scholarly journals Low Energy Excitations in La1.2Sr1.8Mn2O7 investigated by ellipsometry

2020 ◽  
Author(s):  
Ocean Mercier ◽  
Robert Buckley ◽  
Harry Trodahl ◽  
C Bernhard ◽  
B Balakrishnan
Keyword(s):  
Small Polaron ◽  
Low Energy ◽  
Temperature Sensitive ◽  
Temperature Dependent ◽  
Spectral Ellipsometry ◽  
Dependent Behavior ◽  
Spectral Contribution ◽  
Doped Manganites ◽  
Frequency Changes ◽  
American Physical

The low-energy excitations of the bilayered manganite La1.2 Sr1.8 Mn2 O7 have been explored by spectral ellipsometry from two faces of a single crystal over the range from 0.006 to 0.6 eV. This compound is a paramagnetic insulator at ambient temperature, with a transition to a ferromagnetic metal below a Curie temperature (Tc) of 125 K. Both the ab -plane and c -axis temperature-dependent conductivities have been determined. Essentially no temperature-dependent behavior is observed above Tc although below Tc both the phonon and electronic contributions are strongly temperature sensitive. The highest-frequency phonons, especially those involving Mn-O bond stretching, split and show frequency changes consistent with structural results in the literature, and furthermore there is clear evidence of an increase in electron-phonon coupling at and below Tc. We interpret the temperature-dependent electronic spectral contribution in the light of recent calculations that indicate that a mixed phase exists in the doped manganites below Tc, with coexisting regions of an itinerant large-polaron phase and a localized small-polaron phase. © 2005 The American Physical Society.

scholarly journals Low Energy Excitations in La1.2Sr1.8Mn2O7 investigated by ellipsometry

2020 ◽  
Author(s):  
Ocean Mercier ◽  
Robert Buckley ◽  
Harry Trodahl ◽  
C Bernhard ◽  
B Balakrishnan
Keyword(s):  
Small Polaron ◽  
Low Energy ◽  
Temperature Sensitive ◽  
Temperature Dependent ◽  
Spectral Ellipsometry ◽  
Dependent Behavior ◽  
Spectral Contribution ◽  
Doped Manganites ◽  
Frequency Changes ◽  
American Physical

The low-energy excitations of the bilayered manganite La1.2 Sr1.8 Mn2 O7 have been explored by spectral ellipsometry from two faces of a single crystal over the range from 0.006 to 0.6 eV. This compound is a paramagnetic insulator at ambient temperature, with a transition to a ferromagnetic metal below a Curie temperature (Tc) of 125 K. Both the ab -plane and c -axis temperature-dependent conductivities have been determined. Essentially no temperature-dependent behavior is observed above Tc although below Tc both the phonon and electronic contributions are strongly temperature sensitive. The highest-frequency phonons, especially those involving Mn-O bond stretching, split and show frequency changes consistent with structural results in the literature, and furthermore there is clear evidence of an increase in electron-phonon coupling at and below Tc. We interpret the temperature-dependent electronic spectral contribution in the light of recent calculations that indicate that a mixed phase exists in the doped manganites below Tc, with coexisting regions of an itinerant large-polaron phase and a localized small-polaron phase. © 2005 The American Physical Society.

scholarly journals Mapping temperature-dependent conformational change in the voltage-sensing domain of an engineered heat-activated K+ channel

2021 ◽  
Vol 118 (14) ◽  
pp. e2017280118
Author(s):  
Hongbo Chen ◽  
Jiahua Deng ◽  
Qiang Cui ◽  
Baron Chanda ◽  
Katherine Henzler-Wildman
Keyword(s):  
Large Scale ◽  
K Channel ◽  
Temperature Sensitive ◽  
Temperature Dependent ◽  
Voltage Sensing ◽  
Shaker Potassium Channel ◽  
Dependent Behavior ◽  
Solvation Energies ◽  
Dynamics Simulations ◽  
Temperature Dependent Behavior

Temperature-dependent regulation of ion channel activity is critical for a variety of physiological processes ranging from immune response to perception of noxious stimuli. Our understanding of the structural mechanisms that underlie temperature sensing remains limited, in part due to the difficulty of combining high-resolution structural analysis with temperature stimulus. Here, we use NMR to compare the temperature-dependent behavior of Shaker potassium channel voltage sensor domain (WT-VSD) to its engineered temperature sensitive (TS-VSD) variant. Further insight into the molecular basis for temperature-dependent behavior is obtained by analyzing the experimental results together with molecular dynamics simulations. Our studies reveal that the overall secondary structure of the engineered TS-VSD is identical to the wild-type channels except for local changes in backbone torsion angles near the site of substitution (V369S and F370S). Remarkably however, these structural differences result in increased hydration of the voltage-sensing arginines and the S4–S5 linker helix in the TS-VSD at higher temperatures, in contrast to the WT-VSD. These findings highlight how subtle differences in the primary structure can result in large-scale changes in solvation and thereby confer increased temperature-dependent activity beyond that predicted by linear summation of solvation energies of individual substituents.

