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191.
A highly efficient annulative approach towards the construction of the structurally attractive methylenecyclohexane ring was developed through a convenient 1,4-addition of 4-pentenylmagnesium bromide to 2-cyano-2-cycloalkenones followed by a Pd(II)-mediated oxidative cyclization of the resulting ω-unsaturated α-cyano ketones. Based on this newly developed protocol, polycyclic adducts bearing various ring sizes and substitutions can be prepared in moderate to high yields. 相似文献
192.
S. Y. Cheng Y. G. Wang P. Yu Y. J. Cheng J. Tang H. R. Chen W. F. Hsieh 《Laser Physics》2012,22(1):54-59
Using the vertical evaporation technique we fabricated saturable absorbers by transferring the water-soluble single wall carbon
nanotubes (SWCNT) onto a hydrophilic quartz substrate. The fast recovery times of the absorber were measured to be 136 and
790 fs. The modulation depth of the absorber was about 2%. Passive mode-locked Nd:GdVO4 laser using such an absorber was demonstrated. The continuous wave mode-locked pulses with the pulse duration of 12.4 ps
and the repetition of 120 MHz were achieved. The maximum average output power of the mode-locked laser is 2.4 W at the pump
power of 13 W. Such kind of absorber has potential to be put into practical use for high power solid-state laser mode locking. 相似文献
193.
Wei-Ping Chu Jian-Shian Lin Tien-Chai Lin Yu-Sheng Tsai Chen-Wei Kuo Ming-Hua Chung Tsung-Eong Hsieh Lung-Chang Liu Fuh-Shyang Juang Nien-Po Chen 《Optics Communications》2012,285(15):3325-3328
The high haze light-trapping (LT) film offers enhanced scattering of light and is applied to a-Si:H solar cells. UV glue was spin coated on glass, and then the LT pattern was imprinted. Finally, a UV lamp was used to cure the UV glue on the glass. The LT film effectively increased the Haze ratio of glass and decreased the reflectance of a-Si:H solar cells. Therefore, the photon path length was increased to obtain maximum absorption by the absorber layer. High Haze LT film is able to enhance short circuit current density and efficiency of the device, as partial composite film generates broader scattering light, thereby causing shorter wave length light to be absorbed by the P layer so that the short circuit current density decreases. In case of lab-made a-Si:H thin film solar cells with v-shaped LT films, superior optoelectronic performances have been found (Voc = 0.74 V, Jsc = 15.62 mA/cm2, F.F. = 70%, and η = 8.09%). We observed ~ 35% enhancement of the short-circuit current density and ~ 31% enhancement of the conversion efficiency. 相似文献
194.
We demonstrate the use of a nonlinear photonic crystal to generate a harmonic comb and an ultrabroad-band acousto-optic modulator for the field amplitudes and phases of the comb to succeed in synthesizing femtosecond and subfemtosecond optical field waveforms. Nonsinusoidal fields of various shapes are synthesized and verified using shaper-assisted linear cross-correlation. The compact all-solid-state system could lead to the realization of a portable arbitrary optical waveform synthesizer that is analogous in many aspects to an RF function generator. 相似文献
195.
Hsieh SF Hsieh TJ El-Shazly M Du YC Wu CC Hwang TL Wu YC Chang FR 《Natural product communications》2012,7(4):435-440
Two new eremophilenolides, 6beta,8beta,10beta-trihydroxyeremophil-7(11)-en-12,8-olide (1) and 3beta-acetoxy-8alpha-hydroxy-6beta-methoxyeremophila-7(11),9-dien-12,8-olide (2) along with twenty-nine other compounds were obtained from the methanolic extracts of the aerial parts and rhizomes of Farfugium japonicum (L.) Kitam. var. formosanum (Hayata) Kitam. (Compositae = Asteraceae). The structures of the isolated compounds were characterized and identified by spectral techniques. Compounds 5, 6, 10, 12-24, 29, and 30, were reported for the first time from this genus. Cytotoxicity and anti-inflammatory activity of the isolated compounds were evaluated. Compounds 3 and 16 possessed moderate cytotoxicity against human breast cancer cell line (MCF 7). Compounds 3, 16, 25 and 26 exhibited moderate cytotoxicity against hepatoma cells (Hep G2 and Hep 3B). With respect to the anti-inflammatory activity, compounds 15 and 16 (each 10 microg/mL) inhibited superoxide anion generation by human neutrophils in response to fMLP/CB by 92.0% and 87.3%, respectively. 相似文献
196.
A nano-scale decanuclear Zn(II) circular helicate is synthesized without the aid of counteranions during the assembly process, and can be totally disassembled into its reactants by specific anions. 相似文献
197.
