PubMed · 4511201
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H O Persson. 1973. [Lasers. Theory, types, application].. https://pubmed.ncbi.nlm.nih.gov/4511201/
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Matrix-assisted laser desorption/ionization mass spectrometry was used for the characterization of extracted and synthesized oligo(ethylene terephthalate)s. Generally, cyclic oligomers [GT]n could be found in technical yarns and tiles, whereas our synthesized model oligomers mainly consisted of linear chains H-[GT]n-G. In addition, some other distributions could be identified as H-[GH]n-OH and H-[GGT]1-[GT]n-7/-G linear oligomers and H-[GGT]1-[GT]n-1 cyclic oligomers, where G is an ethylene glycol unit, GG is a diethylene glycol unit, caused by impurities of ethylene glycol, and T is a terephthalic acid unit. NMR and IR investigations were carried out to verify these results.
We evaluated the effect of the neodymium:YLF picosecond laser on intraocular lenses (IOLs) during experimental posterior capsulotomy and established the minimum damage threshold for lathe-cut poly(methyl methacrylate) (PMMA) IOLs. Single-piece, biconvex, lathe-cut PMMA lenses were placed in a model eye chamber against a latex membrane with a central area of lens-capsule touch. Energy levels from 40 micro J to 360 microJ pulse (0.4 mJ to 3.6 mJ) with a 0.5 mm line and a spot pattern were tested using different focal offsets. Threshold damage level was determined under the scanning electron microscope after observing the minimal energy level that did not cause damage to or pits in the IOLs. Lenses were then analyzed for size and type of damage. The 0.5 mm line pattern at 160 microJ using 350 microns offset was safe and effective for posterior capsulotomy in vitro. spot pattern caused IOL damage in the form of small pits at much lower energy levels of 80 microJ using 400 microns offset than the line pattern.
We have applied two-step laser mass spectrometry (L2MS) to the qualitative chemical analysis of porphyrin-derived photosensitizer dyes used for detection and photodynamic therapy of cancer. The only ionization technique applied so far to these low-volatility compounds had been fast atom bombardment (FAB), which suffers from problems associated with cluster formation of the porphyrins upon FAB ionization. From FAB and chromatography data, the existence of porphyrin dimers, trimers, and oligomers in commercial photosensitizers was concluded to be crucial for tumor localization, but it is possible that clustering or preformed van der Waals aggregates gave rise to these results. L2MS indicates that commercially available hematoporphyrin derivative and Photofrin II contain no detectable amounts of covalently bound porphyrin oligomers. Synthetic porphyrin dimers and trimers could be unambiguously detected by L2MS.