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排序方式: 共有414条查询结果,搜索用时 15 毫秒
31.
T. Y. Wu M. H. Tsao F. L. Chen S. G. Su C. W. Chang H. P. Wang Y. C. Lin I. W. Sun 《Journal of the Iranian Chemical Society》2010,7(3):707-720
A series of new organic dyes comprising carbazole, iminodibenzyl, and phenothiazine moieties as the electron donors and rhodanine ring as the electron acceptor/anchoring groups were designed and developed for use in dye-sensitized solar cells. HOMO and LUMO energy level tuning was achieved by varying the carbazole, iminodibenzyls and phenothiazine donors. This was evidenced by spectral and electrochemical experiments and density functional theory calculations. Electrochemical studies indicated that the phenothiazine unit was much more effective in lowering the ionization potential than were the iminodibenzyl and carbazole units. The phenothiazine dye shows a solar-energy-to-electricity conversion efficiency (η) of 4.87%; the carbazole and iminodibenzyl dyes show η of 2.54% and 3.52%, respectively. These findings reveal that using carbazole, iminodibenzyl and phenothiazine donors as light-harvesting sensitizers are promising candidates for dye-sensitized solar cells. 相似文献
32.
核磁共振电信号内标法在人体尿液定量分析中的应用 总被引:1,自引:0,他引:1
研究了Varian谱仪核磁共振电信号内标法在人体尿液代谢物浓度测定上的应用,通过实验证明了该方法进行定量分析的可靠性.NMR电信号内标法原理上是通过Varian谱仪去耦通道在常规一维谱图上产生一个参考信号,并利用谱仪软件程序来调整该信号在频谱上的强度、频率、衰减速率等参数.避免了代谢组学中NMR定量实验需要添加已知浓度物质(例如TSP)作为内标而引起的内标物与样品相互作用、谱峰重叠、内标物不溶及弛豫时间太长等问题.研究结果表明,Varian谱仪去耦通道产生的电信号稳定可靠(标准偏差0.36%),能够用于定量分析;当样品浓度大于20 mmol/L或小于2 mmol/L时,该方法测定的相对误差分别为1%和5%.通过配制低浓度的尿液模型样品,验证了电信号内标法测量人体尿液代谢物的浓度的可行性,最后使用该方法测量真实的人体尿液中常见代谢物的浓度,测定结果与医院常用生化分析仪器的测定结果相符. 相似文献
33.
This study explored the relationship between music and speech by examining absolute pitch and lexical tone perception. Taiwanese-speaking musicians were asked to identify musical tones without a reference pitch and multispeaker Taiwanese level tones without acoustic cues typically present for speaker normalization. The results showed that a high percentage of the participants (65% with an exact match required and 81% with one-semitone errors allowed) possessed absolute pitch, as measured by the musical tone identification task. A negative correlation was found between occurrence of absolute pitch and age of onset of musical training, suggesting that the acquisition of absolute pitch resembles the acquisition of speech. The participants were able to identify multispeaker Taiwanese level tones with above-chance accuracy, even though the acoustic cues typically present for speaker normalization were not available in the stimuli. No correlations were found between the performance in musical tone identification and the performance in Taiwanese tone identification. Potential reasons for the lack of association between the two tasks are discussed. 相似文献
34.
Design of quantum VQ iteration and quantum VQ encoding algorithm taking O(√N) steps for data compression
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Vector quantization (VQ) is an important data compression
method. The key of the encoding of VQ is to find the closest vector among
N vectors for a feature vector. Many classical linear search algorithms
take $O(N)$ steps of distance computing between two vectors. The quantum VQ iteration and corresponding quantum VQ encoding algorithm that takes
$O(\sqrt N )$ steps are presented in this paper. The unitary operation of
distance computing can be performed on a number of vectors simultaneously
because the quantum state exists in a superposition of states. The quantum VQ iteration comprises three oracles, by contrast many quantum algorithms have only one oracle, such as Shor's factorization algorithm and Grover's algorithm. Entanglement state is generated and used, by contrast the state in Grover's algorithm is not an entanglement state. The quantum VQ iteration is a rotation over subspace, by contrast the Grover iteration is a rotation over global space. The quantum VQ iteration extends the Grover iteration to the more complex search that requires more oracles. The method of the quantum VQ iteration is universal. 相似文献
35.
Elliptical notches in rectangular beams under pure bending are examined photoelastically. Stress-concentration factors due to a single elliptical notch are obtained for wide ranges of 2a/h andd/h, where 2a, d, andh are the width of notch, depth of notch, and depth of beam, respectively. In particular, the geometries of the optimum elliptical notches producing the least stress concentrations are obtained. Almost the whole elliptical boundary of these notches are stressed to the same peak, which indicates that these notches will probably produce the least stress concentrations among all notches, elliptical or nonelliptical. The graphs herein will enable the designers to find the stress-concentration factors of elliptical notches and to pick out the geometry of the optimum notch which will give the least stress concentration for any given values of 2a/h andd/h. Stresses and the stress-concentration factors at the bottom of the beam opposite the notch are also obtained. These stresses, though smaller in magnitude, are of an opposite sign to the peak stress at the notch. For brittle materials, a smaller tensile stress may be more critical than a large compressive stress; therefore, these stress-concentration factors are also given. 相似文献
36.
