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41.
Chia-Wei?Sun Yih-Ming?Wang Chih-Chung?YangEmail author Yean-Woei?Kiang Long-Sheng?Lu Ming-Jai?Su 《Optical Review》2003,10(5):488-492
In this paper we demonstrated the effectiveness of imaging in a tissue phantom with isotropic scattering using polarization discrimination combined with the time gating method. This simple polarization discrimination technique was shown ineffective when it was applied to filamentous tissues. In this situation, we utilized the time-gated degree of polarization (DOP) imaging technique to show that the DOP measurement was quite effective for high-quality imaging of objects in filamentous tissues. We also applied this technique to the characterization of myocardial tissues and showed the difference between normal and abnormal tissues. In addition, we demonstrated a novel method for target depth determination in a turbid medium based on co-polarized light measurements. This method relied on the strong dependence of transmitted co-polarized intensity on target depth. 相似文献
42.
Wang Ding-An Chen Chih-Chiarng Kiang Yean-Woei Lee Jiun-Haw Yang C.C. 《Optical and Quantum Electronics》2000,32(4-5):585-608
The nonlinear switching effect of an all-semiconductor-optical-amplifier Sagnac interferometer is numerically investigated. The device, stemming from the conventional nonlinear optical loop mirror made of fiber, has a much more compact size and a latency several hundred times smaller than the conventional ones. Numerical simulations are conducted for the case of cw signal operation. It is found that the nonlinear coupling in the MMIWA and the lateral field redistribution as well as the amplification of the signal through the loop structure contribute together to the nonlinear switching. Besides investigating the physical mechanism of the device, we vary relevant parameters to evaluate their influences on device performance. The numerical simulations show good agreement in trend with the experimental results. 相似文献
43.
44.
Chun Kiang Chua Adeline Huiling Loo Prof. Martin Pumera 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(17):5969-5975
Tailoring and enhancing electrocatalytic activity is of the utmost importance from the viewpoints of sustainable energy and sensing. MoS2 and graphene show great promise for the electrocatalysis of many reactions. Given that both graphene and MoS2 are highly anisotropic in nature, with edge planes that are several orders of magnitude more catalytically active than basal planes, a new hybrid material with maximized edge‐plane density to provide efficient electron transfer, high catalytic activity, and conductive cores was engineered. The hybrid material consists of radial MoS2 nanosheets with a high density of edge planes and unsaturated active sulfur atoms as well as interspersed with conductive graphene nanoplatelets. This hybrid material exhibits excellent activity for the hydrogen evolution reaction and the detection of DNA nucleobases. Such a nanoengineered, nanostructured hybrid material may play a major role in future electrocatalytic devices. 相似文献
45.
Chemical Preparation of Graphene Materials Results in Extensive Unintentional Doping with Heteroatoms and Metals
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Dr. Chun Kiang Chua Dr. Adriano Ambrosi Prof. Zdeněk Sofer Dr. Anna Macková Dr. Vladimír Havránek Dr. Ivo Tomandl Prof. Martin Pumera 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(48):15760-15767
Chemical synthesis of graphene relies on the usage of various chemical reagents. The initial synthesis step, in which graphite is oxidized to graphite oxide, is achieved by a combination of chemical oxidants and acids. A subsequent chemical reduction step eliminates/reduces most oxygen functionalities to yield graphene. We demonstrate here that these chemical treatments significantly contaminate graphene with heteroatoms/metals, depending on the procedures followed. Contaminations with heteroatoms (N, B, Cl, S) or metals (Mn, Al) were present at relatively high concentrations (up to 3 at %), with their chemical states dependent on the procedures. Such unintentional contaminations (unwanted doping) during chemical synthesis are rarely anticipated and reported, although the heteroatoms/metals may alter the electronic and catalytic properties of graphene. In fact, the levels of unintentionally introduced contaminants on graphene are often higher than typical levels found on intentionally doped graphene. Our findings are important for scientists applying chemical methods to prepare graphene. 相似文献
46.
Responses of auditory-nerve fibers in anesthetized cats were recorded for synthetic voiceless fricative consonants. The four stimuli (/x/, /s/, /s/, and /f/) were presented at two levels corresponding to speech in which the levels of the vowels would be approximately 60 and 75 dB SPL, respectively. Discharge patterns were characterized in terms of PST histograms and their power spectra. For both stimulus levels, frequency regions in which the stimuli had considerable energy corresponded well with characteristic-frequency (CF) regions in which average discharge rates were the highest. At the higher level, the profiles of discharge rate against CF were more distinctive for the stimulus onset than for the central portion. Power spectra of PST histograms had large response components near fiber characteristic frequencies for CFs up to 3-4 kHz, as well as low-frequency components for all fibers. The relative amplitudes of these components varied for the different stimuli. In general, the formant frequencies of the fricatives did not correspond with the largest response components, except for formants below about 3 kHz. Processing schemes based on fine time patterns of discharge that were effective for vowel stimuli generally failed to extract the formant frequencies of fricatives. 相似文献
47.
Functionalization of Hydrogenated Graphene: Transition‐Metal‐Catalyzed Cross‐Coupling Reactions of Allylic C−H Bonds
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Dr. Chun Kiang Chua Prof. Zdeněk Sofer Prof. Martin Pumera 《Angewandte Chemie (International ed. in English)》2016,55(36):10751-10754
The chemical functionalization of hydrogenated graphene can modify its physical properties and lead to better processability. Herein, we describe the chemical functionalization of hydrogenated graphene through a dehydrogenative cross‐coupling reaction between an allylic C?H bond and the α‐C?H bond of tetrahydrothiophen‐3‐one using Cu(OTf)2 as the catalyst and DDQ as the oxidant. The chemical functionalization was confirmed by X‐ray photoelectron spectroscopy and Fourier transform infrared spectroscopy and visualized by scanning electron microscopy. The functionalized hydrogenated graphene material demonstrated improved dispersion stability in water, bringing new quality to the elusive hydrogenated graphene (graphane) materials. Hydrogenated graphene provides broad possibilities for chemical modifications owing to its reactivity. 相似文献
48.
Zou P Oh SS Kiang KH Low MY Bloodworth BC 《Rapid communications in mass spectrometry : RCM》2007,21(4):614-618
49.
Zou P Oh SS Kiang KH Low MY Koh HL 《European journal of mass spectrometry (Chichester, England)》2007,13(3):233-238
Liquid chromatography ion-trap time-of-flight mass spectrometry was employed to elucidate the fragmentation pathways of an analogue of acetildenafil. Based on the accurate masses of the parent ion, product ions and neutral losses of acetildenafil analogue, its fragmentation pathways were proposed. The information is useful for the on-line structural identification of unknown analogues of acetildenafil found as adulterants in herbal products. 相似文献
50.
We used the atomic force microscope to manipulate and unfold individual molecules of the titin I27 domain and reconstructed its free energy surface using Jarzynski's equality. The free energy surface for both stretching and unfolding was reconstructed using an exact formula that relates the nonequilibrium work fluctuations to the molecular free energy. In addition, the unfolding free energy barrier, i.e., the activation energy, was directly obtained from experimental data for the first time. This Letter demonstrates that Jarzynski's equality can be used to analyze nonequilibrium single-molecule experiments, and to obtain the free energy surfaces for molecular systems, including interactions for which only nonequilibrium work can be measured. 相似文献