One-joule 500-Hz cryogenic Yb:YAG laser driver of composite thin-disk design.

We present results on the development of a cryogenic Yb:YAG multi-pass laser amplifier based on a composite thin-disk design and demonstrate one-joule, diffraction limited, chirped 234-ps pulses with 50% optical-to-optical efficiency. High beam quality was obtained for repetition rates up to 400 Hz. The hardware was disassembled and thoroughly inspected after accumulating 80 hours of use at repetition rates from 100 to 500 Hz and exhibited no signs of damage. This laser driver is now commissioned to a dedicated laboratory where a grating compressor is producing 5.2-ps pulses used in the development of a compact x ray source based on inverse Compton scattering.

Versatile optical laser system for experiments at the European X-ray free-electron laser facility.

We present the main features of the final prototype of a pulsed optical laser, developed for pump-probe and other experiments in conjunction with the femtosecond x-ray beams at the European X-ray free-electron laser facility. Adapted to the temporal x-ray emission pattern of the facility, the laser provides 10 Hz bursts of up to 600 µs duration with intra-burst pulse frequencies as high as 4.5 MHz. In this mode, we have generated pulses as short as 12 fs at 350 W average power during the burst and with beam qualities close to the diffraction limit. This is, to the best of our knowledge, the highest power to date of a few-cycle laser operating at a center wavelength of 800 nm. Important for experimental flexibility, the laser can be configured in various unique ways, enabling, e.g., energy scaling to >3 mJ per pulse through a frequency change down to 100 kHz and the generation of nearly transform limited pulses between 12 fs and 300 fs. In addition to the 800 nm femtosecond beam line, a synchronized long pulse (0.8 ps or 400 ps) 1030 nm beam can be utilized, offering up to 4 kW burst average power, i.e. up to 40 mJ per pulse at 100 kHz. Efficient nonlinear wavelength conversion and tuning through intrinsic and external means further enhance the capabilities of the laser.

High power burst-mode optical parametric amplifier with arbitrary pulse selection.

We present results from a unique burst-mode femtosecond non-collinear optical parametric amplifier (NOPA) under development for the optical - x-ray pump-probe experiments at the European X-Ray Free-Electron Laser Facility. The NOPA operates at a burst rate of 10 Hz, a duty cycle of 2.5% and an intra-burst repetition rate of up to 4.5 MHz, producing high fidelity 15 fs pulses at a center wavelength of 810 nm. Using dispersive amplification filtering of the super-continuum seed pulses allows for selectable pulse duration up to 75 fs, combined with a tuning range in excess of 100 nm whilst remaining nearly transform limited. At an intra-burst rate of 188 kHz the single pulse energy from two sequential NOPA stages reached 180 µJ, corresponding to an average power of 34W during the burst. Acousto- and electro-optic switching techniques enable the generation of transient free bursts of required length and the selection of arbitrary pulse sequences inside the burst.

The endodontic-periodontal lesion: a rational approach to treatment.

When a periapical lesion communicates with a deep periodontal pocket, the etiology can be either endodontic or periodontal. This article clarifies the relationship between pulpal and periodontal disease and presents a systematic approach to the diagnosis and management of endodontic-periodontal lesions. It also presents a case that demonstrates the successful treatment of teeth that appear to be hopelessly diseased.

Guided tissue regeneration: an adjunct to endodontic surgery.

Membrane barriers used in conjunction with periodontal surgery have promoted regeneration of lost marginal attachment. Membrane barriers also may be indicated during surgical endodontics, in selected cases, where primary apical lesions are complicated by the loss of marginal attachment. The indications for using guided tissue regeneration in endodontic surgery are discussed and two cases are presented.

A modern approach to surgical endodontics: ultrasonic apical preparation.

Ultrasonic devices are capable of generating better apical preparations than rotary instruments with less sacrifice of root structure. Regardless of the technique used, good lighting and magnification are necessary to insure an adequate apical preparation.

Postsurgical endodontics.

Apical surgery is known to be an effective and practical way of treating endodontic failures. However, in spite of seemingly proper root end management, surgical failures may occur as a result of lateral canal, dentinal tubule, end retrograde leakage. Since surgical retreatment of such failures would likely result in failure, the alternative of a nonsurgical retreatment should be carefully considered. An understanding of the relationship which exists between the quality of the orthograde treatment and the surgical prognosis is necessary to properly direct the course of treatment.

External root resorption--fact or fancy.

A review of external resorption is presented with an emphasis on a wide range of etiological factors. This case report details the possible pitfalls in basing the diagnosis solely on radiographic interpretation.

[Determination of 5-methoxypsoralen in suntan cosmetics]. / Bestimmung von 5-Methoxypsoralen in Sonnenschutzmitteln.

A method for the determination of 5-methoxypsoralene in suntan-cosmetics is described. After liquid chromatographic clean-up, the final extract is screened by twodimensional thin layer chromatography. For positive extracts 5-methoxypsoralene is analysed quantitatively by capillary gas chromatography, using 5-alpha-cholestane as an internal standard and flame ionization detection (FID). The results were confirmed by gas chromatography-mass spectrometry (GC-MS). The recoveries for suntan-cosmetics of emulsion type were 70% and for tanning oils 90%. Detection limits of the method were 0,1 to 0,5 mg/kg, depending on the sample type. By application of this method 5-methoxypsoralene was detected in 6 of the 21 cosmetic products at levels up to 28 mg/kg.

[Determination of deoxynivalenol and nivalenol in cereals at the microgram/kilogram range]. / Untersuchung von Cerealien auf Deoxynivalenol und Nivalenol im unteren ug/kg-Bereich.

A method is described for the determination of Deoxynivalenol (DON) and Nivalenol (NV). A liquid chromatographic clean-up step is followed by silylation of the extract and the trimethylsilylether are determined by gas-chromatography-mass-spectrometry (GC-MS), monitoring the characteristic ions in the negative chemical ionisation mode. 71% of 42 food-samples were contaminated with DON and 38% with NV. The highest contamination detected was 2000 micrograms/kg DON and 120 micrograms/kg NV in a wheat bran sample. Deoxynivalenol and Nivalenol in concentrations of 10 micrograms/kg can be detected easily by this method.