Pressure Dependence of Photoluminescence of Oligothiophenes

1997 ◽  
Vol 488 ◽  
Author(s):  
L. Rossi ◽  
W. Graupner ◽  
R. Resel ◽  
F. Meghdadi ◽  
G. Leising ◽  
...  
Keyword(s):  
Optical Properties ◽  
Hydrostatic Pressure ◽  
Pressure Dependence ◽  
Structural Changes ◽  
Interchain Coupling ◽  
Conformational Effects

AbstractWe report on the nature of emitting states in two different quaterthiophenes: the unsubstituted quaterthiophenes (T4) and a bridged T4 (T4B), where the bridging have been realized by introducing a second bond between the two central thiophene rings. The effect of the chemical bridging on the photophysics of these compounds have been studied via photoluminescence measurements under hydrostatic pressure, which permit to clarify the influence of interchain coupling, conformational effects and intrachain structural changes on the optical properties.

scholarly journals Pressure Effects on the Optical Properties of NdVO4

Crystals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 237 ◽  
Author(s):  
Enrico Bandiello ◽  
Josu Sánchez-Martín ◽  
Daniel Errandonea ◽  
Marco Bettinelli
Keyword(s):  
Phase Transition ◽  
Optical Properties ◽  
Absorption Band ◽  
Phase Change ◽  
Band Gap ◽  
Pressure Dependence ◽  
Structural Changes ◽  
Pressure Effects ◽  
Absorption Bands ◽  
Fundamental Absorption Band

We report on optical spectroscopic measurements in pure NdVO4 crystals at pressures up to 12 GPa. The influence of pressure on the fundamental absorption band gap and Nd3+ absorption bands has been correlated with structural changes in the crystal. The experiments indicate that a phase transition takes place between 4.7 and 5.4 GPa. We have also determined the pressure dependence of the band-gap and discussed the behavior of the Nd3+ absorption lines under compression. Important changes in the optical properties of NdVO4 occur at the phase transition, which, according to Raman measurements, corresponds to a zircon to monazite phase change. In particular, in these conditions a collapse of the band gap occurs, changing the color of the crystal. The changes are not reversible. The results are analyzed in comparison with those deriving from previous studies on NdVO4 and related vanadates.

scholarly journals Metastable Intermediates as Stepping Stones on the Maturation Pathways of Viral Capsids

mBio ◽  
2014 ◽  
Vol 5 (6) ◽  
Author(s):  
Giovanni Cardone ◽  
Robert L. Duda ◽  
Naiqian Cheng ◽  
Lili You ◽  
James F. Conway ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Large Scale ◽  
Structural Changes ◽  
Energy Landscape ◽  
Potential Hazard ◽  
Stepping Stones ◽  
Scanning Calorimetry ◽  
Conformational Effects ◽  
Capsid Maturation ◽  
Capsid Integrity

ABSTRACT As they mature, many capsids undergo massive conformational changes that transform their stability, reactivity, and capacity for DNA. In some cases, maturation proceeds via one or more intermediate states. These structures represent local minima in a rich energy landscape that combines contributions from subunit folding, association of subunits into capsomers, and intercapsomer interactions. We have used scanning calorimetry and cryo-electron microscopy to explore the range of capsid conformations accessible to bacteriophage HK97. To separate conformational effects from those associated with covalent cross-linking (a stabilization mechanism of HK97), a cross-link-incompetent mutant was used. The mature capsid Head I undergoes an endothermic phase transition at 60°C in which it shrinks by 7%, primarily through changes in its hexamer conformation. The transition is reversible, with a half-life of ~3 min; however, >50% of reverted capsids are severely distorted or ruptured. This observation implies that such damage is a potential hazard of large-scale structural changes such as those involved in maturation. Assuming that the risk is lower for smaller changes, this suggests a rationalization for the existence of metastable intermediates: that they serve as stepping stones that preserve capsid integrity as it switches between the radically different conformations of its precursor and mature states. IMPORTANCE Large-scale conformational changes are widespread in virus maturation and infection processes. These changes are accompanied by the release of conformational free energy as the virion (or fusogenic glycoprotein) switches from a precursor state to its mature state. Each state corresponds to a local minimum in an energy landscape. The conformational changes in capsid maturation are so radical that the question arises of how maturing capsids avoid being torn apart. Offering proof of principle, severe damage is inflicted when a bacteriophage HK97 capsid reverts from the (nonphysiological) state that it enters when heated past 60°C. We suggest that capsid proteins have been selected in part by the criterion of being able to avoid sustaining collateral damage as they mature. One way of achieving this—as with the HK97 capsid—involves breaking the overall transition down into several smaller steps in which the risk of damage is reduced.

Anomalous hydrostatic pressure dependence of the Curie temperature of the Kondo-lattice compound YbNiSn to 38 GPa

1995 ◽  
Vol 52 (22) ◽  
pp. R15699-R15702 ◽  
Author(s):  
A. L. Cornelius ◽  
J. S. Schilling ◽  
D. Mandrus ◽  
J. D. Thompson
Keyword(s):  
Hydrostatic Pressure ◽  
Curie Temperature ◽  
Pressure Dependence ◽  
Kondo Lattice

Degeneracy Factor and Pressure Dependence of Si-Induced Deep Impurity States in AlxGa1-xAs from Transport Experiments under Hydrostatic Pressure

1991 ◽  
Vol 38-41 ◽  
pp. 857-862 ◽  
Author(s):  
S. Azema ◽  
V. Mosser ◽  
Jean Camassel ◽  
R. Piotrzkowski ◽  
Jean-Louis Robert ◽  
...  
Keyword(s):  
Hydrostatic Pressure ◽  
Pressure Dependence ◽  
Deep Impurity ◽  
Impurity States

Temperature Dependence of the Intervalley Deformation Potential of GaAs/AlAs Superlattices Under Hydrostatic Pressure

1997 ◽  
Vol 499 ◽  
Author(s):  
S. Guha ◽  
Q. Cai ◽  
M. Chandrasekhar ◽  
H. R. Chandrasekhar ◽  
Hyunjung Kim ◽  
...  
Keyword(s):  
Hydrostatic Pressure ◽  
Temperature Dependence ◽  
Pressure Dependence ◽  
Type I ◽  
Type Ii ◽  
Deformation Potential ◽  
Intervalley Scattering

ABSTRACTWe have studied the pressure dependence of the type-I and type-II transitions in (GaAs)m/(AlAs)m superlattices by photoluminescence (PL) spectroscopy. From the study of PL linewidths of the type-I exciton as a function of pressure and temperature, we determine the intervalley deformation potential. Beyond the type-I and type-II crossover, the PL linewidth increases both as a function of pressure and temperature. We find that the electron-phonon deformation potential for Γ-X intervalley scattering varies with temperature.

Exciton-related optical properties in zinc-blende GaN/InGaN quantum wells under hydrostatic pressure

2015 ◽  
Vol 252 (4) ◽  
pp. 670-677 ◽  
Author(s):  
C. M. Duque ◽  
A. L. Morales ◽  
M. E. Mora-Ramos ◽  
C. A. Duque
Keyword(s):  
Optical Properties ◽  
Hydrostatic Pressure ◽  
Quantum Wells ◽  
Zinc Blende ◽  
Ingan Quantum Wells

Hydrostatic Pressure Dependence of TCfor SASD Type Crystals

2005 ◽  
Vol 317 (1) ◽  
pp. 115-118 ◽  
Author(s):  
I. E. Lipiński ◽  
J. Kuriata ◽  
N. A. Korynevskii
Keyword(s):  
Hydrostatic Pressure ◽  
Pressure Dependence
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