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排序方式: 共有268条查询结果,搜索用时 31 毫秒
51.
52.
Carla M.B. Gonçalves Liliana C. Tomé Helga Garcia Lúcia Brandão Adélio M. Mendes Isabel M. Marrucho 《Journal of food engineering》2013
Gas permeation properties (permeability, diffusivity and solubility coefficients) were determined for carbon dioxide and oxygen in poly(lactic acid) (PLA) films enriched with 0, 2, 4 and 10 wt.% of different antioxidants, at three temperatures, 284, 293 and 303 K, using a time-lag apparatus. Three antioxidants, a natural, α-tocopherol (AT), and two synthetic, butylated hydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ), were tested. DSC results show that the polymer glass transition temperature slightly decreases with the increase of the antioxidant content. The crystallinity degree of PLA films decreases with the addition of BHT and TBHQ, whereas the incorporation of AT increases the crystallinity of PLA films. The permeability towards water vapour, at 299 K and 45% of relative humidity, and surface energy show a decreased in the wettability of the prepared materials with the increase of the antioxidants content. The incapacity to measure gas permeation in PLA films with 10 wt.% of AT and BHT incorporated was due to phase separation, proved by SEM images. The CO2 and O2 permeation results show that PLA barrier properties can be improved by the incorporation of antioxidants but are strongly dependent on the amount and structure of the antioxidant added. 相似文献
53.
Sjofn Sigurgisladottir Helga Ingvarsdottir Ole J. Torrissen Mireille Cardinal Hannes Hafsteinsson 《Food research international (Ottawa, Ont.)》2000,33(10):187-865
The changes in microstructure and texture during smoking of fresh and frozen/thawed Atlantic salmon was studied in fish from three different origins; ocean-ranched Atlantic salmon (Salmo salar) from Iceland and two groups of farmed Atlantic salmon from northern and western Norway. The muscle fibers from the frozen and thawed fish shrank, and the extracellular space increased compared to the fresh muscle. The muscle fibers from salmon fillets with smaller fiber diameter shrank to a less extent than fibers from salmon material with a larger fiber diameter. After smoking the space between the fibers and the fiber shrinkage increased to a higher extent in the muscle from the salmon that were frozen prior to smoking than muscle smoked from fresh salmon. The initial cross-sectional area of the fibers was not found to be related to the yield during smoking. 相似文献
54.
55.
Seguin G.E. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1995,41(2):387-399
For (n, q)=1 V a qm-ary cyclic code of length n and with generator polynomial g(x), we show that there exists a basis for F(qm) over Fq with respect to which the q-ary image of V is cyclic, if and only if: (i) g(x) is over Fq; or (ii) g(x)=g0(x)(x-γ-q(μ)), g0(x) is over Fq, Fq≠F(qk)=Fq(γ)⊂F(qm ), μ an integer modulo k, and wm-γ has a divisor over F(qk) of degree e=m/k; or (iii) g(x)=g0 (x) Πμϵs(x-γ(-qμ)), g 0(x) is over Fq, Fq≠F(qk)=Fq(γ)⊂F(qm ), S a set of integers module k of cardinality k-1 and wm -μ has a divisor over F(qk) of degree e=m/k. In all of the above cases, we determine all of the bases with respect to which the q-ary image of V is cyclic 相似文献
56.
