295 research outputs found
European Resuscitation Council Guidelines for Resuscitation 2015. Section 7. Resuscitation and support of transition of babies at birth
No full textThe NADP(H) Redox Couple in Yeast Metabolism: Fundamental and Applied Aspects
No full textApplied Science
The effect of thermal fatigue on mechanical properties of thermoset composites
No full textComposite structures are used more frequently in newly designed aircrafts. This results in new difficulties compared to conventional metals during operational life. Especially, the material properties of two different materials can cause side effects, which are unwanted in a structure, for example thermal stresses. Many reports have been written about the difference in damage inflicted by thermal fatigue stresses compared to mechanical fatigue stresses. However, the environmental conditions and stacking sequences used in these reports are extreme and not common in aviation. This thesis focuses on the effect of combined thermal and mechanical fatigue load on the structural integrity of a laminate, but with realistic operations mechanical and environmental loads.In-service F-16 data has been used to get a proper indication of the order of magnitude of mechanical and thermal forces applied on an aircraft during operations. These conditions are applied to a semi-quasi isotropic coupons, which were dominant in the 0 direction, to simulate a more common laminate for an aerospace structure. The residual transverse shear strength, residual bending strength, and stiffness are measured after a mechanical and/or thermal fatigue load has been applied to test specimens. Results show no clear reduction for any of the measured material properties. The main differences in results can be derived from size differences in test coupons. However, all results are within the scattering region of the reference values. Thus, it can be concluded that the structural integrity of a laminate will not be affected negatively by a combined thermal and mechanical fatigue load, if the conditions match the used operational circumstances.Aerospace Engineerin
An enzymic analysis of NADPH production and consumption in Candida utilis
No full textApplied Science
A theoretical analysis of NADPH production and consumption in yeasts
No full textTheoretical calculations of the NADPH requirement for yeast biomass formation reveal that this parameter is strongly dependent on the carbon and nitrogen source. The data obtained have been used to estimate the carbon flow over the NADPH-producing pathways in these organisms, namely the hexose monophosphate pathway and the NADP+-linked isocitrate dehydrogenase reaction. It was calculated that during growth of yeasts on glucose with ammonium as the nitrogen source at least 2% of the glucose metabolized has to be completely oxidized via the hexose monophosphate pathway for the purpose of NADPH synthesis. This figure increases to approximately 20% in the presence of nitrate as the nitrogen source. Not only during growth on glucose but also on other substrates such as xylose. methanol, or acetate the operation of the hexose monophosphate pathway as a source of NADPH is essential, since the N ADP+-isocitrate dehydrogenase reaction alone cannot meet the NADPH demand for anabolism. NADPH production via these pathways requires an expenditure of ATP. Therefore, the general assumption made in calculations of the ATP demand for biomass formation that generation of NADPH does not require energy is, at least in yeasts, not valid.Applied Science
Visuele en niet-visuele effecten van licht
No full textOp dit moment zijn er nieuwe ontwikkelingen op het gebied van verlichting, namelijk dynamische verlichting. Dynamische verlichting is een nabootsing van de dynamiek van het daglicht gedurende de dag door de lichtbron te laten variëren in kleur en intensiteit. Deze nieuwe ontwikkelingen zijn gebaseerd op resultaten uit onderzoeken die gekeken hebben naar het effect van licht op niet-visuele processen in het lichaam zoals onderdrukking van melatonine, circadiane faseverschuivingen, een verhoging van lichaamstemperatuur en hartslagfrequentie, maar ook gedragsveranderingen zoals een verhoging in alertheid en prestatievermogen (Viola et al. 2008). De niet-visuele effecten worden bewerk stelligd door middel van de intrinsieke fotosensitieve retinale ganglion cells (ipRGC) en de klassieke fotoreceptoren, de staaf- en kegelcellen De ipRGCs kunnen zelf een reactie geven op lichtblootstelling maar ze kunnen ook geinnerveerd worden door de staaf- en kegelcellen. Hierbij hebben de S-kegelcellen een inhiberende input op ipRGCs en de M-kegelcellen en L-kegelcellen een exciterende input. Kleurenblindheid is een disfunctie in de staafcellen en laat verscheidene fenotype met verschillende genotype zien. Kleurenblindheid komt tot stand door het ontbreken van fotoreceptoren of door abnormale gevoeligheid van de fotoreceptoren. Doordat zonlicht bestaat uit polychromatisch licht is waarschijnlijk de mogelijkheid tot het synchroniseren van een persoon met een disfunctie van de klassieke fotoreceptoren niet aangetast. Echter bij nieuwe ontwikkelingen op het gebied van verlichting wordt vaak polychromatisch licht gebruikt met specifieke pieken van golflengten binnen het spectrum. Individuen met een andere maximale gevoeligheid zullen de pieken in golflengte mogelijkerwijs buiten het maximale gevoeligheidsspectrum kunnen vallen waardoor de positieve effecten, die bereikt willen worden met de dynamische verlichting, uitblijven. Hoewel dit op dit moment slechts een hypothese is, is het een goed uitgangspunt voor verder onderzoek om in de toekomst optimaal gebruik te kunnen maken van de wellicht positieve effecten van de eigenschappen van licht.
