排序方式: 共有142条查询结果,搜索用时 15 毫秒
1.
M. S. Platz W. R. White D. A. Modarelli S. Celebi 《Research on Chemical Intermediates》1994,20(2):175-193
The photochemistry of diazirines and diazo compounds is not as simple as nitrogen extrusion and carbene formation. The C-H
bonds adjacent to the diazo and diazirine moieties can migrate in the excited state and produce stable products without the
benefit of a relaxed carbene intermediate. Additionally, cyclobutyl substituted systems exhibit carbon migration. It is unfortunate
that the products of photochemical rearrangement of precursor excited states are identical to the products of thermal rearrangement
of carbenes. This has prevented accurate measurement of the yield and absolute reactivity of alkylcarbenes. That pyridine
reacts selectively with carbenes and not with the excited states of their nitrogenous precursors has allowed the separation
of these two pathways and an appreciation of their relative importance with structural variation. 相似文献
2.
Serdar S. Celebi Gow-Jen Tsai George T. Tsao 《Applied biochemistry and biotechnology》1991,27(2):163-171
Immobilization of glucoamylase (EC 3.2.1.3) on Celite R649 bio-catalyst carrier for hydrolysis of maltose and maltodextrin has been investigated in both packed bed and recirculated batch reactors. The kinetics parameters on the hydrolysis of maltose were estimated from the packed bed reactor. It is found that this immobilized enzyme is as efficient as the soluble enzyme in catalyzing hydrolysis of maltose. However, it is less efficient than the soluble enzyme in hydrolyzing 30% (w/v) maltodextrin, giving a maximum dextrose equivalent (DE) value of 96.0% instead of 98.2%. 相似文献
3.
4.
The aim of this paper is to study the laser-induced backside wet cleaning techniques for glass substrates. Two kinds of laser cleaning techniques are proposed in this study. The first involves applying an Nd:YAG laser to the backside of the substrate which is submerged in water. A metal plate is placed below the glass substrate. Most of the laser energy will be absorbed by the metal plate. The metal then vaporizes the water and generates a turbulent bubble flow. The bubble flow removes the alumina particles from the surface of the glass substrate. The second involves using a CO2 laser to generate turbulent bubble flow to remove the particles. Both methods were successfully demonstrated for the removal of submicron particles of 0.5 μm in size. The phenomena of bubble generation and diffusion are presented in the paper. Because the laser is applied to the backside of the substrate, the damage due to the laser heat can be significantly reduced. The quality and efficient of the backside processing is better than those of the front side processing. The proposed techniques have great potential to provide an improved solution for glass cleaning. 相似文献
5.
The article describes the synthesis and extraction properties of a new chiral calix[4]arene Schiff base ligand 5, which has been synthesized from 5,17-diformyl-25,27-bis-(4-nitrobenzyloxy)-26,28-dihidroxycalix[4]arene (4) by treatment with (S)-(-)-1-phenylethylamine. In this synthesis, it was thought to explore the role of chiral, as well as Schiff base sites in the recognition of targeted species ions (such as dichromate anions) as well as neutral/chiral molecules. At low pH, the ligand 5 is more effective for transferring the dichromate anions from an aqueous into a dichloromethane layer; may be due to the protonation of nitrogen atoms. The extraction properties of ligand 5 towards the some selected α -amino acid methylesters are also reported. However, the ligand 5 did not display any selectivity towards the selected α-amino acid methylesters. 相似文献
6.
The B,N-bifunctional catalyst homoboroproline has been applied to a catalytic asymmetric nitroalkene-Michael addition to β-nitrostyrene analogues, showing broad substrate tolerance, high conversions and moderate to good asymmetric induction. The ability of homoboroproline to act as an efficient catalyst based on enamine-formation of the secondary amine, coupled with intramolecular Lewis-acid chelation of the nitro function, in a non-FLP manner, to effect efficient and enantioselective catalysis via a proposed large 10-membered ring transition state is remarkable and reinforced by theoretical calculations. 相似文献
7.
