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Temperature Shift (temperature + shift)

Distribution by Scientific Domains

Physics and Astronomy	40%

Selected Abstracts

Temperature shift of the Fe2+ absorption band in LiNbO3:Fe crystal

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 13 2004
M. H. Yükselici
Abstract The temperature dependence of the Fe2+ absorption band of a strongly oxidized LiNbO3:Fe crystal is reported over the range from 25 to 350 °C, where the effect of temperature on the band is reversible. The band broadens and shifts to lower energy as temperature is increased. The rate at which the absorption peak energy decreases with increasing temperature is calculated as ,6.8 × 10,5 eV/°C from the slope of the straight-line fit to the temperature against peak position energy graph. We propose that the origin of the temperature shift is due to both a shift of the energetic position of impurities and the decrease of the band gap energy. The consistency between the calculated rate by the help of a simplified model which describes the shift of the band gap energy in the frame of the lattice dilation and the observed rate suggests that the lattice dilation might be responsible for the temperature shift of the band. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Mechanical and microstructural investigations into the crack arrest behaviour of a modern 2¼Cr-1 Mo pressure vessel steel

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 2 2001
E. Bouyne
Tests were performed on a 2¼ Cr,1 Mo steel to measure the fracture toughness at initiation, KIc and at arrest, KIa,. The results were compared with those obtained on another pressure vessel steel (A508) of similar strength. Two techniques were used to measure KIa,: (i) isothermal compact crack arrest (CCA) tests, and (ii) specially designed thermal shock experiments using an externally notched ring. These specimens were cooled to ,196 °C and then heated by induction in the centre of the ring to produce very steep thermal gradients. This caused crack initiation from the notch. The crack propagates very rapidly (,500 m s,1,) and stopped when it reached the warmer region of the specimen. The specimens were analysed using an elastic,plastic finite element method to determine KIa values. These tests reveal a greater temperature shift (,100 °C) between KIc and KIa in 2¼ Cr,1 Mo steel than in A508 steel. Detailed metallographical examinations of the micromechanisms of crack propagation and arrest in the 2¼ Cr,1 Mo steel showed that this involves the nucleation of a three-dimensional network of cleavage microcracks which change their direction at bainitic packet boundaries. The remaining uncracked ligaments between the cleavage microcracks break by ductile rupture mechanism [source]

Fluorescence EXAFS for the in situ study on the state of promotors in catalysis

JOURNAL OF SYNCHROTRON RADIATION, Issue 2 2001
Jan-Dierk Grunwaldt
The fluorescence EXAFS (FLEXAFS) technique has been combined with an in situ cell and on-line gas analysis. For this purpose a seven-element silicon drift detector has been used, which has high count rate capabilities and can be operated at room temperature. The potential of this technique is shown by the study of the state of copper promoter atoms in Fe-Cr based high temperature shift (HTS) catalysts. The FLEXAFS measurements revealed that Cu (0.17,1.5 wt%) is present in the metallic state under working conditions of the catalysts but easily re-oxidizes upon air exposure. The reduction behaviour of copper depends strongly on the copper concentration and the pre-treatment, i.e. if the catalysts have been calcined or used in the HTS reaction. For used catalysts, a Cu(I) phase was detected as intermediate during reduction. Its stability was especially high at low copper concentration. [source]

Temperature shift of the Fe2+ absorption band in LiNbO3:Fe crystal

Comparative transcriptome analysis to unveil genes affecting recombinant protein productivity in mammalian cells

BIOTECHNOLOGY & BIOENGINEERING, Issue 1 2009
Joon Chong Yee
Abstract Low temperature culture (33°C) has been shown to enhance the specific productivity of recombinant antibodies in Chinese hamster ovary (CHO) cells but did not affect antibody productivity in hybridoma (MAK) cells. We probed the transcriptional response of both cells undergoing temperature shift using cDNA microarrays. Among the orthologous gene probes, common trends in the expression changes between CHO and MAK are not prominent. Instead, many transcriptional changes were specific to only one cell line. Notably, oxidative phosphorylation and ribosomal genes were downregulated in MAK but not in CHO. Conversely, several protein trafficking genes and cytoskeleton elements were upregulated in CHO but remained unchanged in MAK. Interestingly, at 33°C, immunoglobulin heavy and light chain showed no significant changes in CHO, but the immunoglobulin light chain was downregulated in MAK. Overall, a clear distinction in the transcriptional response to low temperature was seen in the two cell lines. To further elucidate the set of genes responsible for increased antibody productivity, the expression data of low temperature cultures was compared to that of butyrate treatment which increased specific antibody productivity in both cell lines. Genes which are commonly differentially expressed under conditions that increased productivity are likely to reflect functional classes that are important in the productivity changes. This comparative transcriptome analysis suggests that vesicle trafficking, endocytosis and cytoskeletal elements are involved in increased specific antibody productivity. Biotechnol. Bioeng. 2009;102: 246,263. © 2008 Wiley Periodicals, Inc. [source]

Biomass recycling from a riboflavin cultivation with B. subtilis: Lysis, extract production and testing as substrate in riboflavin cultivation

