• 한국축산식품학회지
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• 제37권1호
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• pp.79-86
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• 2017

Aflatoxin $M_1$ ($AFM_1$) after its bioconversion from aflatoxin $B_1$ in animal liver becomes the part of milk while heavy metals get entry into milk and milk products during handling in the supply chain. Aflatoxin $M_1$ and heavy metals being toxic compounds are needed to be monitored continuously to avoid any ailments among consumers of foods contaminated with such toxicants. Thirteen commercially available infant formula milk (IFM) brands available in Pakistani markets were analyzed for the quantitative determination of $AFM_1$ and heavy metals through ELISA and atomic absorption spectrophotometer, respectively. $AFM_1$ was found positive in 53.84% samples while 30.76% samples were found exceeding the maximum EU limit i.e. $0.025 {\mu}g/kg$ for $AFM_1$ in IFM. Heavy metals lead (Pb) and cadmium (Cd) were found below the detection limits in any of the sample, whereas the concentrations of iron (Fe), zinc (Zn) and nickel (Ni) ranged between 45.40-97.10, 29.72-113.50 and <$0.001-50.90 {\mu}g/kg$, respectively. The concentration of Fe in all the tested brands was found in normal ranges while the concentrations of Zn and Ni were found exceeding the standard norms. Elevated levels of $AFM_1$, Zn and Ni in some of the tested IFM brands indicated that a diet completely based on these IFM brands might pose sever health implications in the most vulnerable community i.e., infants.

• 한국진공학회지
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• 제12권4호
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• pp.257-262
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• 2003

n-type과 p-type 다공성 실리콘 (PS)의 구조에 따른 광학적 및 전기적 특성을 조사하였다. 먼저 화학적 에칭에 의하여 다공성 실리콘 시편을 준비했다. 이 시편의 미세구조의 특징을 주로 SEM, AFM, XRD 분석에 의하여 관찰하였으며 그들의 광학적 화학적 특성을 PL과 FTIR을 통해 측정하였다. n-type다공성 실리콘의 상온 PL파장은 p-type 다공성 실리콘이 남색 영역 (400-650 nm)임에 반해 500-650 nm로 이동함을 알 수 있었다. 또한 PS층 위에 ∼40 nm 두께의 반투명한 Cu박막을 rf 스퍼터링법으로 증착하여 PS내의 pore를 Cu로 충전한 시편의 I-V 특성과 EL 특성을 관찰했다.

• 센서학회지
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• 제19권3호
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• pp.214-220
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• 2010

Three-dimensional(3D) structure of specific DNA can be changed between two conformations under an external environmental transition such as pH and salt concentration variations. We have experimentally observed the conformational transitions of i-motif DNA using AFM cantilever bioassay. It is shown that pH change of a solvent induces the bending defleciton change of a cantilever functionalized by i-motif DNA. This indicates that cantilever bioassay enables the label-free detection of DNA structural changes upon pH change. It is implied that cantilever bioassay can be a de novo route to quantitatively understand the conformational transitions of biological molecules under environmental changes.

• Journal of Electrical Engineering and Technology
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• 제5권4호
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• pp.640-645
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• 2010

This paper describes the power generating property of hydrothermally grown ZnO nanorods on a flexible polyethersulfone (PES) substrate. The piezoelectric currents generated by the ZnO nanorods were measured when bending the ZnO nanorod by using I-AFM, and the measured piezoelectric currents ranged from 60 to 100 pA. When the PtIr coated tip bends a ZnO nanorod, piezoelectrical asymmetric potential is created on the nanorod surface. The Schottky barrier at the ZnO-metal interface accumulates elecntrons and then release very quickly generating the currents when the tip moves from tensile to compressed part of ZnO nanorod. These ZnO nanorods were grown almost vertically with the length of 300-500 nm and the diameter of 30-60 nm on the Ag/Ti/PES substrate at $90^{\circ}C$ for 6 hours by hydrothermal method. The metal-semiconductor interface property was evaluated by using a HP 4145B Semiconductor Parameter Analyzer and the piezoelectric effect of the ZnO nanorods were evaluated by using an I-AFM. From the measured I-V characteristics, it was observed that ZnO-Ag and ZnO-Au metal-semiconductor interfaces showed an ohmic and a Schottky contact characteristics, respectively. ANSYS finite element simulation was performed in order to understand the power generation mechanism of the ZnO nanorods under applied external stress theoretically.

