The photochemistry of 2-furaldehyde vapour. II. Photodecomposition: direct photolysis at 253.7 and 313 nm and Hg(3P1)-sensitized decomposition

1976 ◽  
Vol 54 (19) ◽  
pp. 3095-3101 ◽  
Author(s):  
A. Gandini ◽  
J. M. Parsons ◽  
R. A. Back
Keyword(s):  
Quantum Yield ◽  
Pressure Dependence ◽  
Low Pressure ◽  
Major Product ◽  
The Other ◽  
Direct Photolysis

The photolysis of furaldehyde vapour at 253.7 nm, 65 °C, and pressures from about 0.2 to 7 torr, produces CO, propyne, allene, furan, cyclopropene, CO2, and C2H2. The quantum yield of CO approaches 2 at low pressure and decreases towards zero with increasing pressure of furaldehyde or added CO2. Yields of the other products also decrease but show a more complex pressure dependence. A mechanism involving excited furaldehyde and excited C4H4O and C3H4 intermediates is suggested.The Hg(3P1)-photosensitized decomposition gives products very similar to those of the direct photolysis. Photolysis at 313 and 366 nm also leads to similar products but in much lower yields, with the major product, CO, having a quantum yield of about 0.01. Some photopolymerization was observed in all Systems.

Pressure Dependence of Product Yields in the Direct Photolysis of Methanol Vapor at 1849°Å

1973 ◽  
Vol 51 (1) ◽  
pp. 147-148 ◽  
Author(s):  
O. Sonia Herasymowych ◽  
Arthur R. Knight
Keyword(s):  
Quantum Yield ◽  
Exposure Time ◽  
Pressure Dependence ◽  
High Pressures ◽  
Yield Enhancement ◽  
Direct Photolysis ◽  
Methanol Vapor ◽  
Product Yields

Hydrogen and methane yields from the 1849 Å photolysis of methanol vapor in an all-quartz system have been investigated as a function of exposure time and pressure of CH3OH and added CO2.Product yields are decreased by the inert addend, and by the substrate itself at high pressures, in contrast to the collision-induced quantum yield enhancement reported to be occurring in this system.

scholarly journals Multiple actins in drosophila melanogaster

1979 ◽  
Vol 82 (1) ◽  
pp. 86-92 ◽  
Author(s):  
SJ Horovitch ◽  
RV Storti ◽  
A Rich ◽  
ML Pardue
Keyword(s):  
Body Wall ◽  
Flight Muscle ◽  
Cell Types ◽  
Major Product ◽  
The Other ◽  
Stable Form ◽  
Larval Body ◽  
Drosophila Cell ◽  
Muscle Tissues ◽  
Adult Abdomen

The tissue and developmental specificities of the three Drosophila isoactins, originally identified in primary myogenic cultures and in the permanent Schneider L-2 cell line, have been investigated. Of these three isoactins (I, II, and III), actins I and II are stable and actin III is unstable. Two-dimensional polyacrylamide gel electrophoretic analyses of total cellular extracts after 1-h [(35)S]methionine pulses were performed on a large variety of embryonic, larval, and adult muscle and nonmuscle tissues. The results suggest that isoactins II and III are generalized cellular actins found in all drosophila cell types. Actin I, on the other hand, is muscle-associated and is found exclusively in supercontractile muscle (such as larval body wall and larval and adult viscera) including primary myogenic cell cultures. Although actin I synthesis is not detectable during very early embryogenesis, it is detectable by 25 h and actin I is a major stable actin in all larval muscle tissues. Actin I is synthesized in reduced amounts relative to the other actins in late third instar larvae but is again a major product of actin synthesis in the adult abdomen. A stable actin species with the same pI as actin III has been identified in the adult thorax and appears to be unique to flight muscle tissue. This new stable form of thoracic actin may be the result of a stabilization of the actin III found in other tissues or may be an entirely separate gene product.

Hg(63P1)-sensitized decomposition of HNCO vapor and HNCO–H2 mixtures; the reaction of hydrogen atoms with HNCO

1968 ◽  
Vol 46 (4) ◽  
pp. 527-530 ◽  
Author(s):  
N. J. Friswell ◽  
R. A. Back
Keyword(s):  
Quantum Yield ◽  
Cross Section ◽  
Initial Step ◽  
Primary Process ◽  
Hydrogen Atoms ◽  
Direct Photolysis ◽  
A Value ◽  
The Cross

The Hg(63P1)-sensitized decomposition of HNCO vapor has been briefly studied at 26 °C with HNCO pressures from about 3 to 30 Torr. The products detected were the same as in the direct photolysis, CO, N2, and H2. The quantum yield of CO was appreciably less than unity, compared with a value of 1.5 in the direct photolysis under similar conditions. From this and other observations it is tentatively concluded that a single primary process occurs:[Formula: see text]From a study of the mercury-photosensitized reactions in mixtures of HNCO with H2, it was concluded that hydrogen atoms react with HNCO to form CO but not N2. The initial step is probably addition to form NH2CO. From the competition between reaction [1] and the corresponding quenching by H2, the cross section for reaction [1] was estimated to be 2.3 times that of hydrogen.

