Silicon nanowire devices

Transport measurements were carried out on 15–35 nm diameter silicon nanowires grown using SiH4 chemical vapor deposition via Au or Zn particle-nucleated vapor-liquid-solid growth at 440°C. Both Al and Ti/Au contacts to the wires were investigated. The wires, as produced, were essentially intrinsic, although Au nucleated wires exhibited a slightly higher conductance. Thermal treatment of the fabricated devices resulted in better electrical contacts, as well as diffusion of dopant atoms into the nanowires, and increased the nanowire conductance by as much as 10^4. Three terminal devices indicate that the doping of the wires is p type

Chronic label-free volumetric photoacoustic microscopy of melanoma cells in scaffolds in vitro

Visualizing cells in three-dimensional (3D) scaffolds has been one of the major challenges in tissue engineering. Current imaging modalities have limitations. Microscopy, including confocal microscopy, cannot penetrate deeply (> 300 μm) into the scaffolds; X-ray micro-computed tomography (micro-CT) requires staining of the structure with a toxic agent such as osmium tetroxide. Here, we demonstrate photoacoustic microscopy (PAM) of the spatial distribution and temporal proliferation of melanoma cells inside three-dimensionally porous scaffolds with thicknesses over 1 mm. Melanoma cells have a strong intrinsic contrast which is easily imaged by label-free PAM with high sensitivity. Spatial distributions of the cells in the scaffold were well-resolved in PAM images. Moreover, we chronically imaged the same cell/scaffold constructs at different time points over 2 weeks. The number of cells in the scaffold was quantitatively measured from the PAM volumetric information. The cell proliferation profile obtained from PAM correlated well with that obtained using the traditional 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. We believe that PAM will become a useful imaging modality for tissue engineering applications, especially when thick scaffold constructs are involved, and that this modality can also be extended to image other cell types labeled with contrast agents

Study on fatigue experiment for transverse butt weldsunder 2G and 3G weld positions

ABSTRACTAlthough the transverse butt weld method with ceramic backing strip has been widely used in various industrial fields for its fabricational convenience, it is rarely used in offshore industries since the fatigue strength of the weld joint has not been proved sufficiently. This study conducted fatigue tests for series of butt weld specimens with horizontal (2G) and vertical (3G) welding positions in order to verify the fatigue strength compared to S-N curve by DNV (Det Norske Veritas), IIW (International Institute of Welding) and Eurocode 3. The difference of the 2G specimens and the 3G specimens are investigated in terms of angular distortion and the effect on the fatigue strength are analyzed

2D perovskite stabilized phase-pure formamidinium perovskite solar cells.

Compositional engineering has been used to overcome difficulties in fabricating high-quality phase-pure formamidinium perovskite films together with its ambient instability. However, this comes alongside an undesirable increase in bandgap that sacrifices the device photocurrent. Here we report the fabrication of phase-pure formamidinium-lead tri-iodide perovskite films with excellent optoelectronic quality and stability. Incorporation of 1.67 mol% of 2D phenylethylammonium lead iodide into the precursor solution enables the formation of phase-pure formamidinium perovskite with an order of magnitude enhanced photoluminescence lifetime. The 2D perovskite spontaneously forms at grain boundaries to protect the formamidinium perovskite from moisture and suppress ion migration. A stabilized power conversion efficiency (PCE) of 20.64% (certified stabilized PCE of 19.77%) is achieved with a short-circuit current density exceeding 24 mA cm-2 and an open-circuit voltage of 1.130 V, corresponding to a loss-in-potential of 0.35 V, and significantly enhanced operational stability

Link Selection Algorithm of UWB Communications Considering Fading Statistics

This paper presents the link selection algorithm of Ultra Wide Band (UWB) communications considering fading statistics. In this algorithm, UWB devices decide the wireless link considering not only received signal strength but also fading statistics. Fading statistics follows the proposed channel model to the existence of line-of-sight (LOS)

Removal of Traumatic Hematic Cyst of the Orbit Through Sub-Brow Approach

Orbital hematic cyst is characterized by cystic accumulation of hematogenous debris surrounded by a wall of fibrous tissue without an epithelial lining. It is a relatively uncommon benign cyst and occurs secondary to blunt trauma in most cases. We experienced a case of 53-year-old male who presented with proptosis of the left eye. A cystic lesion was found at the superolateral orbital rim of the patient. We report a case of orbital hematic cyst that was resected completely through the sub-brow approach

Perovskite-polymer composite cross-linker approach for highly-stable and efficient perovskite solar cells.

