scholarly journals Studies of an acid-induced species of purple membrane from Halobacterium halobium

1978 ◽  
Vol 171 (2) ◽  
pp. 469-476 ◽  
Author(s):  
T A Moore ◽  
M E Edgerton ◽  
G Parr ◽  
C Greenwood ◽  
R N Perham
Keyword(s):  
Phase Transition ◽  
New Species ◽  
Temperature Dependence ◽  
Ph Dependence ◽  
Low Ph ◽  
Purple Membrane ◽  
Halobacterium Halobium ◽  
Temperature Dependent ◽  
Ph Range ◽  
Increasing Temperature

A new spectral species of the purple membrane of Halobacterium halobium has been observed below pH 3.2. The formation of this new species is temperature-dependent and is favoured by increasing temperature up to the physiological range of the organism. The rate of formation at pH 3.0 and 22 degrees C is 7.9 × 10-3s-1. The spectral distribution and temperature-dependence of the new species suggest that it may be phototransiet O, stabilized by low pH. Flash-photolytic experiments in the pH range 7.2-2.7 show a pH-dependence corresponding to the static events and are consistent with a single protonation of bacteriorhodopsin below pH 3.22. These results can also be interpreted in terms of the stabilization of phototransient O at low pH. The temperature-dependence of the formation of the acid-induced species may reflect a relationship with the phase transition of the membrane.

Origin of ferroelectric phase transition in SbSClxI1-x mixed crystals

2014 ◽  
Vol 28 (30) ◽  
pp. 1450209 ◽  
Author(s):  
A. Audzijonis ◽  
L. Žigas ◽  
R. Sereika ◽  
R. Žaltauskas
Keyword(s):  
Phase Transition ◽  
Free Energy ◽  
Temperature Dependence ◽  
Ferroelectric Phase Transition ◽  
Ferroelectric Phase ◽  
Harmonic Approximation ◽  
Temperature Dependent ◽  
Normal Coordinate ◽  
Unit Cell Parameters ◽  
Cell Parameters

The measurements of SbSCl x I 1-x(x = 0.2) temperature dependent capacitance were carried out. The temperature of ferroelectric phase transition TC ≈340 K was measured experimentally. TC of SbSCl x I 1-x was calculated theoretically in anharmonic and harmonic approximations. TC was calculated in anharmonic approximation using temperature dependence of mean potential energy of Sb atoms as a function of the soft B1u symmetry normal coordinate along c(z)-axis. Moreover, TC was calculated in harmonic approximation using temperature dependence of vibrational thermodynamic functions (Helmholc free energy). TC dependence from unit cell parameters a, b and from mixture composition x was carried out.

scholarly journals Protein aggregation in C-phycocyanin. Studies at very low concentrations with the photoelectric scanner of the ultracentrifuge

1971 ◽  
Vol 122 (4) ◽  
pp. 421-426 ◽  
Author(s):  
R. MacColl ◽  
J. J. Lee ◽  
D. S. Berns
Keyword(s):  
Protein Aggregation ◽  
Temperature Dependence ◽  
Equilibrium Constant ◽  
Ph Dependence ◽  
Sedimentation Velocity ◽  
Scanning System ◽  
High Concentration ◽  
Low Concentrations ◽  
Increasing Temperature ◽  
Schlieren Optics

Solutions of C-phycocyanin of very low concentrations were examined by sedimentation-velocity studies in the Spinco model E ultracentrifuge equipped with a photoelectric scanning system and a monochromator. At sufficiently low concentrations complete disaggregation from the hexamer to the monomer was observed. The equilibrium constant of monomer to hexamer was estimated to be approx. 1030. For studies of aggregation over the complete range of concentration, C-phycocyanins from Phormidium luridum and Lyngbya sp. were used. Sedimentation-velocity studies at high concentration with schlieren optics are reported for C-phycocyanins from Anabaena variabilis and Lyngbya sp. The pH-dependence of aggregation and the temperature-dependence of trimer–hexamer equilibrium for phycocyanins from these algae were found to be similar to those of other C-phycocyanins. The principal feature of the pH-dependence is the dominance of hexamers at the isoelectric point. Increasing temperature increased the amount of hexamer and decreased the amount of trimer.