Ya-Ting Hsieh Nai-Tzu Kuo Eamor M. Woo 《Journal of Thermal Analysis and Calorimetry》2012,107(2):745-756
Abstract
Thermal behavior, miscibility, and crystalline morphology in blends of low-molecular-weight poly(l-lactic acid) (LMw-PLLA) or high-molecular-weight PLLA (HMw-PLLA) with various polyesters such as poly(butylene adipate) (PBA), poly(ethylene adipate) (PEA), poly(trimethylene adipate) (PTA), or poly(ethylene succinate) (PESu), respectively, were explored using differential scanning calorimeter (DSC), and polarized-light optical microscopy (POM). Phase behavior in blends of PLLA with other polyesters has been intriguing and not straight forward. Using a low- and high molecular weight PLLA, this study aimed at mainly using thermal analyses for probing the phase behavior, phase diagrams, and temperature dependence of blends systems composed of PLLA of two different molecular weights (low and high) with a series of aliphatic polyesters of different structures varying in the (CH2/CO) ratio in main chains. The blends of LMw-PLLA/PEA and LMw-PLLA/PTA show miscibility in melt and amorphous glassy states. Meanwhile, the LMw-PLLA/PESu blend is immiscible with an asymmetry-shaped upper critical solution temperature (UCST) at 220–240 °C depending on the blend composition. In contrast to miscibility in LMw-PLLA/PTA and LMw-PLLA/PEA blends, HMw-PLLA with polyesters are mostly immiscible; and HMw-PLLA/PTA blend is the only one showing an asymmetry-shaped UCST phase diagram with clarity points at 195–235 °C (depending on composition). Reversibility of UCST behavior, with no chemical transreactions, in these blends was proven by solvent recasting, gel permeation chromatography, and Fourier transform infrared spectroscopy (FT-IR). Crystalline morphology behavior of the LMw-PLLA/PEA and LMw-PLLA/PTA blends furnishes addition evidence for miscibility in the amorphous phase between LMw-PLLA and PTA or PEA. 相似文献198.
Yu CC Hsieh CR Hsiao G Chen PY Chang ML Yin HW Lee TH Lee CK 《Molecules (Basel, Switzerland)》2012,17(2):2082-2090
Two new abietane type diterpenoids, namely seco-helioscopinolide (1) and 3b,7b-dihydroxy-ent-abieta-8,13-diene-12,16-olide (2) were isolated from the aerial parts of Euphorbia formosana Hayata together with helioscopinolide A (3), helioscopinolide B (4), helioscopinolide C (5) and ent-(5b,8a,9b,10a,12a)-12-hydroxyatis-16-ene-3,14-dione (6). The structures of compounds 1-6 were elucidated by analyzing their spectroscopic data and comparison with the literature. Further biological tests by gelatin zymographic analysis revealed that 3-5 significantly up-regulated the expressions and activation of MMP-2 and -9 in human fibrosarcoma cell line HT1080. 相似文献
199.
Shuchen Hsieh Pei‐Ying Lin Chiung‐Wen Hsieh I‐Tin Li Shu‐Ling Hsieh Chih‐Chung Wu Yun‐Shan Huang Huay‐Min Wang Li‐Wei Tu Kuang‐Hung Cheng Hay‐Yan Jack Wang Deng‐Chyang Wu 《中国化学会会志》2012,59(8):929-933
Carcinoma cell differentiation stage is an important indicator of cell behavior. For example, cell mobility is much higher for poorly‐differentiated hepatocellular carcinoma SK‐Hep‐1 cells than for well‐differentiated HepG2 cells. In this study, we have cultured HepG2 and SK‐Hep‐1 cells on chemically patterned polydimethylsiloxane (PDMS) substrates to observe differences in the adhesion properties and cell structure that occur due to the patterns. Both cell lines showed a preference for the hydrophobic regions on the patterned PDMS surface with SK‐Hep‐1 cells achieving a higher density than HepG2 for the same cell‐count solutions. Further, SK‐Hep‐1 cells adopted the square or hexagonal shape of the surface patterns while HepG2 cells maintained their more rounded shape. AFM force measurement arrays were also performed on the cell surfaces to measure and map adhesion values between the tip and cell surface membrane. These results demonstrate that, in addition to cell shape and size, adhesion expression in hepatocellular carcinoma cells is differentiation stage dependent. Further, the ability of the SK‐Hep‐1 cells to adopt the shape of the substrate pattern indicates they are more structurally labile, which may contribute to their higher mobility. 相似文献
200.
This study focuses on the self-sustained oscillatory flow characteristics between two tandem circular cylinders of equal diameter
placed in a uniform inflow. The Reynolds number (Re
D
), based on the cylinder diameter, was around 1,000 and all experiments were performed in a recirculating water channel. The
streamwise distance between two tandem cylinders ranged within 1.5 ≤ X
c/D ≤ 7.0. Here X
c denotes the center-to-center distance between two tandem cylinders. For all experiments studied herein, quantitative velocity
measurements were performed using hot-film anemometer and the LDV system. The laser sheet technique was employed for qualitative
flow visualization. The wavelet transform was applied to elucidate the temporal variation and phase difference between two
spectral components of the velocity signals detected in the flow field. The remarkable finding was that when two tandem circular
cylinders were spaced at a distance within 4.5 ≤ X
c/D ≤ 5.5, two symmetrical unstable shear layers with a certain wavelength were observed to impinge onto the downstream cylinder.
The responding frequency (f
u
), measured between these two cylinders, was much higher than the natural shedding frequency behind a single isolated cylinder
at the same Re
D
. This responding frequency decreased as the distance X
c/D increased. Not until X
c/D ≥ 6.0, did it recover to the natural shedding frequency behind a single isolated cylinder. Between two tandem cylinders,
the Strouhal numbers (St
c = f
u
X
c/Uc) maintained a nearly constant value of 3, indicating the self-sustained oscillating flow characteristics with a wavelength X
c/3. Here U
c is the convection speed of the unstable shear layers between two tandem cylinders. At Re
D
= 1,000, the self-sustained oscillating characteristics between two tandem circular cylinders were proven to exhibit a sustained
flow pattern, not just a sporadic phenomenon. 相似文献