Biomedical subjects

Cheng-Chung Lee

Publications and source records attributed to Cheng-Chung Lee.

At least 19 recordsLinked to original sources

PubMed2007

A microfluidic platform for sequential ligand labeling and cell binding analysis.

Developing biochemical and cell biological assay for screening biomolecules, evaluating their characteristics in biological processes, and determining their pharmacological effects represents a key technology in biomedical research. A PDMS-based integrated microfluidic platform was fabricated and tested for facilitating the labeling of ligand on the nanogram scale and sequential cell binding analysis in a manner that saves both time and reagents. Within this microfluidic platform, ligand labeling, cell immobolization, and optical analysis are performed in a miniaturized, continuous and semi-automated manner. This microfluidic device for ligand labeling and cell analysis is composed of two functional modules: (i) a circular reaction loop for fluorophore-labeling of the ligand and (ii) four parallel-oriented incubation chambers for immobilization of cells, binding of ligand to different cell populations, and optical evaluation of interactions between the labeled ligand and its cell targets. Epidermal growth factor (EGF) as the ligand and different cell lines with various levels of EGF receptor expression have been utilized to test the feasiblity of this microfluidic platform. When compared to studies with traditional Petri dish handling of cells and tissues, or even microwell analyses, experiments with the microfluidic platform described here are much less time consuming, conserve reagents, and are programmable, which makes these platforms a very promising new tool for biological studies.

Animals↗

PubMed2006

TiO2--Ta2O5 composite thin films deposited by radio frequency ion-beam sputtering.

TiO2--Ta2O5 composite films were prepared by a radio frequency ion-beam sputtering deposition process, and the refractive indices and extinction coefficients of the composite films were found to be between those of the TiO2 and Ta2O5 films. The structure of the as-deposited films was amorphous, and the surface roughness was approximately 0.1 nm. The residual stress of the composite films was less than that of pure TiO2 film. The structure of the composite films after annealing was amorphous, with low surface roughness and slightly increased residual stress. The film containing 6.3% TiO2 displayed better properties than either the pure TiO2 or the pure Ta2O5 film.

Journal Article↗

PubMed2006

Solvent resistant microfluidic DNA synthesizer.

We fabricated a microfluidic DNA synthesizer out of perfluoropolyether (PFPE), an elastomer with excellent chemical compatibility which makes it possible to perform organic chemical reactions, and synthesized 20-mer oligonucleotides on chip.

Chromatography, High Pressure Liquid↗

PubMed2006

Genetic mutation profile of isovaleric acidemia patients in Taiwan.

Isovaleric acidemia (IVA), a rare recessive autosomal disorder, is caused by isovaleryl-CoA dehydrogenase (IVD) deficiency. IVA may present with symptoms during the acute stage of severe metabolic acidosis, ketosis, vomiting, and altered mental status. With the help of newborn screening (NBS) by tandem mass spectrometry (MS/MS), IVA can now be diagnosed presymptomatically. According to statistic data, the incidence of IVA in Taiwan was about 1/365,000. In this study, six IVA patients from five families were investigated and followed-up clinically. As for the timing, two patients were found before MS technique introduced to Taiwan, the others were identified after MS/MS applied to NBS. The blood level of C5-carnitine in our patients was 7.43-18.96 microM (with upper limit in our laboratory <0.51 microM) and all of their urines contained raised amounts of 3-hydroxyisovaleric acid and isovalerylglycine. Molecular analysis of their IVD gene revealed six mutation profiles, among which the 149G-->A (Arg21His) and 1174 C-->T (Arg363Cys) mutations have been reported previously, while the other four mutations, 386A-->G (His100Arg), 347C-->T (Ser87Phe), 1007G-->A (Cys307Tyr) and 1199A-->G (Tyr371Cys), were first reported. Specially, we found 1199A-->G (Tyr371Cys) mutated was a common recurring missense mutation in our population (4 in 10 mutant alleles).

Adult↗

PubMed2006

Microstructure of magnesium fluoride films deposited by boat evaporation at 193 nm.