POLARISED TEMPERATURE DEPENDENT XANES STUDY OF SUPERCONDUCTING La2-xSrxCuO4-y UNDER- AND OVER-DOPED SINGLE CRYSTALS

2002 ◽  
Vol 16 (09) ◽  
pp. 1327-1339 ◽  
Author(s):  
C. CONCHA ◽  
J. GARCIA ◽  
J. BLASCO ◽  
K. B. GARG ◽  
R. K. SINGHAL ◽  
...  
Keyword(s):  
Phase Transition ◽  
Temperature Dependence ◽  
Single Crystals ◽  
The Other ◽  
Planar Geometry ◽  
Temperature Dependent ◽  
Characteristic Temperatures ◽  
Square Planar ◽  
Planar Systems ◽  
Made In

High resolution XANES measurements have been made at the CuK-absorption edge on two La 2-x Sr x CuO 4-y single crystals; one under-doped (x = 0.13) and the other over-doped (x = 0.19). These measurements have been made in E//ab and E//c directions at several temperatures to compare the doping, orientation and temperature dependence in their behaviour. Broadly speaking, their XANES spectra resemble the typical one from a crystal with square-planar geometry and the various fine structure features assigned to the possible transitions they arise due to, particularly in terms of the fact that the 4p band in Cu splits into 4p(π) and 4p(σ) components in these square-planar systems. However, the temperature dependence of the various features in the spectra from the two crystals appear to be opposite in nature and exhibit some characteristic temperatures at which the trend seems to reverse. All the experimental results and their implication are discussed and a possibility of phase transition of these systems at lower temperatures is hinted at.

scholarly journals Denitrification in nitric-acid-treated cattle slurry during storage

1993 ◽  
Vol 41 (2) ◽  
pp. 63-80 ◽  
Author(s):  
O. Oenema ◽  
G.L. Velthof
Keyword(s):  
Nitric Acid ◽  
Ph Dependence ◽  
N2o Emission ◽  
Low Ph ◽  
Nh3 Volatilization ◽  
Cattle Slurry ◽  
N2o Production ◽  
Ph Range ◽  
On Farm ◽  
Complete Homogenization

Lowering the pH of cattle slurry with HNO3 was used to reduce NH3 volatilization during storage and after application. Incubation studies were carried out to examine possible NO3 losses and N2O emission from HNO3 treated slurry during storage. Batches of cattle slurry were treated with various amounts of HNO3 to obtain a pH range of 6.0 to 3.0. The slurries were stirred once or twice a week and stored for 6 months at 15 degrees C. Changes in pH, Eh, NO3- and NH4+ concn, and emissions of N2O, CO2 and CH4 were monitored. The loss of NO3- and the emission of N2O were related to slurry pH, being lowest at low pH. Cumulative loss of NO3- ranged from ~40 mmol/kg for slurries of target pH < or =>5.0 to ~400 mmol/kg for slurries of target pH 6.0. Homogenization of the slurries via stirring and addition of H2O2 decreased NO3- loss and H+ consumption. The strong pH dependence of NO3- loss, the production of N2O and the stoichiometry of H+ consumption and NO3- loss indicated that the loss of NO3- was mainly due to microbiological denitrification. Similar N2O production rates in the presence and absence of C2H2 indicated that nitrification was not an important source of N2O. It is concluded that lowering the pH to values 4.5 as well as regular and complete homogenization of the slurry via stirring are important for the success of the on-farm treatment of slurry with HNO3.

