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Correcting for spatially dependent intrinsic efficiency on a germanium double-sided strip detector to improve nuclear forensics response

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Radiation Detection Technology and Methods 2022年第1期6卷 78-87页

作者： timothy jacom.-hood James Fast Craig Department of Nuclear Engineering Texas A&M UniversityCollege StationTXUSA Pacific Northwest National Laboratory RichlandWAUSA

Purpose The Germanium Gamma-ray Imager(GeGI)is a planar high-purity germanium(HPGe)imaging detector developed by PHDS Co for far-field *** research investigates the detector’s ability for measuring heterogeneous sources in the near field,placed directly on the detector’s faceplate,to perform isotopic mapping for nuclear forensic *** The intrinsic efficiency is strongly dependent on where the photons interact within the *** efficiency varies by up to 20%within the sensitive volume of the *** efficiency was mapped using eight different photons from 123 to 1274 keV emitted from a collimated 154Eu *** were measured at 108 locations to interpolate the efficiency at any point on the detector’s *** The position and energy dependence are uncorrelated,and thus,the absolute efficiency at any position and for any gamma-ray energy can be calculated by the convolution of the spatial and energy *** The results on this research show that detection efficiency for a planar two-sided strip HPGe is spatially dependent and shows typical energy *** spatial dependence,which does not have any additional energy dependence,can be corrected.A 154Eu source was used in this research and was able to spatially calibrate for photon energies ranging from 100 to 1300 *** method is applicable for sources with higher gamma *** advantages of the method demonstrated that after initial in-laboratory calibration,a single measurement in the field can be used to efficiently calibrate the HPGe as a function of photon interaction on the crystal.

关键词： Nuclear forensics Radiation detection Gamma-ray imaging

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Implementation of the Estimating Functions Approach in Asset Returns Volatility Forecasting Using First Order Asymmetric GARCH Models

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Open Journal of Statistics 2015年第5期5卷 455-464页

作者： timothy Ndonye Mutunga Ali Salim Islam Luke Akong’o Orawo Department of Mathematics Egerton University Egerton Kenya

This paper implements the method of estimating functions (EF) in the modelling and forecasting of financial returns volatility. This estimation approach incorporates higher order moments which are common in most financial time series, into modelling, leading to a substantial gain of information and overall efficiency benefits. The two models considered in this paper provide a better in-sample-fit under the estimating functions approach relative to the traditional maximum likely-hood estimation (MLE) approach when fitted to empirical time series. On this ground, the EF approach is employed in the first order EGARCH and GJR-GARCH models to forecast the volatility of two market indices from the USA and Japanese stock markets. The loss functions, mean square error (MSE) and mean absolute error (MAE), have been utilized in evaluating the predictive ability of the EGARCH vis-à-vis the GJR-GARCH model.

关键词： Estimating Function Asymmetric GARCH Volatility Mean Square Error Mean Absolute Error

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Retinoblastoma and treatment: A current evaluation of advanced therapy

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World Journal of Pharmacology 2013年第3期2卷 65-72页

作者： Nisha V Shah Samuel K Houston timothy G Murray Department of Ophthalmology Bascom Palmer Eye Institute University of Miami Miller School of Medicine

Retinoblastoma is the most common primary childhood ocular tumor, affecting nearly 3.5 per million children worldwide. A mutation in the RB1 gene, which presents as either germline or sporadic, along with additional mutational events, promote neoplastic growth in the retina. Fortunately, current treatment protocols result in success rates approaching 99% at specialized centers, with many children maintaining useful vision. Overall, treatment is guided by aggressiveness and size, and is classified by systems such as the ReeseEllsworth System and the International Classification of Retinoblastoma. Due to advances in chemotherapy protocols combined with use of focal laser consolidation, treatment paradigms have shifted from enucleation to external beam radiation therapy to chemotherapy as globe-salvaging therapies. Smaller, less complex tumors may be controlled by plaque radiotherapy or focal laser ablative therapy. However, larger and more complex tumors, such as those that have vitreous or subretinal seeding, require methods of chemoreduction combined with focal consolidation to yield better outcomes. Standard chemotherapy protocols utilize vincristine, etoposide, and carboplatin with or withoutcyclophosphamide. Finally, there has been a recent push in local treatments for retinoblastoma to minimize systemic toxicities. These modalities include intravitreal or subconjunctival injections and more recently, direct chemotherapy administration into the ophthalmic artery. As a result, enucleation is used less often, but remains an important treatment for the most aggressive, refractory cases. The advancement of retinoblastoma treatment looks promising; however, worldwide access to these treatments and the lack of long-term followup of new local treatment modalities constitute current and future challenges.

关键词：视网膜眼肿瘤治疗方法临床分析

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