Effect of ring substituents on the fluorescence spectra of substituted diarylcarbenes

1988 ◽  
Vol 66 (3) ◽  
pp. 491-494 ◽  
Author(s):  
J. C. Scaiano ◽  
D. Weir
Keyword(s):  
Free Radical ◽  
Temperature Dependence ◽  
Fluorescence Spectra ◽  
Excellent Correlation ◽  
Emission Data ◽  
The Difference

The fluorescence spectra of a series of ring-substituted diarylcarbenes have been examined. The solution spectra are generally red shifted by 25–30 nm with respect to the band positions in matrices at 77 K. The difference is believed to reflect emission from non-relaxed conformations at 77 K. Both electron-withdrawing and -donating substituents lead to red shifts in the emission. These shifts are essentially additive, and the carbene emission data show an excellent correlation with free radical fluorescence data for the corresponding diarylmethyl radicals. The temperature dependence of excited carbene lifetimes have been examined for a few representative examples.

PERBANDINGAN METODE EKSTRAKSI MASERASI DAN SOKLETASI TERHADAP AKTIVITAS ANTIOKSIDAN EKSTRAK ETANOL DAUN JAMBU BOL (Syzygium malaccense L.)

2017 ◽  
Vol 3 (1) ◽  
pp. 91
Author(s):  
Henny Nurhasnawati ◽  
Sukarmi Sukarmi ◽  
Fitri Handayani
Keyword(s):  
Antioxidant Activity ◽  
Free Radical ◽  
Vitamin C ◽  
Extraction Methods ◽  
Natural Antioxidant ◽  
Comparison Of Methods ◽  
Activity Test ◽  
Ic50 Value ◽  
The Difference ◽  
Free Radical Activity

Malay apple (Syzygium malaccense L.) is a plant that can be used for treatment. Antioxidants have the activity to reduce free radical compounds which is one of the causes of the emergence of various diseases in humans. The purpose of this study to determine the comparison of methods of maceration and socletation extraction of antioxidant activity of malay apple leaf. Research stages include sampling, plant determination, making of simplisia, maceration extraction and socletation with 70% ethanol solvent and determine the antioxidant activity by UV-Vis spectrophotometry with DPPH (1,1-diphenyl-2-picrylhydrazyl) as free radical. The parameter is IC50 value that is the concentration of antioxidant compound which can cause 50% loss of DPPH free radical activity. Although both methods show very strong antioxidant activity, it can be concluded that the difference in extraction methods has an effect on the antioxidant activity produced. The results of antioxidant activity test showed that socletation methods gave an average IC50 value of 37.67 ppm, this value is higher than maceration methods with an average IC50 value of 47.80 ppm. Malay apple leaf has the potential as a natural antioxidant, although it has a lower IC50 value than vitamin C which is 9.72 ppm.

Comparison of activated clotting times obtained using Hemochron and Medtronic analysers in patients receiving anti-thrombin therapy during cardiac catheterisation

2009 ◽  
Vol 101 (03) ◽  
pp. 535-540 ◽  
Author(s):  
Stanley Chia ◽  
Elizabeth M. Van Cott ◽  
Christopher O. Raffel ◽  
Ik-Kyung Jang
Keyword(s):  
Strong Association ◽  
Cardiac Catheterisation ◽  
Excellent Correlation ◽  
Heparin Group ◽  
Activated Clotting Time ◽  
Cardiac Procedures ◽  
Heparin Administration ◽  
Heparin Anticoagulation ◽  
The Difference ◽  
High Range