Helga Hinze Helmut Holzer 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1985,181(2):87-91
Summary Low concentrations of sulfite or nitrite (about 0.5 mmol) when applied at pH 3.6, caused a rapid and drastic decrease of the concentration of ATP in yeast cells. Under these conditions, alcoholic fermentation was inhibited by sulfite and to a lesser extent by nitrite. Ethanol consumption under aerobic conditions was shown to be more sensitive to nitrite than to sulfite. This indicates a higher sensitivity of respiratory processes to nitrite than to sulfite. Among 15 enzyme activities assayed in extracts from yeast cells after incubation with sulfite or nitrite, glyceraldehyde-3-phosphate dehydrogenase was shown to be the most sensitive. Analysis of the steady-state concentrations of intermediates of alcoholic fermentation in intact yeast cells also implies inhibition by sulfite or nitrite of the glyceraldehyde-3-phosphate dehydrogenase step of fermentation. In contrast to nitrite, sulfite had an additional effect by accumulating the intracellular steady state concentration of glyceraldehyde-3-phosphate 10 to 100-fold over the concentration in the absence of sulfite.In vitro studies on the equilibrium catalyzed by triosephosphate isomerase or aldolase confirmed the postulated shift of equilibrium concentrations by a formation of complex of glyceraldehyde-3-phosphate with sulfite.
Dedicated to Prof. Dr. Franz Lingens at the occasion of his 60th birthday 相似文献
Wirkung von Sulfit und Nitrit auf den ATP-Gehalt und den Kohlenhydrat-Stoffwechsel von Hefe
Zusammenfassung Konzentrationen von Sulfit oder Nitrit um 0.5 mmol bewirken bei der Inkubation mit Hefe bei pH 3,6 in wenigen Minuten einen starken Abfall der ATP-Konzentration in den Zellen. Unter diesen Bedingungen wird die alkoholische Gärung durch Sulfit oder Nitrit gehemmt. Der Alkoholabbau unter aeroben Bedingungen ist empfindlicher gegen Nitrit als gegen Sulfit. Dies deutet auf eine höhere Empfindlichkeit der Atmungskette gegenüber Nitrit als gegenüber Sulfit. Unter 15 verschiedenen Enzymen, deren Aktivität nach der Inkubation von Hefezellen mit Sulfit oder Nitrit in Extrakten bestimmt wurde, erwies sich Glycerinaldehyd-3-phosphat-dehydrogenase als am empfindlichsten. Die Analyse stationärer Konzentrationen von Zwischenprodukten der alkoholischen Gärung in intakten Hefezellen unter der Einwirkung von Sulft oder Nitrit deutet auf Blokkade bei der Glycerinaldehyd-3-phosphat-dehydrogenase-Reaktion. Außerdem erhöht Sulfit die intrazelluläre stationäre Konzentration von Glycerinaldehyd-3-phosphat 10 bis 100 fach gegenüber den Konzentrationen bei Abwesenheit von Sulfit. In-vitro-Versuche über die Beeinflussung des von Triosephosphat-Isomerase oder Aldolase katalysierten Gleichgewichts ergaben bei Gegenwart von Sulfit eine Verschiebung dieser Gleichgewichte in Richtung Glycerinaldehyd-3-phosphat durch Komplexbildung dieser Substanz mit Sulfit.
Dedicated to Prof. Dr. Franz Lingens at the occasion of his 60th birthday 相似文献
57.
Dispatching rules can be automatically generated from scheduling data. This paper will demonstrate that the key to learning an effective dispatching rule is through the careful construction of the training data, \(\{\mathbf {x}_i(k),y_i(k)\}_{k=1}^K\in {\mathscr {D}}\), where (i) features of partially constructed schedules \(\mathbf {x}_i\) should necessarily reflect the induced data distribution \({\mathscr {D}}\) for when the rule is applied. This is achieved by updating the learned model in an active imitation learning fashion; (ii) \(y_i\) is labelled optimally using a MIP solver; and (iii) data need to be balanced, as the set is unbalanced with respect to the dispatching step k. Using the guidelines set by our framework the design of custom dispatching rules, for a particular scheduling application, will become more effective. In the study presented three different distributions of the job-shop will be considered. The machine learning approach considered is based on preference learning, i.e. which dispatch (post-decision state) is preferable to another. 相似文献
58.
