ABSTRACT
A marine bacterium strain 2-40 (2-40) degraded numerous complex carbohydrates, such as agar, chitin and alginate. It may play an important role in altering carbon fluxes in marine environments. End-product analyses revealed that 2-40 synthesized an agarase system that consisted of at least three enzymes, beta-agarase I, beta-agarase II and alpha-agarase, which acted in concert to degrade polymeric agar to D-galactose and 3,6-anhydro-L-galactose. The agarase system was shown to be both cell envelope-associated and extracellular, with the relative concentrations depending on the growth phase. The principal depolymerase, a beta-agarase I, hydrolysed agar to both neoagarotetrose and neoagarobiose, as identified by thin layer chromatography. This agarase had a mass of 98 kD and a Pi of 4.3. The agarase system was repressed by D-glucose and D-galactose and induced by agar, agarose, neoagarobiose, neoagarotetrose and neoagarohexose.
Subject(s)
Glycoside Hydrolases/isolation & purification , Gram-Negative Bacteria/enzymology , Carbohydrate Metabolism , Glycoside Hydrolases/chemistry , Glycoside Hydrolases/metabolism , Gram-Negative Bacteria/classification , Gram-Negative Bacteria/growth & development , Isoelectric Point , Marine Biology , Multienzyme Complexes/chemistry , Multienzyme Complexes/isolation & purification , Multienzyme Complexes/metabolism , Substrate SpecificityABSTRACT
Variable-spacing diffraction gratings may be useful for controlling the deflection of a light beam. We introduce a method for making such a variable grating through the use of variable-frequency surface waves in elastomeric substrates. Elastomers have an extremely low Young's modulus compared with that of conventional solids, which allows surface waves to be created with low power and to travel much more slowly than waves in conventional surface-wave devices. To date, the best results have been obtained with a thin silicone elastomer membrane supported upon the surface of water. It has been found that the propagation speed of such waves is consistent with that in a previously developed analytical model, which predicts the dispersion relationship in terms of the membrane's thickness, tension, and modulus. Such a system has been used to cause a variable deflection of a light beam, in agreement with numerical predictions.
ABSTRACT
Prism light guides are often used for transporting and distributing light. Typically such guides are tubular structures lined with a flexible prismatic sheet material that confines light by means of total internal reflection. Inasmuch as the prismatic material is produced as a flat sheet, such guides require at least one seam in formation of the tubular structure, and the optical imperfection associated with seams is often a dominant loss mechanism. We present a new configuration for the cross-sectional shape of a prism light guide that substantially reduces the loss caused by such seams.
ABSTRACT
Prism light guides are hollow dielectric tubes that use prismatic facets to guide light by means of total internal reflection. An unresolved problem has been to determine the magnitude of loss caused by diffraction in prism light guides. Neither experimental measurement nor an analytical solution has yet been achieved, so we attacked the problem numerically, in two steps. First, we found a way to represent such a transitionally invariant three-dimensional system as an equivalent two-dimensional problem. Second, we employed the finite-difference time-domain algorithm, with periodic boundary conditions, to yield a computation problem of manageable size. We found that the diffraction-induced transmissivity of a prism light guide wall is of the order of the wavelength divided by the prism size-a result that has encouraging practical implications.
ABSTRACT
We present a method of fabricating nonimaging light concentrators from total internal reflection film. A prototype has been made and tested and found to operate in agreement with predictions of ray-tracing codes. The performance of the prototype is comparable with that of concentrators made from specular reflecting materials.
ABSTRACT
Experimental and theoretical studies of the recently patented prism light guide are described [L. A. Whitehead, U.S. Patent 4,260,220 (7 Apr. 1981)]. This device combines the total internal reflection of optical fibers with the low attenuation of air transmission of light. Since it can be moulded from acrylic plastic, the cost of the guide is low enough to make large-scale interior illumination with piped light feasible.
ABSTRACT
A simplified method of ray tracing in cylindrical optical systems of arbitrary cross section is described. The technique involves the projection of a ray's path onto a cross-sectional plane perpendicular to the axis of translational symmetry. It is shown that this projected path obeys a generalized form of Snell's law, enabling application of conventional 2-D ray tracing methods. The approach is illustrated by demonstrating the optical characteristics of the recently patented prism light guide.
