scholarly journals Vibrational Relaxation of the 2ν5 Overtone of CDCl3 Following Tea CO2 Laser Excitation of the ν4 Mode

1994 ◽  
Vol 14 (4) ◽  
pp. 191-200 ◽  
Author(s):  
M. A. Vazquez ◽  
M. L. Azcárate ◽  
E. J. Quel ◽  
L. Doyennette ◽  
C. Rinaldi ◽  
...  
Keyword(s):  
Time Constant ◽  
Rate Constant ◽  
Fluorescence Intensity ◽  
Time Variation ◽  
Vibrational Relaxation ◽  
Laser Excitation ◽  
Fluorescence Decay ◽  
Tea Co2 Laser ◽  
Bending Mode ◽  
Fast Rise

The time variation of the 2ν5 fluorescence intensity was measured in CDCl3 excited in the ν4 C–D bending mode by a TEA CO2 laser operating on the 10P(48) line. A fast rise of the fluorescence, with a time constant ≤ 1 μs Torr, was first observed, showing that a fast equilibration of population occurs between the ν4 and ν5 modes through a ν4 ↔ ν5 Coriolis-assisted intermode transfer and a ν5 ↔ 2ν5 near-resonant ladder-climbing process. Then a first fast fluorescence decay was observed and attributed to a (ν4, ν5) → ν2 intermode transfer with a rate constant of (7.10 ± 1.13)ms-1 Torr-1. At last, a much slower decay, with a rate constant of 0.111 ± 0.015 ms-1 Torr-1, results from the less efficient intermode transfer and V–T,R deexcitation processes involving the ν3 and ν6 states, and which compete to relax the gas to a thermodynamic equilibrium.

Removal of albumin microinjected in rat lung perimicrovascular space

1994 ◽  
Vol 77 (3) ◽  
pp. 1294-1302 ◽  
Author(s):  
X. Ying ◽  
R. Qiao ◽  
S. Ishikawa ◽  
J. Bhattacharya
Keyword(s):  
Hydraulic Conductivity ◽  
Injection Site ◽  
Time Constant ◽  
Airway Pressure ◽  
Fluorescence Decay ◽  
Diffusive Transport ◽  
Liquid Flux ◽  
Tissue Edema ◽  
Lung Expansion ◽  
Blood Flow Increase

We used a microinjection approach to assess hydraulic properties of lung perimicrovascular adventitia (interstitial cuff surrounding microvessels). Isolated blood-perfused rat lungs held at constant airway pressure were microscopically viewed to identify subpleural venules (20 microns diam). Venular adventitia were microinjected with 20 nl of fluorescent albumin (4 g/dl), and then adventitial fluorescence was quantified at the injection site by either photometery or imaging. Nonlinear decay of adventitial fluorescence indicated liquid flux from the injection site into normal interstitium. In some experiments, we determined that the adventitial fluorescence flowed longitudinally along the venule length and filled single lymphatics. The fluorescence decay at the injection site was best described by equations of convective but not diffusive transport. The decay time constant (time to 37% initial), which relates inversely to hydraulic conductivity, increased 10-fold above baseline on lung expansion with airway pressure from 5 to 15 cmH2O (P < 0.05). However, presence or absence of blood flow, increase in filtration pressure, and tissue edema were all without effect on the time constant. Our estimate of the lower limit of baseline adventitial hydraulic conductivity was 5 x 10(-6) ml.cm-2.s-1.cmH2O-1. We conclude that hydraulic conductivity of perimicrovascular adventitia is not augmented by edema but that it is decreased by lung expansion.

Whole-blood red blood cell aggregometer for human and feline blood

1986 ◽  
Vol 251 (6) ◽  
pp. H1205-H1210 ◽  
Author(s):  
M. Tomita ◽  
F. Gotoh ◽  
N. Tanahashi ◽  
P. Turcani
Keyword(s):  
Optical Density ◽  
Time Constant ◽  
Rate Constant ◽  
Whole Blood ◽  
Infrared Light ◽  
Half Time ◽  
Silicon Photodiode ◽  
Initial Decrease ◽  
Vinyl Tube ◽  
Rbc Aggregation

A whole-blood aggregometer of red blood cells (RBC) is described. It consists of a transparent 0.26-cm ID vinyl tube of approximately 30 cm in length containing freshly drawn heparinized blood and a densitometer head that is attached to the tube. The densitometer head consists of an infrared light source of gallium arsenide and a light detector (silicon photodiode) to monitor changes in optical density of the blood in the tube. The tube and densitometer head were installed in a temperature-controlled box at 37 degrees C. The blood in the tube was first subjected to rapid flow with a solenoid so that the wall shear rate of the blood was approximately 500 s-1. The shear gave rise to a rapid increase in optical density of the blood due to dispersion of the blood corpuscles. The blood was then brought abruptly to a full stop. After the flow had stopped the densitometer head revealed a gradual decrease in optical density in association with RBC aggregate formation. The resultant pattern was termed by us an “RBC aggregogram.” The RBC aggregogram exhibited an exponential decay in its initial part, which was followed by an asymptotic decrease. A simple mathematical procedure was employed to calculate the rate constant of the initial decrease from the two values on the RBC aggregogram at 10 and 20 s. The rate constant k10 was 0.192 +/- 0.028 (5.2 s as time constant; 3.6 s as half time) for feline blood and 0.129 +/- 0.012 (7.7 s as time constant; 5.3 s as half time) for human blood. The RBC aggregation rate varied linearly with the hematocrit below 40%.