SummaryAccurate monitoring of anti-thrombin therapy with activated clotting time (ACT) is important to prevent thrombotic and haemorrhagic complications during cardiac catheterisation. Significant variability in ACT tests exists when different analysers are used. Our objective was to compare ACT results obtained using Hemochron→ and Medtronic ACT PLUS→ devices and anti-Xa activity in patients undergoing cardiac catheterisation. Thirty-two patients who received unfractionated heparin or argatroban therapy during cardiac catheterisation were enrolled. Blood sampling was performed to determine ACT values using Hemochron and Medtronic (with high-range cartridges) devices in all patients (n=130 pairs), and anti-Xa activity following heparin administration. In the heparin group, ACT tests (n=95 pairs) showed very good correlation (r=0.84, y=1.31x–0.81; p<0.001). However, Hemochron values were consistently higher and the difference more pronounced with increasing ACT (for ACT>150 sec, mean difference 65 ± 48 sec; p<0.001). Both Hemochron and Medtronic ACT tests correlated well with plasma anti-Xa levels (r=0.85, r=0.81, respectively; p<0.001); Hemochron ACT>300 sec corresponded to anti-Xa>1.48 IU/ml. With concomitant eptifibatide therapy, the divergence in ACT was greater compared to heparin alone. In the argatroban group, ACT tests (n=35 pairs) demonstrated excellent correlation (r=0.94, y=0.61x+79.9; p<0.001). In contrast to the heparin group, ACT values were higher with Medtronic compared to Hemochron. Therefore, despite good correlation between Hemochron and Medtronic ACT results, and strong association with anti-Xa activity, Medtronic ACT values were consistently lower compared to Hemochron following heparin anticoagulation. Paradoxically, Medtronic ACT results were higher after argatroban therapy. Understanding this discrepancy is crucial when using ACT to guide invasive cardiac procedures.

Evaluation of Low-Temperature Properties and the Fragility of Asphalt Binders with Non-Arrhenius Viscosity–Temperature Dependence

2005 ◽  
Vol 1901 (1) ◽  
pp. 44-51 ◽  
Author(s):  
Huachun Zhai ◽  
Delmar Salomon
Keyword(s):  
Temperature Dependence ◽  
Asphalt Binders ◽  
Arrhenius Behavior ◽  
Direct Tension ◽  
Different Temperatures ◽  
Rotational Viscosity ◽  
Liquid Fragility ◽  
The Difference ◽  
Critical Cracking Temperature ◽  
Experimental Values

Rotational viscosities of different asphalt binders were determined at temperatures between 80°C and 185°C. Viscosity–temperature dependence of asphalt binders was described with the use of the Vogel–Tammann–Fulcher (VTF) and the William–Landel–Ferry (WLF) equations. The Vogel temperature ( Tv) and the glass transition temperature ( Tg) for different asphalt binders were determined by fitting experimental values of viscosity at different temperatures with these two equations. For asphalt binders, the difference between Tv and Tg was about 40K. Effects of asphaltenes, aging, chemical modification, and polymer content on these temperatures were evaluated. As asphaltene content increased, both temperatures, Tv and Tg, increased. Different polymers showed different effects on these temperatures. The values of Tv and Tg were correlated with the critical cracking temperature ( Tcr) determined through use of a bending beam rheometer and a direct tension tester. The results suggested that the correlations between Tv, Tg, and Tcr could be used to determine Tcr from the rotational viscosity results tested at high temperature. With simple rotational measurements, a quick estimation of Tcr of asphalt binders could be obtained. Liquid fragility theory was also used to study Tg of asphalt binders. Parameters determined with the VTF and WLF equations indicated that asphalt binders behaved as fragile liquids because of their non-Arrhenius behavior in the temperature range studied.

scholarly journals Exploring the difference in xerogels and organogels through in situ observation

2018 ◽  
Vol 5 (1) ◽  
pp. 170492
Author(s):  
Binglian Bai ◽  
Zhiming Li ◽  
Haitao Wang ◽  
Min Li ◽  
Yukihiro Ozaki ◽  
...  
Keyword(s):  
Liquid Crystalline ◽  
Fluorescence Spectra ◽  
Chemical Properties ◽  
Columnar Structure ◽  
In Situ Observation ◽  
Physico Chemical ◽  
Aggregation Structure ◽  
Ft Ir ◽  
The Difference