Oxidation of NADH and NADPH by Mitochondria from the Yeast Candida utilis
No full textApplied Science
NADH-linked aldose reductase: The key to anaerobic alcoholic fermentation of xylose by yeasts
No full textThe kinetics and enzymology of o-xylose utilization were studied in aerobic and anaerobic batch cultures of the facultatively fermentative yeasts Candida utilis, Pachysolen tannophilus, and Pichia stipitis. These yeasts did not produce ethanol under aerobic conditions. When shifted to anaerobiosis cultures of C. utilis did not show fermentation of xylose; in Pa. tannophilus a very low rate of ethanol formation was apparent, whereas with Pi. stipitis rapid fermentation of xylose occurred. The different behaviour of these yeasts ist most probably explained by differences in the nature of the initial steps of xylose metabolism: in C. utilis xylose is metabolized via an NADPH-dependent xylose reductase and an NAD+-linked xylitol dehydrogenase. As a consequence, conversion of xylose to ethanol by C. utilis leads to an overproduction of NADH which blocks metabolic activity in the absence of oxygen. In Pa. tannophilus and Pi. stipitis, however, apart from an NADPH-linked xylose reductase also an NADH-linked xylose reductase was present. Apparently xylose metabolism via the NADH-dependent reductase circumvents the imbalance of the NAD+/NADH redox system, thus allowing fermentation of xylose to ethanol under anaerobic conditions. The finding that the rate of xylose fermentation in Pa. tannophilus and Pi. stipitis corresponds with the activity of the NADH-linked xylose reductase activity is in line with this hypothesis. Furthermore, a comparative study with various xylose-assimilating yeasts showed that significant alcoholic fermentation of xylose only occurred in those organisms which possessed NADH-linked aldose reductaseApplied Science
Critical Parameters in the Isolation of Mitochondria from Candida-Utilis Grown in Continuous Culture
No full textApplied Science
Phosphorus-31 nuclear magnetic resonance studies of intracellular pH, phosphate compartmentation and phosphate transport in yeasts
No full text31p NMR spectra were obtained from suspensions of Candida utilis, Saccharomyces cerevisiae and Zygosaccharomyces bailii grown aerobically on glucose. Direct introduction of substrate into the cell suspension, without interruption of the measurements, revealed rapid changes in pH upon addition of the energy source. All 3 ~p NMR spectra of the yeasts studied indicated the presence of two major intracellular inorganic phosphate pools at different pH environments. The pool at the higher pH was assigned to cytoplasmic phosphate from its response to glucose addition and iodoacetate inhibition of glycolysis. After addition of substrate the pH in the compartment containing the second phosphate pool decreased. A parallel response was observed for a significant fraction of the terminal and penultimate phosphates of the polyphosphate observed by 31 PNMR. This suggested that the inorganic phosphate fraction at the lower pH and the polyphosphates originated from the same intracellular compartment, most probably the vacuole. In this vacuolar compartment, pH is sensitive to metabolic conditions. In the presence of energy source a pH gradient as large as 0.8 to 1.5 units could be generated across the vacuolar membrane. Under certain conditions net transport of inorganic phosphate across the vacuolar membrane was observed during glycolysis: to the cytoplasm when the cytoplasmic phosphate concentration had become very low due to sugar phosphorylation, and into the vacuole when the former concentration had become high again after glucose exhaustion.Applied Science
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