Temperature-induced phase transition and structural changes in micellar solutions of sodium oleate observed by Raman scattering

1983 ◽  
Vol 87 (13) ◽  
pp. 2436-2443 ◽  
Author(s):  
P. T. T. Wong ◽  
H. H. Mantsch
Keyword(s):  
Phase Transition ◽  
Raman Scattering ◽  
Sodium Oleate ◽  
Structural Changes ◽  
Micellar Solutions

Pressure and Temperature Effects on the Raman Spectra of Aqueous Micellar Solutions of Sodium Oleate

1983 ◽  
Vol 22 ◽  
Author(s):  
P.T.T. Wong ◽  
H.H. Mantsch
Keyword(s):  
Phase Transition ◽  
Sodium Oleate ◽  
Temperature Effects ◽  
Micellar Solution ◽  
Room Temperature ◽  
Structural Changes ◽  
Micellar Solutions ◽  
Micellar Phase ◽  
Aqueous Micellar Solutions ◽  
Pressure And Temperature Effects

Sodium oleate is practically insoluble in water at room temperature. Yet, when heated above the critical micellization temperature (cmt), its solubility increases rapidly and an isotropic optically clear micellar solution is formed. Upon cooling below the critical coagelization temperature (cct), the micellar phase transforms to an opaque curd, the coagel phase. The structural changes and the nature of this phase transition are, however, not well characterized.

Phase transition sequence in the chiral compound 10FHBBBM7* studied by Raman scattering

1999 ◽  
Vol 26 (12) ◽  
pp. 1805-1811 ◽  
Author(s):  
Yu. I. Yuzyuk ◽  
S. Sarmento ◽  
P. Simeao Carvalho ◽  
A. Almeida ◽  
Filipa Pinto ◽  
...  
Keyword(s):  
Phase Transition ◽  
Raman Scattering ◽  
Chiral Compound ◽  
Transition Sequence

scholarly journals Pressure-induced structural phase transition in CaCrO4: Evidence from Raman scattering studies

2005 ◽  
Vol 87 (18) ◽  
pp. 181901 ◽  
Author(s):  
Y. W. Long ◽  
W. W. Zhang ◽  
L. X. Yang ◽  
Y. Yu ◽  
R. C. Yu ◽  
...  
Keyword(s):  
Phase Transition ◽  
Raman Scattering ◽  
Structural Phase Transition ◽  
Structural Phase

The Hexagonal ↔ Orthorhombic Structural Phase Transition in Claringbullite, Cu4FCl(OH)6

2021 ◽  
Author(s):  
Mark D. Welch ◽  
Jens Najorka ◽  
Michael S. Rumsey ◽  
John Spratt
Keyword(s):  
Phase Transition ◽  
Data Storage ◽  
Structural Phase Transition ◽  
Structural Changes ◽  
Structural Phase ◽  
Magnetic Behavior ◽  
Orthorhombic Phase ◽  
New Mineral ◽  
Storage Devices ◽  
Definition Of

ABSTRACT Frustrated magnetic phases have been a perennial interest to theoreticians wishing to understand the energetics and behavior of quasi-chaotic systems at the quantum level. This behavior also has potentially wide applications to developing quantum data-storage devices. Several minerals are examples of such phases. Since the definition of herbertsmithite, Cu3ZnCl2(OH)6, as a new mineral in 2004 and the rapid realization of the significance of its structure as a frustrated antiferromagnetic phase with a triangular magnetic lattice, there has been intense study of its magnetic properties and those of synthetic compositional variants. In the past five years it has been recognized that the layered copper hydroxyhalides barlowite, Cu4BrF(OH)6, and claringbullite, Cu4FCl(OH)6, are also the parent structures of a family of kagome phases, as they also have triangular magnetic lattices. This paper concerns the structural behavior of claringbullite that is a precursor to the novel frustrated antiferromagnetic states that occur below 30 K in these minerals. The reversible hexagonal (P63/mmc) ↔ orthorhombic (Pnma or Cmcm) structural phase transition in barlowite at 200−270 K has been known for several years, but the details of the structural changes that occur through the transition have been largely unexplored, with the focus instead being on quantifying the low-temperature magnetic behavior of the orthorhombic phase. This paper reports the details of the structural phase transition in natural claringbullite at 100−293 K as studied by single-crystal X-ray diffraction. The transition temperature has been determined to lie between 270 and 293 K. The progressive disordering of Cu at the unusual trigonal prismatic Cu(OH)6 site on heating is quantified through the phase transition for the first time, and a methodology for refining this disorder is presented. Key changes in the behavior of Cu(OH)4Cl2 octahedra in claringbullite have been identified that suggest why the Pnma structure is likely stabilized over an alternative Cmcm structure. It is proposed that the presence of a non-centrosymmetric octahedron in the Pnma structure allows more effective structural relaxation during the phase transition than can be achieved by the Cmcm structure, which has only centrosymmetric octahedra.

scholarly journals Pathological transitions in myelin membranes driven by environmental and multiple sclerosis conditions

2018 ◽  
Vol 115 (44) ◽  
pp. 11156-11161 ◽  
Author(s):  
Rona Shaharabani ◽  
Maor Ram-On ◽  
Yeshayahu Talmon ◽  
Roy Beck
Keyword(s):  
Multiple Sclerosis ◽  
Phase Transition ◽  
Lipid Composition ◽  
Environmental Conditions ◽  
Structural Changes ◽  
Environmental Changes ◽  
Hexagonal Phase ◽  
Structural Phase ◽  
Structural Modifications ◽  
Transition Points

Multiple sclerosis (MS) is an autoimmune disease, leading to the destruction of the myelin sheaths, the protective layers surrounding the axons. The etiology of the disease is unknown, although there are several postulated environmental factors that may contribute to it. Recently, myelin damage was correlated to structural phase transition from a healthy stack of lamellas to a diseased inverted hexagonal phase as a result of the altered lipid stoichiometry and low myelin basic protein (MBP) content. In this work, we show that environmental conditions, such as buffer salinity and temperature, induce the same pathological phase transition as in the case of the lipid composition in the absence of MBP. These phase transitions have different transition points, which depend on the lipid’s compositions, and are ion specific. In extreme environmental conditions, we find an additional dense lamellar phase and that the native lipid composition results in similar pathology as the diseased composition. These findings demonstrate that several local environmental changes can trigger pathological structural changes. We postulate that these structural modifications result in myelin membrane vulnerability to the immune system attacks and thus can help explain MS etiology.

Raman scattering inCaFeO3andLa0.33Sr0.67FeO3across the charge-disproportionation phase transition

2005 ◽  
Vol 71 (24) ◽  
Author(s):  
Shankar Ghosh ◽  
N. Kamaraju ◽  
M. Seto ◽  
A. Fujimori ◽  
Y. Takeda ◽  
...  
Keyword(s):  
Phase Transition ◽  
Raman Scattering ◽  
Charge Disproportionation
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