New Fiber-Optic-Based Instrumentation for the Measurement of Low-Temperature Phosphorescence Intensities and Lifetimes

1992 ◽  
Vol 46 (1) ◽  
pp. 126-130 ◽  
Author(s):  
Mary K. Carroll ◽  
Gary M. Hieftje
Keyword(s):  
Steady State ◽  
Low Temperature ◽  
Glass Formation ◽  
Fiber Optic ◽  
Detection Limits ◽  
Sample Cell ◽  
Phosphorescence Lifetime ◽  
Conventional Instrumentation

New fiber-optic instrumentation for phosphorescence-lifetime determinations and for steady-state phosphorescence measurements is shown to perform comparably to conventional instrumentation. The importance of optimal glass formation in the fiber-optic sample cell is considered in some detail. Detection limits for acetophenone, benzophenone, and p-nitrophenol are reported, and phosphorescence lifetimes are measured for several compounds, with values ranging from 2.5 ms to 4.7 s.

Convenient Fiber-Optic-Based Sample Cell for Shpol'skii and Low-Temperature Phosphorescence Spectrometry

1989 ◽  
Vol 43 (3) ◽  
pp. 422-425 ◽  
Author(s):  
Richard T. Madison ◽  
Mary K. Carroll ◽  
Gary M. Hieftje
Keyword(s):  
Low Temperature ◽  
Fiber Optic ◽  
Dynamic Range ◽  
Detection Limits ◽  
Linear Dynamic Range ◽  
Sample Cell ◽  
Linear Dynamic ◽  
Light Guides

A sample cell for observing the Shpol'skii effect at 77 K is described and analytically assessed. The cell employs fiber-optic light guides to transport excitation and emission radiation. The system is compact, inexpensive, and simple to construct from commercially available laboratory components, and it alleviates several problems inherent in conventional refrigerated-cell designs. Detection limits for anthracene, coronene, and pyrene obtained with the sample cell are 8.8 × 10−8 M, 8.4 × 10−7 M, and 3.5 × 10−7 M, respectively. The linear dynamic range for each compound is 2 to 3 orders of magnitude.

A Novel Fiber-Optic-Based Pump-Probe Instrument for the Acquisition of Kinetic Information

1992 ◽  
Vol 46 (2) ◽  
pp. 317-321 ◽  
Author(s):  
Mary K. Carroll ◽  
Gary M. Hieftje
Keyword(s):  
Excited State ◽  
Low Temperature ◽  
Rate Constant ◽  
Fiber Optic ◽  
Intersystem Crossing ◽  
Conformation Change ◽  
Sample Cell ◽  
Pump Probe ◽  
Kinetic Information ◽  
Kinetics Of

A pump-probe instrument is described that utilizes two beams from the same laser and a fiber-optic-based sample cell for low-temperature measurements. The utility of this instrument is demonstrated through an examination of the excited-state kinetics of 2,7-diphenylphenanthrene, for which the rate constant of singlet-to-triplet intersystem crossing is found to be approximately 8 × 105 s−1. This molecule is interesting in that it undergoes an unusual rotational conformation change in the triplet state with a rate constant of 2.4 × 108 s−1 at 77 K.

Electron drift caused by rf field gradient creates many plasma phenomena: An attempt to distinguish the cause and the effect

2011 ◽  
Vol 78 (2) ◽  
pp. 165-174 ◽  
Author(s):  
C. L. XAPLANTERIS ◽  
E. D. FILIPPAKI ◽  
I. S. MISTAKIDIS ◽  
L. C. XAPLANTERIS
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Low Temperature ◽  
Mathematical Models ◽  
Field Gradient ◽  
Collision Frequency ◽  
The Other ◽  
Frequency Effect ◽  
Electron Drift ◽  
Plasma Parameters

AbstractMany experimental data along with their theoretical interpretations on the rf low-temperature cylindrical plasma have been issued until today. Our Laboratory has contributed to that research by publishing results and interpretative mathematical models. With the present paper, two issues are being examined; firstly, the estimation of electron drift caused by the rf field gradient, which is the initial reason for the plasma behaviour, and secondly, many new experimental results, especially the electron-neutral collision frequency effect on the other plasma parameters and quantities. Up till now, only the plasma steady state was taken into consideration when a theoretical elaboration was carried out, regardless of the cause and the effect. This indicates the plasma's complicated and chaotic configuration and the need to simplify the problem. In the present work, a classification about the causality of the phenomena is attempted; the rf field gradient electron drift is proved to be the initial cause.

