5,930 research outputs found

    Terminal deoxynucleotidyltransferase. Serological studies and radioimmunoassay

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    Mouse antisera against calf terminal deoxynucleotidyltransferase (terminal transferase) have been prepared. The sera have been used to characterize terminal transferase both by studying inhibition of enzyme activity and by developing a competition radioimmunoassay using highly purified 125I-labeled terminal transferase. By either assay, anti-terminal transferase serum did not cross-react significantly with calf DNA polymerases alpha and beta, Escherichia coli DNA polymerase I, or the reverse transcriptase of Moloney mouse leukemia virus. The calf terminal transferase did, however, share cross-reactive but not identical determinants with human and murine terminal transferase. The radioimmunoassay could detect as little as 2 ng of terminal transferase/mg of soluble protein in a tissue extract. Thymocytes were found to contain 280 ng of terminal transferase/mg of cell protein or about 1 X 10^(5) molecules/cell; bone marrow had about 1% of the level of enzyme found in thymus. Extracts of spleen, peripheral white blood cells, lymph nodes, liver, muscle, and kidney all lacked detectable antigenicity of terminal transferase. These data indicate that terminal transferase is a tissue-specific enzyme and is not related to other DNA polymerases

    Edited NSSL meso-scale upper air network data in southwestern Oklahoma, 1966 and 1967

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    Cover title."Atmospheric General Circulation Technical Document No. 1.

    Stability of nonuniform rotor blades in hover using a mixed formulation

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    A mixed formulation for calculating static equilibrium and stability eigenvalues of nonuniform rotor blades in hover is presented. The static equilibrium equations are nonlinear and are solved by an accurate and efficient collocation method. The linearized perturbation equations are solved by a one step, second order integration scheme. The numerical results correlate very well with published results from a nearly identical stability analysis based on a displacement formulation. Slight differences in the results are traced to terms in the equations that relate moments to derivatives of rotations. With the present ordering scheme, in which terms of the order of squares of rotations are neglected with respect to unity, it is not possible to achieve completely equivalent models based on mixed and displacement formulations. The one step methods reveal that a second order Taylor expansion is necessary to achieve good convergence for nonuniform rotating blades. Numerical results for a hypothetical nonuniform blade, including the nonlinear static equilibrium solution, were obtained with no more effort or computer time than that required for a uniform blade

    Investigation of laser dynamics, modulation and control by means of intra-cavity time varying perturbation

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    The generation of tunable visible, infrared, and ultraviolet light is examined, along with the control of this light by means of novel mode-locking and modulation techniques. Transient mode-locking of the Nd:YAG laser and generation of short tunable pulses in the visible and the alkali metal inert gas excimer laser systems were investigated. Techniques for frequency conversion of high power and high energy laser radiation are discussed, along with high average power blue and UV laser light sources

    Topological Constraints at the Theta Point: Closed Loops at Two Loops

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    We map the problem of self-avoiding random walks in a Theta solvent with a chemical potential for writhe to the three-dimensional symmetric U(N)-Chern-Simons theory as N goes to 0. We find a new scaling regime of topologically constrained polymers, with critical exponents that depend on the chemical potential for writhe, which gives way to a fluctuation-induced first-order transition.Comment: 5 pages, RevTeX, typo

    Malignant melanoma metastatic to the thyroid gland: a case report and review of the literature.

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    The thyroid gland is a relatively uncommon site for a secondary malignancy; even less common is a case of malignant melanoma metastatic to the thyroid. We describe the case of a 68-year-old man who presented with a neck mass in the posterior triangle. Fine-needle aspiration biopsy (FNAB) identified the mass as a malignant melanoma. The patient had had no known primary skin melanoma. He underwent a left modified radical neck dissection, and the mass was discovered to be a positive lymph node. Postoperatively, he declined to undergo radio- and chemotherapy. Eighteen months later, he returned with a diffusely enlarged thyroid. FNAB again attributed the enlargement to malignant melanoma. Soon thereafter, the patient began experiencing seizures, and on magnetic resonance imaging, he was found to have metastatic disease to the brain. He developed ventilator-dependent respiratory failure and required a subtotal thyroidectomy for the placement of a tracheostomy tube. Patients who present with a thyroid nodule and who have a history of malignancy present a diagnostic dilemma: Is the nodule benign, a new primary, or a distant metastasis? The findings of this case and a review of the literature strengthen the argument that any patient with a thyroid mass and a history of malignancy should be considered to have a metastasis until proven otherwise
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