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941.
Ivan imkovic Gabor Varhegyi Michael J. Antal Anna Ebringerov Tamas Szekely Piroska Szabo 《应用聚合物科学杂志》1988,36(3):721-728
A thermogravimetric/mass spectrometric (TG/MS) system was used to characterize the thermolysis reactions of (4-O-methyl-D -glucurono)-D -xylan. The mass spectrometric peaks, measured as function of time, were attributed to water, methanol, carbon monoxide, carbon dioxide, formaldehyde, formic acid, acetic acid, acetone, acrolein, 2-furaldehyde, and 3-hydroxy-2-penteno-1,5-lactone. The time derivative of the thermogravimetric curve (DTG) consisted of two partially overlapping peaks, indicating a multistep mechanism. The mass spectrometric intensities of the peaks assigned to methanol and 2-furaldehyde coincided with the first DTG peak, suggesting that the first DTG peak represents both dehydration and fragmentation pathways. Methanol, water, formyl group, and carbon dioxide contributed to both of the DTG peaks. This indicates that the dehydration, decarboxylation, and decarbonylation took place in two steps. The compounds observed only in the second DTG peak and later (acetone, formic acid, formaldehyde, acrolein, acetic acid, and 3-hydroxy-2-penteno-1,5-lactone) are probably products of reactions which occur after the collapse of the original polysaccharide structure. 相似文献
942.
Sudarsan Mukhopadhyay Peggy M. Tomasula John B. Luchansky Anna Porto-Fett Jeffrey E. Call 《International journal of food microbiology》2010,142(3):309-317
Effectiveness of a cross flow microfiltration (MF) process for removal of a cocktail of Salmonella enterica serovar Enteritidis species from commercial unpasteurized liquid egg white (LEW) from a local egg breaking plant, while maintaining its functional properties was evaluated. To facilitate MF, LEW was wedge screened, homogenized and then diluted (1:2 w/w) with distilled water containing 0.5% sodium chloride. Diluted unpasteurized LEW was inoculated with five strains of S. Enteritidis (ATCC 4931, ATCC BAA-708, ATCC 49215, ATCC 49218, and ATCC BAA-1045) to a level of approximately 107 CFU/mL of LEW and microfiltered using a ceramic membrane. Process parameters influencing egg white functional properties and pathogen removal efficiency were evaluated. Average permeates flux increased by almost 126% when pH of LEW was adjusted from pH 8 to pH 7 at 25 °C. Microbial removal efficiency was at least, on average, 6.8 Log10 CFU/mL (limit of detection ≤ 0.5 Log10 CFU/mL). Functional property analysis indicated that the MF process did not alter the foaming power of LEW. 相似文献
943.
Minh Van Nguyen Sigurjon Arason Kristin Anna Thorarinsdottir Gudjon Thorkelsson Agusta Gudmundsdóttir 《Journal of food engineering》2010
The influence of different salt concentrations of 6%, 15%, 18% and 24% (w/w) on mass transfer of water and salt during brine salting of cod loins was studied. An increase in salt concentration accelerated water exudation and salt diffusion in the cod loins. Weight gain of the cod loins increased with decreasing salt concentration and the cod loins in the 6% brine had the highest process yield. The salting kinetic parameter values for total and water weight changes decreased with increasing salt concentration. Inversely, higher salting kinetic parameter values for salt weight changes were observed for higher brine concentrations. The samples brined at 18% and 24% had identical effective diffusion coefficients and the highest effective diffusion value was found in the cod loins brined at 15%. 相似文献
944.
Selma Yildizhan Dr. Joop van Loon Prof. Dr. Anna Sramkova Manfred Ayasse Prof. Dr. Cristian Arsene Dr. Cindy ten Broeke Stefan Schulz Prof. Dr. 《Chembiochem : a European journal of chemical biology》2009,10(10):1666-1677
Pheromonally yours : The aphrodisiac pheromones of male Cabbage White butterflies were identified. The small butterfly uses the smaller molecule ferrulactone ( 1 ) to enhance its mating success, while the large butterfly uses the larger compound brassicalactone ( 2 ), which is a new natural product. Both compounds are active in combination with hexahydrofarnesylacetone and phytol.