At present, CNT supported catalysts were prepared by two different methods as NaBH4 reduction and dendrimer templated NaBH4 reduction method to observe the effect of preparation method on the sensitivity and activity of H2O2 reduction. Then, CNT supported PdxAuy bimetallic nanocatalysts having various atomic ratio were synthesized via novel dendrimer templated NaBH4 reduction method. The resulting materials were characterized employing XRD and TEM. Crystallite size of 10 %Pd0.7Au0.3/CNTdendrimer was obtained from XRD 17.1 nm and mean particle size obtained from TEM is about 15 nm. Moreover, the electrochemical behavior of these catalysts was characterized by cyclic voltammetry (CV) and chronoamperometry (CA) techniques. PdxAuy bimetallic nanocatalysts have excellent electrocatalytic properties and great potential for applications in electrochemical detection. The sensitivity and the limit of detection values for the prepared sensor with monometallic 10 % Pd/CNTdendrimer catalysts are 219.78 μA mM?1cm?2 and 2.6 μM, respectively. However, the sensor constructed with 10 %Pd0.7Au0.3/CNTdendrimer modified electrode has a very high sensitivity of 316.89 μA mM?1 cm?2 with a quick response time of 2 s and a wide linear range of 0.001–19.0 mM. In addition, the interference experiment indicated that the 10 % Pd0.7Au0.3/CNTdendrimer nanoparticles have good selectivity toward H2O2. 相似文献
8.
Ozlem Karahan Duygu Avci Vİktorya Avİyente 《Journal of polymer science. Part A, Polymer chemistry》2011,49(14):3058-3068
A series of alkyl α‐hydroxymethacrylate derivatives with various secondary functionalities (ether, ester, carbonate, and carbamate) and terminal groups (alkyl, cyano, oxetane, cyclic carbonate, phenyl and morpholine) were synthesized to investigate the effect of intermolecular interactions, H‐bonding, π–π interactions, and dipole moment on monomer reactivity. All of the monomers except one ester and one ether derivative are novel. The polymerization rates, determined by using photo‐DSC, showed the average trend (aromatic carbamate > hydroxyl > ester > carbonate ~ aliphatic carbamate ~ ether), with several exceptions due to the differences in terminal groups. There is a correlation between the chemical shift differences of the double bond carbons, the calculated dipole moments, and the reactivities only for nonhydrogen bonded monomers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
9.
Ozlem Yazici M. Reyhan Moroglu Husnu Cankurtaran Ozlem Cankurtaran Ferdane Karaman 《Mikrochimica acta》2008,160(4):441-445
The composites of graphite with Ardel?D-100 which is a trademark of a polyester of bisphenol-A with terephthalic and isophthalic acid were used as a sensing material
in a conductometric vapor sensor. The magnitudes of responses are increased in the order of benzene, isobutyl acetate, isoamyl
acetate, ethyl benzene and chloro benzene. This suggests that Ardel?D-100 can be used as a sensing material for chlorobenzene, ethyl benzene and isoamyl acetate. On the other hand, specific
retention volumes of the sensed vapors on Ardel?D-100 coated on graphite were determined by inverse gas chromatography at temperatures between 200 and 260 °C. The distribution
coefficient, K
s of the vapors between stationary and mobile phases in the column was obtained. It was revealed for the first time that the
logarithm of K
s of the solvents varies almost linearly with their responses based on conductometric resistance of the sensing polymer composite.
Subsequently, the study suggests that gas chromatographic retention data can be used in prediction of the conductometric responses
of a polymeric sensor to vapors.
Correspondence: Ferdane Karaman, Department of Chemistry, Yildiz Technical University, 34220 Istanbul-Esenler, Turkey 相似文献
10.
In situ PM‐IRRAS studies of organothiols and organosilane monolayers–ZnO interfaces at high water activities 下载免费PDF全文
Boray Torun Ignacio Giner Guido Grundmeier Ozlem Ozcan 《Surface and interface analysis : SIA》2017,49(1):71-74
In situ photoelastic‐modulated Fourier transform infrared reflection absorption spectroscopy has been applied for the investigation of interfacial stability of organothiol and organosilane monolayer films on nanocrystalline zinc oxide thin films. It has been shown that for octadecyltriethoxysilane films, exposure to high water activities results in physisorption of water in the cross‐linked film. This high water activity at the interface leads to a reversible wet de‐adhesion of the interfacial silanol groups from the ZnO surface. However, the organothiol seems to form a denser monolayer and a stable by S–Zn bond that is resistant to the competition with adsorbed water. The reversible attachment for cross‐linked organosilanol films has been demonstrated for the first time by means of an in situ spectroscopic method on model ZnO surfaces. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献