2008.4
About Instruments Today No. 163
Magnetic Resonance Imaging: Basic to Advance
Magnetic Resonance Imaging: The Basic Theory and Pulse Sequence [ 下載 PDF ]
Ching-nien Chen
Magnetic resonance imaging (MRI) has been developed into an important clinical and diagnostic modality in recent years. It is well accepted by most patients. The article introduces fundamentals of MRI in plain language and illustration figures without cumbersome mathematics and physics. It serves as an introduction of MRI to scientists and the interested general public.
In Vivo Nuclear Magnetic Resonance Spectroscopy [ 下載 PDF ]
Lou-sing Kan
The in vivo nuclear magnetic resonance spectroscopy (NMR) is similar to that of the traditional one except special attention is needed for live samples (living cells and tissues) to ensure their vitality. The proton relaxation times T1 and T2 of cellular fluid of normal cells are different from those of cancerous ones. They can be used as markers of aging in gerontology studies. The T1- and T2- weighted MR images are also constantly being used to aid in MRI clinical diagnostics. The phorphorus-31 NMR is used to monitor the P containing chemicals in cells and tissues. Cellular pH values can be derived from the chemical shift values of the phosphoric acid in cells.
Diffusion MRI: Concept and Its Applications [ 下載 PDF ]
Ching-Po Lin, Pin-Yi, Chiang, Yi-Ping Chao
Molecular diffusion is a physical process due to random translational motion, namely Brownian motion, of molecules with non-zero thermal energy. As the Brownian motion is subject to the surrounding environment, its tract and distribution will reflect the corresponding microstructures. Accordingly, one may use diffusion MRI of water molecules, abundantly supplied in biological tissues, as endogenous probes of subtle brain architecture, such as neuronal integrity, neuronal orientation, and tissue characteristics. Because of its non-invasive feature, diffusion MRI has been applied to the field of neuroscience and used for clinical diagnosis with increasing importance.
Functional Magnetic Resonance Imaging of Human Brain: How to Listen the Brain Symphony [ 下載 PDF ]
Tzu-chen Yeh
Through the use of magnetic resonance imaging (MRI) technique the visual cortices were successfully detected in 1990 by measuring the changes of cerebral blood volumes before and after visual stimulations. Over the years, the technique has evolved into a non-invasive technique, called functional MRI (fMRI), in which the contrast comes from regional changes in endogenous deoxyhemoglobin, cerebral blood flow and/or cerebral blood volume during the stimulation processes. Nowadays, neuro-radiologists often employ the 'pre-surgical brain mapping' by fMRI methods for patients with indications of brain surgery. In this article, an overview of fMRI and the associated image processing interface will be given by introducing the 'performance of a brain symphony'. We hope it can benefit relevant research and applications of local scientists.
Scattering-Type Scanning Near-Field Optical Microscopy—Optical Characterization in sub-10 nm Scale [ 下載 PDF ]
Jen-You Chu, Tien-Jen Wang, You-Chia Chang, Jyi-Tian Yeh, Juen-Kai Wang
The resolution of classical optical microscopy is limited by optical diffraction and cannot reach nanometer scale. Although aperture-type scanning near-field microscopy can overcome this limitation, its spatial resolution is limited to 50 nm and its optical throughput decreases drastically with the decrease in the aperture size, obstructing its application in nanometer-scaled characterization. We have developed an interferometric scattering-type scanning near-field optical microscope which owns a sub-10 num resolution. This microscope takes advantage of the nanometer-scaled tip apex of an atomic force microscope to enhance the localized field between the tip apex and sample. Taking advantage of heterodyne, modulation and optical design technique, it has the ability to record topography, near-field optical and phase artifact-free images at multiple laser wavelengths simultaneously. This technique is highly promising for nanoscaled optical characterization and for mapping out the local field distribution around nanostructures. It is expected that this instrument can make significant contribution to the development of nanoscience and nanotechnology.
Applications of Scanning Near-Field Microscope and Confocal Raman Spectrum on Photovoltaic Devices [ 下載 PDF ]
Yu-Ching Huang, You-Chia Liao, Jui-Hung Hsu, Tsung-Han Lin, Ming-Chung Wu, Wei-Fang Su
The optical diffraction limits the spatial resolution of conventional optical microscope at nanoscale. The development of scanning near-field optical microscope (SNOM) has resolved this limitation and exhibited the ability of imaging with nano-scale resolution. The SNOM has become a popular technique to observe the optical properties of nano-scaled materials. Comparing with traditional Raman spectrum, the confocal Raman spectrum provides optical and chemical mapping capability with high resolution. In this article, we discuss the studies of polymer nanoparticle hybrid materials for photovoltaic devices using these two techniques. The SNOM was used to investigate the nanoscale optical properties of the hybrid material. The confocal Raman spectrum was used to evaluate the morphology change and component distribution.
