Near-field optical power transmission of dipole nano-antennas

Nano-antennas in functional plasmonic applications require high near-field optical power transmission. In this study, a model is developed to compute the near-field optical power transmission in the vicinity of a nano-antenna. To increase the near-field optical power transmission from a nano-antenna, a tightly focused beam of light is utilized to illuminate a metallic nano-antenna. The modeling and simulation of these structures is performed using 3-D finite element method based full-wave solutions of Maxwell’s equations. Using the optical power transmission model, the interaction of a focused beam of light with plasmonic nanoantennas is investigated. In addition, the tightly focused beam of light is passed through a band-pass filter to identify the effect of various regions of the angular spectrum to the near-field radiation of a dipole nano-antenna. An extensive parametric study is performed to quantify the effects of various parameters on the transmission efficiency of dipole nano-antennas, including length, thickness, width, and the composition of the antenna, as well as the wavelength and half-beam angle of incident light. An optimal dipole nanoantenna geometry is identified based on the parameter studies in this work. In addition, the results of this study show the interaction of the optimized dipole nano-antenna with a magnetic recording medium when it is illuminated with a focused beam of light

Transoral laser microsurgery for laryngeal cancer: A primer and review of laser dosimetry

Transoral laser microsurgery (TLM) is an emerging technique for the management of laryngeal and other head and neck malignancies. It is increasingly being used in place of traditional open surgery because of lower morbidity and improved organ preservation. Since the surgery is performed from the inside working outward as opposed to working from the outside in, there is less damage to the supporting structures that lie external to the tumor. Coupling the laser to a micromanipulator and a microscope allows precise tissue cutting and hemostasis; thereby improving visualization and precise ablation. The basic approach and principles of performing TLM, the devices currently in use, and the associated dosimetry parameters will be discussed. The benefits of using TLM over conventional surgery, common complications and the different settings used depending on the location of the tumor will also be discussed. Although the CO2 laser is the most versatile and the best-suited laser for TLM applications, a variety of lasers and different parameters are used in the treatment of laryngeal cancer. Improved instrumentation has lead to an increased utilization of TLM by head and neck cancer surgeons and has resulted in improved outcomes. Laser energy levels and spot size are adjusted to vary the precision of cutting and amount of hemostasis obtained

Establishment and characterization of a low-dose Mycoplasma haemofelis infection model

Hemotropic mycoplasma are small, cell-wall-free bacteria that can infect various mammalian species, including humans. They cannot be cultured in vitro; therefore, animal models play an important role, e.g. for pathogenesis studies. Mycoplasma haemofelis (Mhf) is the most pathogenic of the three feline hemotropic mycoplasma species; it is known to induce severe hemolytic anemia in infected cats. The aims of this study were to establish and characterize a low-dose Mhf transmission model. Five specified pathogen-free cats were subcutaneously exposed to 1000 copies of Mhf per cat corresponding to 0.05 μL of infectious blood with 2×10(7) copies/mL as determined by real-time PCR. All cats became PCR-positive within 34 days post-exposure and reached a maximum blood Mhf load of 10(9) copies/mL, similar to previously reported high-dose infections. In a selected sample of modified Wright-stained blood smears, small epicellular coccoid structures on the surface of the red blood cells were identified by light microscopy. Additionally, using an Mhf rDnaK ELISA, seroconversion was demonstrated in all cats within 4-5 weeks after Mhf exposure. Four out of five cats developed anemia. While three cats showed only mild clinical signs of hemoplasmosis, one cat developed severe anemia and required antibiotic treatment. Our study demonstrated that minimal contact with Mhf infectious blood was sufficient for transmission of the infection and the induction of hemoplasmosis. This low-dose Mhf infection might more accurately mirror the natural route of infection, i.e., by arthropod vectors or aggressive interaction among cats. We therefore recommend this protocol for use in future animal model studies

Electrical detection of spin precession in a metallic mesoscopic spin valve

To study and control the behaviour of the spins of electrons that are moving through a metal or semiconductor is an outstanding challenge in the field of ‘spintronics’, where possibilities for new electronic applications based on the spin degree of freedom are currently being explored. Recently, electrical control of spin coherence and coherent spin precession during transport was studied by optical techniques in semiconductors. Here we report controlled spin precession of electrically injected and detected electrons in a diffusive metallic conductor, using tunnel barriers in combination with metallic ferromagnetic electrodes as spin injector and detector. The output voltage of our device is sensitive to the spin degree of freedom only, and its sign can be switched from positive to negative, depending on the relative magnetization of the ferromagnetic electrodes. We show that the spin direction can be controlled by inducing a coherent spin precession caused by an applied perpendicular magnetic field. By inducing an average precession angle of 180°, we are able to reverse the sign of the output voltage.

Directed Evolution of Artificial Metalloenzymes: Bridging Synthetic Chemistry and Biology

Directed evolution is a powerful algorithm for engineering proteins to have novel and useful properties. However, we do not yet fully understand the characteristics of an evolvable system. In this chapter, we present examples where directed evolution has been used to enhance the performance of metalloenzymes, focusing first on “classical” cases such as improving enzyme stability or expanding the scope of natural reactivity. We then discuss how directed evolution has been extended to artificial systems, in which a metalloprotein catalyzes reactions using abiological reagents or in which the protein utilizes a nonnatural cofactor for catalysis. These examples demonstrate that directed evolution can also be applied to artificial systems to improve catalytic properties, such as activity and enantioselectivity, and to favor a different product than that favored by small‐molecule catalysts. Future work will help define the extent to which artificial metalloenzymes can be altered and optimized by directed evolution and the best approaches for doing so