scholarly journals LCST polymers with UCST behavior

Soft Matter ◽  
2021 ◽  
Author(s):  
Marzieh Najafi ◽  
Mehdi Habibi ◽  
Remco Fokkink ◽  
Wim Hennink ◽  
Tina Vermonden
Keyword(s):  
Block Copolymers ◽  
Aqueous Solutions ◽  
Temperature Dependent ◽  
Dependent Behavior ◽  
Temperature Dependent Behavior

In this study, temperature dependent behavior of dense dispersions of core crosslinked flower-like micelles is investigated. Micelles were prepared by mixing aqueous solutions of two ABA block copolymers with PEG...

scholarly journals Temperature Characterization of Liquid Crystal Dielectric Image Line Phase Shifter for Millimeter-Wave Applications

Crystals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 63
Author(s):  
Henning Tesmer ◽  
Rani Razzouk ◽  
Ersin Polat ◽  
Dongwei Wang ◽  
Rolf Jakoby ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Millimeter Wave ◽  
Insertion Loss ◽  
Phase Shifter ◽  
Ground Plane ◽  
Temperature Dependent ◽  
Differential Phase ◽  
Dependent Behavior ◽  
The Impact ◽  
Temperature Dependent Behavior

In this paper we investigate the temperature dependent behavior of a liquid crystal (LC) loaded tunable dielectric image guide (DIG) phase shifter at millimeter-wave frequencies from 80 GHz to 110 GHz for future high data rate communications. The adhesive, necessary for precise fabrication, is analyzed before temperature dependent behavior of the component is shown, using the nematic LC-mixture GT7-29001. The temperature characterization is conducted by changing the temperature of the LC DIG’s ground plane between −10∘C and 80 ∘C. The orientation of the LC molecules, and therefore the effective macroscopic relative permittivity of the DIG, is changed by inserting the temperature setup in a fixture with rotatable magnets. Temperature independent matching can be observed, while the insertion loss gradually increases with temperature for both highest and lowest permittivity of the LC. At 80 ∘C the insertion loss is up to 1.3dB higher and at −10∘C it is 0.6dB lower than the insertion loss present at 20 ∘C. In addition, the achievable differential phase is reduced with increasing temperature. The impact of molecule alignment to this reduction is shown for the phase shifter and an estimated 85% of the anisotropy is still usable with an LC DIG phase shifter when increasing the temperature from 20 ∘C to 80 ∘C. Higher reduction of differential phase is present at higher frequencies as the electrical length of the phase shifter increases. A maximum difference in differential phase of 72∘ is present at 110 GHz, when increasing the temperature from 20 ∘C to 80 ∘C. Nevertheless, a well predictable, quasi-linear behavior can be observed at the covered temperature range, highlighting the potential of LC-based dielectric components at millimeter wave frequencies.

Temperature-Dependent Tribological Improvements in Low-Energy Nitrogen Ion Implanted Vanadium-Titanium Alloys

2005 ◽  
Author(s):  
C. Ballesteros ◽  
J. A. Garci´a ◽  
M. I. Orti´z ◽  
R. Rodri´guez ◽  
M. Varela
Keyword(s):  
Tribological Properties ◽  
Low Energy ◽  
Temperature Dependent ◽  
Structural Modifications ◽  
Nanocomposite Layer ◽  
Implantation Temperature ◽  
Transmission Electron ◽  
Nitrogen Ion ◽  
Tribological Characterization

A detailed tribological characterization of low-energy, nitrogen implanted V5 at. %Ti alloy is presented. Samples were nitrogen-implanted at an accelerating voltage of 1.2 kV and 1 mA/cm2, up to a dose of 1E19 ions/cm2. The tribological properties of the alloys: microhardness, friction coefficient and wear resistance, have improved after ion implantation and this improvement increases as the implantation temperature increases. The microstructure of the alloys were analysed by transmission electron microscopy. A direct correlation between structural modifications of the nitrogen implanted layer and the improvement in their tribological properties is obtained. For samples implanted at 848 K a nanocomposite layer where the reinforcement particles are TiN precipitates forms. TiN precipitation appears as the responsible of the improvement in the tribological properties.

scholarly journals Mutations affecting the tRNA-splicing endonuclease activity of Saccharomyces cerevisiae.

