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51.
Karsten BP Viani L Gierschner J Cornil J Janssen RA 《The journal of physical chemistry. A》2008,112(43):10764-10773
Small band gap polymers may increase the energy conversion efficiency of polymer solar cells by increased absorption of sunlight. Here we present a combined experimental and theoretical study on the optical and electrochemical properties of a series of well-defined, lengthy, small band gap oligo(5,7-bis(thiophen-2-yl)thieno[3,4-b]pyrazine)s ( E g = 1.50 eV) having alternating donor and acceptor units. The optical absorptions of the ground state, triplet excited state, radical cation, and dication are identified and found to shift to lower energy with increasing chain length. The reduction of the band gap in these alternating small band gap oligomers mainly results from an increase of the highest occupied molecular orbital (HOMO) level. The S 1-T 1 singlet-triplet splitting is reduced from approximately 0.9 eV from the trimeric monomer to -0.5 eV for the pentamer. This significant exchange energy is consistent with the fact that both the HOMO and the lowest unoccupied molecular orbital (LUMO) remain distributed over virtually all units, rather than being localized on the D and A units. 相似文献
52.
Jér?ome?DegallaixEmail author Bram?Slagmolen Chunnong?Zhao Li?Ju David?Blair 《General Relativity and Gravitation》2005,37(9):1581-1589
Thermal lensing is becoming recognized as one of the dominant obstacles to the second generation of laser interferometric
gravitational wave detectors. Very high optical power is required to circulate in the interferometer to reach the sensitivity
goal, creating strong thermal induced wavefront distortion. These effects will be studied at the High Optical Power Test Facility
in Gingin, Western Australia. In this paper, we present simulation results for the first test planned for the middle of 2004.
This experiment will produce 5 kW of optical power circulating inside a Fabry–Perot cavity and will demonstrate large thermal
lensing effects.
Two compensation methods were investigated to offset the negative effect of thermal lensing on the cavity: a compensation
plate within the arm cavity and adaptive laser mode matching. Advantages and disadvantages of both systems are discussed. 相似文献
53.
54.
In the present study the natural abundance of 13C is quantified in agricultural soils in Mexico which have been submitted to different agronomic practices, zero and conventional tillage, retention of crop residues (with and without) and rotation of crops (wheat and maize) for 17 years, which have influenced the physical, chemical and biological characteristics of the soil. The natural abundance of C13 is quantified by near infrared spectra (NIRS) with a remote reflectance fibre optic probe, applying the probe directly to the soil samples.Discriminate partial least squares analysis of the near infrared spectra allowed to classify soils with and without residues, regardless of the type of tillage or rotation systems used with a prediction rate of 90% in the internal validation and 94% in the external validation. The NIRS calibration model using a modified partial least squares regression allowed to determine the δ13C in soils with or without residues, with multiple correlation coefficients 0.81 and standard error prediction 0.5‰ in soils with residues and 0.92 and 0.2‰ in soils without residues. The ratio performance deviation for the quantification of δ13C in soil was 2.5 in soil with residues and 3.8 without residues. This indicated that the model was adequate to determine the δ13C of unknown soils in the −16.2‰ to −20.4‰ range. The development of the NIR calibration permits analytic determinations of the values of δ13C in unknown agricultural soils in less time, employing a non-destructive method, by the application of the fibre optic probe of remote reflectance to the soil sample. 相似文献
55.
Systems out of equilibrium, in stationary as well as in nonstationary regimes, display a linear response to energy impulses simply expressed as the sum of two specific temporal correlation functions. There is a natural interpretation of these quantities. The first term corresponds to the correlation between observable and excess entropy flux yielding a relation with energy dissipation like in equilibrium. The second term comes with a new meaning: it is the correlation between the observable and the excess in dynamical activity or reactivity, playing an important role in dynamical fluctuation theory out-of-equilibrium. It appears as a generalized escape rate in the occupation statistics. The resulting response formula holds for all observables and allows direct numerical or experimental evaluation, for example in the discussion of effective temperatures, as it only involves the statistical averaging of explicit quantities, e.g. without needing an expression for the nonequilibrium distribution. The physical interpretation and the mathematical derivation are independent of many details of the dynamics, but in this first part they are restricted to Markov jump processes and overdamped diffusions. 相似文献
56.
