A comparison study of wavelet transforms for the visualization of differentially methylated regions in DNA samples

The Journal of Supercomputing - DNA methylation analysis has become an important topic in the study of human health. DNA methylation analysis requires not only a specific treatment of DNA samples...     

Characterization of a thermoset by thermal analysis techniques: Criterion to assign the value of the α‐transition temperature by dielectric analysis

A cured thermoset composed of diglycidyl ether of bisphenol A and m‐xylylene diamine as the cure agent was studied with different thermal analysis techniques, including differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and dielectric analysis (DEA). DSC was used to measure the glass‐transition temperature and to check the absence of the heat of reaction. DMA and DEA were used to show the existence of two transitions in the temperature range of −100 to 240°C. The transition at a low temperature corresponded to the β transition. The second one, at a higher temperature, was associated with an α transition. The β transition followed Arrhenius behavior, whereas the α transition followed Vogel behavior. For an analysis of the α transition, different equations, such as the Havriliak–Negami, Vogel, and Williams–Landel–Ferry equations, were used. Important differences related to the fitting parameters were found that depended on the type of equation and the operation mode used. For this reason, a new method for calculating the α‐transition temperature was examined. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2027–2037, 2005     

A new family of synthetic diterpenes that regulates cytokine synthesis by inhibiting IkappaBalpha phosphorylation

The synthesis and the biological evaluation of a new family diterpenes are presented. The synthetic studies were inspired by the structural framework of acanthoic acid (1) and yielded a family of compounds that were evaluated as anti-inflammatory agents. Among them, compounds 2, 10, 12, and 16 exhibited a very low nonspecific cytotoxicity and inhibited the synthesis of TNF-alpha with greater than 65 % efficacy at low micromolar concentrations. Cytokine-specificity studies revealed that these compounds also inhibited the synthesis of the proinflammatory cytokines IL-1beta and IL-6, while inhibition of IL-1ra and IL-8 synthesis was marginal and only occurred at high concentrations. Further studies, through EMSA and Western blot analyses, indicated that these compounds decreased the extent of phosphorylation of IkappaBalpha; this suggests that they exert their anti-inflammatory profile by inhibiting NF-kappaB-mediated cytokine synthesis. These findings imply that these diterpenes represent promising leads for the development of novel anti-inflammatory agents.     

Influence of water absorption on the mechanical properties of a DGEBA (n = 0)/1, 2 DCH epoxy system

The diffusive, calorimetric, and mechanical behavior of a system composed of a diglycidyl ether of bisphenol‐A (DGEBA, n = 0) and 1, 2 diamine cyclohexane (1, 2 DCH) were investigated during water sorption at different temperatures (23, 47, 58, 77, and 100°C). Experimental results showed that the water absorption at these temperatures fitted well to Fick's law. The water moisture content at the equilibrium temperature and the water moisture content at the equilibrium‐curing conditions dependences have been checked. The activation energy for diffusion was calculated obtaining a value 26.01 kJ/mol. Dynamic mechanical analysis of several samples immersed in water at 100°C during different periods of time showed no significant changes in the glass transition temperature, and a decrease in the storage modulus at 2% of water content was observed. Storage modulus remained essentialy constant above that water content. Values of glass transition temperature were corroborated by differential scanning calorimetric measurements. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 353–358, 1999     

Effects of diffusion on the kinetic study of the system BADGE n = 0/m‐xylylenediamine

The curing reactions of an epoxy system composed of a diglycidyl ether of bisphenol A (BADGE n=0) and m‐xylylenediamine (m‐XDA) were studied. Two models, the first based solely on chemical kinetics and the second accounting for diffusion, were used and compared to the experimental data. The epoxy resin was used as received in a first series of experiments. In a second series of experiments, the resin was purified in vacuo (180°C and 1 mmHg). The inclusion of a diffusion factor in the second model allowed for the cure kinetics to be predicted over the whole range of conversion covering both pre‐ and postvitrification stages. The investigation was made in the temperature range 50–110°C, which is considered optimum for the isothermal curing of the epoxy system studied. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2997–3005, 1999     

Lifetime prediction of the epoxy system DGEBA (n = 0)/1,2‐DCH modified with an epoxy reactive diluent by thermogravimetric analysis

