Determination of Hormones Residues in Milk by Gas Chromatography-Mass Spectrometry

The article presents the use of gas chromatography-mass spectrometry (GC-MS) technique in a method for the determination of 18 anabolic hormones from synthetic stilbenes, steroids and resorcylic acid lactones (RALs) groups in raw milk and milk powder. Sample preparation consisted of liquid-liquid extraction with diethyl ether and purification by solid phase extraction (SPE). Prior to instrumental analysis, the reaction of derivatisation with the heptafluorobutyric anhydride or N-methyl-N-trimethylsilyltrifluoroacetamide was performed. Method validation was carried out according to the required performance criteria of the Commission Decision 2002/657/EC. The apparent recovery of all analytes at 1 μg L^?1 (kg^?1) level was ranged between 70.4 and 119.4 % with the coefficients of variation values less than 30 %. The decision limits (CCα) and the detection capabilities (CCβ) were in the range of from 0.11 to 0.44 μg L^?1 (kg^?1) and from 0.19 to 0.75 μg L^?1 (kg^?1), respectively. The procedure has been accredited and successfully applied as a screening method for the presence of hormone residues in the study of commercial samples of milk.     

Cherry (Prunus cerasus cv Montmorency) extract with standardised antioxidant potential as preservative for refrigerated storage of ground pork

Antioxidants occurring naturally are much sought‐after for their safety of use for human nutrition and strong preservative properties. The study was performed to determine the antioxidant potential of sour cherry extract and its effect (equivalent of 20 mg and 40 mg GAE kg^?1) on the quality of ground pork patties during 8‐day storage. The patties were analysed for antioxidant capacity, oxidation, profile of fatty acids, flavour, colour, sensory properties and aerobic bacteria count. Patties with addition of cherry extract (40 mg GAE kg^?1) showed higher antioxidant capacity of 844 ± 149 μmol TE L^‐1 on the last day of the storage than the control group where the result was 480 ± 81 μmol TE L^‐1. The addition of extract caused lower overall increase in lipid oxidation and prevented loss of redness even on the last day of the storage. Flavour changes resulted from oxidation and decrease in the amount of desirable volatile compounds in storage. The application of the extract from Prunus cerasus combined with vacuum packaging inhibited both oxidation and quality deterioration of pork patties in cold storage.     

The study of the interactions between graphene and Ge(001)/Si(001)

The interaction between graphene and germanium surfaces was investigated using a combination of microscopic and macroscopic experimental techniques and complementary theoretical calculations.Density functional theory (DFT) calculations for different reconstructions of the Ge(001) surface showed that the interactions between graphene and the Ge(001) surface introduce additional peaks in the density of states,superimposed on the graphene valence and conduction energy bands.The growth of graphene induces nanofaceting of the Ge(001) surface,which exhibits well-organized hill and valley structures.The graphene regions covered by hills are of high quality and exhibit an almost linear dispersion relation,which indicates weak graphene-germanium interactions.On the other hand,the graphene component occupying valley regions is significantly perturbed by the interaction with germanium.It was also found that the stronger graphene-germanium interaction observed in the valley regions is connected with a lower local electrical conductivity.Annealing of graphene/Ge(001)/Si(001) was performed to obtain a more uniform surface.This process results in a surface characterized by negligible hill and valley structures;however,the graphene properties unexpectedly deteriorated with increasing uniformity of the Ge(001) surface.To sum up,it was shown that the mechanism responsible for the formation of local conductivity inhomogeneities in graphene covering the Ge(001) surface is related to the different strength of graphene-germanium interactions.The present results indicate that,in order to obtain high-quality graphene,the experimental efforts should focus on limiting the interactions between germanium and graphene,which can be achieved by adjusting the growth conditions.     

