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Upper Temperature Limit (upper + temperature_limit)
Selected AbstractsInactivation of Shigella boydii 18 IDPH and Listeria monocytogenes Scott A with Power Ultrasound at Different Acoustic Energy Densities and TemperaturesJOURNAL OF FOOD SCIENCE, Issue 4 2007Edgar Ugarte-Romero ABSTRACT:, The effect of acoustic energy density (AED) on inactivation of Shigella boydii 18 IDPH and Listeria monocytogenes Scott A in a cell suspension was studied at sublethal temperatures and at AEDs of 0.49, 0.85, and 1.43 W/mL. The effect of temperature on ultrasonic inactivation of L. monocytogenes Scott A at 35, 50, and 65 °C was examined at an AED of 1.43 W/mL. Increasing AED increased the rate of inactivation for both S. boydii and L. monocytogenes. The destruction of S. boydii and L. monocytogenes followed 1st order kinetics in a 20-min treatment, except for S. boydii inactivation at 1.43 W/mL where a tailing effect was observed after 15 min. At sublethal temperatures, the D-values of S. boydii were 8.8, 4.3, and 2.5 min for AEDs of 0.49, 0.85, and 1.43 W/mL, whereas those for L. monocytogenes at the 3 AED levels were 31.5, 13.5, and 7.3 min, respectively. Ultrasonic treatment of L. monocytogenes at 35 and 50 °C enhanced inactivation. However, at 65 °C, application of ultrasound did not result in additional inactivation compared to thermal treatment alone at the same temperature. With the experimental conditions and the ultrasound system used in this study, an upper temperature limit for thermosonication was evident above which no added killing due to ultrasound was observed. [source] SHORT-TERM AND LONG-TERM EFFECTS OF TEMPERATURE ON PHOTOSYNTHESIS IN THE DIATOM THALASSIOSIRA PSEUDONANA UNDER UVR EXPOSURES,JOURNAL OF PHYCOLOGY, Issue 3 2007Cristina Sobrino Temperature is expected to modify the effects of ultraviolet radiation (UVR) on photosynthesis by affecting the rate of repair. We studied the effect of short-term (1 h) and long-term (days) acclimation to temperature on UVR photoinhibition in the diatom Thalassiosira pseudonana Hasle et Heimdal. Photosynthesis was measured during 1 h exposures to varying irradiances of PAR and UVR + PAR at 15, 20, and 25°C, the latter corresponding to the upper temperature limit for optimal growth in T. pseudonana. The exposures allowed the estimation of photosynthesis,irradiance (P,E) curves and biological weighting functions (BWFs) for photoinhibition. For the growth conditions used, temperature did not affect photosynthesis under PAR. However, photoinhibition by UVR was highly affected by temperature. For cultures preacclimated to 20°C, the extent of UVR photoinhibition increased with decreasing temperature, from 63% inhibition of PAR-only photosynthesis at 25°C to 71% at 20°C and 85% at 15°C. These effects were slightly modified after several days of acclimation: UVR photoinhibition increased from 63% to 75% at 25°C and decreased from 85% to 80% at 15°C. Time courses of photochemical efficiency (,PSII) under UVR + PAR were also fitted to a model of UVR photoinhibition, allowing the estimation of the rates of damage (k) and repair (r). The r/k values obtained for each temperature treatment verified the responses observed with the BWF (R2 = 0.94). The results demonstrated the relevance of temperature in determining primary productivity under UVR exposures. However, the results suggested that temperature and UVR interact mainly over short (hours) rather than long (days) timescales. [source] Investigation of the structure and phase transitions in the novel A-site substituted distorted perovskite compound Na0.5Bi0.5TiO3ACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2002G. O. Jones Rietveld neutron powder profile analysis of the compound Na0.5Bi0.5TiO3 (NBT) is reported over the temperature range 5,873,K. The sequence of phase transitions from the high-temperature prototypic cubic structure (above 813,K), to one of tetragonal (673,773,K) and then rhombohedral structures (5,528,K) has been established. Coexisting tetragonal/cubic (773,813,K) and rhombohedral/tetragonal (with an upper temperature limit of 145,K between 528 and 673,K) phases have also been observed. Refinements have revealed that the rhombohedral phase, space group R3c, with aH = 5.4887,(2), cH = 13.5048,(8),Å, V = 352.33,(3),Å3, Z = 6 and Dx = 5.99,Mg,m,3, exhibits an antiphase, a,a,a, oxygen tilt system, , = 8.24,(4)°, with parallel cation displacements at room temperature. The tetragonal phase, space group P4bm, with aT = 5.5179,(2), cT = 3.9073,(2),Å, V = 118.96,(1),Å3, Z = 2 and Dx = 5.91,Mg,m,3, possesses an unusual combination of in-phase, a0a0c+ oxygen octahedra tilts, , = 3.06,(2)°, and antiparallel cation displacements along the polar axis. General trends of cation displacements and the various deviations of the octahedral network from the prototypic cubic perovskite structure have been established and their systematic behaviour with temperature is reported. An investigation of phase transition behaviour using second harmonic generation (SHG) to establish the centrosymmetric or non-centrosymmetric nature of the various phases is also reported. [source] The Effects of Supraoptimal Temperatures on Population Growth and Cortical Patterning in Tetrahymena pyriformis and Tetrahymena thermophila: A ComparisonTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2001JOSEPH FRANKEL ABSTRACT. In this investigation, we compare the multiplication rates and morphogenetic responses of the two most studied Tetrahymena species, T. pyriformis and T. thermophila, at supraoptimal temperatures. Although the upper temperature limits differ greatly in the two species, the pattern of growth responses to high temperature is for the most part similar, with some differences in detail. The transient recovery of cell division at the highest temperature that allows cell division, characteristic of T. pyriformis, is observed in a less distinct form in T. thermophila. Moreover, there is a remarkable difference in developmental response, with drastic abnormalities in patterning of oral structures during the transient recovery of cell division in T. pyriformis, and far more limited abnormalities under similar conditions in T. thermophila. The abnormalities result from spatial disorder in the alignment and orientation of basal body pairs within the early oral primordium, followed by failures in the realignment that normally occurs as oral structures (membranelles and undulating membrane) mature. Both the initial spatial disorder and the failures in realignment are far more severe in T. pyriformis than in T. thermophila. [source] | |||||||||||||