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81.
82.
The velocity distribution of liquid flowing in a commercial micromixer has been determined directly by using pulsed-field gradient NMR. Velocity maps with a spatial resolution of 29 microm x 43 microm were obtained by combining standard imaging gradient units with a homebuilt rectangular surface coil matching the mixer geometry. The technique provides access to mixers and reactors of arbitrary shape regardless of optical transparency. Local heterogeneities in the signal intensity and the velocity pattern were found and serve to investigate the quality and functionality of a micromixer, revealing clogging and inhomogeneous flow distributions. 相似文献
83.
Ghasparian A Moehle K Linden A Robinson JA 《Chemical communications (Cambridge, England)》2006,(2):174-176
A crystal structure is reported of the peptide Ac-Ala-Asn-Pro-Asn-Ala-NH2, representing the immunodominant region of the major surface protein on the malaria parasite; the NPNA motif adopts a type-I beta-turn, which is stabilized by hydrogen bonding between the CO of Asn2 and the NH of Ala5 as well as between the O(delta) of Asn2 and the NH of Asn4. 相似文献
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Edward H. Bernhardi Kees O. van der Werf Anton J. F. Hollink Kerstin Wrhoff Ren M. de Ridder Vinod Subramaniam Markus Pollnau 《Laser \u0026amp; Photonics Reviews》2013,7(4):589-598
An integrated intra‐laser‐cavity microparticle sensor based on a dual‐wavelength distributed‐feedback channel waveguide laser in ytterbium‐doped amorphous aluminum oxide on a silicon substrate is demonstrated. Real‐time detection and accurate size measurement of single micro‐particles with diameters ranging between 1 µm and 20 µm are achieved, which represent the typical sizes of many fungal and bacterial pathogens as well as a large variety of human cells. A limit of detection of ∼500 nm is deduced. The sensing principle relies on measuring changes in the frequency difference between the two longitudinal laser modes as the evanescent field of the dual‐wavelength laser interacts with micro‐sized particles on the surface of the waveguide. Improvement in sensitivity far down to the nanometer range can be expected upon stabilizing the pump power, minimizing back reflections, and optimizing the grating geometry to increase the evanescent fraction of the guided modes. 相似文献
87.
Srinivas N Moehle K Abou-Hadeed K Obrecht D Robinson JA 《Organic & biomolecular chemistry》2007,5(19):3100-3105
The turn-forming D-Pro-L-Pro template has been frequently used to promote regular beta-hairpin conformations in cyclic protein epitope mimetics. Here the use of three isomeric biaryl templates has been studied as alternatives to D-Pro-L-Pro in the preparation of beta-hairpin peptidomimetics. The o,o'- o,m'- and m,m'-isomers of carboxymethyl- and aminomethyl-substituted biaryl templates have been incorporated into novel macrocyclic mimics of the naturally occurring cationic antimicrobial peptide protegrin I. The presence of the o-carboxymethyl-o'-aminomethyl-biaryl template within the macrocyclic peptide resulted in the appearance of slowly interconverting atropisomers. Although none of the resulting mimetics adopted stable beta-hairpin structures in aqueous solution, they all nevertheless retained a significant antimicrobial activity against Gram positive and Gram negative bacteria. These mimetics provide interesting starting points for an optimization program in the search for potent and novel antimicrobial compounds. 相似文献
88.
In a medical procedure to comminute kidney stones the patient is subjected to hypersonic waves focused at the stone. Unfortunately such shock waves also damage the surrounding kidney tissue. We present here a model for the mechanical response of the soft tissue to such a high speed loading regime. The material model combines shear induced plasticity with irreversible volumetric expansion as induced, e.g., by cavitating bubbles. The theory is based on a multiplicative decomposition of the deformation gradient and on an internal variable formulation of continuum thermodynamics. By the use of logarithmic and exponential mappings the stress update algorithms are extended from small‐strain to the finite deformation range. In that way the time‐discretized version of the porous‐viscoplastic constitutive updates is described in a fully variational manner. By numerical experiments we study the shock‐wave propagation into the tissue and analyze the resulting stress states. A first finite element simulation shows localized damage in the human kidney. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Equilibrium Pressure Measurements in the System Se/O/Br The saturation pressure or saturation decomposition pressure of SeOBr2,l, Se2Br2,l and SeBr4,s were determined in a membran zero manometer. The decomposition behaviour follows from pressure measurements outside of saturation. From the equilibrium data are derived the Enthalpies of formation: Data see Inhaltsübersicht. Informations about the melting diagrams obtained via the barograms of the condensed compositions SeO2/SeBr4 and Se/Br. 相似文献