti-Gal responses and graft failure in NHP recipients of porcine islet transplantation (PITx).
Intraportal PITx was performed in 35 diabetic NHPs, and graft function was monitored. Early graft failure (EGF) was defined as loss of graft function within a month after PITx. Seven, 19, nine NHPs received immunosuppression (IS) without CD40 pathway blockade (Group I), with anti-CD154 (Group II), and with anti-CD40 (Group III), respectively. The anti-Gal levels on day 0 and day 7 of PITx were measured by ELISA.
The frequency of EGF was significantly lower in Group II (26.3%) than in Group I (100%, P=0.0012) and Group III (77.8%, P=0.0166). While levels of anti-Gal IgG in Group I and anti-Gal IgM in Group III increased on day 7 compared with day 0 (P=0.0156 and 0.0273), there was no increase in either on day 7 in Group II. The ratio of anti-Gal IgM or IgG level on day 7 to that on day 0 (Ratio7/0) was significantly higher in recipients with EGF than without EGF (P=0.0009 and 0.0027). ROC curve analysis of anti-Gal IgM Ratio7/0 revealed an area under the curve of 0.789 (P=0.0003).
IS with anti-CD154 suppressed anti-Gal responses and prevented EGF in PITx. Anti-Gal IgM Ratio7/0, being associated with EGF, is a predictive marker for EGF.
Preview · Article · Sep 2015 · Annals of Laboratory Medicine
[Show abstract][Hide abstract] ABSTRACT: Although Arg-Gly-Asp (RGD) motif-containing disintegrins are associated with integrin inhibition and the activation of various biological processes, little is known about the role of RGD motif-containing disintegrin in vascular development and remodeling. We therefore investigated the role of RGD-containing disintegrin in vascular remodeling in oxygen-induced retinopathy (OIR) mouse model.
EGT022, an RGD-containing disintegrin originated from human a disintegrin and metalloproteinase 15 (ADAM15), was used to investigate the role of the disintegrin in vascular development in OIR mouse model. To analyze the functional effects of EGT022 on retinal vascular development, the immunohistochemistry on mouse retinas after fluorescein isothiocyanate (FITC) perfusion was conducted and the vessel integrity was examined using modified Mile's permeability assay.
EGT022 was able to reduce overall retinopathy scores by 75%, indicating its efficacy in retinal microvessel maturation stimulation. Pericyte coverage was greatly stimulated by EGT022 treatment in OIR mouse model. EGT022 was also effective to significantly improve blood vessel integrity.
RGD-containing disintegrin EGT022 stimulated vascular maturation in OIR mouse model. Experimental results suggest that EGT022 is useful for treatments to improve ischemia in nonproliferative diabetic retinopathy (NPDR), the early stage of diabetic retinopathy.
No preview · Article · Jul 2015 · Current eye research
[Show abstract][Hide abstract] ABSTRACT: The discovery of the surface-enhanced Raman scattering (SERS) effect provided a revolutionary solution to the issue of low sensitivity in Raman spectroscopy. For more widespread application of SERS analysis, however, practical fabrication of well-defined ultrasmall nanostructures having large SERS signal enhancement capability and large-area signal uniformity is still a major challenge. Here, we report that rings-in-mesh Au nanostructures, which can be obtained by the consecutive self-assembly of polystyrene nanospheres and block copolymers (BCPs) with far different length scales, provide multiple advantages for SERS analysis in terms of signal amplification and measurement reproducibility. Significant signal enhancement is achieved by the hierarchical geometry composed of a submicrometer nanomesh and sub-10-nm nanogaps, which can be obtained from the self-assembly phenomena of polystyrene nanospheres and siloxane-based BCPs, respectively. Moreover, the two-dimensionally isotropic characteristics of the concentric nanoring structures eliminate the angular dependence of the SERS signal intensity and provide excellent reproducibility of measurement over a large area.
