Ultraviolet Irradiation of Rubber

1940 ◽  
Vol 13 (3) ◽  
pp. 549-556 ◽  
Author(s):  
P. S. Srinivasan
Keyword(s):  
Ultraviolet Light ◽  
Ultraviolet Irradiation ◽  
Polar Solvent ◽  
Solvent Molecule ◽  
High State ◽  
Polar Solvents ◽  
Absorption Of Light ◽  
Before And After ◽  
Tentative Explanation ◽  
Absorption Phenomenon

Abstract The absorption of light by rubber when dissolved in polar and non-polar solvents was measured before and after exposing the solutions to ultraviolet light in the absence of air. It was found that irradiation with ultraviolet light makes rubber more transparent when in non-polar solvents and less transparent when in polar solvents. The state of rubber in solution is reviewed in the light of present-day knowledge, and a tentative explanation of the absorption phenomenon is suggested on the assumption that the rubber molecule in a polar solvent is depolymerized by the field of the solvent molecule and that ultraviolet light produces both polymerization and depolymerization of rubber, according as rubber initially is in a low or high state of polymerization. A probable support to this concept from measurements of viscosity is indicated.

scholarly journals Recoverable Phospha-Michael Additions Catalyzed by a 4-N,N-Dimethylaminopyridinium Saccharinate Salt or a Fluorous Long-Chained Pyridine: Two Types of Reusable Base Catalysts

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 1159
Author(s):  
Eskedar Tessema ◽  
Vijayanath Elakkat ◽  
Chiao-Fan Chiu ◽  
Jing-Hung Zheng ◽  
Ka Long Chan ◽  
...  
Keyword(s):  
Michael Addition ◽  
Polar Solvent ◽  
Addition Reaction ◽  
High Yield ◽  
Addition Reactions ◽  
Polar Solvents ◽  
Unsaturated Bond ◽  
Base Catalysts ◽  
Michael Additions

Phospha-Michael addition, which is the addition reaction of a phosphorus-based nucleophile to an acceptor-substituted unsaturated bond, certainly represents one of the most versatile and powerful tools for the formation of P-C bonds, since many different electrophiles and P nucleophiles can be combined with each other. This offers the possibility to access many diversely functionalized products. In this work, two kinds of basic pyridine-based organo-catalysts were used to efficiently catalyze phospha-Michael addition reactions, the 4-N,N-dimethylaminopyridinium saccharinate (DMAP·Hsac) salt and a fluorous long-chained pyridine (4-Rf-CH2OCH2-py, where Rf = C11F23). These catalysts have been synthesized and characterized by Lu’s group. The phospha-Michael addition of diisopropyl, dimethyl or triethyl phosphites to α, β-unsaturated malonates in the presence of those catalysts showed very good reactivity with high yield at 80–100 °C in 1–4.5 h with high catalytic recovery and reusability. With regard to significant catalytic recovery, sometimes more than eight cycles were observed for DMAP·Hsac adduct by using non-polar solvents (e.g., ether) to precipitate out the catalyst. In the case of the fluorous long-chained pyridine, the thermomorphic method was used to efficiently recover the catalyst for eight cycles in all the reactions. Thus, the easy separation of the catalysts from the products revealed the outstanding efficacy of our systems. To our knowledge, these are good examples of the application of recoverable organo-catalysts to the DMAP·Hsac adduct by using non-polar solvent and a fluorous long-chained pyridine under the thermomorphic mode in phospha-Michael addition reactions.

The influence of acridine dyes and caffeine on recovery from ultraviolet damage in Eudorina elegans

1975 ◽  
Vol 21 (11) ◽  
pp. 1849-1854 ◽  
Author(s):  
C. L. Kemp ◽  
K. M. Malloy
Keyword(s):  
Dna Synthesis ◽  
Acridine Orange ◽  
Ultraviolet Light ◽  
Ultraviolet Irradiation ◽  
Repair Process ◽  
Repair System ◽  
Acridine Dyes ◽  
Dark Survival ◽  
High Doses ◽  
Ultraviolet Damage

Caffeine and the acridine dyes, acridine orange and acriflavine, were used to examine the repair potential in Eudorina elegans following ultraviolet irradiation. Acridines blocked photoreactivation primarily as a result of absorption of photoreactivating wavelengths, but acridines did not influence dark survival. Therefore, an acridine-sensitive excision–resynthesis–repair process is absent in Eudorina.Caffeine decreased both dark and light survival, the latter only after relatively high doses of ultraviolet light were used for inactivation. The caffeine-sensitive repair process appears to function most actively when the organisms are engaged in DNA synthesis, indicating that a postreplication–repair system exists in Eudorina. However, the data suggest that a repair system not associated with the DNA synthetic phases may also exist.

