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141.
We show that a concentration of light at a metal tip allows near-field optical imaging of single fluorescent dye molecules at very high resolution, despite strong quenching effects. Details as small as 10 nm were observed in the fluorescence patterns of single Cy-3 dyes bound to the termini of DNA. Data evaluation by model fitting determines the positions of the dyes to an accuracy even better than 1 nm and also yields their 3D orientation. The metal tip simultaneously provides high-resolution topographic imaging complementing the optical signal for a detailed surface examination. 相似文献
142.
Generation of intense,carrier-envelope phase-locked few-cycle laser pulses through filamentation 总被引:3,自引:0,他引:3
C.P.?Hauri W.?Kornelis F.W.?Helbing A.?Heinrich A.?Couairon A.?Mysyrowicz J.?BiegertEmail author U.?Keller 《Applied physics. B, Lasers and optics》2004,79(6):673-677
Intense, well-controlled light pulses with only a few optical cycles start to play a crucial role in many fields of physics, such as attosecond science. We present an extremely simple and robust technique to generate such carrier-envelope offset (CEO) phase locked few-cycle pulses, relying on self-guiding of intense 43-fs, 0.84 mJ optical pulses during propagation in a transparent noble gas. We have demonstrated 5.7-fs, 0.38 mJ pulses with an excellent spatial beam profile and discuss the potential for much shorter pulses. Numerical simulations confirm that filamentation is the mechanism responsible for pulse shortening. The method is widely applicable and much less sensitive to experimental conditions such as beam alignment, input pulse duration or gas pressure as compared to gas-filled hollow fibers. PACS 45.65.Ky; 42.65.Re 相似文献
143.
Tris(oxalato)phosphorus acid and its lithium salt 总被引:1,自引:0,他引:1
Wietelmann U Bonrath W Netscher T Nöth H Panitz JC Wohlfahrt-Mehrens M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(10):2451-2458
The conversion of three equivalents of anhydrous oxalic acid with phosphorus pentachloride yields tris(oxalato)phosphorus acid 1, which crystallizes from diethyl ether solutions as protonated diethyl ether complex [(Et2O)2H](+)[P(C2O3)3)]-. The superacidic compound can be used as catalyst for Friedel-Crafts-type reactions. Upon neutralization with lithium hydride, the lithium salt Li[P(C2O3)3] 2 is obtained, which is highly soluble in aprotic solvents and which exhibits a wide voltage window. Thus, the lithium compound is a promising candidate as electrolyte for high performance non-aqueous batteries. 相似文献
144.
The anionic bis(pyrazolyl)(thioimidazolyl)borate ligands BpMt(R) with R = tert-butyl and isopropyl were obtained as their potassium salts by reacting potassium tris(pyrazolyl)borate with the corresponding thioimidazoles in the melt at 150 degrees C. They were applied to form some tetrahedral zinc complexes and identified by the crystal structures of (BpMt(t-Bu))ZnCl and (BpMt(i-Pr))Zn-SC(6)H(4)-p-Cl. 相似文献
145.
Heinrich Winter 《Mathematische Semesterberichte》2004,50(2):191-235
Dieser Beitrag hat seinen Ursprung in Veranstaltungen zur Heuristik im Rahmen meiner Tätigkeit in der fachdidaktischen Ausbildung von Gymnasiallehrern an der hiesigen RWTH. Mehr und mehr habe ich dabei die Überzeugung gewonnen, dass es notwendig ist, Lehramtskandidaten historische, heuristische und pädagogische Aspekte wichtiger mathematischer Inhalte erfahren zu lassen, die innerhalb der fachlichen Ausbildung nicht oder nicht genügend Berücksichtigung finden können und die aber im Hinblick auf den späteren Beruf wesentlich sind. Es wird hiermit weniger für eine Behandlung des Zwei-Quadrate-Satzes in der Schule - wenngleich sehr erwünscht - plädiert, wohl aber könnte dieses Thema Bestandteil eines fachdidaktischen Seminars oder Proseminars sein. Die Einschränkung im obigen Zitat von Hardy war natürlich eine zusätzliche didaktische Herausforderung. Den Gutachtern danke ich für ihre Ermutigung sowie für zahlreiche Verbesserungsvorschläge und Hinweise auf Unklarheiten und Fehler. Ebenso danke ich Herrn Artmann sehr, der eine frühere Fassung gelesen und konstruktiv kritisiert hat.Einige Grafiken wurden mit der dynamischen Mathematiksoftware GEONExT erzeugt. GEONExT ist unter der Adresse http: //geonext.de frei erhältlich. 相似文献
146.
We show that attosecond pulse trains have a natural application in the control of strong field processes. In combination with an intense infrared laser field, the pulse train can be used to microscopically select a single quantum path contribution to a process that would otherwise consist of several interfering components. We present calculations that demonstrate this by manipulating the time-frequency properties of high order harmonics at the single atom level. This quantum path selection can also be used to define a high resolution attosecond clock. 相似文献
147.
Poschalko A Rohr T Gruber H Bianco A Guichard G Briand JP Weber V Falkenhagen D 《Journal of the American Chemical Society》2003,125(44):13415-13426
A novel SUcrose-Based Polymer support (SUBPOL) with tailored morphology suitable for the use in solid-phase peptide synthesis (SPPS) is described, and its application as a hydrophilic affinity matrix for the specific removal of fibrinogen from human plasma is demonstrated. After suspension polymerization of partly methacrylated 2,1':4,6-di-O-isopropylidene sucrose and subsequent removal of the protecting groups, hydrophilic spherical polymer beads were obtained. The morphology of the resulting resin was controlled by variation of the porogen as well as the average degree of substitution with respect to the methacryloyl groups of the monomer mixture. After introduction of amino groups for a permanent attachment of immobilized peptide ligands, prevention of unintended esterification during SPPS was achieved by silylation of remaining hydroxy groups. Alternatively, a Rink amide linker was introduced prior to SPPS to allow cleavage and subsequent analysis of the peptide assembled on the SUBPOL resins. Two hexapeptides of sequence kwiivw and hffflw, consisting of d-amino acids, as well as a 19-mer peptide corresponding to the sequence GSGVRGDFGSLAPRVARQL of the VP1 protein from the foot-and-mouse disease virus (FMDV) were successfully prepared both manually or in a semi-automated process on SUBPOL resins according to the Fmoc/tBu strategy. Yields and purities were comparable to peptides prepared on commercially available polystyrene resins. A specific affinity adsorbent containing the fibrinogen-binding pentapeptide GPRPK was prepared by SPPS on SUBPOL resins of different morphology, and the strong impact of the affinity matrix on adsorption performance was demonstrated. 相似文献
148.
149.
Heinrich Saller 《International Journal of Theoretical Physics》2000,39(2):321-340
The linear particle-antiparticle conjugation C and position space reflection P aswell as the antilinear time reflection T are shown to be inducible by theself-duality of representations for the operation groups SU(2), SL(C2), and R forspin, Lorentz transformations, and time translations, respectively. The definitionof a color-compatible linear CP-reflection for quarks as self-duality induced isimpossible since triplet and antitriplet SU(3)-representations are not linearlyequivalent. 相似文献
150.
Ohne Zusammenfassung 相似文献