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201.
Sin Hyuk Yim Sang-Bum Lee Taeg Yong Kwon Sang Eon Park 《Applied physics. B, Lasers and optics》2014,115(4):491-495
We present a phase coherent laser system with ultra-low phase noise with a frequency difference of 6.9 GHz. The laser system consists of two extended-cavity diode lasers that are optically phase-locked with electrical feedback to the injection current of a slave laser. The bandwidth of the optical phase-locking loop is extended up to 8 MHz. We achieve the residual phase noise of two phase-locked lasers of below ?120 dBrad2/Hz in the offset frequency range of 100 Hz–350 kHz and a flat phase noise of ?127 dBrad2/Hz from 700 Hz to 20 kHz. These results are, to the best of our knowledge, the lowest phase noise level ever reported with two extended-cavity diode lasers. 相似文献
202.
Dark pulse emission in nonlinear polarization rotation-based multiwavelength mode-locked erbium-doped fiber laser 总被引:1,自引:1,他引:0
We experimentally show dark pulse generation in all-normal dispersion multiwavelength erbium-doped fiber laser(EDFL) with a long cavity of figure-of-eight configuration. The EDFL generates a stable multiwavelength laser with 0.47 nm spacing at 24 m W threshold pump power, while the number of lines obtained increases with the pump power. A dark pulse emission is observed as the pump power is increased above 137 m W, with fundamental repetition rate of 29 k Hz and pulse width of 2.7 μs. It is observed that the dark pulse train can be shifted to second-, third-, and fourth-order harmonic dark pulses by carefully adjusting the polarization controller. For the fundamental dark pulse, the maximum pulse energy of 32.4 n J is obtained at pump power of 146.0 mW. 相似文献
203.
Jie Han Dr. Xiao‐Yong Chang Li‐Rong Zhu Mei‐Li Pang Dr. Ji‐Ben Meng Prof. Stephen Sin‐Yin Chui Dr. Siu‐Wai Lai Dr. V. A. L. Roy Dr. 《化学:亚洲杂志》2009,4(7):1099-1107
Chain change : Variations in the position, number, and chain length of the n‐alkoxy chains readily tune the liquid‐crystalline properties of 2,5‐diaryl‐1,3,4‐thiadiazole derivatives from smectic to hexagonal columnar mesophases at room temperature. The calamitic S‐heterocyclic compounds show electrical conductivity in both solid and liquid‐crystal states.
204.
Kakarla Raghava Reddy Byung Cheol Sin Chi Ho Yoo Daewon Sohn Youngil Lee 《Journal of colloid and interface science》2009,340(2):160-165
We report a simple and noncovalent method for coating multiwalled carbon nanotubes (MWCNTs) with polyaniline (PANI) nanospheres using a microemulsion polymerization method. In this method, aniline polymerization is performed with MWCNTs in the presence of sodium dodecyl sulfate (SDS), which serves as both a surfactant and a dopant. Morphological, structural, thermal, and electrical properties of MWCNT–PANI nanocomposites were analyzed. The TEM results of the nanocomposites prepared with surfactant reveal that 30–50-nm-diameter PANI nanospheres were coated on the surface of the MWCNTs. Composites prepared without surfactant were found to be in core–sheath-type cable structures. The conductivities of the nanocomposites synthesized through microemulsion polymerization were found to be one order of magnitude higher than both the conductivities of pure PANI and the composites prepared via in situ chemical polymerization without an assisting SDS surfactant. The mechanism for the formation of nanostructured composites is presented. 相似文献
205.
The detailed ab initio calculations of the electronic structure of α-iron crystals revealed the presence of a narrow interval of specific volumes in the P(V, T=0) isotherm where dP/dV>0. According to the calculations, this anomaly occurs at pressures from ?3 to ?5 GPa and is due to the intensive energy-spectrum rearrangement accompanied by the almost simultaneous appearance of eight electronic topological transitions. 相似文献
206.
We purified phytoestrogens from Pueraria root (Pueraria mirifica from Thailand and Pueraria lobata from Korea), which is used as a rejuvenating folk medicine in Thailand and China. Dried, powdered plant material was extracted with 100% ethanol and further separated by concentration, filtration, and thin layer silica gel chromatography. Using the fractions obtained during separation, we first investigated their cytotoxicity in several cancer cell lines from various tissues. The ethanol-extracted components (PE1, PE4) had significant antiproliferative effects on breast cancer cell lines, including MCF-7, ZR-75-1, MDA-MB-231, SK-BR-3, and Hs578T. Second, we compared these results with the cytotoxic effects of known flavonoids, sterols, and coumarins from Pueraria root. The known compounds were not as effective, and occurred in a different polarity region on HPLC. Third, further separation resulted in the isolation of eight different components (Sub PE-A to -H). One of these, PE-D, affected the growth of some breast cancer cell lines (MCF-7, MDA- MB-231) in a dose- and time-dependent manner, as well as the growth of ovarian (2774) and cervical cancer cells (HeLa). Finally, a transfection assay showed that this component had an estrogenic effect similar to 17beta - estradiol, which activates both estrogen receptor alpha (ERalpha) and ERbeta. The NMR analysis determined that spinasterol (stigmasta-7, 22-dien-3beta-ol) is an active cytotoxic component of Pueraria root. 相似文献
207.