945.
Anna A. Barba Annalisa Dalmoro Felice De Santis Gaetano Lamberti 《Polymer Bulletin》2009,62(5):679-688
This paper describes the development of pH-sensitive poly(methyl methacrylate-acrylic acid) copolymers for the enteric coating
of pharmaceutical products for oral administration. To obtain the dissolution at the desired pH level, different pH-sensitive
polymers are available on the market. Usually, for each desired dissolution pH, an ad hoc polymer is designed. Thus, different
dissolution pH values could ask for completely different polymers. Instead, the materials proposed in this work are copolymers
of the same two monomers, and the different dissolution pH was obtained by changing the volume fraction of the hydrophobic
methyl methacrylate monomer to the hydrophilic acrylic acid monomer. Increasing the volumetric percentage of methyl methacrylate
causes the polymer to dissolve at increasing pH, until the dissolution does not take place at all, and it is replaced by a
slow swelling phenomenon. The copolymers obtained were characterized by differential scanning calorimetry, in order to evaluate
their glass transition temperature, and these latter were related to %MMA. The molecular weights of the pure polymers (PAA,
PMMA) were measured by intrinsic viscosity, to further validate the glass transition temperatures observed. The dissolution
of the copolymers was carefully tested in buffer solutions for a dense set of pH values. A linear relationship between dissolution
pH and volumetric percentage of methyl methacrylate was obtained from these measurements. As a result, for any physiological
compartment, the copolymer which dissolves at the pH of interest can be easily synthesized. 相似文献
946.
Steffen Berger Julia Kunze Patrik Schmuki Darren LeClere Anna T. Valota Peter Skeldon George E. Thompson 《Electrochimica acta》2009,54(24):5942-5948
The present work investigates the formation of nanotubes by anodizing titanium at 20 V in glycerol containing either 0.175 M or 0.35 M NH4F. A photoresist-masking method of thin Ti films allows to use SEM cross-sections to directly obtain information on oxide morphology, layer thickness and metal substrate loss. Therefore not only features of the initial growth stages but also oxide expansion factors can accurately be determined. The expansion factors were found to be 2.4 for the initial formation of a barrier layer, 1.7–1.9 during pore initiation and 2.7–3.1 as the main nanotubes develop. These values (>2.6) suggest substantial contribution to steady state tube growth by a plastic oxide flow mechanism. Combined with RBS efficiency measurements the method presented here allows facile and direct investigation of the mechanism of pore/tube formation. 相似文献
947.
François De Vleeschouwer Nathalie Fagel Anna Pazdur Nadine Mattielli Barbara Fialkiewicz Gaël Le Roux 《The Science of the total environment》2009,407(21):5674-5684
Lead pollution history over Northern Poland was reconstructed for the last ca. 1300 years using the elemental and Pb isotope geochemistry of a dated Polish peat bog. The data show that Polish Pb-Zn ores and coal were the main sources of Pb, other heavy metals and S over Northern Poland up until the industrial revolution. After review of the potential mobility of each element, most of the historical interpretation was based on Pb and Pb isotopes, the other chemical elements (Zn, Cu, Ni, S) being considered secondary indicators of pollution. During the last century, leaded gasoline also contributed to anthropogenic Pb pollution over Poland. Coal and Pb-Zn ores, however, remained important sources of pollution in Eastern European countries during the last 50 years, as demonstrated by a high 206Pb/207Pb ratio (1.153) relative to that of Western Europe (ca. 1.10). The Pb data for the last century were also in good agreement with modelled Pb inventories over Poland and the Baltic region. 相似文献
948.
