3,869 research outputs found

    A Novel Thin NIPAM Gel Cassette Dosimeter for Photon-Beam Radiotherapy

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    The response of thin polymer gel cassettes (called NIPAM gels) to ionizing radiation was investigated in this study. The NIPAM gels were prepared from gelatin, N-isopropyl acrylamide, tetrakis (hydroxymethyl) phosphoniumchloride, and N,Nβ€²-methylene-bis-acrylamide. Gel cassettes were irradiated in a phantom using a linear accelerator, and the polymerization morphology of irradiated NIPAM gel was characterized using scanning electron microscopy. The dose-response sensitivity of the NIPAM gels was evaluated using the differences in optical densities. The optical densities were obtained using a computer-controlled CCD camera that was connected to a planar illumination source for acquisition of optical transmission images. The central axis depth dose profiles of the phantom were extracted, and a comparison with ionization chamber measurements demonstrated similarities in profiles. The sensitivity, linearity of the response, accuracy, and reproducibility of the polymer gel cassettes were acceptable. However, the profiles of the half-blocked field irradiation showed no significant dispersion in the visible region. This study also extensively investigated the spatial stability of the NIPAM gel. The results showed that the gel cassette response remains stable for up to three months after irradiation

    Small B cell lymphocytic lymphoma presenting as obstructive sleep apnea

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    BACKGROUND: Most lymphomas that involve the tonsil are large B cell lymphomas. Large B-cell lymphoma is a high grade malignancy which progresses rapidly. Tonsillar lymphoma usually presents as either a unilaterally enlarged palatine tonsil or as an ulcerative and fungating lesion over the tonsillar area. Small lymphocytic lymphomas (SLL) of the Waldeyer's ring are uncommon. CASE PRESENTATION: We report a 41-year-old male who presented with a ten-year history of snoring. Physical examination revealed smooth bilateral symmetrically enlarged tonsils without abnormal surface change or cervical lymphadenopathy. Palatal redundancy and a narrowed oropharyngeal airway were also noted. The respiratory disturbance index (RDI) was 66 per hour, and severe obstruction sleep apnea (OSA) was suspected. No B symptoms, sore throat, odynophagia or dysphagia was found. We performed uvulopalatopharyngoplasty (UPPP) and pathological examination revealed incidental small B-cell lymphocytic lymphoma (SLL). CONCLUSION: It is uncommon for lymphoma to initially present as OSA. SLL is an indolent malignancy and is not easy to detect in the early stage. We conclude that SLL may be a contributing factor of OSA in the present case

    Mechanics of Optimal Structural Design for Extreme Loads to Peak System Responses

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    [[abstract]]Over the past decades, with the development of modern manufacturing and information technology, demands of smart and economical structural designs have been increasing considerably. Central to this engineering issue is that a good structural design needs to embrace both necessary capabilities to afford critical load distributions and the best arrangement of materials serving the performance criteria using limited resources. Here, a new analysis technique is proposed to achieve optimal structural designs considering peak system responses as design constraints respective to extreme load distributions. We anticipate that the technique will open a door for designing efficient structural systems which satisfy safety requirements under various sophisticated loadings from the environment.[[sponsorship]]Tamkang University[[sponsorship]]Taiwan Association of Wind Engineering[[sponsorship]]Institute of Theoretical and Applied Mechanics, Academy of Sciences of the Czech Republic[[conferencetype]]εœ‹ιš›[[conferencetkucampus]]ζ·‘ζ°΄ζ ‘εœ’[[conferencedate]]20151101~20151102[[booktype]]η΄™ζœ¬[[iscallforpapers]]Y[[conferencelocation]]New Taipe

    Absorption Cross Sections of NH_3, NH_2D, NHD_2, and ND_3 in the Spectral Range 140-220 nm and Implications for Planetary Isotopic Fractionation

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    Cross sections for photoabsorption of NH_3, NH_2D, NHD_2, and ND_3 in the spectral region 140-220 nm were determined at ~298 K using synchrotron radiation. Absorption spectra of NH_2D and NHD_2 were deduced from spectra of mixtures of NH_3 and ND_3, of which the equilibrium concentrations for all four isotopologues obey statistical distributions. Cross sections of NH_2D, NHD_2, and ND_3 are new. Oscillator strengths, an integration of absorption cross sections over the spectral lines, for both A ← X and B ← X systems of NH_3 agree satisfactorily with previous reports; values for NH_2D, NHD_2, and ND_3 agree with quantum chemical predictions. The photolysis of NH_3 provides a major source of reactive hydrogen in the lower stratosphere and upper troposphere of giant planets such as Jupiter. Incorporating the measured photoabsorption cross sections of NH_3 and NH_2D into the Caltech/JPL photochemical diffusive model for the atmosphere of Jupiter, we find that the photolysis efficiency of NH_2D is lower than that of NH_3 by as much as 30%. The D/H ratio in NH_2D/NH_3 for tracing the microphysics in the troposphere of Jupiter is also discussed
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