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91.
92.
The feasibility of laser-based excitation for quenched phosphorescence detection in capillary electrophoresis (CE) was explored for the first time by using a small-size, quadrupled Nd-YAG laser emitting 266 nm pulses (duration, 0.4 ns) at a repetition rate of 7.8 kHz. To provide a continuous phosphorescence background, the phosphorophore 1-bromo-4-naphthalene sulfonic acid (BrNS) was added to the separation buffer. Both experiments and theory show that in laser-induced phosphorescence (LIP) - in contrast with lamp-excited phosphorescence - one normally deals with such high triplet-state phosphorophore concentrations that triplet-triplet annihilation is the major deactivation pathway. This results in a lower quantum yield of the analyte-induced bimolecular quenching interaction and, thus, the observed quenching signal. The situation can be improved by using a cylindrical lens for excitation in order to reduce the irradiance. In this case limits of detection (LODs) similar to those obtained using lamp excitation (1x10(-8) M) were achieved, while the width of the detection window was reduced from about 4 mm to 1 mm. Even under exclusion of triplet-triplet annihilation, i.e., under conditions of low irradiance, for our setup the quenching yields in LIP were smaller than in lamp-based phosphorescence detection. This is due to the repetition rate of the laser (7.8 kHz), which is too high in view of the phosphorescence lifetime (ca. 300 micros at low irradiance). Theory shows that this disadvantageous effect will be fully eliminated if the repetition rate is decreased to 1 kHz. 相似文献
93.
94.
For a small system like a colloidal particle or a single biomolecule embedded in a heat bath, the optimal protocol of an external control parameter minimizes the mean work required to drive the system from one given equilibrium state to another in a finite time. In general, this optimal protocol obeys an integro-differential equation. Explicit solutions both for a moving laser trap and a time-dependent strength of such a trap show finite jumps of the optimal protocol to be typical both at the beginning and at the end of the process. 相似文献
95.
Dali Wang Chunlai Tu Yue Su Chuan Zhang Udo Greiser Xinyuan Zhu Deyue Yan Wenxin Wang 《Chemical science》2015,6(7):3775-3787
Despite of great advances of phospholipids and liposomes in clinical therapy, very limited success has been achieved in the preparation of smart phospholipids and controlled-release liposomes for in vivo drug delivery and clinical trials. Here we report a supramolecular approach to synthesize novel supramolecularly engineered phospholipids based on complementary hydrogen bonding of nucleosides, which greatly reduces the need of tedious chemical synthesis, including reducing the strict requirements for multistep chemical reactions, and the purification of the intermediates and the amount of waste generated relative more traditional approaches. These upgraded phospholipids self-assemble into liposome-like bilayer structures in aqueous solution, exhibiting fast stimuli-responsive ability due to the hydrogen bonding connection. In vitro and in vivo evaluations show the resulted supramolecular liposomes from nucleoside phospholipids could effectively transport drug into tumor tissue, rapidly enter tumor cells, and controllably release their payload in response to an intracellular acidic environment, thus resulting in a much higher antitumor activity than conventional liposomes. The present supramolecularly engineered phospholipids represent an important evolution in comparison to conventional covalent-bonded phospholipid systems. 相似文献
96.
A homogenization framework for the stochastic average meso-scale tread-road interaction with emphasis on macro-scale rolling resistance calculations is presented in this contribution. This framework accounts for large scale, high-frequency penetration of tread rubber by the highest asperities as well as for the nonlinear thermo-viscoelastic material behavior of this tread rubber in the regime of finite strains. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
97.
Kwon TH Armel V Nattestad A Macfarlane DR Bach U Lind SJ Gordon KC Tang W Jones DJ Holmes AB 《The Journal of organic chemistry》2011,76(10):4088-4093
A one-pot synthesis of 2,6-dibromodithieno[3,2-b;2',3'-d]thiophene (dibromo-DTT, 4) was developed. A key step was bromodecarboxylation of DTT-2,6-dicarboxylic acid, obtained by saponification of the diester 1. The donor-acceptor dye DAHTDTT (13), based on a central 2,6-bis[2'-(3'-hexylthienyl)]dithieno[3,2-b;2',3'-d]thiophene core (9), was prepared and incorporated in a dye-sensitized solar cell (DSC), which exhibited an energy conversion efficiency of 7.3% with V(oc) of 697 mV, J(sc) of 14.4 mA/cm(2), and ff of 0.73 at 1 sun. 相似文献
98.
99.
Udo Wegner 《Mathematische Annalen》1931,105(1):256-261
100.
Seifert U 《Physical review letters》2011,106(2):020601
We consider nanosized artificial or biological machines working in steady state enforced by imposing nonequilibrium concentrations of solutes or by applying external forces, torques, or electric fields. For unicyclic and strongly coupled multicyclic machines, efficiency at maximum power is not bounded by the linear response value 1/2. For strong driving, it can even approach the thermodynamic limit 1. Quite generally, such machines fall into three different classes characterized, respectively, as "strong and efficient," "strong and inefficient," and "balanced." For weakly coupled multicyclic machines, efficiency at maximum power has lost any universality even in the linear response regime. 相似文献