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Manifestations of thyroid disease include hyperthyroidism and hypothyroidism. In the past, the diagnosis of thyroid disease has been perplexing due to the multisystemic effects of thyroid hormone and the lack of specificity in laboratory tests. New methods of measuring thyroid function have made screening and diagnosis of thyroid dysfunction both more accurate and cost-effective. Testing for thyroid stimulating hormone (TSH) is now a first-line diagnostic procedure and, in some cases, may be the only test indicated. The general pathophysiology of thyroid, the diagnosis and management of thyroid disease, and current screening recommendations are reviewed here.

Nurse practitioners must be fiscally responsible to obtain reimbursement for services provided. A thorough knowledge of the reimbursement process is required to accomplish this goal. This article explores the reimbursement process, generation of revenue, and personal productivity determination for nurse practitioners. Parameters for billing using the resource-based relative value scale, the Evaluation and Management Documentation Guidelines, the International Classification of Disease, and the Physicians' Current Procedural Terminology code book are explained.

Determining the resolution of a zone plate X-ray microscope is a complicated issue, depending on many factors in addition to the quality of the optic. These include the degree of coherence of the illumination, the illumination spectrum, and the nature of the resolution test object. In this paper, we examine closely how the degree of coherence of the illumination affects the resolution as measured with three typical test patterns. In addition, we determine the extent to which the illumination spectrum affects the resolution. We compare X-ray microscope test images to numerical simulations as a function of coherence and illumination spectrum. We are able to conclude that in these experiments, the resolution of the X-ray microscope is 41 nm, or 40% discrepancy is due to aberrations in the objective zone plate lens.

The polarization and transmission characteristics of freestanding gold transmission gratings, with 200-nm periods, for extreme-ultraviolet (EUV) radiation (1 < 200 nm) have been measured. We find that EUV transmission through the gratings is dominated by the waveguide characteristics of the gratings and that polarization efficiencies of 90% for wavelengths of 121.6 nm are achievable. Both the EUV polarization and transmission properties are in good agreement with a complete vector, numerical solution of Maxwell's equations. The fraction of open area to total area of the grating has been measured using a 10-keV proton beam and was found to be in good agreement with the microscopic slit and wire dimensions that were obtained by scanning electron microscopy. The use of these gratings for particle measurements in the presence of intense EUV radiation is briefly discussed.

Ultrahigh-resolution three-dimensional images of a microscopic test object were made with soft x-rays collected with a scanning transmission x-ray microscope. The test object consisted of two different patterns of gold bars on silicon nitride windows that were separated by approximately 5 micrometers. Depth resolution comparable to the transverse resolution was achieved by recording nine two-dimensional images of the object at angles between -50 and +55 degrees with respect to the beam axis. The projections were then combined tomographically to form a three-dimensional image by means of an algorithm using an algebraic reconstruction technique. A transverse resolution of approximately 1000 angstroms was observed. Artifacts in the reconstruction limited the overall depth resolution to approximately 6000 angstroms; however, some features were clearly reconstructed with a depth resolution of approximately 1000 angstroms.

For the fabrication of large-area, spatially coherent gratings with periods of 100 nm or less, a grating interferometer is preferred over a conventional holographic configuration because of the limited coherence of available sources. Using a configuration that employs two matched fused silica phase gratings and an ArF excimer laser, we obtain high-quality 100-nm gratings in polymethyl methacrylate. We analyze the conditions for achieving high-contrast fringes with such an achromatic holographic configuration and show that the depth of focus depends only on the spatial coherence of the source. We also describe a highly accurate method for calculating the diffraction efficiency of the phase gratings as a function of polarization, incidence angle, and grating structure.