Single layer magnesium fluoride (MgF2) was deposited on fused-silica substrates by a molybdenum boat evaporation process at 193 nm. The formation of various microstructures in relation to the different substrate temperatures and deposition rates were investigated. The relation between these microstructures (including cross-sectional morphology, surface roughness, and crystalline structures), the optical properties (including refractive index and optical loss) and stress, were all investigated. It was found that the laser-induced damage threshold (LIDT) would be affected by the microstructure, optical loss, and stress of the thin film. To obtain a larger LIDT value and better optical characteristics, MgF2 films should be deposited at a high substrate temperature (300 degrees C) and at a low deposition rate (0.05 nm s(-1)).

Journal Article↗

PubMed2006

X-ray photoelectron spectroscopy study of thin TiO2 films cosputtered with Al.

In this study, titanium dioxide (TiO(2)) films were fabricated by cosputtering of a titanium (Ti) target and an aluminum (Al) slice in a smaller area by an ion-beam sputtering deposition method. The sputtered films were postannealed at 450 degrees C. The x-ray photoelectron spectroscopy spectra were categorized by their oxygen bonding variations, which include high-binding-energy oxygen, (HBO), bridging oxygen, low-binding-energy oxygen, and shifts of the binding energies (BEs) of oxygen (O) and Ti signals. The enhancement of HBO and higher BE shifts of the O 1s spectra as a function of cosputtered Al in the film imply the formation of an Al-O-Ti linkage. Corresponding changes in the Ti 2p spectra further confirm the modification of properties of the cosputtered film that results from the variation of the chemical bonding environment. An observed correlation between the chemical structure and optical absorption of the Al cosputtered films can be used to modify the optical properties of the film.

Journal Article↗

PubMed2006

Effect of the working gas of the ion-assisted source on the optical and mechanical properties of SiO2 films deposited by dual ion beam sputtering with Si and SiO2 as the starting materials.

Silicon and fused-silica targets are used as the starting materials for depositing silicon oxide (SiO2) films. The SiO2 films are prepared by a dual ion beam sputtering deposition system with a main ion source and an ion-assisted source with different working gases. The films deposited are then examined and compared by using a visible spectrophotometer, a Fourier-transform IR spectrophotometer, an atomic force microscope, and contact angle instruments. A Twyman-Green interferometer is employed to study the film stress by phase-shift interferometry. All the SiO2 films show excellent optical properties with extra-low extinction coefficients (below 2x10(-5)) and have no water absorption. When the working gas is O2 for the ion-assisted source, the deposited SiO2 films show good properties in terms of stress and roughness and with a good molecular bonding structure order for both targets. However, SiO2 films deposited from the fused-silica target had a larger contact angle, while those deposited from the silicon target had 2.5 times the deposition rate.

Journal Article↗

PubMed2006

Investigation of thermal annealing of optical properties and residual stress of ion-beam-assisted TiO2 thin films with different substrate temperatures.

Titanium oxide films were prepared by ion-beam-assisted deposition on glass substrates at various substrate temperatures. The effect of the temperature of thermal annealing from 100 degrees C to 300 degrees C on the optical properties and residual stress was investigated. The influence on the stoichiometry and residual stress of titanium oxides deposited at different substrate temperature was discussed. The residual-stress was minimum and the extinction coefficient was maximum at an annealing temperature of 200 degrees C with a substrate temperature of 150 degrees C. However, when the substrate temperature was increased to 200 degrees C and 250 degrees C, the residual stress was minimum and the extinction coefficient was maximum at an annealing temperature of 250 degrees C. The spectra of x-ray photoelectron spectroscopy reveal that the films lost oxygen and slowly generated lower suboxides at the annealing temperature at which the residual stress was minimum and the extinction coefficient was maximum. As the annealing temperature increased above the temperature at minimum stress, the lower suboxides began to capture oxygen and form stable oxides. TiO2 films deposited at substrate temperatures of 200 degrees C and 250 degrees C were more stable than films deposited at 150 degrees C.

Journal Article↗

PubMed2006

Crystal structure of infectious bursal disease virus VP2 subviral particle at 2.6A resolution: implications in virion assembly and immunogenicity.