scholarly journals Some Recent Developments in Atomic Lifetime Determinations

1986 ◽  
Vol 39 (5) ◽  
pp. 829 ◽  
Author(s):  
P Hannaford ◽  
RM Lowe
Keyword(s):  
Laser Excitation ◽  
Pulsed Laser ◽  
Fluorescence Decay ◽  
Gas Discharge ◽  
Rare Gas ◽  
Time Resolved ◽  
Atomic Systems ◽  
Refractory Elements ◽  
Wide Range ◽  
Recent Developments

A lifetimes technique that is readily applicable to neutral and singly ionised atoms of a wide range of elements, including the highly refractory elements, is reviewed. With this technique an atomic vapour of the element under study is generated by cathodic sputtering in a low pressure rare-gas discharge and fluorescence decay signals emitted by the vapour following pulsed laser excitation are recorded directly in a fast transient digitiser. Theoretical expressions are presented for the form of the time-resolved fluor~scence signal appropriate to the collisional environment of a rare-gas sputtering discharge. A summary is given of the atomic systems studied to date using this technique, and some new results for Sm and Ba are compared with recently reported results for these elements.

scholarly journals Refolding of urea-denatured adenylate kinase

1998 ◽  
Vol 333 (2) ◽  
pp. 401-405 ◽  
Author(s):  
Hong-jie ZHANG ◽  
Xiang-rong SHENG ◽  
Xian-ming PAN ◽  
Jun-mei ZHOU
Keyword(s):  
Secondary Structure ◽  
Rate Constant ◽  
Fluorescence Intensity ◽  
Adenylate Kinase ◽  
Surface Hydrophobicity ◽  
Native Structure ◽  
Fast Process ◽  
Ans Binding ◽  
First Order ◽  
Partially Folded Intermediate

The refolding of urea-denatured adenylate kinase (EC 2.7.4.3) has been followed by formation of the secondary structure, change of surface hydrophobicity and recovery of catalytic activity. During refolding of adenylate kinase with a 20–80-fold dilution of 4 M urea-denatured enzyme at 10 °C, the formation of the secondary structure is a fast process with a rate constant of > 0.16 s-1. Transient enhancement of the 8-anilino-1-naphthalenesulphonate (ANS) fluorescence intensity is followed by a fluorescence decrease to the level equal to the value characteristic of native enzyme. The desorption of ANS binding fluorescence is relatively slow and can be fitted to a first order reaction with a rate constant of 0.004 s-1 when the ANS is present in the dilution buffer. The desorption of ANS-binding fluorescence is accelerated in the presence of nucleotide substrates. The rate constants are increased to 0.049, 0.029, 0.028 and 0.029 s-1 in the presence of 1 mM AMP, MgATP, ATP and ADP respectively. The refolding rate constant calculated from the initial fluorescence intensity after mixing ANS with protein at different refolding intervals is 0.016 s-1, which is faster than those obtained when ANS is present throughout the refolding process, indicating that the binding of ANS with a partially folded intermediate retards its further refolding to its native structure. The reactivation rate is even faster than the rates of refolding monitored in the absence of substrates, showing that the refolding is accelerated in the presence of the substrates. A possible refolding pathway and the accelerating effect of substrates are discussed.

scholarly journals Temperaturabhängigkeit der Absorption und Fluoreszenz von Tetracen und Perylen/Tetracen in Flüssigkristallen / The Temperature Dependence of Absorption and Fluorescence of Tetracene and PeryleneI Tetracene in Liquid Crystals

1979 ◽  
Vol 34 (11) ◽  
pp. 1301-1304 ◽  
Author(s):  
G. Ullrich ◽  
A. Schmillen
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Binary System ◽  
Fluorescence Intensity ◽  
Decay Time ◽  
Wavelength Region ◽  
Fluorescence Decay ◽  
Liquid Crystal Phase ◽  
Clearing Point ◽  
Fluorescence Decay Time

At the clearing point the extinction and the fluorescence intensity of pure tetracene mixtures decrease rapidly. This is explained as due to a forced scattering in the liquid crystal phase. In the binary system perylene/tetracene the polarisation of absorption and emission in the wavelength region of tetracene is inverted and the corresponding fluorescence decay time increases with temperature

scholarly journals A Test for Bottlenecks in the Vibrational Relaxation of CH3Cl and CH3Br by Ar

1988 ◽  
Vol 9 (1-3) ◽  
pp. 47-62 ◽  
Author(s):  
Kenneth M. Beck ◽  
Robert J. Gordon
Keyword(s):  
Decay Rate ◽  
Relaxation Rate ◽  
Vibrational Relaxation ◽  
Energy Levels ◽  
Fluorescence Decay ◽  
Rotational Relaxation ◽  
Translational Energy ◽  
Time Resolved ◽  
Level Model ◽  
Relaxing Gas

The method of time-resolved optoacoustics was used to measure the rate of vibrational relaxation of CH3Cl(ν6) and CH3Br(ν6) by Ar. The pressure pulses generated by the relaxing gas revealed that the rate of production of translational energy from ν6 = 1 is approximately twice the decay rate of IR fluorescence from ν3 = 1. No evidence was found for a previously proposed bottleneck in rotational relaxation, which would have resulted in an acoustic relaxation rate slower than the fluorescence decay. The faster rates observed here can be explained qualitatively by a rapid energy release from energy levels above ν3 which precedes the IR fluorescence. A simple three-level model, however, is unable to explain our observations quantitatively.

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