Fourier transform x-ray holography has been used to image gold test objects with submicrometer structure, resolving features as small as 60 nanometers. The hologram-recording instrument uses coherent 3.4-nanometer radiation from the soft x-ray undulator beamline X1A at the National Synchrotron Light Source. The specimen to be imaged is placed near the first-order focal spot produced by a Fresnel zone plate; the other orders, chiefly the zeroth, illuminate the specimen. The wave scattered by the specimen interferes with the spherical reference wave from the focal spot, forming a hologram with fringes of low spatial frequency. The hologram is recorded in digital form by a charge-coupled device camera, and the specimen image is obtained by numerical reconstruction.

We have developed a high-resolution alignment technique which utilizes the partial polarization property of fine period transmission gratings. It is especially useful when the grating period is sufficiently small so that there are no visible diffracted orders. This technique uses a photoelastic modulator (PEM) to produce an intensity signal that is proportional to the sine of twice the angle between the grating lines and the PEM crystal axis. The experimentally demonstrated resolution of this technique on 200-nm period gold transmission gratings is better than 1 sec of arc. This technique was developed to align x-ray transmission gratings for spectroscopy and interferometry applications.

The metabolism of Prototheca zopfii was investigated in an attempt to establish the specific function of its growth factor, thiamin. A study of the oxidative decomposition of various substrates by this organism demonstrated that the addition of catalytic amounts of thiamin to vitamin-deficient cells causes a pronounced stimulation in the rate of oxygen utilization during the degradation of certain compounds. The phosphoric ester of thiamin is known to be the prosthetic group of carboxylase. The fact that this enzyme is involved in the decomposition of pyruvic acid suggested that this alpha-keto acid might be an important intermediate product in the metabolism of Prototheca. Pyruvic acid, however, was not included in the list of organic substances which Barker had reported as utilized by this alga. Barker's observations were confirmed, but subsequent experiments led to serious doubts as to the validity of his interpretation. Further investigations resulted in the establishment of environmental conditions which permit this alga to readily decompose pyruvic acid, as well as nearly all other organic acids tested. This can be accomplished by providing a millieu of sufficiently low pH to insure the presence of undissociated acid molecules. The stimulatory effect on the rate of oxygen consumption, caused by the addition of minute amounts of thiamin to suspensions of vitamin-deficient cells of Prototheca respiring pyruvic acid, indicates that the presence of thiamin results in the synthesis of enzyme systems which are involved in the decomposition of pyruvic acid. Experimental data on the oxidation of pyruvic acid and other organic compounds are discussed in the light of various hypotheses which have been advanced concerning the rôle of carboxylase in the decomposition of pyruvic acid. The conservative conclusion which can be drawn from the available information is that there appears to be no justification for a belief that thiamin and carboxylase are functional in biochemical reactions other than in decarboxylation and carboxylation processes. The discovery of the ability of Prototheca to utilize substituted and dicarboxylic acids led to further studies on the mechanism of oxidative assimilation. The results of these investigations are in agreement with those of Clifton and Logan, and of Doudoroff, and indicate the existence of a relatively simple chemical mechanism of assimilation rather than of a strictly energetic coupling of catabolic and anabolic reactions. A consideration of possible mechanisms for the oxidative assimilation of pyruvic and lactic acids indicates acetic acid as the most likely starting point for the assimilatory process proper. Experimental investigations of the mode of acetate breakdown began with studies on the oxidation of glycolic acid. This substance is shown to be an oxidation catalyst in the metabolism of Prototheca zopfii. The exact nature of the catalytic function has not yet been determined.

Barker's study on the nutritive requirements of Prototheca zopfii indicated that this colorless alga fails to grow in the absence of small amounts of yeast extract. A study of the growth factor requirements of Prototheca has shown that the active constituent of yeast extract necessary for the growth of this organism is thiamin (vitamin B(1)). Thiamin can fully replace the complex yeast material and allows, in the basal medium used, a maximum cell yield in concentrations of 1-3 x 10(-7)M. Thiamin as such, however, is not essential for the growth of Prototheca zopfii. The alga can develop equally well if supplied with both the thiazole and pyrimidine constituents of this vitamin. These appear to be needed in equimolar proportions. Maximum cell yield is obtained with 3 x 10(-8)M concentrations of the two components.