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1.
KL Britton HF Rogers Y Asano T Dairi Y Kato TJ Stillman DW Rice 《Acta crystallographica. Section D, Biological crystallography》1998,53(4):124-126
The novel NAD+-linked opine dehydrogenase from a soil isolate Arthrobacter sp. strain 1C belongs to an enzyme superfamily whose members exhibit quite diverse substrate specificites. Crystals of this opine dehydrogenase, obtained in the presence or absence of co-factor and substrates, have been shown to diffract to beyond 1.8 ? resolution. X-ray precession photographs have established that the crystals belong to space group P21212, with cell parameters a = 104.9, b = 80.0, c = 45.5 ? and a single subunit in the asymmetric unit. The elucidation of the three-dimensional structure of this enzyme will provide a structural framework for this novel class of dehydrogenases to enable a comparison to be made with other enzyme families and also as the basis for mutagenesis experiments directed towards the production of natural and synthetic opine-type compounds containing two chiral centres. 相似文献
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Bottger I Schedel-Niedrig T Timpe O Gottschall R Havecker M Ressler T Schlogl R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(10):1870-1876
The catalytically active copper phase for the partial oxidation of methanol is studied by means of time-resolved extended X-ray absorption fine structure (EXAFS) spectroscopy combined with the detection of the catalytic turnover. It is found that the active form of the copper is a strained nanocrystalline form of the metal. The metal is no longer made up from large crystallites but contains a defect structure in which oxygen is already intercalated. 相似文献
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F. Wagner C. P. João J. Fils T. Gottschall J. Hein J. Körner J. Limpert M. Roth T. Stöhlker V. Bagnoud 《Applied physics. B, Lasers and optics》2014,116(2):429-435
We report on the development of a preamplifier module for temporal contrast enhancement and control at petawatt-class lasers. The module is based on an ultrafast optical parametric amplifier (uOPA), which produces temporally clean pulses at the 60 μJ level for seeding a chirped pulse amplification (CPA) system, namely the petawatt facility PHELIX. The amplifier module allows for gain reduction in the following amplifiers, resulting in an attenuation of amplified spontaneous emission (ASE) by more than 4 orders of magnitude. Since the ASE of a CPA system linearly depends on the seeding energy, we were able to demonstrate a continuous variation of the temporal contrast by tuning the gain of the uOPA. 相似文献
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Thomas Gottschall Tobias Meyer Martin Baumgartl Cesar Jauregui Michael Schmitt Jürgen Popp Jens Limpert Andreas Tünnermann 《Laser \u0026amp; Photonics Reviews》2015,9(5):435-451
During the past decade coherent anti‐Stokes Raman scattering (CARS) microscopy has evolved to one of the most powerful imaging techniques in the biomedical sciences, enabling the label‐free visualization of the chemical composition of tissue in vivo in real time. While the acquisition of high‐contrast images of single cells up to large tissue sections enables a wide range of medical applications from routine diagnostics to surgical guidance, to date CARS imaging is employed in fundamental research only, essentially because the synchronized multiple wavelength pulsed laser sources required for CARS microscopy are large, expensive and require regular maintenance. Laser sources based on optical fibers can overcome these limitations combining highest efficiency and peak powers with an excellent spatial beam profile and thermal stability. In this review we summarize the different fiber‐based approaches for laser sources dedicated to coherent Raman imaging, in particular active fiber technology and passive fiber‐based frequency conversion processes, i.e. supercontinuum generation, soliton self‐frequency shift and four‐wave mixing. We re‐evaluate the ideal laser parameters for CARS imaging and discuss the suitability of different laser concepts for turn‐key operation required for routine application in clinics.
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Rothhardt J Eidam T Hädrich S Jansen F Stutzki F Gottschall T Andersen TV Limpert J Tünnermann A 《Optics letters》2011,36(3):316-318
We present a high-average-power femtosecond laser system at 520 nm central wavelength. The laser system delivers sub-500 fs pulses with 135 W average power at a pulse repetition rate of 5.25 MHz. Excellent beam quality is provided by high power fiber amplifiers and maintained during frequency doubling, resulting in a beam quality factor of M2<1.2. To our knowledge, the system presented here is the highest average power green laser source generating femtosecond pulses with diffraction-limited beam quality. 相似文献
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In this paper we discuss the recovery of derivatives and thecomputation of rigorous and useful upper bounds for the pointwiseerror in the recovered derivatives, for finite element approximationsof the Laplace equation with Neumann boundary conditions, especiallyat points close to or on a smooth, curved boundary. We analyzethe dipole image technique for the case of curved boundaries,and show how to compute reliable recovered derivatives and errorbounds even in the limiting case of points lying on the curvedboundary. Numerical experiments show reasonably tight errorbounds for points both close to and away from a curved boundary. 相似文献
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F. J. Lüke W. Schlegel F. Gabor F. Pittner R. Linke W. König U. Hilgenfeldt W. Hubl H. -J. Thiele D. Meißner B. Krüger M. Knoll A. Gottschall W. Tessenow U. Meyer W. Dummler G. A. Cumme H. Ehle R. Bublitz A. Horn Z. Drzeniek R. Lamerz H. -D. Haubeck C. Wagener 《Analytical and bioanalytical chemistry》1990,337(1):97-103
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An accurate, reliable, and reproducible analytical method using HPLC/MS/MS for the determination of tulathromycin residues in bovine liver and porcine kidney via their common hydrolytic fragment (CP-60,300) was developed and validated. Briefly, the method involved an initial acid treatment of intact tissues, which yielded the common fragment (CP-60,300). A portion of the acid hydrolyzate was purified by SPE using a strong cation exchange cartridge. Evaporation of the purified extract was followed by reconstitution in aqueous buffer and analysis by HPLC/MS/MS under isocratic conditions. The developed method provided acceptable sensitivity for determinative surveillance of tulathromycin in porcine kidney and bovine liver with an LOQ of 7.50 and 2.75 microg/g, respectively. The overall recovery and precision of 45 determinations of each tissue were 97.8% (5.3%) for porcine kidney and 96.9% (7.9%) for bovine liver. Accuracy, precision, linearity, specificity, and ruggedness were demonstrated. An HPLC/MS/MS method was also developed for use in these tissues as a confirmatory assay following modifications to the MS detection parameters. The confirmatory method demonstrated acceptable sensitivity for confirmatory evaluation of tulathromycin in porcine kidney and bovine liver at tolerances of 15 and 5.5 microg/g, respectively. 相似文献
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Schulz M Riedel R Willner A Mans T Schnitzler C Russbueldt P Dolkemeyer J Seise E Gottschall T Hädrich S Duesterer S Schlarb H Feldhaus J Limpert J Faatz B Tünnermann A Rossbach J Drescher M Tavella F 《Optics letters》2011,36(13):2456-2458
We report on a Yb:YAG Innoslab laser amplifier system for generation of subpicsecond high energy pump pulses for optical parametric chirped pulse amplification (OPCPA) at high repetition rates. Pulse energies of up to 20 mJ (at 12.5 kHz) and repetition rates of up to 100 kHz were attained with pulse durations of 830 fs and average power in excess of 200 W. We further investigate the possibility to use subpicosecond pulses to derive a stable continuum in a YAG crystal for OPCPA seeding. 相似文献