Light scattering and the absolute characterization of macromolecules

Methods in Lignin Chemistry

Third-order optical susceptibilities of liquids and solids

An authentication system comprising a medium (2) having a plurality of elements (3), the elements being distinctive, detectable and disposed in an irregular pattern or having an intrinsic irregularity. Each element is characterized by a determinable attribute distinct from a two-dimensional coordinate representation (4) of simple optical absorption or simple optical reflection intensity. An attribute and position of the plurality of elements, with respect to a position reference, is detected. A processor generates an encrypted message (8-10) including at least a portion of the attribute and position of the plurality of elements. The encrypted message is recorded in physical association with the medium. The elements are preferably dichroic fibers, and the attribute is preferably a polarization or dichroic axis, which may vary over the length of a fiber. An authentication of the medium based on the encrypted message may be authenticated with a statistical tolerance, based on a vector mapping of the elements of the medium, without requiring a complete image of the medium and elements to be recorded.

System and method for authentication of goods

A system and method for authenticating documents and content thereof. A counterfeit resistant document recording medium is provided, having thereon a predefined unique document identifier and at least one security feature. The recording medium is thereafter imprinted with document content, which typically varies between documents. The document content is stored in a database, indexed by an associated document identifier. The document may then be authenticated by checking the security feature and comparing the stored document content with a perceived document content. The system provides a number of opportunities for commercial exploitation, including sales of identified recording media, recording of information in a database, on-line authentication transactions, differential accounting for document validations and counterfeit identifications, imprinting devices, authentication devices, and the like. The system prevents counterfeiting of valuable documents through casual means by providing both physical and logical security.

System and method for production and authentication of original documents

A new method for the calculation of the Rayleigh factor from low angle light scattering measurements is developed. This method does not require a uniform intensity illuminating beam, hence efficiently utilizes all the beam from a focused laser source. Scattering volume is then very small, reducing sample volume and interference from contaminant particles. All the parameters necessary for the calculation of the Rayleigh factor (including the exact dependence on sample refractive index) are measurable, hence absolute calibration is possible. Over-all error is estimated to be less than 2.3% under specified conditions. Measurements are possible at scattering angles as small as 2° obviating the need for angular extrapolations in the determination of molecular weight of most dissolved samples. Rayleigh factors at 22°C, 633 nm, and a scattering angle of 4° for water, methanol, benzene, and toluene, were found to be, respectively, 0.907, 2.56, 12.15, and 13.45 × 10−6 cm−1.

Low angle laser light scattering-absolute calibration.

The Rayleigh factors and depolarization ratios at 6328 A have been measured for carbon disulfide, toluene, benzene, chloroform, carbon tetrachloride, cyclohexane, butanone, acetone, methanol, and water using an improved model of the low-angle laser light-scattering (LALLS) photometer. Small errors in some of the Rayleigh factors published using an earlier model of this instrument have been revealed. Depolarization ratios are measured by a new method involving detection of the full cone of forward scattered light.

Low-angle laser light scattering - rayleigh factors and depolarization ratios.

Effluent from a gel-permeation chromatographic column has been simultaneously and continuously monitored with a differential refractometer and a low-angle laser light-scattering (LALLS) photometer. This provides a true and direct determination of molecular weight distribution rather than through a calibration method as obtained by conventional GPC techniques. Computer assisted data reduction provides a rapid determination of Mw, Mn, Mz, Mw/Mn, as well as a plot of molecular weight distribution. Samples of very narrow molecular weight distribution (MWD) polystyrene from Pressure Chemicals Co. and relatively wide MWD samples of poly(methyl methacrylate) in chloroform have been characterized.

Gel-permeation chromatography: X. Molecular weight detection by low-angle laser light scattering

Method and apparatus for authenticating documents such as government notes and currency, stock certificates, and the like by marking the document with an encapsulated dyed liquid crystal material and examining the document for unique optical characteristics of the mark. Reading apparatus for the document measures changes in reflectivity of the liquid crystal mark with changes in an electrical field applied thereto. In other embodiments, reflectivity is measured at a plurality of different wavelengths. In one embodiment, the dye absorbs in regions of the electromagnetic spectrum "invisible" to the human eye and the reading apparatus monitors reflectivity changes at these invisible wavelengths.

Marking and authenticating documents with liquid crystal materials

Moderately narrow band, tunable, birefringent filters are disclosed using zero-twist liquid crystal cells as variable retarders in a Lyot-type birefringent filter. These filters can achieve analytically useful levels of resolution and stray-light ratios for costs that are competitive with prism and grating monochromators. These birefringent filters can be tuned and/or rendered opaque by the application of a suitable voltage to the cells. Thus, a variety of different optical instruments can be constructed with no moving parts. Power requirements are negligible. A useful filter can be designed to occupy a volume less than one cubic inch. These properties render such a filter ideally suited to microprocessor control.

Wilbur Kaye

Papers

Low angle laser light scattering-absolute calibration.

Low-angle laser light scattering - rayleigh factors and depolarization ratios.

Gel-permeation chromatography: X. Molecular weight detection by low-angle laser light scattering

Marking and authenticating documents with liquid crystal materials

Liquid crystal tuned birefringent filter