Owing to cumulative effects of microwave irradiation and solid-liquid PTC without solvent methodology, conditions for alkylations of potassium acetate by n-octyl or n-cetyl halides are nearly quantitative within 2 minutes on appreciable quantities. 相似文献
57.
Colpaert F Mangelinckx S Denolf B De Kimpe N 《The Journal of organic chemistry》2012,77(14):6023-6032
Reaction of N-tert-butanesulfinyl α-halo imines with alkoxides afforded new N-tert-butanesulfinyl 2-amino acetals in good to excellent yield. These N-tert-butanesulfinyl 2-amino acetals are convenient precursors for the TMSOTf-promoted synthesis of the corresponding N-protected α-amino aldehydes and ketones, as well as for the HCl-promoted synthesis of 2-amino acetal hydrochlorides and α-amino ketone and α-amino aldehyde hydrochlorides in high yield. Via this method, an asymmetric synthesis of (S)-cathinone hydrochloride (er 94:6) was achieved. 相似文献
58.
Bram Neirinck Jan Fransaer Omer Van der Biest Jef Vleugels 《Electrochemistry communications》2009,11(1):57-60
Electrophoretic deposition (EPD) is a cheap and simple processing technique based on the movement of charged particles in an electrical field (electrophoresis) followed by deposition of these particles on the electrode that attracted them [O. VanderBiest, L.J. Vandeperre, Electrophoretic deposition of materials, Annu. Rev. Mater. Sci. 29 (1999) 327–352]. If not for electrolysis, water would be the solvent of choice instead of the currently commercially used organics. In this work we prove that high voltages can be used for electrophoretic deposition from aqueous suspensions without decomposition of water when applying an asymmetric alternating electric field. The experimental results show that deposits formed using these fields have a green density and surface comparable and even better than those typically obtained using the classic EPD systems. As a result volatile, expensive and environmentally unfriendly solvents are no longer a necessity. 相似文献
59.
B Verbelen V Leen L Wang N Boens W Dehaen 《Chemical communications (Cambridge, England)》2012,48(73):9129-9131
A new one-step synthetic method towards 3- and 3,5-arylated BODIPY dyes via palladium-catalysed C-H arylation has been developed and its scope has been investigated. 相似文献
60.
Cornelis B Moonen M Wouters J 《The Journal of the Acoustical Society of America》2012,131(6):4743-4755
This paper evaluates noise reduction techniques in bilateral and binaural hearing aids. Adaptive implementations (on a real-time test platform) of the bilateral and binaural speech distortion weighted multichannel Wiener filter (SDW-MWF) and a competing bilateral fixed beamformer are evaluated. As the SDW-MWF relies on a voice activity detector (VAD), a realistic binaural VAD is also included. The test subjects (both normal hearing subjects and hearing aid users) are tested by an adaptive speech reception threshold (SRT) test in different spatial scenarios, including a realistic cafeteria scenario with nonstationary noise. The main conclusions are: (a) The binaural SDW-MWF can further improve the SRT (up to 2 dB) over the improvements achieved by bilateral algorithms, although a significant difference is only achievable if the binaural SDW-MWF uses a perfect VAD. However, in the cafeteria scenario only the binaural SDW-MWF achieves a significant SRT improvement (2.6 dB with perfect VAD, 2.2 dB with real VAD), for the group of hearing aid users. (b) There is no significant degradation when using a real VAD at the input signal-to-noise ratio (SNR) levels where the hearing aid users reach their SRT. (c) The bilateral SDW-MWF achieves no SRT improvements compared to the bilateral fixed beamformer. 相似文献