Experimental and numerical optimization of beam shapes for short-pulse ultraviolet laser cutting processing

AbstractIn this work the effect of elliptical beam shapes on cutting performance of silicon is studied experimentally using a Diode Pumped Solid State Q-switched UV laser operating at the wavelength of 355 nm. Elliptical beams are investigated by varying scanning speed, repetition rate and average output power. It is shown that a short elliptical beam with 6×230 μm dimension forms a deeper groove at higher cutting speed and lower average output power compared to a longer elliptical beam. A numerical model of the laser cutting process is also described. Some validation results for single and multi-pulse cutting are shown

Smart antimicrobial efficacy employing pH-sensitive ZnO-doped diamond-like carbon coatings

One of the main challenges in endoprosthesis surgeries are implant-associated infections and aseptic-loosenings, caused by wear debris. To combat these problems, the requirements to surfaces of endoprostheses are wear-resistance, low cytotoxicity and antimicrobial efficacy. We here present antimicrobial coatings with a smart, adaptive release of metal ions in case of infection, based on ZnO-nanoparticles embedded in diamond-like carbon (DLC). The Zn2+ ion release of these coatings in aqueous environments reacts and adapts smartly on inflammations accompanied by acidosis. Moreover, we show that this increased ion release comes along with an increased toxicity to fibroblastic cells (L929) and bacteria (Staphylococcus aureus subsp. aureus, resistant to methicillin and oxacillin. (ATCC 43300, MRSA) and Staphylococcus epidermidis (ATCC 35984, S. epidermidis). Interestingly, the antimicrobial effect and the cytotoxicity of the coatings increase with a reduction of the pH value from 7.4 to 6.4, but not further to pH 5.4

Low 1f noise single-layer YBa2Cu3Ox dc SQUID at 77 K

Low 1f noise single-layer YBa2Cu3Ox dc SQUID at 77 K / B. Stritzker ... - In: Applied physics letters. 60. 1992. S. 3048-305

Synthesis of epitaxial ß-SiC by C60-carbonization of silicon

By deposition of C60 on silicon at temperatures smaller than 1000 °C the formation of thin epitaxial β‐SiC films on Si was successful. This low‐temperature regime can be important for the application of SiC in microelectronic devices. C60 was deposited on Si(001) and Si(111) in ultrahigh vacuum at constant deposition rates for some hours. The temperature of the Si substrates ranged between 800 and 900 °C. The thickness and the composition of the formed layers are determined by Rutherford backscattering (RBS). The thickness of the layers varied between about 50 nm and 1 μm depending on the deposition parameters. From the shape of the RBS spectra and the x‐ray‐diffraction (XRD) scans, only β‐SiC can be identified. The Θ–2Θ XRD spectra show preferred orientation of β‐SiC on Si(001) and Si(111), respectively. Additional XRD pole figure measurements demonstrate the heteroepitaxial growth of β‐SiC on Si. The orientational relationships β‐SiC(001)[110]∥Si(001)[110] and SiC(111)[1̄10]∥Si(111)[1̄10] can be extracted. The formation of growth defects (twins) can be observed