scholarly journals Temperature-Dependent Morphology Evolution of Boron Nitride and Boron Carbonitride Nanostructures

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Wei Li ◽  
Huan Yang ◽  
Shuaifeng Chen ◽  
Qing Chen ◽  
Lijie Luo ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Bulk Diffusion ◽  
Systematic Investigation ◽  
Temperature Dependent ◽  
Boron Carbonitride ◽  
Alloy Droplet ◽  
Different Temperatures ◽  
Diffusion Rates ◽  
Cylindrical Nanotubes ◽  
Rates Of Growth

Boron nitride (BN) and boron carbonitride (BCN) nanostructures with versatile morphology were synthesized at different temperatures. The morphologies such as smooth microspheres, nanoflake-decorated microspheres, solid nanowires, hollow nanotubes (bamboo-like nanotubes, quasi-cylindrical nanotubes, and cylindrical nanotubes), and nanosheet-assembled microwires have been observed. Systematic investigation showed that the reaction temperature was responsible for the versatile morphologies through influencing the guiding effect of catalyst alloy droplet and the diffusion rates of growth species. The diffusion rate differences between surface diffusion (along the surface of the droplet) and bulk diffusion (through the bulk of the droplet) at different reaction temperatures were suggested to affect the final structure of the BN and BCN nanostructures.

scholarly journals Towards a better understanding of the dynamics of Aphis spiraecola Patch (Homoptera: Aphididae) populations in commercial alpine yarrow fields

2010 ◽  
Vol 42 (2) ◽  
pp. 103 ◽  
Author(s):  
Zulfaidah Penata Gama ◽  
Pablo Morlacchi ◽  
Giuseppe Carlo Lozzia ◽  
Johann Baumgärtner ◽  
Anna Giorgi
Keyword(s):  
Natural Enemy ◽  
Distributed Delay ◽  
Structured Populations ◽  
Temperature Dependent ◽  
Optimum Sample Size ◽  
Aphis Spiraecola ◽  
Different Temperatures ◽  
Mechanistic Basis ◽  
Age Structured ◽  
Optimum Sample

The spatial distribution of Aphis spiraecola Patch was studied in two commercial yarrow fields located in the Swiss and Italian Alps and represented by Taylor’s (1961) power law. The respective parameters indicate a highly aggregated distribution and lead to a high optimum sample size of 400-500 plants in the design of a sampling program. Opportunities for reducing the sampling efforts are discussed. The infestation patterns were studied on the basis of Vansickle’s (1977) time varying distributed delay adequate for modelling the dynamics of age-structured populations. Published literature data were used to parametrize the functions representing the temperature-dependent duration and survival of the nymphal and adult stage. Likewise, literature data were available to obtain reliable estimates for the parameters of the fecundity function comprising the reproductive profile and the number of nymphs produced at different temperatures. The field data were used to parametrize the functions for wing formation and a compound mortality compromising the effects of plant senescence, stem cutting and natural enemies. The model satisfactorily represented the observed infestation patterns. However, there are opportunities for improving parameter estimation and validation. Moreover, the separation of the compound mortality into host plant and natural enemy effects would improve the mechanistic basis of the model and lead towards a tool that could be used to study bottom-up and top-down effects in the yarrow-aphid-natural enemy system.

scholarly journals Effect of Sintering Temperature on Metal-Insulator Phase Transition in La1-xCaxMnO3 Perovskites

2020 ◽  
Vol 2 (1) ◽  
pp. 37-42
Author(s):  
Arunachalam M ◽  
Thamilmaran P ◽  
Sakthipandi K
Keyword(s):  
Phase Transition ◽  
Bulk Modulus ◽  
Sintering Temperature ◽  
Magnetic Sensors ◽  
Temperature Dependent ◽  
Metal Insulator ◽  
Wide Range ◽  
Different Temperatures ◽  
Insulator Phase Transition

Lanthanum calcium based perovskites are found to be advantageous for the possible applications in magnetic sensors/reading heads, cathodes in solid oxide fuel cells, and frequency switching devices. In the present investigation La0.3Ca0.7MnO3 perovskites were synthesised through solid state reaction and sintered at four different temperatures such as 900, 1000, 1100 and 1200˚ C. X-ray powder diffraction pattern confirms that the prepared La0.3Ca0.7MnO3 perovskites have orthorhombic structure with Pnma space group. Ultrasonic in-situ measurements have been carried out on the La0.3Ca0.7MnO3 perovskites over wide range of temperature and elastic constants such as bulk modulus of the prepared La0.3Ca0.7MnO3 perovskites was obtained as function of temperature. The temperature-dependent bulk modulus has shown an interesting anomaly at the metal-insulator phase transition. The metal insulator transition temperature derived from temperature-dependent bulk modulus increases from temperature 352˚ C to 367˚ C with the increase of sintering temperature from 900 to 1200˚ C.