No preview · Article · Jul 2015 · Chemistry of Materials
[Show abstract][Hide abstract] ABSTRACT: Sinus of Valsalva aneurysms are rare. Sinus of Valsalva aneurysms are frequently associated with ventricular septal defect (VSD) and aortic regurgitation. They often remain asymptomatic until abruptly presenting with acute chest pain and heart failure secondary to rupture. Here, we describe a case of 20-year-old man who presented with chest pain with a history of VSD. Initial work-up concluded that the patient had VSD associated membranous septal aneurysm. Four years later, the patient presented with symptoms of heart failure. Work-up showed that the ruptured sinus of Valsalva aneurysm was the cause of symptoms. Due to its close proximity to the aortic annulus, sinus of Valsalva aneurysm should be differentiated from membranous septal aneurysm.
Preview · Article · Jun 2015 · Journal of cardiovascular ultrasound
[Show abstract][Hide abstract] ABSTRACT: As social recognition with respect to safety has recently improved, actions to prevent safety accidents and prepare appropriate measures for them have been actively taken. In particular, children are exposed to crimes such as kidnapping and abduction. To prevent child accidents, studies on smart device-based location tracking technologies have been conducted continuously. However, the global positioning system (GPS) technology used for location tracking cannot detect the location of the target accurately and has security vulnerabilities such as exposure of location information. To solve these problems, we propose an emotion recognition-based child location tracking (ER-CLT) system. The proposed ER-CLT system receives the child's audio data and determines whether the child is in an emergency situation by extracting emotional information from the audio data. The ER-CLT system improves the accuracy of location tracking compared to existing studies and provides secure location tracking functions by using encryption, authentication, integrity, and privacy protection.
No preview · Article · May 2015 · Journal of Internet Technology
[Show abstract][Hide abstract] ABSTRACT: Phase change memory (PCM) is one of the most promising candidates for next-generation non-volatile memory devices due to its high speed, excellent reliability, and outstanding scalability. However, the high switching current of PCM devices has been a critical hurdle to realize low-power operation. Although one solution is to reduce the switching volume of the memory, the resolution limit of photolithography hinders further miniaturization of device dimensions. In this study, we employed unconventional self-assembly geometries obtained from blends of block copolymers (BCPs) to form ring-shaped hollow PCM nanostructures with an ultra-small contact area between a phase-change material (Ge2Sb2Te5) and a heater (TiN) electrode. The high-density (approximately 0.1 terabits per square inch) PCM nanoring arrays showed extremely small switching current of 2 − 3 µA. Furthermore, the relatively small reset current of the ring-shaped PCM compared to the pillar-shaped devices is attributed to smaller switching volume, which is well supported by electro-thermal simulation results. This approach may also be extended to other non-volatile memory device appli-cations such as resistive switching memory and magnetic storage devices, where the control of nanoscale geometry can significantly affect device performances.
Full-text · Article · Apr 2015 · Chemistry of Materials
[Show abstract][Hide abstract] ABSTRACT: Chronic total occlusions (CTOs) are common in patients with peripheral arterial disease (PAD). This study aimed to examine the feasibility and reliability of a CTO induced by a thin biodegradable polymer (polyglycolic acid) coated copper stent in a porcine femoral artery. Novel thin biodegradable polymer coated copper stents (9 mm long) were crimped on an angioplasty balloon (4.5 mm diameter × 12 mm length) and inserted into the femoral artery. Histopathologic analysis was performed 35 days after stenting. In five of six stented femoral arteries, severe in-stent restenosis and total occlusion with collateral circulation were observed without adverse effects such as acute stent thrombosis, leg necrosis, or death at 5 weeks. Fibrous tissue deposition, small vascular channels, calcification, and inflammatory cells were observed in hematoxylin-eosin, Carstair's, and von Kossa tissue stains; these characteristics were similar to pathological findings associated with CTOs in humans. The neointima volume measured by micro-computed tomography was 93.9 ± 4.04 % in the stented femoral arteries. CTOs were reliably induced by novel thin biodegradable polymer coated copper stents in porcine femoral arteries. Successful induction of CTOs may provide a practical understanding of their formation and application of an interventional device for CTO treatment.