Thermogravimetric analysis was used to predict the lifetime of two three‐component systems of diglycidyl ether of bisphenol A (n = 0)/1,2‐diamine cyclohexane [DGEBA (n = 0)/1,2‐DCH] modified with different concentrations of an epoxy reactive diluent, vinylcyclohexene dioxide (VCHD). Experimental results were treated using two methods. The first method was independent of the degradation mechanism, and the second was based on the thermodegradation kinetic mechanism. The activation energies of the reaction were determined using the Flynn–Wall–Ozawa method. These values were compared with those obtained using Kissinger's method. From experimental results it was found that the optimum temperature of service for these materials were different, so one or the other must be selected, depending on the application temperature considered. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3835–3839, 2003     

Determination of dielectric and calorimetric properties in the cure reaction of two thermosets by dielectric analysis and differential scanning calorimetry

Dielectric analysis and differential scanning calorimetry were used to study the cure reaction of an epoxy resin (the diglycidyl ether of bisphenol A (DGEBA) (n = 0)) and two curing agents, ie 1,2‐diamine cyclohexane (1,2‐DCH) and m‐xylylenediamine (m‐XDA). Various dielectric properties, such as the relaxed permittivity, unrelaxed permittivity and dipole strength, were determined as a function of the curing time, temperature and conversion. The dielectric curing properties observed were related to geometric and energetic aspects of the samples. Analysis of the results shows that the relaxed permittivity and dipole strength are higher for the system DGEBA (n = 0)/1,2‐DCH than for the system DGEBA (n = 0)/m‐XDA. Copyright © 2005 Society of Chemical Industry     

Effects of diffusion on the kinetic study and TTT cure diagram for an epoxy/diamine system

The curing reactions of an epoxy system consisting of a diglycidyl ether of bisphenol A (BADGE n = 0) and 1,2-diamine cyclohexane (DCH) were studied to determine a time–temperature–transformation (TTT) isothermal cure diagram for this system. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and a solubility test were used to obtain the different experimental data reported. Two models, one based solely on chemical kinetics and the other accounting for diffusion, were used and compared to the experimental data. The inclusion of a diffusion factor in the second model allowed for the cure kinetics to be predicted over the whole range of conversion covering both pre- and post-vitrification stages. The investigation was made in the temperature range 60–100°C, which is considered optimum for the isothermal curing of the epoxy system studied. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1931–1938, 1998     

Influence of an epoxy reactive diluent on the thermal degradation process of the system DGEBA n = 0/1,2 DCH

The thermal degradation of two epoxy systems diglycidyl ether of bisphenol A (DGEBA n = 0)/1,2‐diamine cyclohexane (DCH) containing different concentrations of an epoxy reactive diluent, vinylcyclohexene dioxide (VCHD), was studied by thermogravimetric analysis to determine the reaction mechanism of the degradation process for these two systems. Values of the activation energy, necessary for this study, were calculated by using various integral and differential methods. Values obtained by using the different methods were compared to the value obtained by Kissinger's method, which does not require a knowledge of the reaction mechanism. All the experimental results were compared to master curves in the range of Doyle's approximation (20–35% of conversion). Analysis of the results suggests that the two reaction mechanisms are R_n and F_n deceleratory type in contrast with the sigmoidal A₂ type of the system with filler and the sigmoidal A₄ type of the system without additives. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1199–1207, 2004     

Distribution of CGRP in the minipig brainstem

For the first time, an in‐depth study has been made of the distribution of fibers and cell bodies containing calcitonin gene‐related peptide (CGRP) in the minipig brainstem using an indirect immunoperoxidase technique. The animals studied were not treated with colchicine. Cell bodies containing CGRP were found in 20 nuclei/regions of the brainstem. These perikarya were located in somatomotor, brachiomotor and raphae nuclei, nucleus ambiguus, substantia nigra, nucleus reticularis tegmenti pontis, nucleus prepositus hypoglossi, nuclei olivaris inferior and superior, nuclei pontis, formatio reticularis, nucleus dorsalis tegmenti of Gudden, and in the nucleus reticularis lateralis. Fourteen of the 20 brainstem nuclei showed a high density of immunoreactive cell bodies. In comparison with other species, the minipig, together with the rat, show the most widespread distribution of cell bodies containing CGRP in the mammalian brainstem. Immunoreactive fibers were also observed in the brainstem. However, in the minipig brainstem the density of these fibers is low, as in many brainstem nuclei only single immunoreactive fibers were observed. A high density of immunoreactive fibers was only observed in the pars caudalis of the nucleus tractus spinalis nervi trigemini and in the nucleus ventralis tegmenti of Gudden. According to the observed anatomical distribution of the immunoreactive structures containing CGRP, the peptide could be involved in motor, somatosensory, gustative, and autonomic mechanisms. Microsc. Res. Tech. 77:374–384, 2014. © 2014 Wiley Periodicals, Inc.