Study Of Al Surface Segregation In Icosahedral A162Cu25.5Fe12.5

1998 ◽  
Vol 553 ◽  
Author(s):  
M. GIL-GAVATZ ◽  
D. Rouxel ◽  
P. Pigeat ◽  
B. Weber ◽  
J.-M. Dubois
Keyword(s):  
Surface Segregation ◽  
Vacuum Chamber ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Electron Spectrometer ◽  
Temperature Dependent ◽  
Self Diffusion ◽  
Different Temperatures ◽  
High Vacuum Chamber

AbstractSurface segregation of aluminium was observed during oxidation experiments of icosahedral A162Cu25.5 Fel12.5, performed in-situ and at different temperatures in the ultra-high vacuum chamber of a scanning Auger electron spectrometer. Two regimes, below and above 770K, were observed in relation with severe segregation of Al atoms at the surface for T > 770K. We postulate that this temperature dependent segregation rate is representative of the aluminium transport towards the surface of the quasicrystal. By analogy with classical diffusion experiments, we can thus determine reasonable estimates of the activation energy for Al self-diffusion in this quasicrystal. The results are consistent with the existence of phason flips below 770K and thermal vacancies above this temperature.

scholarly journals Role of Arabidopsis Splicing factor SF1 in Temperature-Responsive Alternative Splicing of FLM pre-mRNA

2020 ◽  
Vol 11 ◽  
Author(s):  
Keh Chien Lee ◽  
Kyung Sook Chung ◽  
Hee Tae Lee ◽  
Jae-Hyeok Park ◽  
Jeong Hwan Lee ◽  
...  
Keyword(s):  
Alternative Splicing ◽  
Flowering Time ◽  
Crop Yields ◽  
Transcript Level ◽  
Splicing Factor ◽  
Loss Of Function ◽  
Temperature Dependent ◽  
Temperature Responsive ◽  
Different Temperatures

Small changes in temperature affect plant ecological and physiological factors that impact agricultural production. Hence, understanding how temperature affects flowering is crucial for decreasing the effects of climate change on crop yields. Recent reports have shown that FLM-β, the major spliced isoform of FLOWERING LOCUS M (FLM)—a flowering time gene, contributes to temperature-responsive flowering in Arabidopsis thaliana. However, the molecular mechanism linking pre-mRNA processing and temperature-responsive flowering is not well understood. Genetic and molecular analyses identified the role of an Arabidopsis splicing factor SF1 homolog, AtSF1, in regulating temperature-responsive flowering. The loss-of-function AtSF1 mutant shows temperature insensitivity at different temperatures and very low levels of FLM-β transcript, but a significantly increased transcript level of the alternative splicing (AS) isoform, FLM-δ. An RNA immunoprecipitation (RIP) assay revealed that AtSF1 is responsible for ambient temperature-dependent AS of FLM pre-mRNA, resulting in the temperature-dependent production of functional FLM-β transcripts. Moreover, alterations in other splicing factors such as ABA HYPERSENSITIVE1/CBP80 (ABH1/CBP80) and STABILIZED1 (STA1) did not impact the FLM-β/FLM-δ ratio at different temperatures. Taken together, our data suggest that a temperature-dependent interaction between AtSF1 and FLM pre-mRNA controls flowering time in response to temperature fluctuations.

scholarly journals Influence of urea on methyl $$\upbeta$$-D-glucopyranoside in alkali at different temperatures

Cellulose ◽  
2019 ◽  
Vol 26 (18) ◽  
pp. 9413-9422 ◽  
Author(s):  
Maria Gunnarsson ◽  
Merima Hasani ◽  
Diana Bernin
Keyword(s):  
Conformational Changes ◽  
Chemical Shifts ◽  
Regenerated Cellulose ◽  
Temperature Dependent ◽  
Hydroxymethyl Group ◽  
Overhauser Effect ◽  
Specific Manner ◽  
Acting Mechanism ◽  
Different Temperatures ◽  
Dissolution Efficiency

Abstract The dissolution efficiency plays an important role on the properties of regenerated cellulose-based products. Urea is known to be one of the additives aiding to improve cellulose dissolution in the NaOH(aq) system. The acting mechanism caused by urea has been debated and one of the hypothesis is that urea could induce a conformational change on cellulose, which promotes dissolution. Here we used NMR spectroscopy on a model system for cellulose, namely, methyl $$\upbeta$$β-D-glucopyranoside ($$\upbeta$$β-MeO-Glcp) and compared chemical shifts and J couplings, which both are indicators for conformational changes, as a function of temperature and upon the addition of urea. We found that in NaOH(aq), the hydroxymethyl group changes its conformation in favour of the population of the gt rotamer, while the presence of urea induced temperature dependent conformational changes. Heteronuclear Overhauser effect experiments showed that urea associates with cellulose but in a non-specific manner. This suggests that urea rather than binding to the carbohydrate, changes the chemical environment inducing a change in conformation of $$\upbeta$$β-MeO-Glcp and likely also for cellulose when dissolved in NaOH(aq) with urea.

Kinetic paths of B2 and DO3 order parameters: Experiment

1989 ◽  
Vol 4 (5) ◽  
pp. 1140-1142 ◽  
Author(s):  
L. Anthony ◽  
B. Fultz
Keyword(s):  
Thermal Equilibrium ◽  
Nearest Neighbor ◽  
Order Parameters ◽  
Temperature Dependent ◽  
Critical Temperatures ◽  
Subsequent Evolution ◽  
X Ray ◽  
Rates Of Change ◽  
Temperature Dependences ◽  
Different Temperatures

Rapidly quenched powders of Fe3Al were subjected to thermal annealings at temperatures well below the critical temperatures for B2 and DO3 ordering. X-ray diffractometry was used to measure the subsequent evolution of B2 and DO3 long-range order. It was found that the relative rates of change of B2 and DO3 order parameters were temperature dependent; hence at different temperatures the alloy passed through different states of order en route to thermal equilibrium. These temperature dependences of “kinetic paths” can be understood in terms of a theory of kinetic paths based on the kinetic master equation. The theory indicates that the temperature dependence of the observed kinetic paths originates from having first-nearest-neighbor interactions that are stronger than second-nearest-neighbor interactions. This seems consistent with previous thermodynamic analyses of critical temperatures of Fe3Al.

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