The structure of amorphous SiO2 exposed to ArF excimer laser irradiation was examined. Threshold fluence for causing ablation with a single pulse depended on sample preparation: more specifically, 1 J/cm2 for thermally grown SiO2 films on silicon and 2.5 J/cm2 for bulk SiO2. It was found that the bond angle of Si-O-Si was reduced by irradiation near the interface of thermally grown SiO2 films. In contrast, evolution of the bond angle by irradiation was absent in both the bulk SiO2 and SiO2 film-near the top surface, even though the concentration of puckered four-membered rings deduced from Raman spectra dramatically increased. It is assumed that planar three-membered rings were generated in the SiO2 thin layer near the interface, and puckered four-membered rings were generated in the bulk SiO2. The concentration of both the Si3+ and Si2+ structure was increased at a fluence of 800 mJ/cm2 with an increasing number of pulses, although generation of both was absent at higher fluence for a single pulse. The author proposes that the structure of SiO2 is created by flash heating and quenching by pulse laser irradiation. Structural similarities were found between the irradiated SiO2 and SiO2 at high temperatures. 相似文献
Aliphatic dicarboxylic acid/aliphatic diol‐derived polyesters, poly(butylene succinate) and poly(butylene succinate/adipate), have been hydrolytically degraded in the melt in high‐temperature and high‐pressure water over a wide temperature range of 180–300 °C for periods of up to 30 min. The formation/decomposition of succinic acid (SA), adipic acid (AA), and butane‐1,4‐diol (BD), plus the molecular weight change of PBS and PBSA were then investigated. SA and AA were recovered at maximum yields of 65–80%, whereas BD was recovered at a maximum yield of only 30%, probably because of its decomposition. The obtained results were compared with those reported for aliphatic hydroxycarboxylic acid‐derived polyesters and aromatic dicarboxylic acid/aliphatic diol‐derived polyesters.
The heterotrich ciliate Blepharisma japonicum produces red pigment blepharismins, which function as self-defense toxin against predators and as a photoreceptor for step-up photonegativity. The dibenzoperylenequinone moiety of blepharismins was shown to be biosynthesized via the polyketide pathway. In this paper, the starter units of the biosynthetic pathway of blepharismins were determined to be isovaleryl-CoA and butyryl-CoA by HPLC, LC/ESI-MS, and 1H and 2H NMR analyses of the pigments obtained from feeding experiment of l-leucine or sodium butyrate in excess and deuterium-labeled l-leucine. 相似文献
Nickel pincer complex 1 was prepared by the treatment of nickel pincer 2 with AgBF4. Cationic nickel pincer complex 1 was air-stable and easy to handle, and was successfully applied to Michael addition and Mizoroki-Heck reaction. 相似文献
A simple and highly sensitive method called stir bar sorptive extraction (SBSE) and thermal desorption (TD)-gas chromatography-mass spectrometry (GC-MS), which is used for the determination of trace amounts of 5-chloro-2-(2,4-dichlorophenoxy)phenol (triclosan) in river water samples, is described. A stir bar coated with polydimethylsiloxane (PDMS) is added to a 10mL water sample and stirring is carried out for 120min at room temperature (25 degrees C) in a vial. Then, the PDMS stir bar is subjected to TD-GC-MS. The detection limit of triclosan is 5ngL(-1) (ppt). The method shows linearity over the calibration range (0.02-20mugL(-1)) and the correlation coefficient is higher than 0.997 for triclosan standard solution. The recovery of triclosan in river water samples ranges from 91.9 to 108.3% (RSD: 4.0-7.0%). This simple, accurate, sensitive, and selective analytical method may be used in the determination of trace amounts of triclosan in river water samples. 相似文献