The structural protein VP2 of infectious bursal disease virus (IBDV) spontaneously forms a dodecahedral T=1 subviral particle (SVP), and is a primary immunogen of the virus. In this study, the structure of IBDV SVP was determined in a cubic crystal and refined to 2.6A resolution. It contains 20 independent VP2 subunits in a crystallographic asymmetric unit. Each subunit is folded mainly into a shell domain and a protrusion domain, both with the Swiss-roll topology, plus a small helical base domain. Three VP2 subunits constitute a tight trimer, which is the building block of IBDV (sub)viral particles. The structure revealed a calcium ion bound to three pairs of symmetry-related Asp31 and Asp174 to stabilize the VP2 trimer. Our results of treatment of SVP with EGTA, a Ca(2+)-chelating reagent, indicated that the metal-ion may be important not only in maintaining highly stable quaternary structure but also in regulating the swelling and dissociation of the icosahedral particles. A Ca(2+)-dependent assembly pathway was thus proposed, which involves further interactions between the trimers. The 20 independent subunits showed conformational variations, with the surface loops of the protrusion domain being the most diverse. These loops are targets of the neutralizing antibodies. Several common interactions between the surface loops were clearly observed, suggesting a possible major conformation of the immunogenic epitopes.

Amino Acid Sequence↗

PubMed2006

Effects of temperature on columnar microstructure and recrystallization of TiO2 film produced by ion-assisted deposition.

Titanium oxide thin films were deposited by electron-beam evaporation with ion-beam-assisted deposition. The effect of the substrate temperature and annealing temperature on the columnar microstructure and recrystallization of titanium oxide was studied. The values of the refractive index varied from 2.26 to 2.4, indicating that the different substrate temperatures affected the film density. X-ray diffraction revealed that all films were amorphous as deposited. At annealing temperatures from 100 degrees C to 300 degrees C, only the anatase phase was formed. As the substrate temperature increased from 150 degrees C to 200 degrees C to 250 degrees C, the recrystallization temperature fell from 300 degrees C through 250 degrees C to 200 degrees C. Changing the substrate temperature resulted in the formation of various types of columnar microstructure, as determined by scanning-electron microscopy. Different columnar structures resulted in different surface morphologies, as measured by atomic-force microscopy.

Journal Article↗

PubMed2006

Rugate filter made with composite thin films by ion-beam sputtering.

Composite films of Ta-Si oxide with refractive indices that varied from 1.48 to 2.15 were realized by using rf ion-beam sputtering. All the composite films were amorphous and had a surface roughness of less than 0.3 nm. The inhomogeneity of the composite was discussed, and a rugate filter was designed and fabricated by automatic computer control.

Journal Article↗

PubMed2006

How the monitoring curve is affected by the thermal shift of a filter during deposition.

The thermal shift of dense-wavelength-division-multiplexing (DWDM) filters that is caused by nonconstant temperature during fabrication invokes a spectrum shift and an error in the optical thickness of the layer before the matching layer. The relation between the thermal shift and the optical thickness of the layer before the matching layer was calculated. Five kinds of narrow-bandpass filters were fabricated, and their thermal shifts were measured and compared with the theoretical model. By using this technique, we were able to predict the thermal shift of DWDM filters from the abnormal behavior of the layer before the matching layer during deposition.

Journal Article↗

PubMed2006

Influence of monitor passband width on the layer thickness determination during deposition of a dense-wavelength-division-multiplexing filter.

The monitor passband width of an optical monitor is an important parameter for the fabrication of a dense-wavelength-division-multiplexing (DWDM) filter. The peak insertion loss and transmittance of one-cavity narrow-bandpass filters (NBPFs) were analyzed by using different passband widths. The simulation monitoring curves of the last layer of the first, second, third, and fourth cavities of a five-cavity DWDM filter with different monitor passband widths were investigated. The last layer of each cavity is very sensitive to the monitor passband width, showing that the monitor passband width of an optical monitor should be less than half the designed passband width. This analysis demonstrates the successful fabrication of a five-cavity DWDM filter.