• 한국정밀공학회지
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• 제25권10호
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• pp.41-47
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• 2008

This study aims to obtain machining characteristics during AFM (Atomic force Microscope) machining of silicon wafers and to monitor the machining states using acoustic emission. As in micro scale machining, two distinct regimes of deformation, i. e. ploughing regime and cutting regime were observed. First, the transition between the two regimes are investigated by analyzing the "pile-up" during machining. As far as in process monitoring is concerned, in the ploughing repime, no chips have been formed and related AE RMS values are relatively low, In the mean time, in the cutting regime, the RMS values are significantly higher than the ploughing regime, with apparent chip formation. From the results, we found out that the proposed scheme can be used for the monitoring of nanomachining, especially for the characterization of nanocutting mode transition.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권2호
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• pp.1333-1335
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• 2007

We studied the surface defects and the current distributions of ITO thin films by reflected electron energy loss spectroscopy (REELS) and conductiveatomic force microscope (c-AFM). The ohmic behavior of ITO thin film was observed at $230\;^{\circ}C$ annealed sample. The defects related to the electronic structure decreased after anneal process.

• Transactions on Electrical and Electronic Materials
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• 제5권4호
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• pp.143-147
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• 2004

Surface defects and bulk defects on SOI wafers are studied. Two new metrologies have been proposed to characterize surface and bulk defects in epitaxial layer transfer (ELTRAN) wafers. They included the following: i) laser scattering particle counter and coordinated atomic force microscopy (AFM) and Cu-decoration for defect isolation and ii) cross-sectional transmission electron microscope (TEM) foil preparation using focused ion beam (FIB) and TEM investigation for defect morphology observation. The size of defect is 7.29 urn by AFM analysis, the density of defect is 0.36 /cm$^2$ at as-direct surface oxide defect (DSOD), 2.52 /cm$^2$ at ox-DSOD. A hole was formed locally without either the silicon or the buried oxide layer (Square Defect) in surface defect. Most of surface defects in ELTRAN wafers originate from particle on the porous silicon.

• Progress in Superconductivity
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• 제9권2호
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• pp.127-135
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• 2008

We study the effects of phonon interaction on the superconducting pairing in the high $T_c$ superconductors (HTSC). Using coupled BCS gap equations, we found that phonon interaction can induce a s-wave component to the d-wave gap, mediated by Antiferromagnetic (AFM) spin fluctuations, in the (D+iS) form. However, $T_c$ is not enhanced compared to the pure d-wave pairing without phonon interaction. On the other hand, anisotropic phonon interaction can dramatically enhance the d-wave pairing and $T_c$ itself, together with the AFM spin fluctuation interaction. This ($D_{AFM}+D_{ph}$) type pairing exhibits strongly reduced isotope coefficient despite the large enhancement of $T_c$ by phonon interaction.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.1391-1395
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• 2006

In non-contact mode atomic force microscopy, the response of a resonating tip is used to measure the nanoscale topography and other properties of a sample surface. However, the tip-surface interactions can affect the tip response and destabilize the non-contact mode control. Especially it is difficult to obtain a good scanned image of high adhesion surfaces such as polymers using conventional hard NCHR tip and non-contact mode control. In this study, experimental investigation is made on the non-contact mode imaging and we report the microcantilever having low stiffness (OMCL) is useful to measure the properties of samples such as elasticity. In addition, we proved that it was adequate to use low stiffness microcantilever to obtain a good scanned image in AFM for the soft and high adhesion sample.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.320-323
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• 2000

We attempted to fabricate polyurethane derivatives (PU-CN, PU-DCM) LB films by using LB method. Also, we investigated the monolayer behavior at the air-water interface by surface pressure-area ($\pi$-A) isotherms. And, the surface morphologies and the physicochemical properties of LB films were investigated by atomic force microscopy (AFM) and UV-vis spectroscopy, respectively. Also, the electrical properties of polyurethane derivatives LB films were investigated by using the conductivity and the dielectric constant. In the AFM images, we conclude that surface morphology of PU-DCM LB films is smooth and homogeneous and has optimal hydrophobicity and good stability, whereas PU-CN LB films give rougher surfaces with more excess material. In the I-V characteristics, the conductivity is different as to the polyurethane derivatives, it is considered that this phenomena could be described by the difference of lumophore pendant which was adhered at PU main chain.