Pressure- and temperature-dependent inelastic neutron scattering study of the phase transition and phonon lattice dynamics in para-terphenyl

2021 ◽  
Author(s):  
Qingan Cai ◽  
Michael McIntire ◽  
Luke L. Daemen ◽  
Chen Li ◽  
Eric L. Chronister
Keyword(s):  
Phase Transition ◽  
Neutron Scattering ◽  
Temperature Dependence ◽  
Lattice Dynamics ◽  
Inelastic Neutron Scattering ◽  
Ambient Pressure ◽  
Inelastic Neutron ◽  
Temperature Dependent ◽  
Scattering Study ◽  
Neutron Scattering Study

Inelastic neutron scattering has been performed on para-terphenyl at temperatures from 10 to 200 K and under pressures from the ambient pressure to 1.51 kbar. The temperature dependence of phonons,...

scholarly journals Experimental determination of the temperature dependence of oxygen-isotope fractionation between water and chitinous head capsules of chironomid larvae

2021 ◽  
Author(s):  
Alex Lombino ◽  
Tim Atkinson ◽  
Stephen J. Brooks ◽  
Darren R. Gröcke ◽  
Jonathan Holmes ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Oxygen Isotope ◽  
Oxygen Isotopes ◽  
Isotope Fractionation ◽  
Temperature Dependent ◽  
Oxygen Isotope Fractionation ◽  
Chironomid Larvae ◽  
Increasing Temperature ◽  
The Relationship

AbstractOxygen-isotope values of invertebrate cuticle preserved in lake sediments have been used in palaeoenvironmental reconstructions, generally with the assumption that fractionation of oxygen isotopes between cuticle and water ($$\upalpha_{\text{cuticle}-\text{H}_{2}\text{O}}$$ α cuticle - H 2 O ) is independent of temperature. We cultured chironomid larvae in the laboratory with labelled oxygen-isotope water and across a range of closely controlled temperatures from 5 to 25 °C in order to test the hypothesis that fractionation of oxygen isotopes between chironomid head capsules and water ($$\upalpha_{\text{chironomid}-\text{H}_{2}\text{O}}$$ α chironomid - H 2 O ) is independent of temperature. Results indicate that the hypothesis can be rejected, and that $$\upalpha_{\text{chironomid}-\text{H}_{2}\text{O}}$$ α chironomid - H 2 O decreases with increasing temperature. The scatter in the data suggests that further experiments are needed to verify the relationship. However, these results indicate that temperature-dependence of $$\upalpha_{\text{chironomid}-\text{H}_{2}\text{O}}$$ α chironomid - H 2 O should be considered when chironomid δ18O is used as a paleoenvironmental proxy, especially in cases where data from chironomids are combined with oxygen-isotope values from other materials for which fractionation is temperature dependent, such as calcite, in order to derive reconstructions of past water temperature.

Structural transition of VO2 (A) nanorods studied by vibrational spectroscopies

RSC Advances ◽  
2014 ◽  
Vol 4 (35) ◽  
pp. 18055-18060 ◽  
Author(s):  
Jiwei Hou ◽  
Jianwu Zhang ◽  
Zhongping Wang ◽  
Zengming Zhang ◽  
Zejun Ding
Keyword(s):  
Phase Transition ◽  
Raman Spectrum ◽  
Raman Spectra ◽  
Structural Transition ◽  
Temperature Dependent ◽  
Vibrational Spectroscopies ◽  
Increasing Temperature ◽  
Induce Phase ◽  
Induce Phase Transition

The temperature-induce phase transition of VO2 (A) nanorods was observed from the Raman spectrum. Temperature-dependent Raman spectra of the VO2 (A) during the increasing temperature.