Full-text · Article · Apr 2015 · Journal of Materials Science Materials in Medicine
[Show abstract][Hide abstract] ABSTRACT: Flexible memory is the fundamental component for data processing, storage, and radio frequency communication in flexible electronic systems. Among several emerging memory technologies, phase-change random-access memory (PRAM) is one of the strongest candidate for next-generation nonvolatile memories due to its remarkable merits of large cycling endurance, high speed, and excellent scalability. Although there are a few approaches for flexible phase-change memory (PCM), high reset current is the biggest obstacle for the practical operation of flexible PCM devices. In this paper, we report a flexible PCM realized by incorporating nanoinsulators derived from a Si-containing block copolymer (BCP) to significantly lower the operating current of the flexible memory formed on plastic substrate. The reduction of thermal stress by BCP nanostructures enables the reliable operation of flexible PCM devices integrated with ultrathin flexible diodes during more than 100 switching cycles and 1000 bending cycles.
[Show abstract][Hide abstract] ABSTRACT: The multiple measurement vector problem (MMV) is a generalization of the
compressed sensing problem that addresses the recovery of a set of jointly
sparse signal vectors. One of the important contributions of this paper is to
reveal that the seemingly least related state-of-art MMV joint sparse recovery
algorithms - M-SBL (multiple sparse Bayesian learning) and subspace-based
hybrid greedy algorithms - have a very important link. More specifically, we
show that replacing the $\log\det(\cdot)$ term in M-SBL by a rank proxy that
exploits the spark reduction property discovered in subspace-based joint sparse
recovery algorithms, provides significant improvements. In particular, if we
use the Schatten-$p$ quasi-norm as the corresponding rank proxy, the global
minimiser of the proposed algorithm becomes identical to the true solution as
$p \rightarrow 0$. Furthermore, under the same regularity conditions, we show
that the convergence to a local minimiser is guaranteed using an alternating
minimization algorithm that has closed form expressions for each of the
minimization steps, which are convex. Numerical simulations under a variety of
scenarios in terms of SNR, and condition number of the signal amplitude matrix
demonstrate that the proposed algorithm consistently outperforms M-SBL and
other state-of-the art algorithms.
Full-text · Article · Mar 2015 · IEEE Transactions on Signal Processing
[Show abstract][Hide abstract] ABSTRACT: In this paper, we developed a novel molecularly imprinted conducting polymer (MICP) system consisting of porous poly(pyrrole-co-pyrrole-3-carboxylic acid) copolymer matrices for the recognition of theophylline (THEO), a drug molecule. Various porous MICP (p-MICP) films were made using colloidal lithography and examined via gravimetric technique [e.g. gold quartz crystal microbalances (QCMs)]. They showed faster sensing response than a planar MICP film due to the increased THEO binding sites obtained from porous structures. Thus, this lithographical approach to MICP sensors can enable the rebind of a specific template to be increased to achieve improved sensor capacity.
Full-text · Article · Jan 2015 · Sensors and Actuators B Chemical
[Show abstract][Hide abstract] ABSTRACT: Polysaccharide, despite its effect, is hard to apply for coating on stent surface because its own properties such as insoluble in water, fragmentation and deactivation easily. The aim of this study was to optimize the coating conditions for fucoidan on a bare metal stent (BMS), and to evaluate the inhibitory effect of a fucoidan-coated stent on in-stent restenosis (ISR). Three different coating approaches were attempted (designated as multi-layer coating, single-layer coating, and dual coating). Unlike other approaches, it was hard to notice the irregular, blotched or the cracks area in the polymer on the BMS surface in dual coating group. And the release of fucoidan was continued to 24 h and inhibits smooth muscle cell proliferation, when compared to the control, with approximately 42.7% at 3 days and 51.3% at 7 days of culture. In animal study using rabbit iliac artery, histopathological restenosis area were smaller in fucoidan-coated group compared to BMS group (38.6%, p = 0.062 in 148. 9 μg/stent, and 40.6%, p = 0.048 in 250 μg/stent of fucoidan coating group at 4 weeks of post-implantation) and a lower degree of strut coverage were shown in the fucoidan-coated stent group, as compared to the BMS group. These results suggest that dual coating is an appropriate method for fucoidan coating on BMS, and its inhibitory effect can be utilized for the suppression of ISR.
Full-text · Article · Jan 2015 · Progress in Organic Coatings