Initial mode of radical pair formation in n-hydrocarbons irradiated at 1.5 and 4.2 K

The ESR spectra of X-irradiated (at 1.5 and 4.2 K) single crystals of n-decane-d₂₂, n-decane-h₂₂ and their mixtures have been measured at 1.5 and 4.2 K. It is concluded that almost all alkyl radicals are inherently formed in pairs in a fairly random fashion and that the spacial distribution of the radicals depends on the irradiation temperatures. In the crystal of n-decane-d₂₂, a 1,3-carbon intrachain radical pair is identified together with a number of very close interchain pairs which are formed between almost all kinds of the first neighboring chains. The crystal of n-decane-h₂₂ gives considerably larger spacial distribution of radicals, indicating a remarkable mass effect on the radical pair formation.     

Radiation-Induced Polymerization of Tetrafluoroethylene

Polymerization of tetrafluoroethylene was carried out in bulk at low temperatures by initiation with γ-rays from a ⁶⁰ Co source. It was found that a remarkable postpolymerization takes place even in the liquid phase. Kinetical analysis has been made of the in-source and postpolymerizations. An activation energy of 2.7 kcal/mole was obtained for the in-source polymerization and 10.3 kcal/mole for the postpolymerization. The long lifetime of polymer radicals in the liquid phase at -78°C seems to be due to the slow recombination rate of the polymer radicals, based on the rodlike shape of the polymer radicals.     

Direct detection of nanoparticles and components in smoke by time-of-flight mass spectrometry with soft plasma ionization

A new system combining a soft plasma ionization (SPI) source with a time-of-flight mass spectrometer (TOFMS) has been successfully developed and applied to direct and on-line analysis of nanoparticles in smoke generated during combustion of mosquito coils with no sample preparation. The mass spectra of nanoparticles in smoke were examined in conjunction with the effects of species, pressure and current of the SPI discharge on fragmentation. The results indicated that a maximum mass of m/z 1576 was detectable when the following optima SPI conditions were satisfied: a He gas pressure of 1000 Pa with an air pressure of 1600 Pa and a discharge current of 110 mA. Furthermore, considering the results for emission spectra we suppose an ionization mechanism of SPI in which excitation and ionization of nitrogen molecule is promoted by the presence of He gas, leading to promote the smoke sample ionization. The mass spectrum of nanoparticles showed specific patterns of a peak interval of 74 which were assigned to triacetylene (1,3,5-hexatriyne). The most abundant peak in the mass spectrum, at m/z 452, was assigned to triacontanoic acid.     

Identification of gas emanated from human skin: methane, ethylene, and ethane.

We investigated whether methane, ethylene and ethane gas can be detected in gas emanating from human skin, which is called skin gas. Skin gas was collected with a homemade stainless-steel trap system, which was cooled with liquid nitrogen, and analyzed with a gas chromatograph fitted with a flame ionization detector (FID). Skin-gas samples were obtained by covering a hand for 30 min with a polyfluorovinyl bag in which pure helium gas was introduced. The bag, the trap system and GC were set up online to avoid any contamination by air. Methane, ethylene and ethane in skin gas were successfully collected at an average amount emanated for 30 min (from ten subjects) of 150 +/- 63, 20 +/- 11 and 17 +/- 8 [mean +/- SD] pg/cm2, respectively.     

Pulse radiolysis study on free radical scavenger edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one)

The reactions between edaravone and various one-electron oxidants such as (*)OH, N(3)(*), Br(2)(-), and SO(4)(-), have been studied by pulse radiolysis techniques. The transient species produced by the reaction of edaravone with (*)OH radical shows an absorption band with lambda(max)=320 nm, while the oxidation by N(3)(*), Br(2)(-), SO(4)(-) and CCl(3)OO(*) results in an absorption band with lambda(max)=345 nm. Different from the previous reports, the main transient species by the reaction of edaravone with (*)OH radical in the absence of O(2) is attributed to OH-adducts. At neutral condition (pH 7), the rate constants of edaravone reacting with (*)OH, N(3)(*), SO(4)(-), CCl(3)OO(*), and e(aq)(-) are estimated to be 8.5x10(9), 5.8x10(9), 6x10(8), 5.0x10(8) and 2.4x10(9)dm(3)mol(-1)s(-1), respectively. From the pH dependence on the formation of electron adducts and on the rate constant of edaravone with hydrated electron, the pK(a) of edaravone is estimated to be 6.9+/-0.1.     

