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Impeding (99)Tc(IV) mobility in novel waste forms.

ABSTRACT: Technetium ((99)Tc) is an abundant, long-lived radioactive fission product whose mobility in the subsurface is largely governed by its oxidation state. Tc immobilization is crucial for radioactive waste management and environmental remediation. Tc(IV) incorporation in spinels has been proposed as a novel method to increase Tc retention in glass waste forms during vitrification. However, experiments under high-temperature and oxic conditions show reoxidation of Tc(IV) to volatile pertechnetate, Tc(VII). Here we examine this problem with ab initio molecular dynamics simulations and propose that, at elevated temperatures, doping with first row transition metal can significantly enhance Tc retention in magnetite in the order Co>Zn>Ni. Experiments with doped spinels at 700?°C provide quantitative confirmation of the theoretical predictions in the same order. This work highlights the power of modern, state-of-the-art simulations to provide essential insights and generate theory-inspired design criteria of complex materials at elevated temperatures.

SUBMITTER: Lee MS

PROVIDER: S-EPMC4931311 | biostudies-literature | 2016 Jun

REPOSITORIES: biostudies-literature

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Impeding (99)Tc(IV) mobility in novel waste forms.

Lee Mal-Soon MS Um Wooyong W Wang Guohui G Kruger Albert A AA Lukens Wayne W WW Rousseau Roger R Glezakou Vassiliki-Alexandra VA

Nature communications 20160630

Technetium ((99)Tc) is an abundant, long-lived radioactive fission product whose mobility in the subsurface is largely governed by its oxidation state. Tc immobilization is crucial for radioactive waste management and environmental remediation. Tc(IV) incorporation in spinels has been proposed as a novel method to increase Tc retention in glass waste forms during vitrification. However, experiments under high-temperature and oxic conditions show reoxidation of Tc(IV) to volatile pertechnetate, T ...[more]

PMID: 27357121

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Project description:PurposeAs an autoimmune inflammatory disorder, active thyroid-associated ophthalmopathy (TAO) is managed optimally by immunosuppression. In this study, we aimed to evaluate octreotide scintigraphy and the level of serum extraocular muscle antibodies in TAO activity.Patients and methodsThis prospective study comprised 304 patients with active TAO (the clinical activity score; CAS?3), 73 with inactive TAO (CAS<3), 128 with Graves' disease (GD) without ophthalmopathy, and 100 healthy subjects. Moderate-to-severe active TAO patients (CAS?5) received intravenous injection of methylprednisolone; mild active patients (3?CAS?4) received periocular injection of triamcinolone acetonide. 99Tcm-octreotide scintigraphy and serum levels of calsequestrin, uveal auto-antigen with coiled-coil domains and ankyrin repeats (UACA) and G2s antibodies were detected before and after treatment.Results99Tcm-octreotide scintigraphy was positive in active TAO patients (97%) with elevated uptake ratio (UR) (P<0.05), and showed a significant correlation with CAS (r=0.816, P<0.01). After treatment both UR and CAS decreased significantly (P<0.05). The receiving operator characteristic curve (ROC) showed that the best UR threshold for discriminating active and inactive TAO was 1.34 (sensitivity, 100%; specificity, 89.4%). The level of serum calsequestrin antibody was higher in active TAO (P<0.05), showed a significant correlation with CAS (r=0.738, P<0.05), and also decreased after treatment (P<0.05). The best serum calsequestrin antibody threshold of the ROC curve was 138?ng/l (sensitivity, 88.4%; specificity, 89.2%). The UACA antibody was elevated in both TAO and GD patients (P<0.05), with no significant difference (P>0.05). As to G2s, no significant difference was found between all groups (P>0.05). Moreover, six GD patients (4.69%) with elevated calsequestrin developed active TAO 12 weeks later.Conclusion99Tcm-octreotide scintigraphy played a critical role in the evaluation of the clinical activity and therapeutic efficacy of TAO. Autoimmunity against calsequestrin in the pathogenesis of the eye muscle components may provide further objective evidence of myopathy in active TAO. Furthermore, calsequestrin antibody may predict myopathy in active TAO.

Project description:PurposeSentinel lymph node (SLN) biopsy has proven to reliably stage the clinically negative neck in early-stage oral squamous cell carcinoma (OSCC). [99mTc]Tc-tilmanocept may be of benefit in OSCC with complex lymphatic drainage patterns and close spatial relation to SLNs.MethodsA prospective within-patient evaluation study was designed to compare [99mTc]Tc-tilmanocept with [99mTc]Tc-nanocolloid for SLN detection. A total of 20 patients with early-stage OSCC were included, who underwent lymphoscintigraphy with both tracers. Both lymphoscintigraphic images of each patient were evaluated for SLN detection and radiotracer distribution at 2-4 h post-injection.ResultsThe injection site's remaining radioactivity was significantly lower for [99mTc]Tc-tilmanocept (29.9%), compared with [99mTc]Tc-nanocolloid (60.9%; p < 0.001). Radioactive uptake in SLNs was significantly lower for [99mTc]Tc-tilmanocept (1.95%) compared with [99mTc]Tc-nanocolloid (3.16%; p = 0.010). No significant difference was seen in SLN to injection site ratio in radioactivity between [99mTc]Tc-tilmanocept (0.066) and [99mTc]Tc-nanocolloid (0.054; p = 0.232). A median of 3.0 and 2.5 SLNs were identified with [99mTc]Tc-tilmanocept and [99mTc]Tc-nanocolloid, respectively (p = 0.297). Radioactive uptake in higher echelon nodes was not significantly different between [99mTc]Tc-tilmanocept (0.57%) and [99mTc]Tc-nanocolloid (0.86%) (p = 0.052). A median of 2.0 and 2.5 higher echelon nodes was identified with [99mTc]Tc-tilmanocept and [99mTc]Tc-nanocolloid, respectively (p = 0.083).Conclusion[99mTc]Tc-tilmanocept had a higher injection site clearance, but at the same time a lower uptake in the SLN, resulting in an SLN to injection site ratio, which was not significantly different from [99mTc]Tc-nanocolloid. The relatively low-radioactive uptake in SLNs of [99mTc]Tc-tilmanocept may limit intraoperative detection of SLNs, but can be overcome by a higher injection dose.

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Impeding (99)Tc(IV) mobility in novel waste forms.

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Impeding (99)Tc(IV) mobility in novel waste forms.

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