Circadian Rhythm of Locomotion and its Temperature Dependence in Blattella Germanica

1971 ◽  
Vol 54 (1) ◽  
pp. 187-198
Author(s):  
HANS DREISIG ◽  
ERIK TETENS NIELSEN
Keyword(s):  
Circadian Rhythm ◽  
Light Intensity ◽  
Temperature Dependence ◽  
Blattella Germanica ◽  
Temperature Dependent ◽  
Continuous Darkness ◽  
Expected Time ◽  
Different Temperatures ◽  
Free Running ◽  
Increasing Temperature

1. The activity in Blattella germanica was investigated under standard conditions. Periods of latency and increment were recognized. 2. The free-running rhythm in continuous darkness was determined at different temperatures and showed about the same period. The free-running rhythm in continous light could not be determined unless the light intensity was extremely low. 3. The period of activity was not released immediately after a change from light to darkness if this was advanced in relation to the normal time. The activity was then only slightly advanced. 4. Delay of the onset of darkness caused the activity to diminish gradually after the usual time of change from light to dark. 5. If the temperature was lowered some time before the expected time of activity in continuous darkness the activity was advanced much more than normally. If the temperature was raised the activity was delayed. 6. Based upon these and other studies, a theory is advanced which explains the activity rhythms in insects as being the result of the interaction between a gradually increasing, temperature-dependent sensitization and different thresholds of release determined by light and temperature. A theory is propounded concerning the temperature-independence of the free-running rhythm in continuous darkness, assuming a temperature-dependent threshold of release.

Study on Phase Stability of Hexagonal Ba(Ti0.95Fe0.05)O3-δ Ceramic via Temperature-Dependent X-Ray Diffraction

2015 ◽  
Vol 1083 ◽  
pp. 55-59
Author(s):  
Da Yong Lu ◽  
Yan Dong Wang ◽  
Shu Zhen Cui ◽  
Dan Dan Han
Keyword(s):  
Phase Transition ◽  
Curie Temperature ◽  
Phase Stability ◽  
Perovskite Structure ◽  
Oxygen Vacancies ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray ◽  
Defect Complexes ◽  
Increasing Temperature

The crystalline structure of the hexagonal Ba (Ti0.95Fe0.05)O3−δ(BTF) ceramic were directly measured using a temperature-dependent XRD technique. Different from the traditional structural transitions of rhombohedral-orthorhombic (−90 °C), orthorhombic-tetragonal (−10 °C), and tetragonal-cubic (i.e., the Curie temperatureTC= 130 °C) for BaTiO3, the phase transition from hexagonal to any phase above for BTF cannot occur atTCeven up to 300 °C. Increasing temperature cannot give rise to the occupation of oxygen vacancies by environmental oxygen absorbed. The lattice electro-neutrality maintained by Fe3+-VO-Fe3+defect complexes is predominant in BTF. This experiment clarifies the phase stability of the hexagonal perovskite structure aboveTCup to 300 °C.

scholarly journals Investigations into the effect of acid on the spectral and kinetic properties of purple membrane from Halobacterium halobium

1980 ◽  
Vol 189 (3) ◽  
pp. 413-420 ◽  
Author(s):  
M E Edgerton ◽  
T A Moore ◽  
C Greenwood
Keyword(s):  
Kinetic Parameters ◽  
Conformational Change ◽  
Reducing Agents ◽  
Purple Membrane ◽  
Buffering Capacity ◽  
Kinetic Properties ◽  
Halobacterium Halobium ◽  
Spectral Changes ◽  
Temporal Placement ◽  
Ph Range

The formation and reversal of the acid species of purple membrane generated below pH 4.00 (22 degrees C) is studied together with the photochemical cycle over the pH range 6.40–3.20. The buffering capacity of the membrane reaches a peak at pH 4.30, indicating the possibility of a conformational change taking place. The generation of the new spectral species can take place in the dark and is unaffected by the addition of reducing agents. Kinetic parameters measured indicate that the group being titrated below pH 4.00 could be the same as that protonated in the formation of intermediate O. The temporal placement of intermediate O after M in the photochemical cycle is shown to be incompatible with the data presented here. Reneutralization of acidified purple membrane shows that the spectral changes in acid are reversible but the phototransient properties are altered.

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