The results of ab initio calculations are presented for the specific energy, pressure, and elastic constants of an aluminum fcc single crystal with subnormal densities at T=0. Kinks in the elastic constant vs. density curves are revealed which are caused by the electronic topological transitions. An analysis of the mechanical stability of aluminum fcc crystal at negative pressures suggests that the polymorphic transition to a noncubic structure is possible. A method is suggested for taking into account the thermal nuclear excitation and the influence of zero-point vibrations on the pressure dependence of crystal density. 相似文献
208.
Lindsey G. Mackay Daniel Burke Michael J. Welch Susan Tai Chris Mussell Gavin O’Connor Della Sin Cheng Wing-chi 《Accreditation and quality assurance》2007,12(9):459-464
Under the auspices of the Comité Consultatif pour la Quantité de Matière (CCQM) a laboratory intercomparison, CCQM-P68, was
co-ordinated by the National Measurement Institute of Australia (NMIA) in 2005 involving the analysis of the steroid 19-norandrosterone
(19-NA) in human urine. 19-NA is the major metabolite of nandrolone, a commonly abused anabolic agent. It is routinely tested
by many sports drug testing laboratories and several national metrology institutes have developed reference methods to provide
reference values for the certification of reference materials. The material distributed for the intercomparison was a freeze-dried
human urine candidate reference material containing 19-NA at a level close to the allowed World Anti-Doping Agency (WADA)
cut-off for this anabolic agent, i.e. 2 ng/ml. Four national/designated metrology institutes participated in the intercomparison
and their results for this complex analysis were in excellent agreement, with a relative standard deviation (RSD) of only
1.7%. The expanded uncertainties at the 95% level of confidence for the reported results ranged from 3.7 to 7.0% at the 2.15 ng/g
level. 相似文献
209.
Della W.M Sin 《Analytica chimica acta》2004,508(2):147-158
A sensitive and robust method using isotope dilution gas chromatography-electron capture negative chemical ionization mass spectrometry (GC-ECNI-MS) was developed and validated for the analysis of quinoxaline-2-carboxylic acid (QCA) in porcine liver. [2H4]QCA was added to liver samples which were then deproteinated with 2% metaphosphoric acid in 20% methanol. Followed by sequential extraction with water-saturated ethyl acetate and phosphate buffer, the buffer extracts were subject to solid-phase extraction clean-up by mixed mode anion-exchange columns. QCA was derivatized with N-methyl-N-tert-butyldimethylsilyltrifluoroacetamide (MTBSTFA) prior to GC-ECNI-MS determination. For unambiguous identification, a second GC-ECNI-MS experiment was performed on suspected positive samples which were derivatized independently with another derivatization agent, trimethylsilyldiazomethane. Excellent recovery and precision were obtained and the limit of quantitation was 0.7 μg/kg (S/N>60). Method ruggedness by Taguchi orthogonal array technique is also presented. 相似文献
210.
Waihung Lo Lau Mei Ng Hong Chua Peter H. F. Yu Shirley N. Sin Po-Keung Wong 《Applied biochemistry and biotechnology》2003,107(1-3):581-591
Batch biosorption experiments were conducted to investigate the removal of Cu2+ ions from aqueous solutions by a series of bacterial strains isolated from a local activated sludge process. The characteristics
of 12 isolates were identified and examined for their ability to bind Cu2+ ions from aqueous solution. Among the isolates, two species exhibited biosorption capacity >40 mg of Cu/g of dry cell. Isotherms
for the biosorption of copper on bacterial cells were developed and compared, and the equilibrium data fitted well to the
Langmuir and Freundlich isotherm models. The biosorption of copper increased significantly with increasing pH from 2.0 to
6.0 regardless of the species. More than 90% of copper sorbed on the cells of Bacillus sp. could be recovered by washing with 0.1 M HNO3 for 5 min. The performance of two different desorption processes was also tested and compared. The results show that five
biosorption and desorption cycles are a better operation process than five successive biosorptions followed by one desorption
to remove and recover copper from aqueous solution. The biosorbent could be used for at least five biosorptions and desorption
cycles without loss of copper removal capacity. It can be concluded that the activated sludge or sludge-isolated bacteria
could be a potential biosorbent for copper removal. 相似文献