The apatite-group minerals of the general formula, M10(ZO4)6X2 (M = Ca, Sr, Pb, Na…, Z = P, As, Si, V…, and X = F, OH, Cl…), are remarkably tolerant to structural distortion and chemical substitution, and consequently are extremely diverse in composition (e.g., Kreidler and Hummel 1970; McConnell 1973; Roy et al. 1978; Elliott 1994). Of particular interest is that a number of important geological, environmental/paleoenvironmental, and technological applications of the apatite-group minerals are directly linked to their chemical compositions. It is therefore fundamentally important to understand the substitution mechanisms and other intrinsic and external factors that control the compositional variation in apatites.

The minerals of the apatite group are listed in Table 1⇓, and representative compositions of selected apatite-group minerals are given in Table 2⇓. Also, more than 100 compounds with the apatite structure have been synthesized (Table 3⇓). Phosphate apatites, particularly fluorapatite and hydroxylapatite, are by far the most common in nature and are often synonymous with “apatite(s)”. For example, fluorapatite is a ubiquitous accessory phase in igneous, metamorphic, and sedimentary rocks and a major constituent in phosphorites and certain carbonatites and anorthosites (McConnell 1973; Dymek and Owens 2001). Of particular importance in biological systems, hydroxylapatite and fluorapatite (and their carbonate-bearing varieties) are important mineral components of bones, teeth and fossils (McConnell 1973; Wright et al. 1984; Grandjean-Lecuyer et al. 1993; Elliott 1994; Wilson et al. 1999; Suetsugu et al. 2000; Ivanova et al. 2001).

View this table:

 Table 1. 
Summary of the apatite-group minerals



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 Table 2. 
Representative compositions and unit-cell parameters of selected apatite-group minerals.



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 Table 3. 
Formulas of selected synthetic compounds with the apatite structure.



Following Fleischer and Mandarino (1995), Table 1⇑ also includes melanocerite-(Ce), tritomite-(Ce), and tritomite-(Y), the compositions …

Compositions of the Apatite-Group Minerals: Substitution Mechanisms and Controlling Factors

A broadband wire grid polarizer (400) for the visible spectrum has a plurality of elongated elements (1240) supported on a substrate (1210). A region (1250) having a lower refractive index than the refractive index of the substrate is disposed between the elements and the substrate to reduce the longest wavelength at which resonance occurs.

Broadband wire grid polarizer for the visible spectrum

A wire grid polarizer (300) for polarizing an incident light beam (130) comprises a substrate having a first surface. A grid or array of parallel, elongated, composite wires (310) is disposed on the first surface (307), and each of the adjacent wires are spaced apart on a grid period less than a wavelength of incident light. Each of the wires comprises an intra-wire substructure (315) of alternating elongated metal (330a-i) wires and elongated dielectric layers (350a-i).

Wire grid polarizer

To determine glucose or other constituents of the human or animal body, a stabilized near-infrared radiation beam containing two alternating wavelengths that have approximately equal extinction coefficients in the tissue, is directed onto the sample area, the transmitted signal alternating component is zeroed by tuning one of the wavelengths, the extracellular-to-intracellular fluid ratio of the tissue is changed by exerting varying mechanical pressure on the tissue, or the ratio is allowed to change as a result of the natural pulsation. The alternating component of the transmitted beam power is measured in the changed fluid ratio state. The amplitude of the alternating-current (AC) signal given by the detector, is taken to represent glucose concentration or the difference from a preset reference concentration.

Electromagnetic method and apparatus to measure constituents of human or animal tissue

The present invention relates to the noninvasive measurement of blood hematocrit and hemoglobin content using differential optical absorption of two or more wavelengths of light during blood volume changes. The method is also useful for noninvasive measurements of other blood analytes, such as glucose, where variations in hematocrit or blood hemoglobin concentration cause errors in the measurement.

Noninvasive measurement of hematocrit and hemoglobin content by differential optical analysis

A great variety of compounds occur in nature or have been synthesized in the laboratory that crystallize with the apatite structure. We have investigated a number of the apatites and found them to be excellent laser hosts for neodymium and holmium. The apatites described in this paper were grown using the Czochralski method, have low optical losses in the pump and emission spectral regions for neodymium and holmium, and the hosts have been developed to readily accept large concentrations of doping ions. This paper describes the crystal growth, physical properties, spectroscopy, and laser performance of this family of new laser materials.

Laser properties of nd(+3) and ho(+3) doped crystals with the apatite structure.

An infrared wire grid polarizer is fabricated on an infrared transmissive substrate and consists of alternating transmissive and conductive zones disposed thereon. These polarizers are particularly well suited for use with acoustic-optic tunable filters and can be employed as input and output polarizers therewith. A method of manufacturing a wire grid polarizer with at least 4000 conductors per millimeter is disclosed. The infrared transmissive substrate is selected from the group consisting of silicon crystal and gallium arsenide crystal.

An automated acousto-optic tunable filter infrared analyzer system useable in a variety of industrial and commercial control applications. The system relies upon a narrow band pass tunable acousto-optic filter which is selectively tuned by predetermined rf frequency signals to selectively transmit the narrow band pass of interest which corresponds to a specific molecular species for identification and analysis. The system includes a microcomputer and associated memory function to measure and compare detected signals from an infrared detector which converts the filtered infrared signal to an electrical signal. The memory provides control signals for the computer and for controlling the sequence and frequency of rf energy applied to tune the filter. In this way, the near to mid range infrared can be analyzed for absorption bands corresponding to predetermined molecular species such as combustion product gases, and a feedback signal generated to control the combustion process.

Automated acousto-optic infrared analyzer system

Silicate Oxyapatites: New High‐Energy Storage Laser Hosts for Nd+3

An improved infrared acousto-optic tunable filter is provided by an acousto-optic birefringent crystal having polished, uncoated input and output faces normal to the radiation incident-on or diffracted-by the crystal, respectively, and wherein crystallographic axis is oriented at about 21 degrees to the incident infrared radiation, rf transducer means coupled to the crystal for tuning or selecting a narrow bandwidth infrared wavelength of interest, and input and output wire grid polarizer are aligned with the crystal. The input wire grid polarizer is aligned to polarize the input infrared radiation in the same plane as the plane of the b-c crystalline axes of the crystal. The output wire grid polarizer is disposed with the parallel conductors aligned transversely to the conductors of the input polarizer, so that only the selected or tuned bandwidth of interest is transmitted through the output polarizer.

Kenneth B. Steinbruegge

Papers

Laser properties of nd(+3) and ho(+3) doped crystals with the apatite structure.

Wire grid polarizer

Automated acousto-optic infrared analyzer system

Silicate Oxyapatites: New High‐Energy Storage Laser Hosts for Nd+3

Infrared acousto-optic tunable filter