Mid-infrared Fe:ZnSe laser achieves output energy scaling at room temperature
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olution wets its surface. This is significant because it demonstrates that liquid does not reach the bulk of the biofilm and no chemical change occurs in the biofilm exposed to 60–70% ethanol—a range commonly thought to be disinfectant. To further describe the fluid-repellent nature of the biofilm, the researchers examined the influence of topography. These biofilms naturally have an undulating surface at the 10s–100s μm scale. Confocal microscopy showed that drops containing a fluorescent dye stained only on the top layer of the biofilm and did not penetrate into the grooves of the surface. This demonstrates that the biofilm exhibited Cassie–Baxter wetting, a state which traps gas within the topography and is common for many superhydrophobic surfaces. However, epoxy replicates of the surface did not reproduce the contact angle behavior of the biofilm. This shows that a combination of the topography and a dynamic chemistry of the ECM are responsible for liquid repellency. The researchers demonstrated that water repellency on the macroscopic scale may provide bacteria an additional defense mechanism to antimicrobial agents. The researchers are careful to note that this strain of bacteria is commonly found in soil, so biofilms that are constantly submerged in water will likely exhibit different behavior. Yet this research demonstrates that some sterilization techniques, such as soaking in disinfectant, may not be effective for certain types of bacteria. Scott Cooper
important atmospheric constituents have absorption lines in the 2–10 μm “molecular fingerprint” region. Mid-IR lasers are thus suitable candidates for applications in space optical communications, as well as in remote sensing, trace gas analysis, laser surgery, and medical diagnosis. Lasers based on II–VI compounds doped with transition metals (such as Fe-doped binary and ternary chalcogenides) with a gain bandwidth of up to 50% of the central wavelength constitute a viable
route for broadly tunable mid-IR coherent sources. They can provide very high power levels with good beam quality, but realizing these in practice has been a challenge. While some sources have been developed, the output energy levels have been unacceptably low. N.-S. Myoung, S.B. Mirov, and colleagues from the University of Alabama at Birmingham have now achieved energy scaling in a 4.3 μm Fe:ZnSe mid-IR laser at room temperature by optimizing the fabrica-
Bio Focus
Bacterial biofilm demonstrates nonwetting behavior
Contact angle
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Mid-infrared Fe:ZnSe laser achieves output energy scaling at room temperature
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he development of a compact midinfrared (mid-IR) laser operating over a 2–10 μm spectral range has been a challenge for several decades. This range contains the atmospheric transparency window that allows for easy passage of radiation to the earth’s surface. Many
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VOLUME 36 • MARCH 2011
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The new D8 DISCOVER with DAVINCI Move up to the XRD2 dimension in X-ray diffraction n DAVINCI.SNAP-LOCK & DAVINCI.MODE: alignment-free compon
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