In-situ measurement of Auramine-O adsorption on macroporous adsorption resins at low temperature using fiber-optic sensing

2021 ◽  
Vol 213 ◽  
pp. 240-247
Author(s):  
Tursunjan Aydan ◽  
Jing-Jing Yang ◽  
Turghun Muhammad ◽  
Fei Gao ◽  
Xiao-Xia Yang ◽  
...  
Keyword(s):  
Low Temperature ◽  
Fiber Optic ◽  
In Situ Measurement ◽  
Auramine O ◽  
Macroporous Adsorption Resins ◽  
Fiber Optic Sensing

Luminescence Studies on Low Temperature Synthesized ZnGa2O4:Ln3+ (Ln = Tb and Eu) Nanoparticles

2008 ◽  
Vol 8 (11) ◽  
pp. 5776-5780 ◽  
Author(s):  
C. Manikyala Rao ◽  
V. Sudarsan ◽  
R. S. Ningthoujam ◽  
U. K. Gautam ◽  
R. K. Vatsa ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Oleic Acid ◽  
Steady State ◽  
Low Temperature ◽  
Ethylene Glycol ◽  
Urea Hydrolysis ◽  
Lanthanide Ions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Broad Emission

ZnGa2O4 nanoparticles doped with lanthanide ions (Tb3+ and Eu3+) were prepared at a low temperature of 120 °C based on urea hydrolysis in ethylene glycol medium. X-ray diffraction studies have confirmed that strain associated with nanoparticles changes as Tb3+ gets incorporated in the ZnGa2O4 lattice. Based on steady state emission and excitation studies of ZnGa2O4:Tb nanoparticles, it has been inferred that ZnGa2O4 host is characterized by a broad emission around 427 nm and there exists energy transfer between the host and Tb3+ ions. Unlike this, for ZnGa2O4:Eu nanoparticles, very poor energy transfer between the host and Eu3+ ions is observed. These nanoparticles when coated with ligands like oleic acid results in their improved dispersion in organic solvents like chloroform and dichloromethane.

Hysteresis and Reversible Cold Inactivation of Maize Phosphoenolpyruvate Carboxylase

1990 ◽  
Vol 45 (1-2) ◽  
pp. 42-46 ◽  
Author(s):  
Leszek A. Kleczkowski ◽  
Gerald E. Edwards
Keyword(s):  
Zea Mays ◽  
Steady State ◽  
Low Temperature ◽  
Protein Concentration ◽  
Zea Mays L ◽  
Stable Form ◽  
Pep Carboxylase ◽  
High Ph ◽  
Hysteretic Effect ◽  
Cold Inactivation

Abstract Maize (Zea mays L.) leaf phosphoenolpyruvate (PEP) carboxylase (PEPCase) (EC 4.1.1.31) showed a lag in activity when assayed after storage at 0-4 °C. The lag was promoted by high pH on storage (7.8 -8.5) and was observed over a range of assay pH (7.1 -8.5). Thermal reacti­vation of the cold-stored enzyme by assay temperature (18 °C) accounted for most of the hysteretic effect, but presence of PEP in the reaction mixture was required to completely eliminate the lag. Based on steady-state rates after the lag, stability of PEPCase in the cold was inde­pendent of protein concentration . It is suggested that low temperature and high pH induce a change in the oligomerization state of PEPCase, resulting in a less active but relatively stable form of the enzyme. The lag probably reflects a reversal of this process, promoted by assay temperature and presence of PEP.

scholarly journals Treatment of Cells and Tissues with Chromate Maximizes Mitochondrial 2Fe2S EPR Signals

2019 ◽  
Vol 20 (5) ◽  
pp. 1143 ◽  
Author(s):  
William Antholine ◽  
Jeannette Vasquez-Vivar ◽  
Brendan Quirk ◽  
Harry Whelan ◽  
Pui Wu ◽  
...  
Keyword(s):  
Steady State ◽  
Low Temperature ◽  
Complex I ◽  
White Blood Cells ◽  
Steady State Concentration ◽  
Complex Ii ◽  
Epr Method ◽  
Epr Signal ◽  
State Concentration ◽  
Terminal Cluster

In a previous study on chromate toxicity, an increase in the 2Fe2S electron paramagnetic resonance (EPR) signal from mitochondria was found upon addition of chromate to human bronchial epithelial cells and bovine airway tissue ex vivo. This study was undertaken to show that a chromate-induced increase in the 2Fe2S EPR signal is a general phenomenon that can be used as a low-temperature EPR method to determine the maximum concentration of 2Fe2S centers in mitochondria. First, the low-temperature EPR method to determine the concentration of 2Fe2S clusters in cells and tissues is fully developed for other cells and tissues. The EPR signal for the 2Fe2S clusters N1b in Complex I and/or S1 in Complex II and the 2Fe2S cluster in xanthine oxidoreductase in rat liver tissue do not change in intensity because these clusters are already reduced; however, the EPR signals for N2, the terminal cluster in Complex I, and N4, the cluster preceding the terminal cluster, decrease upon adding chromate. More surprising to us, the EPR signals for N3, the cluster preceding the 2Fe2S cluster in Complex I, also decrease upon adding chromate. Moreover, this method is used to obtain the concentration of the 2Fe2S clusters in white blood cells where the 2Fe2S signal is mostly oxidized before treatment with chromate and becomes reduced and EPR detectable after treatment with chromate. The increase of the g = 1.94 2Fe2S EPR signal upon the addition of chromate can thus be used to obtain the relative steady-state concentration of the 2Fe2S clusters and steady-state concentration of Complex I and/or Complex II in mitochondria.

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