Schlapschy M Gruber H Gresch O Schäfer C Renner C Pfreundschuh M Skerra A 《Protein engineering, design & selection : PEDS》2004,17(12):847-860
CD30, the so-called Reed-Sternberg antigen, constitutes a promising cell-specific target for the treatment of Hodgkin's lymphoma. Starting from the previously characterized cognate HRS3 mouse monoclonal antibody, the bacterially produced functional Fab fragment was humanized by grafting the CDRs from the mouse antibody framework on to human immunoglobulin consensus sequences. This procedure led to a 10-fold decreased antigen affinity, which surprisingly was found to be mainly due to the VH domain. To improve the antigen-binding activity, an in vitro evolution strategy was employed, wherein random mutations were introduced into the humanized VH domain by means of error-prone PCR, followed by a filter sandwich Escherichia coli colony screening assay for functional Fab fragments using a recombinant extracellular domain of the CD30 antigen. After three cycles of in vitro affinity maturation, the optimized Fab fragment huHRS3-VH-EP3/1 was identified, which carried four exchanged residues within or close to the VH CDRs and had an affinity that was almost identical with that of the murine HRS3 Fab fragment. The resulting humanized Fab fragment was fully functional with respect to CD30 binding both in ELISA with the recombinant antigen and in FACS experiments with CD30-positive L540CY cells. In the light of the previously successful clinical application of an alphaCD30 x alphaCD16 bispecific mouse quadroma antibody derived from HRS3, the humanized Fab fragment comprises an important step towards the construction of a fully recombinant therapeutic agent. The combination of random mutagenesis and colony filter screening assay that was successfully applied here should be generally useful as a method for the rapid functional optimization of humanized antibody fragments. 相似文献
59.
Enzymatic alcoholysis of cod liver oil, with an immobilized lipase, was carried out in supercritical carbon dioxide. The enzyme
was catalytically active under the experimental conditions used. The reaction medium was investigated to preferentially extract
ethyl esters, synthesized during the course of the experiment, from the unconverted cod liver oil substrate and side-products.
The effect of pressure changes on the amount of tri-, di-, and monoglycerides and ethyl esters, present in both the extract
and the remaining lipid residue, was determined. Furthermore, the fatty acid compositions of the lipid classes were analyzed,
and the relative amounts of both eicosapentaenoic acid and docosahexaenoic acid to palmitic acid were determined. The results
show that it is possible to preferentially extract the synthesized ethyl esters at low pressures. The extract collected at
9 MPa contained 64 g ethyl esters/100 g extract, while the total amount of all other lipid classes detected was 19 g/100 g
extract. As the pressure was increased, the relative amount of the other lipid classes detected in the extract, especially
triglycerides, was enhanced. The relative amounts of both eicosapentaenoic acid and docosahexaenoic acid to palmitic acid
increased for some lipid classes in the extract. This increase was most pronounced for the monoglyceride lipid class. The
integration of biocatalysis and product fractionation, applied in this study, suggests that the potential for biocatalysis
in industrial processes is considerably wider than had been thought. 相似文献
60.
The extent to which a glove modifies the risks from hand-transmitted vibration is quantified in ISO 10819:1996 by a measure of glove transmissibility determined with one vibration magnitude, one contact force with a handle and only three subjects. This study was designed to investigate systematically the vibration transmissibility of four 'anti-vibration' gloves over the frequency range 16-1600 Hz with 12 subjects, at six magnitudes of vibration (0.25-8.0 ms(-2) r.m.s.) and with six push forces (5 N to 80 N). The four gloves showed different transmissibility characteristics that were not greatly affected by vibration magnitude but highly dependent on push force. In all conditions, the variability in transmissibility between subjects was as great as the variability between gloves. It is concluded that a standardised test of glove dynamic performance should include a wide range of hands and a range of forces representative of those occurring in work with vibratory tools. STATEMENT OF RELEVANCE: The transmission of vibration through anti-vibration gloves is highly dependent on the push force between the hand and a handle and also highly dependent on the hand that is inside the glove. The influence of neither factor is well reflected in ISO 10819:1996, the current standard for anti-vibration gloves. 相似文献