A thermal module design for advanced packaging

A hybrid silicon wafer-scale multi-chip packaging design was chosen as the basis for a high performance, high power dissipation vehicle suitable for VLSI/ULSI applications. The package supports 25 chips (l x l cm), each capable of dissipating as much as 40 W. The heat generated by the chips is removed by water channels in the underlying structure. Deep- (about 1000 μm), and shallow- (about 100 μm. deep), channel designs, with a water flow rate of 499 cc/sec, and 39 cc/sec, respectively, have been analyzed. Both designs are capable of keeping circuit temperature rise small, while maintaining a uniform chip temperature. The temperature distribution of the thermal module was obtained by solving the 2-D heat conduction equation for isolated heat sources (the chips), and heat sinks (the water channels). Assuming that each of the 25 chips dissipates 40 W/cm², and heat is removed only via water flow, the maximum chip tempertaure(t _cc which occurs at the center of a chip) rise relative to inlet water temperature is 11.4° C, and 19.0° C for the deep, and shallow designs, respectively. The maximumt _cc variation between chips on the module (the same as the water temperature rise), for the cases analyzed, is 0.5° C for the deep-channel design, and 6° C for the shallow-channel design (calculated at 25° C inlet water temperature, and an optimum flow rate). For the extremely-uneven powered case (all chips except one at the inlet end are powered at 40 W/chip), the maximum temperature increases between inlet water temperature and chip temperature,t _cc , remain relatively the same, but the maximumt _cc variations between chips on the module increase to 11.4° C, and 19° C for the deep, and shallow designs, respectively, as might be expected. The temperature variation on a powered chip is less than 3° C for both the deep- and shallow-channel designs.     

Preparation and characterization of precipitated zinc silicates

The study aimed to obtain highly dispersed particles of zinc silicate, a potential filler of polymers or a paint pigment, by precipitation from solutions of sodium metasilicate and of zinc salts. The technique of silicate precipitation was worked out, and the conditions causing precipitation were optimized. The temperature, sodium metasilicate solution flow rate and concentration of zinc salts were selected so as to obtain silicates of the lowest possible bulk density, and which had low water‐absorbing capacity and high paraffin oil‐absorbing capacity. In the study, the effects of precipitation parameters were examined on the principal physicochemical properties of the silicates, the structure and uniform character of silicate particles, particle size distribution, and the surface morphology. Particular attention was devoted to the particle size distribution and the tendency to form primary agglomerates (aggregates) and secondary agglomerates, using dynamic light scattering (DLS). Studies were undertaken to develop a technique which could prevent formation of silicate particle agglomerates. With this aim, the silicates' surface was modified either during their precipitation or by the so‐called dry technique. For the modification, silane coupling agents were applied. The extent of silicate surface hydrophobicity was examined by estimation of the enthalpies of immersion of the modified silicate surface. The silicates obtained were tested as fillers of rubber mixtures (in butadiene–styrene rubber). © 2003 Society of Chemical Industry     

Hydroxyalkylation of parabanic acid. III. Polymers from parabanic acid and ethylene carbonate

The influence of initial molar ratio of reagents, amount of catalyst, and temperature of reaction between parabanic acid and ethylene carbonate on structure of product was studied. The reaction led to the opening of the trioxoimidazolidine ring, resulting in formation of thermally resistant linear polymeric products constructed of urea and oxoamidoester subunits linked via imide bond. The percentage of side products was estimated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1443–1449, 2006     

Statistical evaluation of different technological and rheological tests of Polish wheat varieties for bread volume prediction

Forty‐two Polish wheat flour were used to establish correlation coefficients between protein content, Zeleny test, falling number value, amylograph viscosity, farinograph water absorption, bread volume and rheological properties of dough, as shown by use of a extrusion chamber and alveograph. The equations expressing the changes of bread volume and flour water absorption as a function of significantly correlated parameters were calculated. The correlations and their significance depended on wheat quality and the alveographic parameters were significantly correlated with the dough extrusion parameters. The dough extrusion parameters were significantly correlated only with the water absorption of soft wheats. The dough rheological tests were correlated to a greater extent with the values of the Zeleny test than to the protein content. The prediction of the bread volume as a function of flour quality parameters and dough rheological properties was best done by grouping wheat varieties into specific qualitative classes.     

Influence of silicon on the wetting-bond strength-structure relationship in the AlSi11/Al2O3 joints

The subject of the work was to study the effect of Si alloying addition to the aluminum on the bond strength properties, wettability, and structure of interface in the AlSi11/Al₂O₃ joints. Taking advantage of the sessile drop method, the wetting of alumina substrates by liquid AlSi11 alloy or Al was studied. The sessile drop tests were carried out in the temperature range between 1023 and 1223 K, under a vacuum of 0.2 mPa for 30 or 120 minutes of contact. The shear strength results demonstrated significant improvement of shear strength of AlSi11/Al₂O₃ joints due to the application of silicon as an alloying addition to aluminum. Microstructural investigations of interface indicated that the silicon crystals were formed at the AlSi11/Al₂O₃ interface, which influenced the strengthening of these joints. A conclusion could be drawn, that the interface structure influenced the increase of the shear strength of AlSi11/Al₂O₃ joints.