CMOS-MEMS Micromechanical Resonators [ 下載 PDF ]
Ching-Liang Dai, Pin-Hsu Kao
Filters become important electronic components as electronic industry develops rapidly. Resonators are often applied as filters. In this article, we present the development of resonators and describe two kinds of micro resonators, which are micromechanical tunable resonator and high frequency micromechanical resonator fabricated by our research team. The principle, simulation and experiment of the resonators will be investigated in this paper. Experiments show that the micromechanical tunable resonator has a resonant frequency of 4.8 kHz and a Q-factor of 500, and the tunable-range of resonant frequency is about 6.8% at the tuning voltage of 0–25 V. On the other hand, the high frequency micromechanical resonator has a resonant frequency of 39.5 MHz. and a Q-factor of 806.
Applications of Gas Chromatography in Air Pollutant Analysis [ 下載 PDF ]
Chieh-Heng Wang, Chang-Feng Ou Yang, Jia-Lin Wang
This paper discusses the applications of gas chromatography (GC) in air pollutant analysis. Because of the large vapor pressure, high volatility, and, hence, the gaseous nature of organic air pollutants, GC inherited with powerful separation capability and a large selection of detection methods is particularly suited for analyzing these species in the ambient air. Depending on the abundance of an air pollutant, either constant pressure-volume sample loop injection or on-line enrichment method can be coupled with a commercially available GC, interfaced by automation software and hardware, to perform automated analysis. By doing so, several systems have been developed in our laboratory to monitor air pollutants such as: CO, CH4, chlorofluorocarbons (CFCs), perfluorocarbons (PFCs), as well as volatile organic compounds (VOCs). These air pollutants measured by the techniques discussed are significant to the environmental issues ranging from indoor air quality, smog formation, ozone depletion, as well as green house effect.
The Electrical Circuit Design of Optoelectronic Eyeglasses [ 下載 PDF ]
Yu-Chieh Chen
Optoelectronic Eyeglasses is a supplementary apparatus which consists of head-type display and CCD module. With image processing technology, the image can be enhanced and displayed at the front of the user's eye. Therefore, the drawbacks of optical eyeglasses can be overcome using the above described novel technology. Because real-time image processing is highly essential for Optoelectronic Eyeglasses, FPGA (field programmable gate array), which is multifunctional and can operate at high frequencies, is employed for the implementation of Optoelectronic Eyeglasses. This manuscript uses Optoelectronic Eyeglasses as an example to demonstrate how to employ FPGA for performing color processing on RGB raw data, displaying images on LCOS (liquid crystal on silicon), and examining high-frequency parameters of signal wires.
Continuous Particle Separation by Evaporation Force [ 下載 PDF ]
Da-Jeng Yao, Po-Yu Chen
When the size of object shrunk down to micro scale, some physical characteristics could be applied to biotechnology because of scale effects. This paper has put forward a brand-new conceptions, utilizes evaporating force and structural design to separate particles naturally. Laminar flow characteristics of microfluidic system is used to separate particles. The principle to drive liquid in microfluidic system is evaporation force which idea came from plants. The evaporating region similar to vents of plants was designed at the end of microchannel to drive liquid spontaneously. The samples with and without particles, were injected into fluidic system, and particles in the flow were fixed on each layer of laminar flow. The particles, flow into separating region, moved with streamline cross theirs center to different branches. Thus, different size of particles could be separated spontaneously.
Development of Micro-Electro-Mechanical System Technology for High-Power Light-Emitting Diode Applications [ 下載 PDF ]
Ray-Hua Horng
This paper describes how to introduce the micro-electro-mechanical system (MEMS) technology to the LEDs fabrication process for high-power LEDs application. It contains the wafer bonding, electroplating, mirror processing and surface roughening techniques. Using these MEMS technologies, the epitaxial growth substrate can be replaced by the transparent substrate or the substrate with mirror and high thermal dissipassion. It can result in LEDs with high power and high efficiency for the applications of backlight and solid state lighting.