Solvent–gelator interactions play a key role in mediating organogel formation and ultimately determine the physico-chemical properties of the organogels and xerogels. The ethanol organogels of 1,4-bis[(3,4,5-trihexyloxy phenyl)hydrazide]phenylene (TC6) were investigated in situ by FT-IR, Raman and fluorescence spectra, and XRD, and it was confirmed that the intermolecular interaction and aggregation structure of TC6 ethanol organogels were quite different from those of xerogels. Simultaneously, unprecedented phase transition from organogel to suspension upon heating was observed in ethanol organogel, and the suspension phase exhibited lytropic liquid crystalline behaviour with a rectangular columnar structure. This study may open the possibility to design new gelators with a new dimension of versatility.

Methodology for Measurement of Density of Liquid Oxides

2020 ◽  
Vol 7 (2) ◽  
Author(s):  
Jan Hrbek ◽  
Bence Mészáros ◽  
Mykhaylo Paukov ◽  
Martin Kudláč
Keyword(s):  
High Temperature ◽  
Temperature Dependence ◽  
Extreme Conditions ◽  
Nuclear Accidents ◽  
System A ◽  
Different Temperatures ◽  
Density Values ◽  
Properties Of Materials ◽  
The Difference

Abstract Measurement of physical properties of materials in extreme conditions, such as high temperature, is limited by technological challenges. Nevertheless, modeling of several phenomena relies on the existence of experimental data for their validation. In this study, a method suitable for determination of density in a liquid phase at high temperature is proposed and tested on Al2O3–ZrO2 system. A methodology for acquiring the temperature dependence of density for radioactive materials is proposed and is aimed to refine severe nuclear accidents modeling. The oxide was melted in an induction furnace with a cold crucible. The measurement was based on evaluation of the volume of the melt at different temperatures, in a range from 2100 to 2400 °C. The densities of the oxide in the solid-state and the skull-layer were measured using a pycnometer. A temperature dependence of the density was established and the results were compared with literature. The difference between existing data and the measured values in this work was less than 5%. Thus, the proposed methodology provides reliable density values in extreme conditions.

scholarly journals Temperature Dependence and Anisotropic Effects in the Thermal Properties of Hen Egg-White Lysozyme Crystals

Symmetry ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1279
Author(s):  
Syou Maki ◽  
Seiji Fujiwara ◽  
Seiichi Tanaka ◽  
Eka Erzalia ◽  
Mizuki Kato ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Thermal Properties ◽  
Temperature Dependence ◽  
Superconducting Magnet ◽  
Egg White ◽  
Hen Egg White Lysozyme ◽  
Egg White Lysozyme ◽  
Hen Egg White ◽  
The Difference ◽  
Hen Egg

We measured the thermal conductivity (λ) and thermal diffusivity (α) of tetragonal hen egg-white lysozyme (HEWL) crystals by the transient short-hot wire method. The crystals were grown by two different methods: Magnetically levitated crystals were realized with a superconducting magnet, the c-axis of which was perpendicularly orientated in the direction of the wire, and naturally grown crystals realized by the two-liquid method, grown randomly. We confirmed the temperature dependence in both the λ and α properties by measuring the variations in temperature and by statistical analysis. These properties differed slightly depending on the presence or absence of a magnetic field applied during the crystal growth. We hypothesize that the difference originated from the orientation of the crystals caused by the magnetic field. The statistical analyses demonstrated the possibility that asymmetric thermal conduction in the protein crystals provides anisotropic effects of the thermal properties.

scholarly journals Temperature dependence of Ti:Sapphire fluorescence spectra for the design of cryogenic cooled Ti:Sapphire CPA laser

2017 ◽  
Vol 25 (6) ◽  
pp. 6954 ◽  
Author(s):  
Harry Burton ◽  
Christopher Debardelaben ◽  
Wafa Amir ◽  
Thomas A. Planchon
Keyword(s):  
Temperature Dependence ◽  
Fluorescence Spectra
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