Genetics ◽  
1988 ◽  
Vol 118 (4) ◽  
pp. 609-617
Author(s):  
M Winey ◽  
M R Culbertson
Keyword(s):  
Growth Defect ◽  
Temperature Sensitive ◽  
Gene Products ◽  
Endonuclease Activity ◽  
Temperature Dependent ◽  
Direct Role ◽  
Trna Splicing

Abstract Two unlinked mutations that alter the enzyme activity of tRNA-splicing endonuclease have been identified in yeast. The sen1-1 mutation, which maps on chromosome 12, causes temperature-sensitive growth, reduced in vitro endonuclease activity, and in vivo accumulation of unspliced pre-tRNAs. The sen2-1 mutation does not confer a detectable growth defect, but causes a temperature-dependent reduction of in vitro endonuclease activity. Pre-tRNAs do not accumulate in sen2-1 strains. The in vitro enzyme activities of sen1-1 and sen2-1 complement in extracts from a heterozygous diploid, but fail to complement in mixed extracts from separate sen1-1 and sen2-1 haploid strains. These results suggest a direct role for SEN gene products in the enzymatic removal of introns from tRNA that is distinct from the role of other products known to affect tRNA splicing.

scholarly journals Lactococcal Plasmid pNP40 Encodes a Novel, Temperature-Sensitive Restriction-Modification System

2004 ◽  
Vol 70 (9) ◽  
pp. 5546-5556 ◽  
Author(s):  
Jonathan O'Driscoll ◽  
Frances Glynn ◽  
Oonagh Cahalane ◽  
Mary O'Connell-Motherway ◽  
Gerald F. Fitzgerald ◽  
...  
Keyword(s):  
Restriction Enzymes ◽  
Temperature Sensitive ◽  
Temperature Dependent ◽  
Modification System ◽  
Restriction Modification System ◽  
Naturally Occurring ◽  
Low Copy Number ◽  
Encoding Genes ◽  
Restriction Modification ◽  
Specific Mrna

ABSTRACT A novel restriction-modification system, designated LlaJI, was identified on pNP40, a naturally occurring 65-kb plasmid from Lactococcus lactis. The system comprises four adjacent similarly oriented genes that are predicted to encode two m5C methylases and two restriction endonucleases. The LlaJI system, when cloned into a low-copy-number vector, was shown to confer resistance against representatives of the three most common lactococcal phage species. This phage resistance phenotype was found to be strongly temperature dependent, being most effective at 19°C. A functional analysis confirmed that the predicted methylase-encoding genes, llaJIM1 and llaJIM2, were both required to mediate complete methylation, while the assumed restriction enzymes, specified by llaJIR1 and llaJIR2, were both necessary for the complete restriction phenotype. A Northern blot analysis revealed that the four LlaJI genes are part of a 6-kb operon and that the relative abundance of the LlaJI-specific mRNA in the cells does not appear to contribute to the observed temperature-sensitive profile. This was substantiated by use of a LlaJI promoter-lacZ fusion, which further revealed that the LlaJI operon appears to be subject to transcriptional regulation by an as yet unidentified element(s) encoded by pNP40.

Temperature Dependent Behavior of the Canine Medial Collateral Ligament

1987 ◽  
Vol 109 (1) ◽  
pp. 68-71 ◽  
Author(s):  
Savio L.-Y. Woo ◽  
Thay Q. Lee ◽  
Mark A. Gomez ◽  
Shigeru Sato ◽  
Frederic P. Field
Keyword(s):  
Medial Collateral Ligament ◽  
Viscoelastic Properties ◽  
Cyclic Load ◽  
Tensile Load ◽  
Temperature Dependent ◽  
Collateral Ligament ◽  
Dependent Behavior ◽  
Proportional Relationship ◽  
C 32 ◽  
Increasing Temperature

The temperature dependent tensile behavior of ligament was investigated from 2°C to 37°C. Nondestructive cyclic tests were performed on ten canine femur-medial collateral ligament-tibia (FMT) complexes at sequential temperatures of 22°C, 22°C, 27°C, 32°C, 37°C, and again at 22°C. The samples were rested at zero load between tests for sufficient time periods to allow for full recovery from the ligament’s time and history dependent viscoelastic properties. Ten additional FMT complexes were sequentially tested in a similar fashion, but at temperatures of 22°C, 22°C, 2°C, 6°C, 14°C, and 22°C. All canine FMT complexes showed temperature dependent viscoelastic properties: the measured area of hysteresis decreased with increasing temperature; the cyclic load relaxation behavior plateaued to a higher value at lower temperatures; and the tensile load at a predetermined ligament substance strain level had an inversely proportional relationship with respect to temperature.

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