Journal Article↗

PubMed2006

Microstructure-related properties at 193 nm of MgF2 and GdF3 films deposited by a resistive-heating boat.

MgF2 and GdF3 materials, used for a single-layer coating at 193 nm, are deposited by a resistive-heating boat at specific substrate temperatures. Optical characteristics (transmittance, refractive index, extinction coefficient, and optical loss) and microstructures (morphology and crystalline structure) are investigated and discussed. Furthermore, MgF2 is used as a low-index material, and GdF3 is used as a high-index material for multilayer coatings. Reflectance, stress, and the laser-induced damage threshold (LIDT) are studied. It is shown that MgF2 and GdF3 thin films, deposited on the substrate at a temperature of 300 degrees C, obtain good quality thin films with high transmittance and little optical loss at 193 nm. For multilayer coatings, the stress mainly comes from MgF2, and the absorption comes from GdF3. Among those coatings, the sixteen-layer design, sub/(1.4L 0.6H)8/air, shows the largest LIDT.

Journal Article↗

PubMed2006

Chirped-cavity dispersion-compensation filter design.

A new basic structure of a dispersive-compensation filter, called a chirped-cavity dispersion-compensator (CCDC) filter, was designed to offer the advantages of small ripples in both reflectance and group-delay dispersion (GDD). This filter provides a high dispersion compensation, like the Gires-Tournois interferometer (GTI) filter, and a wide working bandwidth, like the chirped mirror (CM). The structure of the CCDC is a cavity-type Fabry-Perot filter with a spacer layer (2 mH or 2 mL) and a chirped high reflector. The CCDC filter can provide a negative GDD of -50 fs2 over a bandwidth of 56 THz with half the optical thickness of the CM or the GTI.

Journal Article↗

PubMed2006

Estimating air quality in a traffic tunnel using a forecasting combination model.

This study compared three forecasting methods based on their accuracy or absolute errors in forecasting air pollution in a traffic tunnel: the Grey model (GM), the Crank-Nicholson implicit scheme model, and the forecasting combination model (FCM). Three criteria, root mean square error (RMSE), the mean absolute error (MAE) and mean absolute percentage error (MAPE), were applied to the models and the FCM model displayed all of the characteristics of a good forecasting model. The correlation coefficient (r) for the FCM model equaled 0.94 (Upwind), 0.98 (Middle) and 0.98 (Downwind). This study indicated that FCM can be used to accurately forecast CO pollution in the Kaohsiung Cross Harbor Tunnel.

Air Pollutants↗

PubMed2005

Characterization of AlF3 thin films at 193 nm by thermal evaporation.

Aluminum fluoride (AlF3) was deposited by a resistive heating boat. To obtain a low optical loss and high laser-induced damage threshold (LIDT) at 193 nm, the films were investigated under different substrate temperatures, deposition rates, and annealing after coating. The optical property (the transmittance, refractive index, extinction coefficient, and optical loss) at 193 nm, microstructure (the cross-sectional morphology, surface roughness, and crystalline structure), mechanical property (stress), and LIDT of AlF3 thin films have been studied. AlF3 thin films deposited at a high substrate temperature and low deposition rate showed a lower optical loss. The highest LIDT occurred at the substrate temperature of 150 degrees C. The LIDT of the films prepared at a deposition rate of 2 A/s was higher than that at other deposition rates. The annealing process did not influence the optical properties too much, but it did increase the LIDT and stress.

Journal Article↗

PubMed2005

Influence of thermal annealing and ultraviolet light irradiation on LaF3 thin films at 193 nm.

Lanthanum fluoride (LaF3) thin films were prepared by resistive heating evaporation and electron-beam gun evaporation under the same deposition rate, deposition substrate temperature, and vacuum pressure. The coated LaF3 films were then treated by heat annealing and UV light irradiation. The optical properties, microstructures, stress, and laser-induced damage threshold (LIDT) at a wavelength of 193 nm were investigated. The surface roughness, optical loss, stress, and LIDT of the films were improved after the annealing. The films had better properties when irradiated by UV light as compared with heat annealing.

Journal Article↗