Effects of ultraviolet light on synchronized Chinese hamster ovary cells; potentiation by hydroxyurea

1977 ◽  
Vol 28 (1) ◽  
pp. 29-48
Author(s):  
K. Burg ◽  
A.R. Collins ◽  
R.T. Johnson
Keyword(s):  
Dna Synthesis ◽  
Ultraviolet Light ◽  
Hela Cells ◽  
Chinese Hamster Ovary ◽  
Ultraviolet Irradiation ◽  
Chromosome Structure ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Ovary Cells

We have examined the effects of hydroxyurea on u.v.-irradiated Chinese hamster CHO-KI cells. Ultraviolet irradiation followed by incubation with hydroxyurea causes only slight disruption of DNA and chromosome structure in CHO-KI cells compared with HeLa cells. There is, however, a clear potentiation by hydroxyurea of the u.v. killing of CHO-KI cells, which is most pronounced at those points in the cycle which are reported to have small DNA precursor pools. This potentiation is reduced when DNA precursors are provided together with hydroxyurea. These data are discussed in terms of an uncoupling of excision and repair DNA synthesis.

Ultrastructural Changes in Euglena After Ultraviolet Irradiation

1973 ◽  
Vol 13 (3) ◽  
pp. 799-809
Author(s):  
A. MICHAELS ◽  
A. GIBOR
Keyword(s):  
Ultraviolet Light ◽  
Ultraviolet Irradiation ◽  
Euglena Gracilis ◽  
Structural Changes ◽  
Ultrastructural Changes ◽  
Electron Microscopic ◽  
Bleaching Process ◽  
In Cells

The structural changes associated with the ultraviolet-induced bleaching of light-grown cells of Euglena gracilis were investigated. Our light- and electron-microscopic observations of the bleaching process indicate that there is a continuity of plastid structure in cells 5 generations after receiving a bleaching dose of ultraviolet light. There seems to be a continuous dilution of the plastid thylakoids and a decrease in plastid size in the bleaching cells. There also seems to be a change in the position of the plastids in relation to the mitochondria in the bleaching cells. The plastids and possibly the mitochondria are the only organelles which are affected by the ultraviolet irradiation. The continuity of plastids in bleaching cells of Euglena is discussed in relation to the proposed effect of the ultraviolet light.

scholarly journals COUNTERACTING THE RETARDING AND INHIBITORY EFFECTS OF STRONG ULTRAVIOLET ON FUCUS EGGS BY WHITE LIGHT

1942 ◽  
Vol 25 (3) ◽  
pp. 391-397 ◽  
Author(s):  
D. M. Whitaker
Keyword(s):  
Ultraviolet Light ◽  
White Light ◽  
Ultraviolet Irradiation ◽  
Wave Length ◽  
Considerable Degree ◽  
Inhibitory Effects ◽  
Degree Of Recovery ◽  
Damaging Effects

1. Strong dosages (20,000–50,000 ergs per mm.2) of ultraviolet light, predominantly of the wave-length 2537 Å, greatly retard and inhibit the development of rhizoids in Fucus eggs irradiated at about 8 hours after fertilization. 2. If white light shines on the eggs after the irradiation by ultraviolet is terminated, the white light causes a considerable degree of recovery from the retarding and inhibiting effects. 3. If strong white light shines on the eggs during the ultraviolet irradiation, its effect is even more marked in protecting the cells from the damaging effects of the ultraviolet.

Evidences of Conformational Fluctuations of 2-methylaminofluorenone and 2-dimethylaminofluorenone in Polar Solvents

2004 ◽  
Vol 59 (3) ◽  
pp. 105-112 ◽  
Author(s):  
M. Józefowicza ◽  
J. R. Heldta ◽  
J. Heldta ◽  
J. Heldta
Keyword(s):  
Fluorescence Spectra ◽  
Polar Solvent ◽  
Reorganization Energy ◽  
Outer Sphere ◽  
Fluorescence Decay ◽  
Absorption And Fluorescence Spectra ◽  
Exponential Functions ◽  
Polar Solvents ◽  
Ground State Dipole Moment ◽  
Reorganization Energies

