Bioremediation of toluene‐contaminated air using an external loop airlift bioreactor

An external loop airlift bioreactor (ELAB) has been used to capture and degrade toluene from a contaminated air stream. Using a spinning sparger, the toluene could be transferred from small, uniform bubbles into the aqueous culture media with an overall mass transfer coefficient as high as 1.1 h^?1. Due to the very volatile nature of toluene, Pseudomonas putida (ATCC 23973) was cultured and maintained on benzyl alcohol, the first intermediate compound in the metabolic degradation pathway for toluene. Consequently, before successful continuous operation of the ELAB with toluene‐contaminated air, Pseudomonas putida was acclimatized to toluene by using 30 min intermittent sparging of contaminated air into the bioreactor. Continuous sparging of toluene‐contaminated air could then be successfully carried out with 100% capture and biodegradation efficiency at a contaminated air concentration of 15 mg dm^?3 and a loading rate of 35 mg dm^?3 h^?1. Higher concentrations and loading rates were only partially degraded. Although this capture matches only the low rates reported earlier using biofilters to remediate toluene, the ELAB operates using submerged culture and requires no packing which can plug during biofilter operation. In this study, Pseudomonas putida grew on toluene at a maximum specific growth rate of only 0.05 h^?1. © 2003 Society of Chemical Industry     

Self-aligned chemically assisted ion-beam-etched GaAs/(Al,Ga)Asturning mirrors for photonic applications

It is shown that totally reflecting turning mirrors can be fabricated in GaAs/(Al,Ga)As graded-index separate-confinement-heterostructure single-quantum-well (GRIN-SCH SQW) material using Ti metal masking and Cl₂ chemically assisted ion-beam-etching (CAIBE). Combined with ridge waveguides, these techniques have been used to make turning-mirror cleaved-facet lasers that have acceptable external slope efficiencies with a modest estimated increase in threshold current. Scanning electron microscope examination of the mirrors indicates some residual roughness attributed to the edge definition of the deposited titanium film. The mirror loss is estimated to be 68% for these particular turning mirrors. These components, which continue to be developed and improved, are being applied to increasingly sophisticated and demanding photonic programs     

A method for quantization scale factor selection in MPEG2 videosequence encoding using a bilayer fuzzy expert system

This paper presents a method for intelligent selection of the quantization scale factor used for varying bit rate and quality in the MPEG2 video encoding standard. The goal is to select the quantization scale factor, above which noticeable quality degradation occurs. This method uses a bilayer fuzzy logic system to aggregate measurements taken on the block level. The rulebases are designed around the characteristics of the human visual system (HVS). A qualitatively sensitive quantization scale factor can be chosen by taking advantage of the HVS characteristics     

Tumor immunology

Malignant tumors express antigens that may stimulate and serve as targets for antitumor immunity. Virally induced tumors usually contain integrated proviral genomes in theircellulargenomes and often express viral genome-encoded proteins that may stimulate specific host immune responses. Antigens unique to individual tumors that stimulate specific rejection of transplanted tumors have been demonstrated only in experimental animals. Other tumor antigens that potentially can stimulate immune responses are shared by different tumors. These include products of mutated or rearranged oncogenes or tumor-suppressor genes. Tumors may also overexpress tissue differentiation antigens or embryonic antigens, which also have the potential to be recognized by the immune system. The recent identification of tumor antigens recognized by cytotoxic T cells opens up new possibilities for constructing chemically defined antigens for specific immunotherapy. Treatment of malignant tumors in humans by immunologic approaches, although theoretically attractive, has not yet succeeded on a large scale. Important progress in immunotherapy of cancer is emerging with several different treatment modalities.