Corneal ablation with new 193 nm solid-state laser: preliminary experiments.

PURPOSE: To assess the ability of a newly developed 193 nm solid-state laser to ablate the cornea. SETTING: Osaka University, Osaka, Japan. METHODS: A prototype laser engine was developed by combining a 1547 nm laser diode, fiber amplifiers, and 5 stages of a frequency-conversion system using CsLiB6O10 crystals as the last stage. Poly(methyl methacrylate) (PMMA) plates were exposed to the prototype laser beam to determine the relationship between the fluence and ablation rate. Laser irradiation of porcine corneas was performed to induce morphological changes, and the quality of the lesions was determined by light and scanning electron microscopy. RESULTS: The relationship between the fluence and ablation rate of the 193 nm solid-state laser was comparable to that of the argon-fluoride excimer laser. Light and scanning electron microscopy of the porcine corneas showed that the linear and square lesions had sharp, clean edges. CONCLUSIONS: Smooth ablations of PMMA plates and porcine corneas were obtained by the laser. Further investigations must be conducted to determine whether this laser can be an alternative laser source for keratorefractive surgery.

Molecular and isotopic evidence for the processing of starchy plants in Early Neolithic pottery from China.

Organic residue analysis of ancient ceramic vessels enables the investigation of natural resources that were used in daily cooking practices in different part of the world. Despite many methodological advances, the utilization of plants in pottery has been difficult to demonstrate chemically, hindering the study of their role in ancient society, a topic that is especially important to understanding early agricultural practices at the start of the Neolithic period. Here, we present the first lipid residue study on the Chinese Neolithic pottery dated to 5.0 k - 4.7 k cal BC from the Tianluoshan site, Zhejiang province, a key site with early evidence for rice domestication. Through the identification of novel molecular biomarkers and extensive stable isotope analysis, we suggest that the pottery in Tianluoshan were largely used for processing starchy plant foods. These results not only highlight the significance of starchy plants in Neolithic southern China but also show a clear difference with other contemporary sites in northern Eurasia, where pottery is clearly orientated to aquatic resource exploitation. These differences may be linked with the early development of rice agriculture in China compared to its much later adoption in adjacent northerly regions.

Processing of membrane protein crystal using ultraviolet laser irradiation.

We demonstrated the processing of a membrane protein crystal, using a pulsed UV laser soft ablation (PULSA) technique. Irradiation with deep-UV laser pulses at a wavelength of 193 nm successfully processed not only single crystals of the membrane transporter protein AcrB but also nylon loops and cryoprotectants at a cryogenic temperature. Nonprocessed parts of the crystals exhibited no signs of crack or denaturation after the laser exposure. The trimmed crystals were found to be of high resolution for X-ray diffraction data collection. The results described here indicate that PULSA processing is an effective tool for membrane protein crystals, as well as for soluble protein crystals.