Volatile monocarbonyl compounds of arctic bramble (Rubus arcticus L.) at various stages of ripeness

Summary Volatile carbonyl compounds of arctic brambles at various stages of ripeness were analyzed as their 2,4-DNPH's by a combined TLC-GLC-MS method. Twenty-one different carbonyl compounds could be identified. During the ripening process the content of most carbonyl compounds increased, the largest changes occuring in the amounts of acetaldehyde, pentenal, acetone, acetonn and diacetyl but the content of hexenal decreased.

---

Zusammenfassung Die leichtflüchtigen Carbonylverbindungen der Brombeere wurden in verschiedenen Stufen der Reife als 2,4-DNPH mit der kombinierten DC-GC-MS-Methode analysiert. 21 verschiedene Carbonylverbindungen wurden entdeckt. Während des Reifens vermehrte sich die Quantität der meisten Carbonylverbindungen; die größten Veränderungen geschahen in der Menge des Acetaldehyds, Pentenals, Acetons, Acetons und Diacetyls. Der Gehalt an Hexenal verminderte sich.

     

The influence of water activity on the stability of vulgaxanthin I

Summary The stability of vulgaxanthin I at 100 °C is dependant on the water activity of the system. The half-life of vulgaxanthin I was found to be three times greater ata ₁ 0.20 than at 1.00. The rate constants for vulgaxanthin I degradation varied exponentially with respect to water activity and belowa _w=0.50 the stability was not improved.

---

Einfluß der Wasseraktivität auf die Stabilität von Vulgaxanthin I

Zusammenfassung Die Stabilität von Vulgaxanthin I hängt von der Aktivität des Wassers im System ab. Die Halbwertszeit von Vulgaxanthin I war beia _w = 0,20 dreimal so groß wie beia _w = 1,00. Die Verteilungskoeffizienten für die Zersetzung von Vulgaxanthin I in Abhängigkeit von der Wasseraktivität zeigen einen exponentiellen Zusammenhang, so daß die Stabilität bei Werten füra _w kleiner 0,50 nicht mehr zunahm.

     

Understanding mobile contexts

Mobile urban environments present a challenge for context-aware computers because they differ from fixed indoor contexts such as offices, meeting rooms, and lecture halls in many important ways. Internal factors such as tasks and goals are different—external factors such as social resources are dynamic and unpredictable. An empirical, user-centred approach is needed to understand mobile contexts. In this paper, we present insights from an ethnomethodologically inspired study of 25 adult urbanites in Helsinki. The results describe typical phenomena in mobility: how situational and planned acts intermesh in navigation, how people construct personal and group spaces, and how temporal tensions develop and dissolve. Furthermore, we provide examples of social solutions to navigation problems, examine mobile multitasking, and consider design implications for mobile and context-aware human–computer interaction.

Preparation and characterization of Au/CeO2–Al2O3 monoliths

Porous CeO₂–Al₂O₃ monoliths with hierarchical pore structure were prepared by mixing boehmite particles with solutions containing different amounts of cerium chloride and aluminum nitrate. The monoliths were functionalized with gold nanoparticles using the incipient wetness method. The resulting materials were characterized by X-ray diffraction, nitrogen sorption, mercury porosimetry, UV–vis spectroscopy and transmission electron microscopy. The catalysts were tested in liquid phase glucose oxidation, comparing continuously stirred batch reactor and continuous-flow fix-bed reactor setups.     

Flavonoids, sugars and fruit acids of alpine bearberry (Arctostaphylos alpina) from Finnish Lapland

Alpine bearberry (Arctostaphylos alpina L.) is a special circumpolar edible berry primarily used for household purposes but with greater potential in commercial applications than utilized thus far. In this study, the flavonoids of alpine bearberry were investigated with HPLC-DAD and HPLC-MS, and the sugars and fruit acids as trimethylsilyl derivates with GC-FID. The most abundant anthocyanin was cyanidin-3-O-galactoside accounting for over 95% of the anthocyanins. Eight other anthocyanins existed in trace amounts only, the richest of them being cyanidin-3-O-arabinoside and cyanidin-3-O-glucoside. Cyanidin accounted for over 99% of the anthocyanin aglycones. All the flavonols identified were glycosides of quercetin. Majority of the sugars were glucose and fructose while the most abundant fruit acid was quinic acid. The unique anthocyanin composition of alpine bearberry encourages advanced use of the berry as a food ingredient in private households and in industrial applications. In addition, it serves as a unique reference material for research purposes.     