Layered hydroxide nickel benzoates: Hydrothermal synthesis, structure characterization, and exfoliation reaction

Mussel adhesive proteins have received considerable attention due to their ability to bind strongly to many surfaces under water. Key structural features of these proteins include a large number of 3,4-dihydroxyphenyl-L-ALANIN (DOPA) and positively charged lysine residues. We elucidate the effects of solution pH, in the pH range 3-9, on adsorption kinetics, adsorbed amount, and layer structure on silicon oxynitride by employing Dual Polarization Interferometry. As a comparison, the cationic globular protein lysozyme was also investigated. The zeta-potential of the silicon oxynitride substrate was determined as a function of pH, and the isoelectric point was found to be below pH 3. Mefp-1 is positively charged at pH<10, and thus, the protein is expected to have an electrostatic attraction for the surface at all pH values investigated. The adsorbed amount and the initial adsorption rate were found to increase with solution pH, and no significant desorption occurred due to rinsing with pure water. The layer thickness after rinsing was 3-4 nm, except at pH 3, where the adsorption was limited to a small amount. Covalent cross-linking of the Mefp-1 layer with NaIO(4) resulted in a small but significant compaction and increase in refractive index of the layer. The results are discussed in terms of the role of DOPA and electrostatic interactions for the adsorption of Mefp-1 to silicon oxynitride.     

Grafting of Tetrafluoroethylene onto Polyethylene by Pre-irradiation Technique

Grafting of tetrafluoroethylene onto polyethylene was carried out by a pre-irradiation technique. It was found that grafting proceeds very rapidly at -35°C in the liquid phase of tetrafluoroethylene. Takathene, which was prepared by a radiation process at Takasaki Radiation Chemistry Research Establishment, was found to be most suitable for grafting compared to other polyethylenes. The specific surface is extremely high in the Takathene, and this may be the most important reason for the high grafting speed. On the other hand, IR measurements of the grafted copolymers showed a characteristic absorption band at 1110 cm-1 which may be attributed to the structure of the grafting (branching) position. It was also found that grafted polytetrafluoroethylene can be crystallized during grafting. This is the first case of grafted polymers being in a crystalline state.     

Detection of nanoparticles and components in smoke by time-of-flight mass spectrometry

A time-of-flight mass spectrometry (TOFMS) with a newly laboratory-made sampling cone interface fitted to an atmospheric pressure chemical ionization (APCI) positive ion source was successfully applied to easy, rapid on-line measurements of nanoparticles and components generated during combustion. The mass spectra for smoke from a mosquito coil ranged up to m/z 1202, corresponding to 1.2 nm with the carboneous material density as graphite 2.2 g cm⁻³. Typical m/z peaks were assigned to such synthetic pyrethroids, as d-allethrin and d-tetramethrin, at m/z 303 and 332, respectively. A specific pattern with a peak-to-peak interval of 74 was recognized in the higher mass range. The interval of 74 was confirmed by measuring with a standard silica solution in a positive ion mode using a conventional APCI interface under the same APCI conditions. The mass spectrum of the silica solution had a pattern with peak interval of 44 which was assigned to SiO. These results indicate that the pattern with an interval of 74 in the mass spectrum of the mosquito coil smoke is sample-derived peak. We assumed that the interval of m/z 74 is assigned to identified as triacetylene (1,3,5-hexatriyne) that is generated during the combustion.     

Phase diagram of the fcc(1 1 0) surfaces with adsorbate-induced missing-row reconstructions

The phase diagram of the fcc(1 1 0) surfaces with missing-row reconstructions induced by adatoms, is calculated by use of the Blume–Emmery–Griffiths model. In the model, we introduce adatom–adatom interactions to determine surface structures and dipole–dipole interactions to describe the effect of zigzag adsorption. The interactions between nearest-neighbor (NN) and next-nearest-neighbor (NNN) rows are considered. The calculation of the temperature versus adatom chemical potential phase diagram is performed using mean-field approximation. It is indicated that if NN and NNN interactions are competitive, there appear either dipole or coverage modulated (incommensurate) phases at high temperatures for a wide range of the interactions.     

Radiation-Induced Copolymerization of Chlorotrifluoroethylene with Olefins

The copolymerizations of chlorotrifluoroethylene with propylene and isobutylene were carried out at 0 ～ ?78°C by γ-ray irradiation. It was found that alternating copolymers are obtained over a wide range of monomer composition for both systems. The alternating copolymer of chlorotrifluoroethylene with isobutylene was found to be highly crystalline, but the copolymer of chlorotrifluoroethylene with propylene was found to be amorphous. The copolymerizations were considered to proceed via a radical mechanism, but in the case of the isobutylene-chlorotrifluoroethylene system a cationic polymerization also takes place simultaneously at ?78°C.