Erasable Optical Fluorescent Data Storage (EOFS)

A novel principle for optical storage is described which is based on organic fluorescent dyes. The information carrier is the lattice of molecular crystals and the information is read out by solid state fluorescence. The information can be erased by a specific crystal transformation

An E.P.R. study of some transition metal impurities in silver chloride and silver bromide

The electron paramagnetic resonance (E.P.R.) and photosensitivity of silver chloride and silver bromide doped with a number of transition metal ions" has been investigated. The valent state, lattice position and site symmetry of the impurities are discussed in relation to the E.P.R. spectra and the chemical properties of the ions. The E.P.R. spectra of trivalent chromium in AgCl and AgBr are analysed. The principal spectrum at 95K in both halides has orthorhombic symmetry with axes in the directions. Subsidiary spectra are also observed with tetragonal and orthorhombic symmetries. The possible arrangements of the two charge compensating silver ion vacancies around the trivalent ion are discussed. The principal spectrum is shown to be consistent with a centre in which the Cr3+ ion is associated with a nearest and a next nearest cation vacancy. The lines joining the vacancies to the Cr3+ ion are at an angle of 1350 • Other centres are proposed to explain the subsidiary spectra. The Cr3+ resonances are studied at temperatures up to 500K. The broadening of the fine structure lines at high temperatures is used to . determine the activation energy for vacancy motion around the C~ ion in each of the centres observed. A set of lines which increase in intensity as the sample is warmed above room temperature is assigned to the Cr3+ ion associated with a single next nearest cation vacancy. The spin Hamiltonian parameters of the spectra of Cr3+ in the chloride and the bromide are compared. The substitutional incorporation of the Cr3+ ion is contrasted with the interstitial incorporation of the Fe 3 + ion which has a similar radius. A dewar and cavity for use at 4.2K are described. The E.P.R. spectra of ytterbium, erbium and dysprosium in AgCl are presented. The resonances are assigned to the trivalent state of these ions and the ground states are derived from the experimental g-values. The symmetries of the spectra are used to derive the probable arrangements of vacancies about the rare earth ions. Preliminary investigations of the E.P.R. and optical properties of the remaining rare earths and the 4d and 5d series ions in AgCI are presented. The rare earths other than europium are thought to be present only in the trivalent state in AgCI. The stable valent state is discussed in relation to the chemical properties of the rare earths. The E.P.R. and electrical measurements available to date on the lattice site and vacancy association of transition ions in AgCI and AgBr are summarised. The results are used to show that association with nearest neighbour vacancies is most likely for ions which are relatively large compared with the Ag+ ion. Small impurity ions are shown to be more likely to be associated with next nearest cation vacancies

Photonic hydrogel sensors

Analyte-sensitive hydrogels that incorporate optical structures have emerged as sensing platforms for point-of-care diagnostics. The optical properties of the hydrogel sensors can be rationally designed and fabricated through self-assembly, microfabrication or laser writing. The advantages of photonic hydrogel sensors over conventional assay formats include label-free, quantitative, reusable, and continuous measurement capability that can be integrated with equipment-free text or image display. This Review explains the operation principles of photonic hydrogel sensors, presents syntheses of stimuli-responsive polymers, and provides an overview of qualitative and quantitative readout technologies. Applications in clinical samples are discussed, and potential future directions are identified

Photonic Hydrogel Sensors

Analyte-sensitive hydrogels that incorporate optical structures have emerged as sensing platforms for point-of-care diagnostics. The optical properties of the hydrogel sensors can be rationally designed and fabricated through self-assembly, microfabrication or laser writing. The advantages of photonic hydrogel sensors over conventional assay formats include label-free, quantitative, reusable, and continuous measurement capability that can be integrated with equipment-free text or image display. This Review explains the operation principles of photonic hydrogel sensors, presents syntheses of stimuli-responsive polymers, and provides an overview of qualitative and quantitative readout technologies. Applications in clinical samples are discussed, and potential future directions are identified

Laser Spectroscopy for Atmospheric and Environmental Sensing

Lasers and laser spectroscopic techniques have been extensively used in several applications since their advent, and the subject has been reviewed extensively in the last several decades. This review is focused on three areas of laser spectroscopic applications in atmospheric and environmental sensing; namely laser-induced fluorescence (LIF), cavity ring-down spectroscopy (CRDS), and photoluminescence (PL) techniques used in the detection of solids, liquids, aerosols, trace gases, and volatile organic compounds (VOCs)

NASA thesaurus. Volume 1: Hierarchical Listing

There are over 17,000 postable terms and nearly 4,000 nonpostable terms approved for use in the NASA scientific and technical information system in the Hierarchical Listing of the NASA Thesaurus. The generic structure is presented for many terms. The broader term and narrower term relationships are shown in an indented fashion that illustrates the generic structure better than the more widely used BT and NT listings. Related terms are generously applied, thus enhancing the usefulness of the Hierarchical Listing. Greater access to the Hierarchical Listing may be achieved with the collateral use of Volume 2 - Access Vocabulary and Volume 3 - Definitions

NASA patent abstracts bibliography: A continuing bibliography. Section 1: Abstracts (supplement 07)

This bibliography is issued in two sections: Section 1 - Abstracts, and Section 2 - Indexes. This issue of the Abstract Section cites 158 patents and applications for patent introduced into the NASA scientific and technical information system during the period of January 1975 through June 1975. Each entry in the Abstract Section consists of a citation, an abstract, and, in most cases, a key illustration selected from the patent or application for patent. This issue of the Index Section contains entries for 2830 patent and application for patent citations covering the period May 1969 through June 1975. The index section contains five indexes -- subject, inventor, source, number and accession number