Search results for "Hexane"
showing 10 items of 467 documents
Thermal desorption gas chromatography with mass spectrometry study of outgassing from polymethacrylimide foam (Rohacell®)
2015
Polymethacrylimide foams are used as light structural materials in outer-space devices; however, the foam closed cells contain volatile compounds that are outgassed even at low temperatures. These compounds ignite as plasmas under outer-space radiation and the intense radio-frequency fields used in communications. Since plasmas may cause spacecraft fatal events, the conditions in which they are ignited should be investigated. Therefore, qualitative and quantitative knowledge about polymethacrylimide foam outgassing should be established. Using thermogravimetric analysis, weight losses reached 3% at ca. 200°C. Thermal desorption gas chromatography with mass spectrometry detection was used to…
Isomerization and increase in the antioxidant properties of lycopene from Momordica cochinchinensis (gac) by moderate heat treatment with UV-Vis spec…
2014
International audience; Momordica cochinchinensis (gac) is a plant rich in lycopene. This pigment tends to solubilize in oil and get damaged during extraction. The impact of heating on cis-isomerization of oil-free lycopene in hexane was studied at 50 and 80°C during 240min with UV-Vis spectrometry, DAD-HPLC and TEAC test. The initial all-trans-form isomerized to the 13-cis isomer more rapidly at 80°C. After this treatment, 16% of the lycopene compounds were in the 9-cis-form. This isomer triggered an increase in the antioxidant properties which was detectable from concentrations above 9% and resulted in a change from 2.4 to 3.7μmol Trolox equivalent. It is thus possible to increase the bio…
Initiatoren für die polymerisation des trioxane. 20. Mitt. über polyoxymethylene1
1963
Die Polymerisation des Trioxans bei 60°C in Cyclohexan mit verschiedenen kationischen Initiatoren wurde untersucht. Die aktivsten Initiatoren sind Acetylperchlorat, Perchlorsaure, FeCl3 und SnCl4. Die Molekulargewichte der erhaltenen Polyoxymethylene sind bei den aktivsten Initiatoren am hochsten. Der Einflus der ubertragung durch Wasser und der kinetischen Kettenlange auf die Molekulargewichte wird diskutiert. Wahrend der Polymerisation kann durch den Initiator eine Spaltung bereits gebildeter Makromolekule erfolgen, welche die Molekulargewichte stark reduziert. Die Frage der Cokatalyse bei der kationischen Polymerisation des Trioxans mit Ansolvosauren wurde untersucht. Bei der Polymerisat…
Copper(II) and nickel(II) chelates with dihydrogen Trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetate(2−) ion (H2CDTA2−). Synthesis, XRD structure a…
1996
Abstract Stoichiometric reactions of metal hydroxycarbonates with the acid trans -1,2-cyclohexanediaminotetraacetic acid (H 4 CDTA) in water under reduced pressure yielded [Cu(H 2 CDTA)]·H 2 O ( I ) and [Ni(H 2 CDTA) (H 2 O)]·4H 2 O ( II ). Both compounds were characterized by TG-DTA analysis, spectral properties (IR, reflectance and RSE) and X-ray diffraction. In I the copper(II) atom exhibits a distorted square-base coordination (type 4+1) by chelation of one H 2 CDTA 2− ligand through two N and two O (carboxylate) at the square base and one O (carboxylic) at the apex of the coordination polyhedron; a second carboxymethyl group of H 2 CDTA 2− remains free. In II the H 2 CDTA 2− chelating …
Cilomilast counteracts the effects of cigarette smoke in airway epithelial cells.