Did Chemisorption Become an Obsolete Method With Advent of Tem? Comparison of Mean Particle Size and Distribution of Silver on Alumina

Abstract  

Silver particle size and dispersion on a Ag/Al₂O₃ for HC-SCR were examined by means of chemisorption and TEM. Experimental results showed that determination of the accurate mean particle size (mps) is challenging and that the both applied methods have specific characteristics increasing the inaccuracy in the results which has to be taken into account in evaluation of catalytic activity. The results from TEM imaging were found to depend highly on the mode in which the surface was scanned (bright field versus dark field). Generally the point resolution was higher in dark field but the obtained mps did not increased along with the increasing silver loading. The main limitation with the O₂-chemisorption was related to the choice of the stoichiometric factor between the adsorbent and silver atoms. However, together these techniques support each other and help to give a more realistic picture of the mean silver particle size, distribution and indications of the oxidation states on the alumina support.     

Ultra high performance liquid chromatography–mass spectrometric analysis of oxidized free fatty acids and acylglycerols

A fast ultra high performance liquid chromatography (UHPLC)–electrospray ionization (ESI)–mass spectrometric (MS) method was developed for simultaneous analysis of free fatty acids (FFAs), monoacylglycerols (MAG), diacylglycerols (DAG), triacylglycerols (TAG), and their oxidized equivalents. Effect of elevated column temperature was studied in order to optimize the chromatography of closely eluting peaks and to reduce high back pressure formed in UHPLC. The elevated temperature enabled high flow rate, better mass transfer, and therefore more narrow peaks and better separation of the analytes. The new method was applied to the analysis of total lipid extracts of lipolysis samples prepared by an artificial digestion model in order to investigate oxidized lipids and changes in their profiles in the chyme. Over 150 compounds were identified from the extracts. The UHPLC–ESI–MS method was proved to be fast, highly selective, and sensitive. Compared to a previously used high performance LC–ESI–MS method, the new UHPLC–ESI–MS method was over five times faster and consumed one tenth of the solvents while producing comparable quantitative results. Practical applications: Edible oils and fats contain mainly TAGs, the lipolysis of which produces FFAs and MAGs with minor DAG components. These compounds are susceptible to oxidation in the stomach, and therefore the analysis of the oxidation products is important. Fast determination of FFAs and acylglycerols is also important in quality control of biodiesel. Our new method enables accurate and sensitive determination of different molecular species present in digested and processed samples with minimal sample preparation requirements. In this respect, the new method is applicable to large scale and fast screening of biological samples for lipidomic and metabolomic studies.     

A 3D model for the free-breathing direct methanol fuel cell: Methanol crossover aspects and validations with current distribution measurements

A three-dimensional model has been developed for the free-breathing direct methanol fuel cell (DMFC) assuming steady-state isothermal and single-phase conditions. Especially the MeOH crossover phenomenon is investigated and the model validations are done using previous cathodic current distribution measurements. A free convection of air is modelled in the cathode channels and diffusion and convection of liquid (anode) and gaseous species (cathode) in the porous transport layers. The MeOH flow in the membrane is described with diffusion and protonic drag. The parameter ψ$\psi$ in the model describes the MeOH oxidation rate at the cathode and it is fitted according to the measured current distributions. The model describes the behaviour of the free-breathing DMFC, when different operating parameters such as cell temperature, MeOH concentration and flow rate are varied in a wide range. The model also predicts the existence of the experimentally observed electrolytic domains, i.e. local regions of negative current densities. Altogether, the developed model is in reasonable agreement with both the measured current distributions and polarization curves. The spatial information gained of mass transfer phenomena inside the DMFC is valuable for the optimization of the DMFC operating parameters.     

Co-administration of a nanosuspension of a poorly soluble basic compound and a solution of a proton pump inhibitor--the importance of gastrointestinal pH and solubility for the in vivo exposure

In Sigfridsson et al. (2011, Drug Dev Ind Pharm, 37:243-251), there was no difference in plasma concentration of BA99 when administering the drug as nanosuspension or microsuspension and analyzing the blood samples by liquid chromatography-mass spectrometry. This was related to the dissolved amount of drug in the gastric tract, which was high enough to support fast absorption when the drug reached the small intestine. One single physicochemical property (pK(a), about 3 for BA99) abolished the benefit of small particles. These results were further confirmed in the present study, where a proton pump inhibitor, AZD0865, was used to elevate the gastric pH and then drastically decreased the gastric solubility. In this way, BA99 could be considered as a model compound for a neutral substance. By increasing the gastric pH to 5-6 and 8-9, respectively, in rats, the plasma concentrations of BA99, after administering nanosuspensions, were unchanged compared with untreated (i.e. no AZD0865) animals. For microsuspensions of the test compound, on the other hand, the exposure of BA99 was 2- to 3-fold lower than for nanosuspensions at both pHs. Moreover, the blood concentrations of BA99 administered as microsuspension were also 2- to 3-fold lower compared with untreated (no AZD0865) individuals receiving both nanoparticles and microparticles of BA99. Obviously, for neutral compounds, with similar physicochemical properties as the present compound, size reduction will be crucial for increased plasma exposure. For basic compounds, with similar physicochemical properties as the present compound, the crucial step for absorption is the dissolution and solubility in the gastric tract.