25 research outputs found
Entropy and Complexity Analyses in Alzheimer’s Disease: An MEG Study
Alzheimer’s disease (AD) is one of the most frequent disorders among elderly population and it is considered the main cause of dementia in western countries. This irreversible brain disorder is characterized by neural loss and the appearance of neurofibrillary tangles and senile plaques. The aim of the present study was the analysis of the magnetoencephalogram (MEG) background activity from AD patients and elderly control subjects. MEG recordings from 36 AD patients and 26 controls were analyzed by means of six entropy and complexity measures: Shannon spectral entropy (SSE), approximate entropy (ApEn), sample entropy (SampEn), Higuchi’s fractal dimension (HFD), Maragos and Sun’s fractal dimension (MSFD), and Lempel-Ziv complexity (LZC). SSE is an irregularity estimator in terms of the flatness of the spectrum, whereas ApEn and SampEn are embbeding entropies that quantify the signal regularity. The complexity measures HFD and MSFD were applied to MEG signals to estimate their fractal dimension. Finally, LZC measures the number of different substrings and the rate of their recurrence along the original time series. Our results show that MEG recordings are less complex and more regular in AD patients than in control subjects. Significant differences between both groups were found in several brain regions using all these methods, with the exception of MSFD (p-value < 0.05, Welch’s t-test with Bonferroni’s correction). Using receiver operating characteristic curves with a leave-one-out cross-validation procedure, the highest accuracy was achieved with SSE: 77.42%. We conclude that entropy and complexity analyses from MEG background activity could be useful to help in AD diagnosis
Oxidant-NO dependent gene regulation in dogs with type I diabetes: impact on cardiac function and metabolism
<p>Abstract</p> <p>Background</p> <p>The mechanisms responsible for the cardiovascular mortality in type I diabetes (DM) have not been defined completely. We have shown in conscious dogs with DM that: <it>1</it>) baseline coronary blood flow (CBF) was significantly decreased, <it>2</it>) endothelium-dependent (ACh) coronary vasodilation was impaired, and <it>3</it>) reflex cholinergic NO-dependent coronary vasodilation was selectively depressed. The most likely mechanism responsible for the depressed reflex cholinergic NO-dependent coronary vasodilation was the decreased bioactivity of NO from the vascular endothelium. The goal of this study was to investigate changes in cardiac gene expression in a canine model of alloxan-induced type 1 diabetes.</p> <p>Methods</p> <p>Mongrel dogs were chronically instrumented and the dogs were divided into two groups: one normal and the other diabetic. In the diabetic group, the dogs were injected with alloxan monohydrate (40-60 mg/kg iv) over 1 min. The global changes in cardiac gene expression in dogs with alloxan-induced diabetes were studied using Affymetrix Canine Array. Cardiac RNA was extracted from the control and DM (n = 4).</p> <p>Results</p> <p>The array data revealed that 797 genes were differentially expressed (P < 0.01; fold change of at least ±2). 150 genes were expressed at significantly greater levels in diabetic dogs and 647 were significantly reduced. There was no change in eNOS mRNA. There was up regulation of some components of the NADPH oxidase subunits (gp91 by 2.2 fold, P < 0.03), and down-regulation of SOD1 (3 fold, P < 0.001) and decrease (4 - 40 fold) in a large number of genes encoding mitochondrial enzymes. In addition, there was down-regulation of Ca<sup>2+ </sup>cycling genes (ryanodine receptor; SERCA2 Calcium ATPase), structural proteins (actin alpha). Of particular interests are genes involved in glutathione metabolism (glutathione peroxidase 1, glutathione reductase and glutathione S-transferase), which were markedly down regulated.</p> <p>Conclusion</p> <p>our findings suggest that type I diabetes might have a direct effect on the heart by impairing NO bioavailability through oxidative stress and perhaps lipid peroxidases.</p
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Cerium, uranium, and plutonium behavior in glass-bonded sodalite, a ceramic nuclear waste form.
Glass-bonded sodalite is being developed as a ceramic waste form (CWF) to immobilize radioactive fission products, actinides, and salt residues from electrometallurgical treatment of spent nuclear reactor fuel. The CWF consists of about 75 mass % sodalite, 25 mass % glass, and small amounts of other phases. This paper presents some results and interpretation of physical measurements to characterize the CWF structure, and dissolution tests to measure the release of matrix components and radionuclides from the waste form. Tests have been carried out with specimens of the CWF that contain rare earths at concentrations similar to those expected in the waste form. Parallel tests have been carried out on specimens that have uranium or plutonium as well as the rare earths at concentrations similar to those expected in the waste forms; in these specimens UCl{sub 3} forms UO{sub 2} and PuCl{sub 3} forms PuO{sub 2}. The normalized releases of rare earths in dissolution tests were found to be much lower than those of matrix elements (B, Si, Al, Na). When there is no uranium in the CWF, the release of cerium is two to ten times lower than the release of the other rare earths. The low release of cerium may be due to its tetravalent state in uranium-free CWF. However, when there is uranium in the CWF, the release of cerium is similar to that of the other rare earths. This trivalent behavior of cerium is attributed to charge transfer or covalent interactions among cerium, uranium, and oxygen in (U,Ce)O{sub 2}
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Characterization of a glass-bonded ceramic waste form loaded with U and Pu
This paper presents microscopic characterization of four samples of a ceramic waste form (CWF) developed for disposal of actinide-containing electrorefiner salts. The four samples were prepared to investigate the influence of water content and the Pu:U ratio on CWF microstructure and performance. While the overall phase content is not strongly influenced by either variable, the presence of water in the initial zeolite has a detectable effect on CWF microstructure. It is found to influence the distribution of the major actinide host phase, a (U,Pu)O{sub 2} mixed oxide
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XAF/XANES studies of plutonium-loaded sodalite/glass composite waste forms.
A sodalite/glass ceramic waste form has been developed to immobilize highly radioactive nuclear wastes in chloride form, as part of an electrochemical cleanup process. Simulated waste forms have been fabricated which contain plutonium and are representative of the salt from the electrometallurgical process to recover uranium from spent nuclear fuel. X-ray absorption fine structure spectroscopy (XAFS) and x-ray absorption near-edge spectroscopy (XANES) studies were performed to determine the location, oxidation state and form of the plutonium within these waste forms. Plutonium, in the non-fission-element case, was found to segregate as plutonium(IV) oxide with a crystallite size of at least 20 nm. With fission elements present, the crystallite size was about 2 nm. No plutonium was observed within the sodalite or glass in the waste form