X-ray Emission Hazards from Ultrashort Pulsed Laser Material Processing in an Industrial Setting.

Interactions between ultrashort laser pulses with intensities larger than 1013 W/cm2 and solids during material processing can lead to the emission of X-rays with photon energies above 5 keV, causing radiation hazards to operators. A framework for inspecting X-ray emission hazards during laser material processing has yet to be developed. One requirement for conducting radiation protection inspections is using a reference scenario, i.e., laser settings and process parameters that will lead to an almost constant and high level of X-ray emissions. To study the feasibility of setting up a reference scenario in practice, ambient dose rates and photon energies were measured using traceable measurement equipment in an industrial setting at SCHOTT AG. Ultrashort pulsed (USP) lasers with a maximum average power of 220 W provided the opportunity to measure X-ray emissions at laser peak intensities of up to 3.3 × 1015 W/cm2 at pulse durations of ~1 ps. The results indicate that increasing the laser peak intensity is insufficient to generate high dose rates. The investigations were affected by various constraints which prevented measuring high ambient dose rates. In this work, a list of issues which may be encountered when performing measurements at USP-laser machines in industrial settings is identified.

Enzymatic hydrolysis of poly(ethyleneterephthalate) used for and analysed by pore modification of track-etched membranes.

The potential of limited enzymatic poly(ethylene terephthalate) (PET) surface hydrolysis for the modification of track-etched (TE) membranes was investigated. Cutinases 1 and 2 from Thermobifida cellulosilytica as well as a fusion protein of cutinase 1 with the polymer binding module from the polyhydroxyalkanoate depolymerase of Alcaligenes faecalis (Thc_Cut1_PBM) were shown to hydrolyse highly crystalline PET TE membranes with a pore diameter of ∼120nm at very narrow size distribution. Furthermore the effects of surface chemistry were investigated by comparison of enzymatic hydrolysis by Thc_Cut1_PBM of "as received" PET TE membranes with two surface functionalized versions towards a "hydrophilic" and a more "hydrophobic" surface. The effects of adsorbed protein and the efficacy of cleaning steps after enzymatic treatment were elucidated by complementary methods for surface analysis and membrane characterization. With the optimized cleaning protocol, all adsorbed protein could be removed from the enzyme-treated membranes and effects of chemical surface functionalization of the PET TE membranes were demonstrated. The highest efficiency of enzymatic surface hydrolysis was observed for the original PET TE membranes, leading to an 0.36% weight loss corresponding to a removal of ∼3nm PET from the entire surface of the porous membrane. This correlates very well with the measured increase of barrier pore diameter by 4nm (a radius reduction? of 2nm), leading to about a two-fold increased water permeability.

Ultrasound-enhanced enzymatic hydrolysis of poly(ethylene terephthalate).

The application of ultrasound was found to enhance enzymatic hydrolysis of poly(ethylene terephthalate) (PET). After a short activation phase up to 6.6times increase in the amount of released products was found. PET powder with lower crystallinity of 8% was hydrolyzed faster when compared to PET with 28% crystallinity. Ultrasound activation was found to be around three times more effective on powders vs. films most likely due to a larger surface area accessible to the enzyme.

Building an antifouling zwitterionic coating on urinary catheters using an enzymatically triggered bottom-up approach.

Catheter associated urinary tract infections are common during hospitalization due to the formation of bacterial biofilms on the indwelling device. In this study, we report an innovative biotechnology-based approach for the covalent functionalization of silicone catheters with antifouling zwitterionic moieties to prevent biofilm formation. Our approach combines the potential bioactivity of a natural phenolics layer biocatalytically conjugated to sulfobetaine-acrylic residues in an enzymatically initiated surface radical polymerization with laccase. To ensure sufficient coating stability in urine, the silicone catheter is plasma-activated. In contrast to industrial chemical methods, the methacrylate-containing zwitterionic monomers are polymerized at pH 5 and 50 °C using as an initiator the phenoxy radicals solely generated by laccase on the phenolics-coated catheter surface. The coated catheters are characterized by X-ray photoelectron spectroscopy (XPS), Fourier transformed infrared (FTIR) analysis, atomic force microscopy (AFM), and colorimetrically. Contact angle and protein adsorption measurements, coupled with in vitro tests with the Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus in static and dynamic conditions, mimicking the operational conditions to be faced by the catheters, demonstrate reduced biofilm formation by about 80% when compared to that of unmodified urinary catheters. The zwitterionic coating did not affect the viability of the human fibroblasts (BJ-5ta) over seven days, corresponding to the extended useful life of urinary catheters.