2010
Abstract Cigarette smoke extracts (CSE) alter TLR4 expression and activation in bronchial epithelial cells. Cilomilast, a phosphodiesterase-4 inhibitor, inhibits cigarette smoke-induced neutrophilia. This study was aimed to explore whether cilomilast, in a human bronchial epithelial cell line (16-HBE), counteracted CSE effects. In particular, TLR4 expression, IP-10 and IL-8 release, lymphocyte and neutrophil chemotactic activity and ERK and IkBa phosphorylation in CSE and LPS-stimulated 16-HBE were assessed. CSE increased TLR4 expression, reduced IP-10 release and lymphocyte chemotactic activity and increased IL-8 release and neutrophil chemotactic activity. Cilomilast reduced TLR4 expressi…
Guest exchange in dimeric capsules formed by tetra-urea calix[4]arenes
2008
Ten tetra-urea calix[4]arene derivatives with different ether residues (methyl, pentyl, benzyl, all combinations of methyl and pentyl, 1,3-dibenzyl-2,4-dipentyl), including also the tetrahydroxy compound and the 1,3-dipentyl ether, were synthesised. Their urea groups were substituted with a lipophilic residue to ensure sufficient solubility in cyclohexane. Thus, kinetics for the exchange of the included guest (benzene) against the solvent (cyclohexane) could be followed by 1H NMR spectroscopy. The apparent first order rate constants decrease with increasing size of the ether residues from methyl to benzyl by more than three orders of magnitude. This can be understood by a decreasing flexibi…
Enhanced thermodynamic and kinetic stability of calix[4]arene dimers locked in the cone conformation.
2004
Wide rim tetraurea derivatives (2a,b) have been prepared from a calix[4]arene rigidified in the cone conformation by two diethyleneglycol ether bridges between adjacent oxygens. In comparison to the analogous tetraurea derivatives (3a,b) of a tetrapentoxy calix[4]arene, 2a,b show an increased thermodynamic stability in mixtures of CDCl(3) and DMSO-d(6). Their kinetic stability as expressed by the rate of guest exchange (benzene or cyclohexane against the solvent benzene-d(6)) is also strongly increased by factors of 30-38. Noticeable differences for the inclusion of selected guests are found.
Effectiveness of Duloxetine Compared With Pregabalin and Gabapentin in Diabetic Peripheral Neuropathic Pain
2013
This study aimed to compare the effectiveness of duloxetine (DLX) and the anticonvulsants pregabalin (PGB) and gabapentin (GBP) for the treatment of diabetic peripheral neuropathic pain (DPNP) in routine clinical care.Data from a 6-month, noninterventional study involving 2575 patients in whom treatment of DPNP was initiated with or changed to DLX, PGB, or GBP (n=1523) were analyzed post hoc; patients treated with other medications or combinations were excluded from this analysis. Propensity scoring was used to compare patient groups, assessing Brief Pain Inventory (BPI), Clinical and Patient Global Impression (CGI/PGI), the Hospital Anxiety and Depression Scale (HADS), the Sheehan Disabili…
The pheromonal role of cuticular hydrocarbons in Drosophila melanogaster
1997
0265-9247 (Print) Journal Article Research Support, Non-U.S. Gov't Review; Pheromones play a crucial role in mate stimulation and discrimination. In the fruit fly Drosophila, the most abundant cuticular hydrocarbons act as sex pheromones during courtship behavior. There are several active molecules and they compose a sex- and species-specific pheromonal bouquet. Different species from the Drosophila melanogaster subgroup have adopted alternative systems of chemical mate recognition. Recent exploration of these interspecific variations, and of intraspecific variations, has led to the characterization of genes and to the mapping of structures that process the production and perception of chem…
Prenatal perfluoroalkyl substance exposure and neuropsychological development throughout childhood: The INMA Project.
2021
Abstract Background Perfluoroalkyl substances (PFASs) have been related to neurodevelopmental toxicity in animals. However, human studies are inconclusive. Objectives To evaluate the association between prenatal PFAS exposure and neuropsychological development during childhood. Methods 1240 mother–child pairs from the Spanish INMA Project were analyzed. Perfluorohexanesulfonic acid (PFHxS), perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), and perfluorononanoic acid (PFNA) were measured in first-trimester maternal plasma. Neuropsychological development was assessed at 14 months, 4–5 and 7 years covering four domains: general cognitive, general motor, attention, and working me…