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41.
Microwave assisted micellar extraction (MAME) coupled with solid phase microextraction (SPME) and HPLC-UV determination have been used for the determination of five organochlorine pesticides from agricultural soil samples. A non-ionic surfactant, Polyoxyethlylene 10 Lauryl Ether was used, and the different variables for the optimization of MAME and SPME procedures were studied. This method was applied successfully to the determination of these pesticides in several kinds of agricultural soil samples with different characteristics. Most of the compounds studied can be recovered in good yields with R.S.D. lower than 9% and detection limit ranged between 56-96 ng g−1 for the pesticides studied. 相似文献
42.
Halko R Padrón Sanz C Sosa Ferrera Z Santana Rodríguez JJ 《Journal of AOAC International》2006,89(5):1403-1409
A simple and fast analytical method was developed for the determination of benzimidazole fungicides (benomyl, carbendazim, thiabendazole, and fuberidazole) in soil samples. The analytes were extracted from the soil samples by means of conventional microwave-assisted extraction, using the non-ionic surfactants polyoxyethylene 10 lauryl ether (POLE) and oligoethylene glycol monooalkyl ether (Genapol X-080) as extractants. Determinations were made by using liquid chromatography with direct fluorescence detection. The use of an analytical column Symmetry C-18 offered short retention times of analytes without the need of any pH regulators with mobile phase methanol-water (50 + 50, v/v). The best results were obtained using 5% (v/v) POLE as extractant with recoveries of the fungicides in spiked soil samples between 71 and 105%. The results were compared with those obtained when Soxhlet extraction was applied to the same soil samples. 相似文献
43.
Background
Presenilin-1 (PS1) is a transmembrane protein first discovered because of its association with familial Alzheimer’s disease. Mice with null mutations in PS1 die shortly after birth exhibiting multiple CNS and non-CNS abnormalities. One of the most prominent features in the brains of PS1?/? embryos is a vascular dysgenesis that leads to multiple intracerebral hemorrhages. The molecular and cellular basis for the vascular dysgenesis in PS1?/? mice remains incompletely understood. Because the extracellular matrix plays key roles in vascular development we hypothesized that an abnormal extracellular matrix might be present in endothelial cells lacking PS1 and examined whether the lack of PS1 affects expression of fibronectin a component of the extracellular matrix known to be essential for vascular development.Results
We report that primary as well as continuously passaged PS1?/? endothelial cells contain more fibronectin than wild type cells and that the excess fibronectin in PS1?/? endothelial cells is incorporated into a fibrillar network. Supporting the in vivo relevance of this observation fibronectin expression was increased in microvascular preparations isolated from E14.5 to E18.5 PS1?/? embryonic brain. Reintroduction of PS1 into PS1?/? endothelial cells led to a progressive decrease in fibronectin levels showing that the increased fibronectin in PS1?/? endothelial cells was due to loss of PS1. Increases in fibronectin protein in PS1?/? endothelial cells could not be explained by increased levels of fibronectin RNA nor based on metabolic labeling studies by increased protein synthesis. Rather we show based on the rate of turnover of exogenously added biotinylated fibronectin that increased fibronectin in PS1?/? endothelial cells results from a slower degradation of the fibronectin fibrillar matrix on the cell surface.Conclusions
These studies show that PS1 regulates the constitutive turnover of the fibronectin matrix in endothelial cells. These studies provide molecular clues that may help to explain the origin of the vascular dysgenesis that develops in PS1?/? embryonic mice.44.
Teodoro Cordova-Fraga Modesto Sosa Martha Alicia Hernandez-Gonzalez Jose Antonio Reyes-Aguilera Sergio Solorio Chystian Ramirez Evelia Bautista-Flores Guadalupe Reynaga Mario Avila-Rodriguez Jose Maria De la Roca-Chiapas 《Applied magnetic resonance》2012,42(2):161-167
Magnetic resonance imaging (MRI) of the gastrointestinal (GI) tract is still limited due to the lack of widely available oral
contrast agents (OCA). The availability of OCA for MRI of the GI tract is a necessity; different fruits might be implemented
as OCA in order to solve this need throughout the year. The objective of this study is to present an alternative fruit as
a clinical OCA for MRI of the GI tract, Achras sapota L. (common medlar). Both physical and chemical characterization of the medlar was performed. It was also tested in situ and
in vivo as an OCA for MRI of the GI tract. Results showed that this fruit had a diamagnetic behavior, although it has enough
iron, manganese and copper to contrast the GI tract in T
1- and T
2-weighted images. Thus we conclude that the medlar fruit has shown a potential as an OCA in GI evaluation by MRI, so it can
be considered as an alternative in complementation of natural OCA. 相似文献
45.