This paper presents the development of an analytical method to determine the parameters of orientation and deformability of transversely isotropic cylinders of rock using the Council for Scientific Industrial Research (CSIR) triaxial cell under isotropic biaxial loading. The mathematical formulation is based upon the elastic and anisotropic constant transformation presented by Lekhnitskii (in: JJ. Brandstatter (Ed.), Theory of Elasticity of an Anisotropic Elastic Body, Holden-Day Series in Mathematical Physics, Holden Day Inc., San Francisco, 1963, 404p). By using three rosettes with four gages each, the method herein proposed permits the determination of the global tridimensional deformability characteristics of a rock cylinder, using only the local bidimensional deformation measurements provided by the rosette's gages. The new analytical method gives the direction and dip of the isotropy plane together with the magnitude of anisotropic elastic constants for transversely isotropic rocks of Class A (rocks with no visible symmetry planes) and Class B (with visible symmetry planes). No restrictions on the direction of the symmetry planes are imposed. This determination is obtained from strains measured in only one biaxial compression test performed with the CSIR cell on the overcore obtained from in situ stress test. 相似文献
949.
Anna T. Backes Kathrin Reinmuth-Selzle Anna Lena Leifke Kira Ziegler Carola S. Krevert Georg Tscheuschner Kurt Lucas Michael G. Weller Thomas Berkemeier Ulrich Pschl Janine Frhlich-Nowoisky 《International journal of molecular sciences》2021,22(14)
The allergenic and inflammatory potential of proteins can be enhanced by chemical modification upon exposure to atmospheric or physiological oxidants. The molecular mechanisms and kinetics of such modifications, however, have not yet been fully resolved. We investigated the oligomerization and nitration of the grass pollen allergen Phl p 5 by ozone (O3), nitrogen dioxide (NO2), and peroxynitrite (ONOO–). Within several hours of exposure to atmospherically relevant concentration levels of O3 and NO2, up to 50% of Phl p 5 were converted into protein oligomers, likely by formation of dityrosine cross-links. Assuming that tyrosine residues are the preferential site of nitration, up to 10% of the 12 tyrosine residues per protein monomer were nitrated. For the reaction with peroxynitrite, the largest oligomer mass fractions (up to 50%) were found for equimolar concentrations of peroxynitrite over tyrosine residues. With excess peroxynitrite, the nitration degrees increased up to 40% whereas the oligomer mass fractions decreased to 20%. Our results suggest that protein oligomerization and nitration are competing processes, which is consistent with a two-step mechanism involving a reactive oxygen intermediate (ROI), as observed for other proteins. The modified proteins can promote pro-inflammatory cellular signaling that may contribute to chronic inflammation and allergies in response to air pollution. 相似文献
950.
We validated the lethality of three time and temperature regimens for commercial processing of whole muscle beef jerky. A total of ca. 8.9 log CFU per strip of multiple-strain cocktails of Escherichia coli O157:H7, Salmonella Typhimurium, or Listeria monocytogenes were separately applied onto the surface of beef strips that were treated as follows: (i) inoculated but not marinated or (ii) inoculated and then marinated. A total of three beef strips for each treatment in each of three trials were separately inoculated with a cocktail of one of the three pathogens and placed on the top, middle, and bottom racks of a loading truck. The strips on the rack were loaded into a commercial smokehouse and cooked and dried for 1.5, 2.5, or 3.5 h at a target temperature of 180 degrees F (82.2 degrees C) with constant (natural hickory) smoking, but without the addition of humidity. Regardless of how the strips were treated or where the strips were placed on the loading rack, drying for 1.5, 2.5, or 3.5 h to a target temperature of 180 degrees F (average of 177.2 +/- 5.6 degrees F [80.7 +/- 3.1 degrees C]), with constant smoke at an initial average relative humidity of 63.1% to a final average relative humidity of 20.9% resulted in a decrease of > or = 7.3 log CFU per strip (> or = 6.9 log CFU/g) for each of the three pathogen cocktails. Of note, marinated strips that were cooked and dried for 2.5 and 3.5 h or nonmarinated strips cooked or dried for 3.5 h also satisfied the U.S. Food Safety and Inspection Service standard of identity (moisture-to-protein ratio < or = 0.75:1) and/or shelf-stability (water activity < or = 0.8) requirements for jerky. 相似文献