The absorption and fluorescence spectra of 2-methylaminofluorenone (2MAFl) and 2-dimethylaminofluorenone (2DMAFl) were determined at 293 K in a variety of solvents with different polarities. The spectral data were used, in combination with the 2MAFl and 2DMAFl ground state dipole moment (μg), to evaluate μe of the S1 state, to determine the outer-sphere solvent reorganization energy λouter, and the intramolecular reorganization energies: λ1 (associated with vibrations for which hv < kT) and λi(hv > kT). At 77 K the fluorescence spectra in a non-polar solvent are shifted to longer wavelengths. In polar solvents, for both molecules the behavior is opposite. The fluorescence decay data for 2MAFl and 2DMAFl in non-polar solvents are very well fitted by oneexponential functions, while in polar solvents by two-exponential functions. The spectroscopic data distinctly show that both studied molecules in polar solvents form an inhomogeneous emitting system.

Urine TRH immunoreactivity in hypothyroid and hyperthyroid patients

1984 ◽  
Vol 105 (4) ◽  
pp. 482-486 ◽  
Author(s):  
Anna-Stina Suhonen ◽  
Juhani Leppäluoto ◽  
Jorma Salmi
Keyword(s):  
Healthy Subjects ◽  
Ammonium Acetate ◽  
Polar Solvent ◽  
Primary Hypothyroidism ◽  
Exchange Chromatography ◽  
Reverse Phase ◽  
Before And After ◽  
Hypothyroid Patients ◽  
Hyperthyroid Patients ◽  
Serum Tsh

Abstract. Urine samples from 8 healthy subjects, from 16 patients with primary hypothyroidism and 8 patients with Graves' hyperthyroidism were pre-purified in SP-Sephadex-C-25 cation-exchange-chromatography, subjected to reverse phase high-pressure liquid chromatography (HPLC) with 0.01 M ammonium acetate pH 4 as a polar and propanol as a non-polar solvent with a 1%/min gradient and assayed in our TRH radioimmunoassay. Urine TRH-immunoreactivity levels were measured before and after 3 months of treatment with thyroxine or methimazole. The urine TRH-levels in healthy subjects were 5.5 ± 1.4 ng/l (mean ± sem, n = 8). In the hypothyroid patients, the urine TRH levels were 50.6 ±40 ng/l before and 71.7 ± 45.3 ng/l after 3 months of treatment with thyroxine. These values did not significantly differ from those in healthy subjects. The large variations were due to highly elevated values in 3 patients. In 2 hypothyroid patients with initially high urine TRH values, 67 and 657 ng/l, urine TRH was measured 5 and 18 months later and was found to have decreased to 5 and 11 ng/l. In the hyperthyroid patients, urine TRH levels were 10.3 ± 3.9 ng/l before and 8.9 ± 3.3 ng/l after the treatment with methimazole and did not differ significantly from the levels in healthy subjects. After 3 months of treatment, the hyper- and the hypothyroid patients were euthyroid. Our results show, that, except in 2 hypothyroid patients, there does not appear to be any relationship between urine TRH levels and serum TSH or thyroid hormone levels in hypothyroid and hyperthyroid patients.

scholarly journals Association between Washing Residue on the Feet and Tinea Pedis in Diabetic Patients

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Kimie Takehara ◽  
Ayumi Amemiya ◽  
Yuko Mugita ◽  
Yuichiro Tsunemi ◽  
Yoko Seko ◽  
...  
Keyword(s):  
Ultraviolet Light ◽  
Tinea Pedis ◽  
Educational Programs ◽  
Foot Ulcers ◽  
Diabetic Patients ◽  
Before And After ◽  
Foot Washing

Tinea pedis (TP) may lead to the development of foot ulcers in diabetic patients; thus, its prevention in diabetic patients is important. TP occurs after dermatophytes on the skin scales of TP patients attach to the feet. Therefore, it is necessary to remove the scales and dermatophytes, and this can be performed using various methods, including foot washing. This study aimed to objectively examine the association between the presence of TP and foot-washing habits. We included 33 diabetic patients, and, of these, 17 had TP. The presence of washing residue on the feet was determined by applying a fluorescent cream to the participants’ feet, and images of the feet were captured under ultraviolet light before and after foot washing. Our results showed that diabetic patients with TP had higher levels of washing residue on their feet than those without TP. The importance of washing feet to prevent TP needs to be emphasized through educational programs for diabetic patients. Furthermore, the development of an effective foot-washing technique is essential.

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