We study the effect of Rashba spin-orbit coupling on the Hofstadter spectrum of a two-dimensional tight-binding electron system in a perpendicular magnetic field. We obtain the generalized coupled Harper spin-dependent equations which include the Rashba spin-orbit interaction and solve for the energy spectrum and spin polarization. We investigate the effect of spin-orbit coupling on the fractal energy spectrum and the spin polarization for some characteristic states as a function of the magnetic flux α and the spin-orbit coupling parameter. We characterize the complexity of the fractal geometry of the spin-dependent Hofstadter butterfly with the correlation dimension and show that it grows quadratically with the amplitude of the spin-orbit coupling. We study some ground state properties and the spin polarization shows a fractal-like behavior as a function of α, which is demonstrated with the exponent close to unity of the decaying power spectrum of the spin polarization. Some degree of spin localization or distribution around +1 or -1, for small spin-orbit coupling, is found with the determination of the entropy function as a function of the spin-orbit coupling. The excited states show a more extended (uniform) distribution of spin states. 相似文献
46.
Luiz Carlos Matioli Wilfredo Sosa Jinyun Yuan 《Computational Optimization and Applications》2012,52(1):281-292
A family of nonempty closed convex sets is built by using the data of the Generalized Nash equilibrium problem (GNEP). The sets are selected iteratively such that the intersection of the selected sets contains solutions of the GNEP. The algorithm introduced by Iusem-Sosa (Optimization 52:301?C316, 2003) is adapted to obtain solutions of the GNEP. Finally some numerical experiments are given to illustrate the numerical behavior of the algorithm. 相似文献
47.
Shibatomi K Narayama A Abe Y Iwasa S 《Chemical communications (Cambridge, England)》2012,48(59):7380-7382
The practical synthesis of 4,4,4-trifluorocrotonaldehyde (1) and its application to enantioselective 1,4-additions are described. The organocatalytic 1,4-addition of 1 with several nucleophiles such as heteroaromatics, alkylthiols and aldoximes afforded the corresponding products, each bearing a trifluoromethylated stereogenic center with high optical purity. A resulting product was converted into an MAO-A inhibitor, befloxatone. 相似文献
48.
Kana Kobayashi-Taguchi Takashi Saitou Yoshiaki Kamei Akari Murakami Kanako Nishiyama Reina Aoki Erina Kusakabe Haruna Noda Michiko Yamashita Riko Kitazawa Takeshi Imamura Yasutsugu Takada 《Molecules (Basel, Switzerland)》2022,27(10)
Fibroadenomas (FAs) and phyllodes tumors (PTs) are major benign breast tumors, pathologically classified as fibroepithelial tumors. Although the clinical management of PTs differs from FAs, distinction by core needle biopsy diagnoses is still challenging. Here, a combined technique of label-free imaging with multi-photon microscopy and artificial intelligence was applied to detect quantitative signatures that differentiate fibroepithelial lesions. Multi-photon excited autofluorescence and second harmonic generation (SHG) signals were detected in tissue sections. A pixel-wise semantic segmentation method using a deep learning framework was used to separate epithelial and stromal regions automatically. The epithelial to stromal area ratio and the collagen SHG signal strength were investigated for their ability to distinguish fibroepithelial lesions. An image segmentation analysis with a pixel-wise semantic segmentation framework using a deep convolutional neural network showed the accurate separation of epithelial and stromal regions. A further investigation, to determine if scoring the epithelial to stromal area ratio and the SHG signal strength within the stromal area could be a marker for differentiating fibroepithelial tumors, showed accurate classification. Therefore, molecular and morphological changes, detected through the assistance of computational and label-free multi-photon imaging techniques, enable us to propose quantitative signatures for epithelial and stromal alterations in breast tissues. 相似文献
49.
Akari Narayama Sosa Israel González Alejandro Trejo Álvaro Miranda Fernando Salazar Miguel Cruz-Irisson 《Journal of computational chemistry》2020,41(31):2653-2662
Recently, the need of improvement of energy storage has led to the development of Lithium batteries with porous materials as electrodes. Porous Germanium (pGe) has shown promise for the development of new generation Li-ion batteries due to its excellent electronic, and chemical properties, however, the effect of lithium in its properties has not been studied extensively. In this contribution, the effect of surface and interstitial Li on the electronic properties of pGe was studied using a first-principles density functional theory scheme. The porous structures were modeled by removing columns of atoms in the [001] direction and the surface dangling bonds were passivated with H atoms, and then replaced with Li atoms. Also, the effect of a single interstitial Li in the Ge was analyzed. The transition state and the diffusion barrier of the Li in the Ge structure were studied using a quadratic synchronous transit scheme. 相似文献
50.
Prof. Dr. Taku Shoji Sho Takagaki Yukino Ariga Akari Yamazaki Mutsumi Takeuchi Prof. Dr. Akira Ohta Dr. Ryuta Sekiguchi Dr. Shigeki Mori Prof. Dr. Tetsuo Okujima Prof. Dr. Shunji Ito 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(9):1931-1935
In this paper, we describe an efficient and atom-economical synthesis of highly functionalized pyrroles, pentafulvenes, and pyrrolopyridines by [2+2] cycloaddition–retroelectrocyclization of N-substituted propargylamines with tetracyanoethylene, followed by the treatment of the resulting tetracyanobutadiene derivatives with silica gel. In this reaction, silica gel plays an important role to promote the intramolecular cyclization to afford the heterocyclic products from the tetracyanobutadiene intermediates. The products were obtained selectively depending on the substituent on the nitrogen atom of the starting propargylamines. 相似文献