Experimental demonstration and observation of a plasmon wave occuring at a GaAs-Au-GaN interface.

Integration of surface plasmon structures using semiconductor materials is limited due to the difficulties encountered in maintaining the resonance conditions upon packaging. We propose here a technology process allowing us to bond two semiconductors, such as gallium nitride (GaN) and gallium arsenide (GaAs), through a thin metal layer. This solution allows the excitation of a surface plasmon wave in an integrated classical Kretschmann configuration. The Letter presents various metal bonding conditions employed for Au deposited on both GaN/sapphire and GaAs substrates aiming at semiconductor-metal-semiconductor interfaces transparent at telecom wavelengths. The process conditions for the bondings are optimized using Ti/Au (3 nm/30 nm) layers on each of the wafers to be bonded under an applied pressure of 500 mbar at a low temperature of 250°C.

High responsivity GaNAsSb p-i-n photodetectors at 1.3 microm grown by radio-frequency nitrogen plasma-assisted molecular beam epitaxy.

GaNAsSb/GaAs p-i-n photo notdetectors with an intrinsic GaNAsSb photoabsorption layer grown at 350 degrees C, 400 degrees C, 440 degrees C and 480 degrees C, have been prepared using radio-frequency nitrogen plasma-assisted molecular beam epitaxy in conjunction with a valved antimony cracker source. The i-GaNAsSb photoabsorption layer contains 3.3% of nitrogen and 8% of antimony, resulting in DC photo-response up to wavelengths of 1350 nm. The device with i-GaNAsSb layer grown at 350 degrees C exhibits extremely high photoresponsivity of 12A/W at 1.3 microm. These photodetectors show characteristics which strongly suggest the presence of carrier avalanche process at reverse bias less than 5V.

Optical devices for ultra-compact photonic integrated circuits based on III-V/polymer nanowires.

We demonstrated the potential application of III-V/polymer nanowires for photonic integrated circuits in a previous paper. Hereby, we report the use of a spot size converter based on 2D reverse nanotaper structure in order to improve the coupling efficiency between the nanowire and optical fiber. A total coupling enhancement of up to a factor 60 has been measured from an 80 nm x 300 nm cross-section tip which feeds an 300 nm-side square nanowire at its both ends. Simultaneously, micro-radius bends have been fabricated to increase the circuit density; for a radius of 5 microm, the 90 masculine bend losses were measured as low as 0.60 dB and 0.80 dB for TE and TM polarizations respectively.

Susceptibility testing of Mycobacterium tuberculosis: comparison of the BACTEC TB-460 method and flow cytometric assay with the proportion method.

Tuberculosis is a leading cause of morbidity and mortality worldwide. Susceptibility testing of the causative agent, Mycobacterium tuberculosis, is critical for control of the disease. This study compared the flow cytometric susceptibility assay with the proportion method and the BACTEC TB-460 system. There was agreement between the flow cytometric and proportion methods for 73 (94%) of 78 isoniazid tests, and complete agreement for 26 ethambutol and rifampicin tests. In contrast, the proportion and BACTEC methods failed to agree for 22%, 15% and 8% of isoniazid, ethambutol and rifampicin tests, respectively. These findings indicated that susceptibility testing by the flow cytometric assay is accurate, with results available within 24 h of initiation of the testing procedure.

Interleukin-6 enhances production of anti-OspC immunoglobulin G2b borreliacidal antibody.

Protection against infection with Borrelia burgdorferi is dependent primarily on induction of complement-dependent antibody that can kill the spirochete. Measuring the production of sustained high levels of borreliacidal antibody is thus paramount for determining potential vaccine efficacy. We investigated the borreliacidal antibody response in sera and the amount of antibody produced by cultured lymph node cells of C3H/HeJ mice vaccinated with outer surface protein C (OspC). We showed that recombinant OspC was a weak stimulant of borreliacidal antibody production compared to whole cells of OspC-expressing B. burgdorferi. Mice vaccinated with B. burgdorferi in adjuvant produced a high level (titer, 5,120) of anti-OspC borreliacidal antibody, which waned rapidly. Similarly, borreliacidal antibody production by cultured lymph node cells from vaccinated mice peaked soon after vaccination and then decreased. Treatment of lymph node cells with interleukin-6 (IL-6) augmented borreliacidal antibody production, particularly immunoglobulin G2b, whereas treatment with anti-IL-6 inhibited the borreliacidal response. These findings demonstrate a previously unrecognized role for IL-6 in borreliacidal antibody production that may have important implications for vaccine development.

Flow cytometric testing of susceptibilities of Mycobacterium avium to amikacin, ciprofloxacin, clarithromycin and rifabutin in 24 hours.

OBJECTIVE: To develop a biologically safe flow cytometric susceptibility test that depends on detection and enumeration of actively growing Mycobacterium avium organisms in drug-free and antimycobacterial agent-containing medium. METHODS: Prior to analysis by flow cytometry, all M. avium susceptibility test samples were inactivated by exposure to paraformaldehyde. The susceptibilities of 20 clinical isolates of M. avium to amikacin, ciprofloxacin, clarithromycin, and rifabutin were tested by the flow cytometric and BACTEC methods. RESULTS: Agreement was 97% between the results of the two methods. The results of flow cytometric susceptibility tests were available 24 h after inoculation of drug-containing medium, while the BACTEC method required 4-8 days to complete. CONCLUSIONS: The flow cytometric assay is safe, simple and reproducible.

Evaluation of field desorption mass spectrometry for the analysis of polyethylene.

Field desorption mass spectrometry (FD-MS) has been evaluated for the analysis of low molecular weight polyethylene by using samples in the molecular weight range 600-2000 u as determined by gel permeation chromatography. The repeat units and end groups were characterized by FD-MS, but it was demonstrated that accurate molecular weight distribution data cannot be obtained for polyethylene by FD-MS because there is mass discrimination against the higher molecular weight polymers.