Vinyl bromide as a surrogate for determining vinyl chloride reductive dechlorination potential

Site evaluation for bioremediation of chlorinated ethenes may need treatability studies to assess the reductive dechlorination potential of vinyl chloride (VC). Dehalogenation of vinyl bromide (VB) was investigated as a surrogate measurement for the dechlorination potential of VC. VB dehalogenation rates and kinetics were studied and compared with those of VC by a methanogenic reductive dechlorinating enrichment culture that was dominated by Dehalococcoides species and by microcosms from two chloroethene-contaminated sites. The enrichment culture dehalogenated VB to ethene at higher rates than VC at similar concentrations. VB was dehalogenated with a higher enzyme affinity than was VC, as indicated by their half-velocity constants, 240 +/- 150 and 21 +/- 8 microM, for VC and VB, respectively. Cross-inhibition study exhibited some evidence for competitive inhibition between VC and VB, suggesting that their degradation might be catalyzed by the same enzyme in the culture. Laboratory microcosm studies using subsurface soil and groundwater from two contaminated sites demonstrated that the production of the reductive dehalogenation product (ethene) could be detected faster with VB as a substrate than with VC. As a result, a substantially shorter (up to 5-10 times) incubation time would be required to detect the same level of reductive dehalogenation activity using VB as a surrogate for VC in treatability assessments.     

Fibres as carriers for Lactobacillus rhamnosus during freeze-drying and storage in apple juice and chocolate-coated breakfast cereals

The capability of different fibre preparations to protect the viability and stability of Lactobacillus rhamnosus during freeze-drying, storage in freeze-dried form and after formulation into apple juice and chocolate-coated breakfast cereals was studied. In freeze-drying trials wheat dextrin and polydextrose proved to be promising carriers for the L. rhamnosus strains: both freeze-drying survival and storage stability at 37 degrees C were comparable to the control carrier (sucrose). Using apple fibre and inulin carriers resulted in powders with fairly good initial freeze-drying survival but with poor storage stability at 37 degrees C. When fresh L. rhamnosus cells were added into apple juice (pH 3.5) together with oat flour with 20% beta-glucan the survival of the cells was much better at 4 degrees C and at 20 degrees C than with sucrose, wheat dextrin and polydextrose, whereas with freeze-dried cells no protective effect of oat flour could be seen. The stability of freeze-dried L. rhamnosus cells at 20 degrees C was higher in chocolate-coated breakfast cereals compared to low pH apple juice. Similar to freeze-drying stability, wheat dextrin and polydextrose proved to be better carriers than oat flour in chocolate-coated breakfast cereals. Regardless of their differing capability to adhere to fibre preparations the two L. rhamnosus strains studied gave parallel results in the stability studies with different carriers.     

Acoustic Properties of Aerogels: Current Status and Prospects

Noise reduction remains an important priority in the modern society, in particular, for urban areas and highly populated cities. Insulation of buildings and transport systems such as cars, trains, and airplanes has accelerated the need to develop advanced materials. Various porous materials, such as commercially available foams and granular and fibrous materials, are commonly used for sound mitigating applications. In this review, a special class of advanced porous materials, aerogels, is examined, and an overview of the current experimental and theoretical status of their acoustic properties is provided. Aerogels can be composed of inorganic matter, synthetic or natural polymers, as well as organic/inorganic composites and hybrids. Aerogels are highly porous nanostructured materials with a large number of meso- and small macropores; the mechanisms of sound absorption partly differ from those of traditional porous absorbers possessing large macropores. The understanding of the acoustic properties of aerogels is far from being complete, and experimental results remain scattered. It is demonstrated that the structure of the aerogel provides a complex three-dimensional architecture ideally suited for promising high-performance materials for acoustic mitigation systems. This is in addition to the numerous other desirable properties that include low density, low thermal conductivity, and low refractive index.