A method for mercury analysis and speciation in drinking water was developed, which involved stir bar sorptive extraction (SBSE) with in situ propyl derivatization and thermal desorption (TD)-GC-MS. Ten millilitre of tap water or bottled water was used. After a stir bar, pH adjustment agent and derivatization reagent were added, SBSE was performed. Then, the stir bar was subjected to TD-GC-MS. The detection limits were 0.01 ng mL(-1) (ethylmercury; EtHg), 0.02 ng mL(-1) (methylmercury; MeHg), and 0.2 ng mL(-1) (Hg(II) and diethylmercury (DiEtHg)). The method showed good linearity and correlation coefficients. The average recoveries of mercury species (n=5) in water samples spiked with 0.5, 2.0, and 6.0 ng mL(-1) mercury species were 93.1-131.1% (RSD<11.5%), 90.1-106.4% (RSD<7.8%), and 94.2-109.6% (RSD<8.8%), respectively. The method enables the precise determination of standards and can be applied to the determination of mercury species in water samples. 相似文献
A method for the simultaneous measurement of benzophenone (BP) sunscreen compounds, its derivatives 2,4-dihydroxybenzophenone (BP-1), 2-hydroxy-4-methoxybenzophenone (BP-3), 2-hydroxy-4-methoxy-4'-methylbenzophenone (BP-10), 2-hydroxybenzophenone (2OH-BP), 3-hydroxybenzophenone (3OH-BP) and 4-hydroxybenzophenone (4OH-BP), in water samples was developed using stir bar sorptive extraction (SBSE) with in situ derivatization followed by thermal desorption (TD)-gas chromatography-mass spectrometry (GC-MS). The detection limit is 0.5-2 ng L(-1) (ppt) for the seven BPs. The method shows good linearity and the correlation coefficients are equal to or higher than 0.990 for all the analyte. The average recoveries of BPs range from 102.0 to 128.1% (RSD<15.4%, n=6). Trace amounts of BPs in river water samples were determined by the present method. 相似文献
To investigate the solid-state complexation of nitrogen-bridged calixarene analogues, azacalix[7]arene heptamethyl ether 1 has been prepared by applying a "5 + 2"-fragment coupling approach using Buchwald-Hartwig aryl amination reaction aided by our previously devised temporal N-silylation protocol. X-ray crystallographic analysis revealed that azacalix[7]arene 1 adopted a highly distorted 1,2-alternate conformation in the solid state as a result of intramolecular NH/O hydrogen bonding interactions and steric repulsion between the methoxy groups. In the crystal, molecules of 1 are mutually interacted by intermolecular NH/O and CH/pi interactions to establish one-dimensional (1D) hexane-filled nanochannel crystal architecture. Similarly to our recently reported azacalix[6]arene 2, the desolvated crystalline powder material of 1 was capable of selectively and rapidly adsorbing CO2 among the four main components of the atmosphere. The adsorption capacity of 1 for CO2 nearly doubled as compared to that of 2 because of the formation of the 1D nanochannel with almost twice the volume of the latter. 相似文献
A novel water‐soluble N‐methyl‐D‐aspartate (NMDA) receptor antagonist ATGDMAP 1 as synthesized and the effect of 1 on NMDA receptors was studied using voltage‐clamp recordings of recombinant NMDA receptors expressed in Xenopus oocytes. The compound 1 inhibited macroscopic currents in NR1/NR2A, NR1/NR2B, NR1/NR2C and NR1/NR2D receptor subtypes in oocytes voltage‐clamped at ‐70 mV. Mutant NR1/NR2B receptors containing NR1(T648A) or NR1(T648S) had very large holding currents when voltage‐clamped at ‐70 mV compared to that of wild‐type NMDA receptors, because these mutants generate constitutively open channels. ATGDMAP 1 and Mg2+, a channel blocker of the NMDA receptor, reduced the large holding currents needed for mutant NMDA receptors. These data indicate that ATGDMAP 1 directly acts on the channel pores of the NMDA receptor. 相似文献
Chiral trianglamine-Cu(OAc)2 complex was found to be an efficient catalyst for enantioselective Henry reaction between nitromethane and various aldehydes to provide β-hydroxynitoroalkanes with high enantiomeric excesses under solvent-free conditions. 相似文献