A matrix-free, high sensitivity, nanostructured silicon surface assisted laser desorption/ionization mass spectrometry (LDI-MS) method fabricated by metal-assisted etching was investigated. Effects of key process parameters, such as etching time, substrate resistance and etchant composition, on the nanostructured silicon formation and its LDI-MS efficiency were studied. The results show that the nanostructured silicon pore depth and size increase with etching time, while MS ion intensity increases with etching time to 300 s then decreases until 600 s for both low resistance (0.001–0.02 Ω cm) and high resistance (1–100 Ω cm) silicon substrates. The nanostructured silicon surface morphologies were found to directly affect the LDI-MS signal ion intensity. By characterizing the nanostructured silicon surface roughness using atomic force microscopy (AFM) and sample absorption efficiency using fluorescence microscopy, it was further demonstrated that the nanostructured silicon surface roughness was highly correlated to the LDI-MS performance. 相似文献
37.
Xiao-Dong Li Hong Zhang Yoshiyuki Miyamoto Yong-Jian Tang Chao-Yang Wang 《Structural chemistry》2014,25(1):177-185
A novel type of three-dimensional (3D) tetrahedral silsesquioxane-based porous frameworks (TSFs) with diamond-like structure was computationally designed using the density functional theory (DFT) and classical molecular mechanics (MM) calculations. The hydrogen adsorption and diffusion properties of these TSFs were evaluated by the methods of grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations. The results reveal that all designed materials possess extremely high porosity (87–93 %) and large H2 accessible surface areas (5,268–6,544 m2 g?1). Impressively, the GCMC simulation results demonstrate that at 77 K and 100 bar, TSF-2 has the highest gravimetric H2 capacity of 29.80 wt%, while TSF-1 has the highest volumetric H2 uptake of 65.32 g L?1. At the same time, the gravimetric H2 uptake of TSF-2 can reach up to 4.28 wt% at the room temperature. The extraordinary performances of these TSF materials in hydrogen storage made them enter the rank of the top hydrogen storage materials so far. 相似文献
38.
Hung CC Su YN Tsao PN Chen PC Lin SJ Lin CH Mu SC Liu CA Chang YC Lin WL Hsieh WS Hsu SM 《Electrophoresis》2007,28(6):894-899
Congenital central hypoventilation syndrome (CCHS) is a rare neurological disorder characterized by abnormal autonomic central nervous system control of breathing during sleep. Mutations in the paired-like homeobox 2B (PHOX2B) gene, including point mutation, frameshift, and polyalanine expansion, are associated with the pathogenesis of CCHS. In this study, PHOX2B mutations were analyzed in seven CCHS patients, their family members, and 1520 healthy individuals from the general population using CE to provide high sensitivity and resolution screening for the PHOX2B polyalanine polymorphism. Seven mutations in the PHOX2B gene, including two frameshift mutations and five polyalanine expansions in the 20-residue polyalanine tract, were identified. The various phenotypes observed in CCHS patients with PHOX2B mutations suggest that the size of the expansion allele is associated with the CCHS risk. In addition, significant differences were found in allele and genotype distributions between the healthy individuals. Alleles (GCN)(20) and (GCN)(15) had the highest population incidence rates of 94.84 and 4.51%, respectively, with the remaining alleles, (GCN)(13) and (GCN)(7), accounting for 0.59 and 0.06%, respectively. Therefore, it has been demonstrated that CE can be used to improve the detection of polyalanine expansions in the PHOX2B gene. The attractive alternative method is a promising tool for the detection of disorders involving trinucleotide repeat tracts. 相似文献
39.
A new designed and analyzed silicon-on-insulator (SOI) waveguide Michelson interferometer (SMI) sensor is proposed in this paper. The authors compare an optical SMI sensor, a silicon-on-insulator Bragg waveguide grating (SBG) sensor, and a fiber Bragg grating sensor (FBG) for temperature sensing in medicine applications. The SMI sensor has 20 times sensing more accuracy than the FBG sensor. Moreovr, the full width at half maximum (FWHM) of the pass-band frequency responses of our proposed SMI can be designed much narrower than FBG and SBG sensors for sensing resolution enhancement. Further, the improved characteristics of the SMI demonstrated in this paper could pave the way for future high density temperature monitoring medicine applications. 相似文献
40.
The reactivity of melezitose hydroxyls is studied during tritylation in pyridine. Some novel derivatives of melezitose are prepared. An acetyl is transferred from the 4- to the 6-position after detritylation of 3 and 4. The structures of the products are proved by elemental analysis;
1
H,
13
C, and
1
H-
1
H COSY NMR spectra;IR spectra; and fast-atom bombardment mass spectrometry. 相似文献