scholarly journals Diaminoterephthalate–α-lipoic acid conjugates with fluorinated residues

2019 ◽  
Vol 15 ◽  
pp. 981-991
Author(s):  
Leon Buschbeck ◽  
Aleksandra Markovic ◽  
Gunther Wittstock ◽  
Jens Christoffers
Keyword(s):  
Quantum Yield ◽  
Lipoic Acid ◽  
Photoelectron Spectroscopy ◽  
Functional Unit ◽  
Gold Surface ◽  
The Other ◽  
Self Assembled Monolayers ◽  
High Signal ◽  
Amidation Reaction ◽  
Assembled Monolayers

Two bifunctional diaminoterephthalate (DAT) fluorescence dyes were prepared in a three-step sequence including one deprotection reaction. One functional unit is α-lipoic acid (ALA) for binding the dye to gold surfaces. It was introduced to the DAT scaffold by an amidation reaction. The other functional unit is a para-(trifluoromethyl)benzyl group for facile detection of the surface-bound material by X-ray photoelectron spectroscopy (XPS). This residue was introduced by reductive amination of the DAT scaffold with the respective benzaldehyde derivative. In one compound (60% yield over three steps) the ALA unit is directly bound to the DAT as a relatively electron-withdrawing amide. In solution (CH2Cl2), this material shows strong fluorescence (quantum yield 57% with emission at 495 nm, absorption maximum at 420 nm). The other compound (57% yield over three steps) possesses a propylene spacer between the ALA and the DAT units for electronic decoupling, thus, bathochromic shifts are observed (absorption at 514 nm, emission at 566 nm). The quantum yield is, however, lower (4%). Self-assembled monolayers on a gold surface of both compounds were prepared and characterized by high-resolution XPS of the C 1s, O 1s, S 2p, N 1s and F 1s emissions. The high signal-to-noise ratios of the F 1s peaks indicated that trifluoromethylation is an excellent tool for the detection of surface-bound materials by XPS.

Zur Struktur der Schuster-Bande / On the Structure of the Schuster Band

1972 ◽  
Vol 27 (11) ◽  
pp. 1687-1688
Author(s):  
Roland Weisbeck
Keyword(s):  
Emission Spectrum ◽  
Polyatomic Molecule ◽  
Microwave Discharge ◽  
Low Pressure ◽  
The Other ◽  
Α Band

Abstract The emission spectrum of a low pressure microwave discharge in ammonia reveals the Schuster band between 5600 and 5700 Å superposed by many intense lines, about one half of which belong to the α-band of the NH2 radical. The other lines have not been identified; presumably, they may be ascribed to a polyatomic molecule consisting of N and H atoms.

scholarly journals Comparison of the degradation of molecular and ionic ibuprofen in a UV/H2O2 system

2018 ◽  
Vol 77 (9) ◽  
pp. 2174-2183 ◽  
Author(s):  
Rongkui Su ◽  
Liyuan Chai ◽  
Chongjian Tang ◽  
Bo Li ◽  
Zhihui Yang
Keyword(s):  
Quantum Yield ◽  
Rate Constant ◽  
Degradation Rate ◽  
Molecular Form ◽  
Degradation Kinetics ◽  
Dominant Role ◽  
Radical Scavenging ◽  
Operating Conditions ◽  
Direct Photolysis ◽  
H2o2 System

Abstract The advanced oxidation technologies based on •OH can effectively degrade the pharmaceutical and personal care products under operating conditions of normal temperature and pressure. In this study, direct photolysis of ibuprofen (IBU) is slow due to the relatively low molar extinction coefficient and quantum yield. Compared to direct photolysis, the degradation kinetics of IBU was significantly enhanced in the UV/H2O2 system, mainly by •OH radical mediated oxidation. In the UV/H2O2 system, the degradation rate of ionic IBU was slightly faster than that of the molecular form. Kinetic analysis showed that the second-order reaction rate constant of ionic IBU (5.51 × 109 M−1 s−1) was higher than that of the molecular form (3.43 × 109 M−1 s−1). The pseudo first-order rate constant for IBU degradation (kobs) increased with increasing H2O2 dosage. kobs can be significantly decreased in the presence of natural organic matter (NOM), which is due to (i) NOM radical scavenging effects (dominant role) and (ii) UV absorption. The degradation of IBU was inhibited by HCO3–, which was attributed to its scavenging effect. Interestingly, when NO3– was present in aqueous solution, a slight increase in the degradation rate was observed, which was due to NO3– absorbing photons to generate •OH at a low quantum yield. No obvious effects were observed when SO42 and Cl− were present.

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