排序方式: 共有33条查询结果,搜索用时 15 毫秒
1.
A base-free rhodium-catalyzed Mizoroki-Heck (M-H) reaction using potassium aryltrifluoroborates as the arylating agent of alkenes and acetone as a green "oxidant" is described. Thanks to the ready availability of organoboranes, this reaction should constitute an interesting alternative to conventional M-H reactions using aryl halides. 相似文献
2.
Claudia Mureşanu Lucian Copolovici Florina Pogącean 《Central European Journal of Chemistry》2005,3(4):592-604
The inhibitory effect of para-nitrophenol on the catalytic reaction of catalase was investigated. Michaelis-Menten kinetic parameters were determined from
Lineweaver-Burk plots obtained in the absence or in the presence of the inhibitor. The inhibitor pattern, revealed by the
Lineweaver-Burk plots, suggested a fully mixed inhibition mechanism. Spectrophotometric monitoring of the indicator reaction:
in conjunction with initial rate measurements was employed for the kinetic determination of the inhibitor. Calibration plots
of initial rate vs. para-nitrophenol concentration were linear in the concentration range 0.9·10−5–2.5·10−5 mol/L and the detection limit was 3·10−6 mol/L (417 μg/L) para-nitrophenol. Interferences from other phenolic compounds like orto-cresole, meta-and orto-nitrophenol were observed. 相似文献
3.
We prove the almost sure existence of absolutely continuous spectrum at low disorder for the Anderson model on the simplest example of a product of a regular tree with a finite graph. This graph contains loops of unbounded size. 相似文献
4.
Victor Bulacovschi Aurelian Stanciu Iulian Rusu Adrian C
ilean Florina Ungureanu 《Polymer Degradation and Stability》1998,60(2-3):487-491
Three new chemically crosslinked polyurethanes were synthesized. Their behaviour in organic solvents and in dynamic heating conditions was studied. Predictions regarding the thermal stability have been made by using the isoconversion kinetic method. 相似文献
5.
Gheorghe Daniela Neacsu Ana Contineanu Iulia Anghel Elena Maria Teodorescu Florina Chican Irina Elena Perisanu Stefan Tanasescu Speranta 《Journal of Thermal Analysis and Calorimetry》2019,138(2):1233-1242
Journal of Thermal Analysis and Calorimetry - A systematic thermodynamic study has been performed for a series of nitrates having cations derived from the α-amino acids glycine (Gly),... 相似文献
6.
We prove persistence of absolutely continuous spectrum for the Anderson model on a general class of tree-like graphs. 相似文献
7.
Catalin Schiopu Corina Flangea Florina Capitan Alina Serb Željka Vukelić Svjetlana Kalanj-Bognar Eugen Sisu Michael Przybylski Alina D. Zamfir 《Analytical and bioanalytical chemistry》2009,395(8):2465-2477
We report here on a preliminary investigation of ganglioside composition and structure in human hemangioma, a benign tumor
in the frontal cortex (HFC) in comparison to normal frontal cortex (NFC) tissue using for the first time advanced mass spectrometric
methods based on fully automated chip-nanoelectrospray (nanoESI) high-capacity ion trap (HCT) and collision-induced dissociation
(CID). The high ionization efficiency, sensitivity and reproducibility provided by the chip-nanoESI approach allowed for a
reliable MS-based ganglioside comparative assay. Unlike NFC, ganglioside mixture extracted from HFC was found dominated by
species of short glycan chains exhibiting lower overall sialic acid content. In HFC, only GT1 (d18:1/20:0), and GT3 (d18:1/25:1)
polysialylated species were detected. Interestingly, none of these trisialylated forms was detected in NFC, suggesting that
such components might selectively be associated with HFC. Unlike the case of previously investigated high malignancy gliosarcoma,
in HFC one modified O-Ac-GD2 and one modified O-Ac-GM4 gangliosides were observed. This aspect suggests that these O-acetylated structures could be associated with cerebral tumors having reduced malignancy grade. Fragmentation analysis by
CID in MS2 mode using as precursors the ions corresponding to GT1 (d18:1/20:0) and GD1 (d18:1/20:0) provided data corroborating for
the first time the presence of the common GT1a and GT1b isomers and the incidence of unusual GT1c and GT1d glycoforms in brain
hemangioma tumor.
相似文献
8.
9.
Florina D. Covaciu D. Alina Magdas Olivian Marincas Zaharie Moldovan 《Analytical letters》2017,50(17):2665-2676
ABSTRACTA sensitive and selective method was developed to determine pesticides in carrots by gas chromatography–mass spectrometry following the development of an optimized extraction procedure. The method was validated for 30 organochlorine pesticides for gas chromatography with electron capture detection obtaining limit of detection from 0.18 to 0.92?µg/kg except for cis- and trans-permenthrin. Twenty-six carrot samples were analyzed and six pesticides were detected. The results compared with the accepted maximum residue levels in correlation to crop origin. 相似文献
10.
Zamfir AD Serb A Vukeli Ž Flangea C Schiopu C Fabris D Kalanj-Bognar S Capitan F Sisu E 《Journal of the American Society for Mass Spectrometry》2011,22(12):2145-2159
Gangliosides (GGs), sialic acid-containing glycosphingolipids, are known to be involved in the invasive/metastatic behavior
of brain tumor cells. Development of modern methods for determination of the variations in GG expression and structure during
neoplastic cell transformation is a priority in the field of biomedical analysis. In this context, we report here on the first
optimization and application of chip-based nanoelectrospray (NanoMate robot) mass spectrometry (MS) for the investigation
of gangliosides in a secondary brain tumor. In our work a native GG mixture extracted and purified from brain metastasis of
lung adenocarcinoma was screened by NanoMate robot coupled to a quadrupole time-of-flight MS. A native GG mixture from an
age-matched healthy brain tissue, sampled and analyzed under identical conditions, served as a control. Comparative MS analysis
demonstrated an evident dissimilarity in GG expression in the two tissue types. Brain metastasis is characterized by many
species having a reduced N-acetylneuraminic acid (Neu5Ac) content, however, modified by fucosylation or O-acetylation such as Fuc-GM4, Fuc-GM3, di-O-Ac-GM1, O-Ac-GM3. In contrast, healthy brain tissue is dominated by longer structures exhibiting from mono- to hexasialylated sugar
chains. Also, significant differences in ceramide composition were discovered. By tandem MS using collision-induced dissociation
at low energies, brain metastasis-associated GD3 (d18:1/18:0) species as well as an uncommon Fuc-GM1 (d18:1/18:0) detected
in the normal brain tissue could be structurally characterized. The novel protocol was able to provide a reliable compositional
and structural characterization with high analysis pace and at a sensitivity situated in the fmol range. 相似文献