Pre-nuclear level of I-129 in Chinese loess-paleosol sections: A search for the natural I-129 level for dating in terrestrial environments

Due to its long half-life (15.7 Myr), radioactive I-129 has great potential for dating geologic materials as old as 100 Myr. Thus, knowing the natural level of I-129 is crucial to dating applications. The initial ratio of I-129/I-127 in the ocean has been quantified by a number of researchers who have reached a consensus value. However, the applicability of I-129 dating in the terrestrial environment remains problematic because the lack of an initial I-129/I-127 value. In this work, samples of loess-paleosol sections from the Chinese Loess Plateau (CLP) were analyzed for I-129/I-127, aiming to provide an Initial I-129/I-127 ratio that can be adopted for dating purposes in terrestrial environments. A value of (2.0 +/- 1.0) x 10(-11) for the I-129/I-127 ratio was found in two investigated loess-paleosol sections from Xifeng and Luochuan, China. This ratio is one order of magnitude higher than the initial value reported for the marine environment. Alteration of the natural initial I-129 In the investigated samples due to the downward migration of anthropogenic I-129 and by excess fissiogenic I-129 from uranium was not supported. Consequently, the I-129/I-127 ratio measured is considered to be a pristine value, and the difference from that In the marine systems is attributed to an Isotopic dilution effect. (C) 2018 Elsevier Ltd. All rights reserved

¹²⁹I and its species in the East China Sea: level, distribution, sources and tracing water masses exchange and movement

Anthropogenic I-129 as a long-lived radioisotope of iodine has been considered as an ideal oceanographic tracer due to its high residence time and conservative property in the ocean. Surface water samples collected from the East China Sea (ECS) in August 2013 were analyzed for I-129, I-127 and their inorganic chemical species in the first time. The measured I-129/I-127 ratio is 1-3 orders of magnitude higher than the pre-nuclear level, indicating its dominantly anthropogenic sources. Relatively high I-129 levels were observed in the Yangtze River and its estuary, as well as in the southern Yellow Sea, and I-129 level in seawater declines towards the ECS shelf. In the open sea, I-129 and I-127 in surface water exists mainly as iodate, while in Yangtze River estuary and some locations, iodide is dominated. The results indicate that the Fukushima nuclear accident has no detectable effects in the ECS until August 2013. The obtained results are used for investigation of interaction of various water masses and water circulation in the ECS, as well as the marine environment in this region. Meanwhile this work provides essential data for evaluation of the possible influence of the increasing NPPs along the coast of the ECS in the future

Non-fragile state estimation for discrete Markovian jumping neural networks

In this paper, the non-fragile state estimation problem is investigated for a class of discrete-time neural networks subject to Markovian jumping parameters and time delays. In terms of a Markov chain, the mode switching phenomenon at different times is considered in both the parameters and the discrete delays of the neural networks. To account for the possible gain variations occurring in the implementation, the gain of the estimator is assumed to be perturbed by multiplicative norm-bounded uncertainties. We aim to design a non-fragile state estimator such that, in the presence of all admissible gain variations, the estimation error converges to zero exponentially. By adopting the Lyapunov–Krasovskii functional and the stochastic analysis theory, sufficient conditions are established to ensure the existence of the desired state estimator that guarantees the stability of the overall estimation error dynamics. The explicit expression of such estimators is parameterized by solving a convex optimization problem via the semi-definite programming method. A numerical simulation example is provided to verify the usefulness of the proposed methods

Accelerator Mass Spectrometry Analysis of Ultra-Low-Level ¹²⁹I in Carrier-Free AgI-AgCl Sputter Targets

Separation of carrier-free iodine from low-level iodine samples and accurate measurement of ultra-low-level I-129 in microgram iodine target are essential but a bottleneck in geology and environment research using naturally produced I-129. This article presents a detection technique of accelerator mass spectrometry (AMS) for accurate determination of ultra-low-level I-129 in carrier-free AgI-AgCl sputter targets. Copper instead of aluminum was selected as the suitable sample holder material to avoid the reaction of AgI-AgCl powder with aluminum. Niobium powder was selected as thermally and electrically conductive matrix to be mixed with AgI-AgCl powder, in order to obtain and maintain a stable and high iodine ion current intensity, as well as less memory effect and low background level of I-129. The most optimal ratio of the Nb matrix to the AgI-AgCl powder was found to be 5:1 by mass. The typical current of I-127(5+) using AgI-AgCl targets with iodine content from 5 to 80 mu g was measured to be 5 to 100 nA. Four-year AMS measurements of the I-129/I-127 ratios in standards of low iodine content and the machine blanks showed a good repeatability and stability.</p

Enhancing malaria diagnosis through microfluidic cell enrichment and magnetic resonance relaxometry detection

Despite significant advancements over the years, there remains an urgent need for low cost diagnostic approaches that allow for rapid, reliable and sensitive detection of malaria parasites in clinical samples. Our previous work has shown that magnetic resonance relaxometry (MRR) is a potentially highly sensitive tool for malaria diagnosis. A key challenge for making MRR based malaria diagnostics suitable for clinical testing is the fact that MRR baseline fluctuation exists between individuals, making it difficult to detect low level parasitemia. To overcome this problem, it is important to establish the MRR baseline of each individual while having the ability to reliably determine any changes that are caused by the infection of malaria parasite. Here we show that an approach that combines the use of microfluidic cell enrichment with a saponin lysis before MRR detection can overcome these challenges and provide the basis for a highly sensitive and reliable diagnostic approach of malaria parasites. Importantly, as little as 0.0005% of ring stage parasites can be detected reliably, making this ideally suited for the detection of malaria parasites in peripheral blood obtained from patients. The approaches used here are envisaged to provide a new malaria diagnosis solution in the near future.Singapore-MIT Alliance for Research and Technology Cente

Serum proteomic profiling and haptoglobin polymorphisms in patients with GVHD after allogeneic hematopoietic cell transplantation

We studied serum proteomic profiling in patients with graft versus host disease (GVHD) after allogeneic hematopoietic cell transplantation (allo-HCT) by two-dimensional gel electrophoresis (2-DE) and mass spectrometry analysis. The expression of a group of proteins, haptoglobin (Hp), alpha-1-antitrypsin, apolipoprotein A-IV, serum paraoxonase and Zn-alpha-glycoprotein were increased and the proteins, clusterin precursor, alpha-2-macroglobulin, serum amyloid protein precursor, sex hormone-binding globulin, serotransferrin and complement C4 were decreased in patients with extensive chronic GVHD (cGVHD). Serum haptoglobin (Hp) levels in patients with cGVHD were demonstrated to be statistically higher than in patients without cGVHD and normal controls (p < 0.01). We used immunoblotting and PCR in combination with 2-DE gel image analysis to determine Hp polymorphisms in 25 allo-HCT patients and 16 normal donors. The results demonstrate that patients with cGVHD had a higher incidence of HP 2-2 phenotype (43.8%), in comparison to the patients without cGVHD (0%) and normal donors (18.7%), suggesting the possibility that specific Hp polymorphism may play a role in the development of cGVHD after allo-HCT. In this study, quantitative serum Hp levels were shown to be related to cGVHD development. Further, the data suggest the possibility that specific Hp polymorphisms may be associated with cGVHD development and warrant further investigation