BIOTECHNOLOGY & BIOENGINEERING, Issue 6 2006
Karlheinz Bretz
Abstract Autolysis of riboflavin-producing B. subtilis can be induced by pH, lack of carbon source, and the buffer system. Stress factors like temperature shift or oxygen dearth enhance the autolysis process. After cultivation of a riboflavin-producing strain, the pH of the whole culture broth was adjusted to 6.5,7.5. At a temperature of 40°C, autolysis started after 1 h. Adding a defined amount of commercially available endo- and exo-proteases enhanced both auto- and proteo-lysis. Optimization of endo- and exo-protease concentrations and of the time increased the degree of proteolysis. Additionally, the amount of DNA and Protein trapped in the riboflavin crystals could be significantly reduced by autolysis. After autolysis, the cultivation broth was centrifuged and the supernatant was cross-flow filtrated with a cut off of 10 kDa. Using this autolysate instead of yeast extract as a medium component for riboflavin production with B. subtilis, a riboflavin yield of 77% was obtained in comparison with the standard cultivation on yeast extract. © 2006 Wiley Periodicals, Inc. [source]

Dielectric properties of thallium gallium diselenide layered crystal in the incommensurate phase

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 9 2005
entürk
Abstract The dielectric measurements of the layered crystal were studied in temperature range of successive phase transitions. The measurements revealed that the phase transition occurred in 242 K is an incommensurate phase transition. When the sample is annealed at a stabilized temperature in the incommensurate phase, a remarkable memory effect has been observed on cooling run. The mechanism of the memory effect in the incommensurate phase of the semiconducting ferroelectric TlGaSe2 can be interpreted in the frame of the theory of defect density waves. This theory claims that the memory effect is the result of pinning of the incommensurate structure by the lattice inhomogeneities. With decreasing the annealing temperature the phase transition temperature shifts to lower temperatures gradually. Moreover, the peak intensities also increase gradually. In addition to these effects, the phase transition temperature shifts to lower temperatures with increasing annealing time. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Stream Temperature Surges Under Urbanization and Climate Change: Data, Models, and Responses,

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 2 2007
Kären C. Nelson
ABSTRACT: Multiple anthropogenic stressors, including increased watershed imperviousness, destruction of the riparian vegetation, increased siltation, and changes in climate, will impact streams over the coming century. These stressors will alter water temperature, thus influencing ecological processes and stream biota. Quantitative tools are needed to predict the magnitude and direction of altered thermal regimes. Here, empirical relationships were derived to complement a simple model of in-stream temperature [developed by Caissie et al. Canadian Journal of Civil Engineering25 (1998) 250; Journal of Hydrology251 (2001) 14], including seasonal temperature shifts linked to land use, and temperature surges linked to localized rainstorms; surges in temperature averaged about 3.5°C and dissipated over about 3 h. These temperature surges occurred frequently at the most urbanized sites (up to 10% of summer days) and could briefly increase maximum temperature by >7°C. The combination of empirical relationships and model show that headwater streams may be more pervasively impacted by urbanization than by climate change, although the two stressors reinforce each other. A profound community shift, from common cold and coolwater species to some of the many warmwater species currently present in smaller numbers, may be expected, as shown by a count of days on which temperature exceeds the "good growth" range for coldwater species. [source]

POTENTIAL IMPACTS OF CLIMATE CHANGE ON CALIFORNIA HYDROLOGY,

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 4 2003
Norman L. Miller
ABSTRACT: Previous reports based on climate change scenarios have suggested that California will be subjected to increased wintertime and decreased summertime streamflow. Due to the uncertainty of projections in future climate, a new range of potential climatological future temperature shifts and precipitation ratios is applied to the Sacramento Soil Moisture Accounting Model and Anderson Snow Model in order to determine hydrologic sensitivities. Two general circulation models (GCMs) were used in this analysis: one that is warm and wet (HadCM2 run 1) and one that is cool and dry (PCM run B06.06), relative to the GCM projections for California that were part of the Third Assessment Report of the Intergovernmental Panel on Climate Change. A set of specified incremental temperature shifts from 1.5°C to 5.0°C and precipitation ratios from 0.70 to 1.30 were also used as input to the snow and soil moisture accounting models, providing for additional scenarios (e.g., warm/dry, cool/wet). Hydrologic calculations were performed for a set of California river basins that extend from the coastal mountains and Sierra Nevada northern region to the southern Sierra Nevada region; these were applied to a water allocation analysis in a companion paper. Results indicate that for all snow-producing cases, a larger proportion of the streamflow volume will occur earlier in the year. The amount and timing is dependent on the characteristics of each basin, particularly the elevation. Increased temperatures lead to a higher freezing line, therefore less snow accumulation and increased melting below the freezing height. The hydrologic response varies for each scenario, and the resulting solution set provides bounds to the range of possible change in streamflow, snowmelt, snow water equivalent, and the change in the magnitude of annual high flows. An important result that appears for all snowmelt driven runoff basins, is that late winter snow accumulation decreases by 50 percent toward the end of this century. [source]

Internal friction investigation of reverse martensitic transformation in oil-quenched Ni64Al36 alloy

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2008
Z. C. Zhou
Abstract Low-frequency internal friction investigation of reverse martensitic transformation in oil-quenched Ni64Al36 alloy has been carried out using a multifunctional internal friction apparatus from room temperature to 400 °C and additionally differential scanning calorimetry and X-ray diffraction experiments were also completed. It has been shown that an internal friction peak presents at about 220 °C in the internal friction,temperature curve during heating for the oil-quenched Ni64Al36 alloy but not for the furnace-cooled Ni64Al36 alloy. The peak still appears during cooling and the peak temperature shifts to lower temperature. The changes of the peak temperature positions cannot be visibly observed when the vibration frequency is changed. The peak heights increase with decreasing vibration frequency and increasing heating rate, being linearly directly proportional to It has been suggested that the internal friction peak results from reverse martensitic transformation of L10 , , during heating and originates from martensitic transformation of , , L10 during the subsequent cooling process. The influence of the thermal cycles on the transformation is not observed for the limited thermal cycles. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]