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Rhamnolipid as a potent natural biosurfactant has a wide range of potential applications, including enhanced oil recovery (EOR), biodegradation, and bioremediation. Rhamnolipid is composed of rhamnose sugar molecule and beta-hydroxyalkanoic acid. The rhamnosyltransferase 1 complex (RhlAB) is the key enzyme responsible for transferring the rhamnose moiety to the beta-hydroxyalkanoic acid moiety to biosynthesize rhamnolipid. Through transposome-mediated chromosome integration, the RhlAB gene was inserted into the chromosome of the Pseudomonas aeruginosa PAO1-rhlA(-) and Escherichia coli BL21 (DE3), neither of which could produce rhamnolipid. After chromosome integration of the RhlAB gene, the constitute strains P. aeruginosa PEER02 and E. coli TnERAB did produce rhamnolipid. The HPLC/MS spectrum showed that the structure of purified rhamnolipid from P. aeruginosa PEER02 was similar to that from other P. aeruginosa strains, but with different percentage for each of the several congeners. The main congener (near 60%) of purified rhamnolipid from E. coli TnERAB was 3-(3-hydroxydecanoyloxy) decanoate (C(10)-C(10)) with mono-rhamnose. The surfactant performance of rhamnolipid was evaluated by measurement of interfacial tension (IFT) and oil recovery via sand-pack flooding tests. As expected, pH and salt concentration of the rhamnolipid solution significantly affected the IFT properties. With just 250 mg/L rhamnolipid (from P. aeruginosa PEER02 with soybean oil as substrate) in citrate-Na(2)HPO(4), pH 5, 2% NaCl, 42% of oil otherwise trapped was recovered from a sand pack. This result suggests rhamnolipid might be considered for EOR applications.

The ring closing metathesis on appropriate vinyl or allyl aminoboranes (1 or 2) gives azaboracycloalkenes (3 or 4) which can be converted to azaborolides (5) or azaborines (6).

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1,2-Dihydro-1,2-azaborines (1c, 1d, and 1e) have been prepared by the reaction of the corresponding 2,3-dihydro-1H-1,2-azaborol-3-yllithium reagents (1c, 1d, and 1e). The reaction of 1e with Py3Mo(CO)3 and BF3·OEt2 affords Mo(CO)3 complex 5e, while the reaction of 1c with Cr(CH3CN)3(CO)3 affords Cr(CO)3 complex 6c. X-ray structures of 5e and 6c show that the metals are η6-bound to the 1,2-dihydro-1,2-azaborine rings.

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An all-fiber wavelength-division multiplexer (WDM) based on the nonreciprocity of the birefringence to the polarization states is proposed. The transfer function of a Sagnac interferometer is wavelength dependent if the loop birefringence of the interferometer consists of both circular and linear parts. Theoretical analysis shows that the output characteristics of this WDM are similar to those of a fiber taper-based device. Both the bandwidth and the peak wavelength of the new WDM can be tuned by changing the loop birefringence. Experimental prototypes exhibit a channel isolation greater than 25 dB with peak passband insertion loss of less than 1 dB.

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