Manipulation of grain boundaries in polycrystalline perovskite is an essential consideration for both the optoelectronic properties and environmental stability of solar cells as the solution-processing of perovskite films inevitably introduces many defects at grain boundaries. Though small molecule-based additives have proven to be effective defect passivating agents, their high volatility and diffusivity cannot render perovskite films robust enough against harsh environments. Here we suggest design rules for effective molecules by considering their molecular structure. From these, we introduce a strategy to form macromolecular intermediate phases using long chain polymers, which leads to the formation of a polymer-perovskite composite cross-linker. The cross-linker functions to bridge the perovskite grains, minimizing grain-to-grain electrical decoupling and yielding excellent environmental stability against moisture, light, and heat, which has not been attainable with small molecule defect passivating agents. Consequently, all photovoltaic parameters are significantly enhanced in the solar cells and the devices also show excellent stability

Photoacoustic microscopy of neovascularization in three-dimensional porous scaffolds in vivo

It is a challenge to non-invasively visualize in vivo the neovascularization in a three-dimensional (3D) scaffold with high spatial resolution and deep penetration depth. Here we used photoacoustic microscopy (PAM) to chronically monitor neovascularization in an inverse opal scaffold implanted in a mouse model for up to six weeks. The neovasculature was observed to develop gradually in the same mouse. These blood vessels not only grew on top of the implanted scaffold but also penetrated into the scaffold. The PAM system offered a lateral resolution of ~45 μm and a penetration depth of ~3 mm into the scaffold/tissue construct. By using the 3D PAM data, we further quantified the vessel area as a function of time

Frequency correlation property of Ultra Wideband Channel in Office environments

본 논문은 사무실 환경에서 측정된 초광대역 통신채널의 주파수 응답 사이의 상관관계를 모델링하고 있다. 측정은 주파수 영역에서 회로망 분석기를 바탕으로 한 측정시스템을 통해 이루어졌으며 3개의 서로 다른 사무실 환경의 46개 송, 수신지점에서 총 23,000개의 채널응답이 얻어졌다. 주파수에 따른 채널 이득사이의 상관관계를 나타내는 변수로는 상관계수 (Correlation Coefficient)가 사용되어, 주파수 이격에 따른 상관계수 값의 변화를 가시경로의 존재 유무에 따라 선형 모델로 모델링하였다. 아울러 역푸리에 변환 (Inverse Fast Fourier Transform, IFFT)을 통해 얻어낸 시간영역의 채널응답을 바탕으로 지연함수 값을 얻어내고 그에 따른 연관대역폭 (Coherence bandwidth)을 산출하여 그 결과값을 주파수 영역에서의 결과 값과 비교하였다

The 5'-end transitional CpGs between the CpG islands and retroelements are hypomethylated in association with loss of heterozygosity in gastric cancers

BACKGROUND: A loss of heterozygosity (LOH) represents a unilateral chromosomal loss that reduces the dose of highly repetitive Alu, L1, and LTR retroelements. The aim of this study was to determine if the LOH events can affect the spread of retroelement methylation in the 5'-end transitional area between the CpG islands and their nearest retroelements. METHODS: The 5'-transitional area of all human genes (22,297) was measured according to the nearest retroelements to the transcription start sites. For 50 gastric cancer specimens, the level of LOH events on eight cancer-associated chromosomes was estimated using the microsatellite markers, and the 5'-transitional CpGs of 20 selected genes were examined by methylation analysis using the bisulfite-modified DNA. RESULTS: The extent of the transitional area was significantly shorter with the nearest Alu elements than with the nearest L1 and LTR elements, as well as in the extragenic regions containing a higher density of retroelements than in the intragenic regions. The CpG islands neighbouring a high density of Alu elements were consistently hypomethylated in both normal and tumor tissues. The 5'-transitional methylated CpG sites bordered by a low density of Alu elements or the L1 and LTR elements were hypomethylated more frequently in the high-level LOH cases than in the low-level LOH cases. CONCLUSION: The 5'-transitional methylated CpG sites not completely protected by the Alu elements were hypomethylated in association with LOH events in gastric cancers. This suggests that an irreversible unbalanced decrease in the genomic dose reduces the spread of L1 methylation in the 5'-end regions of genes