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11.
Carbonyl sulfide (COS), a component of volcanic gas emissions and interstellar gas clouds, is shown to be an efficient condensing agent in the context of phosphate chemistry in aqueous solutions. We report that high-energy aminoacyl-phosphate anhydrides and aminoacyl adenylates are generated in solutions containing amino acids, COS, and the corresponding phosphate molecule. We further show that the mixed anhydrides of amino acids and inorganic phosphate are phosphorylating agents, producing pyrophosphate in better than 30% yield in the presence of Ca2+ precipitates. The amino acid dependent activations of phosphate reported here, which occur in parallel with the production of peptides, suggest that these two reactions may have shared a common intermediate on the prebiotic Earth. 相似文献
12.
In this study, Tungsten Oxide (WO3) thin films were prepared by Chemical Spray Pyrolysis (CSP) and Spin Coating (SC) techniques and it was investigated effects of technique and parameter on the films. WO3 thin films were deposited on ITO (Indium Tin Oxide) coated glasses. The structural, optical and electrochromic properties of the WO3 thin films were characterized by XRD, SEM, UV, and CV measurements. The sharpest (200) peak was observed in the XRD spectra and optical band gaps were calculated around 2.6~3.1 eV via UV-Vis spectra for all of the samples. Micro fibrous reticulated surface (filamentous like) morphology for the films deposited by CSP technique and smooth surface morphology with high optical transmittance for the film deposited by SC Technique were obtained from SEM images. In addition to these results, it was revealed that all the samples exhibit good electrochromic performance. 相似文献
13.
Necati Özdemir Om Prakash Agrawal Beyza Billur İskender Derya Karadeniz 《Nonlinear dynamics》2009,55(3):251-260
This paper presents an eigenfunctions expansion based scheme for Fractional Optimal Control (FOC) of a 2-dimensional distributed
system. The fractional derivative is defined in the Riemann–Liouville sense. The performance index of a FOC problem is considered
as a function of both state and control variables, and the dynamic constraints are expressed by a Partial Fractional Differential
Equation (PFDE) containing two space parameters and one time parameter. Eigenfunctions are used to eliminate the terms containing
space parameters and to define the problem in terms of a set of generalized state and control variables. For numerical computation
Grünwald–Letnikov approximation is used. A direct numerical technique is proposed to obtain the state and the control variables.
For a linear case, the numerical technique results into a set of algebraic equations which can be solved using a direct or
an iterative scheme. The problem is solved for different number of eigenfunctions and time discretization. Numerical results
show that only a few eigenfunctions are sufficient to obtain good results, and the solutions converge as the size of the time
step is reduced. 相似文献
14.
A novel synthetic method is introduced to prepare the biologically important montagnetol and erythrin compounds starting from a 1,3-benzodioxin-4-one, synthesized from commercially available orsellinic acid and erythritol. 相似文献
15.
16.
Leman Tarhan 《Applied biochemistry and biotechnology》1991,31(2):109-117
Polyvinylalcohol crosslinked with terephthaldicarboxaldehyde and was modified with 2-amino-4,6-dichloro-s-triazine. Optimum
conditions for immobilization of catalase on modified and gelatine-coated modified polyvinylalcohol were investigated. Activity
variations with respect to pH, temperature, stability behavior, andk
m(appl) values were investigated for the native and immobilized catalases. Rate constants for H2O2 decomposition and for inactivation of immobilized catalase were determined using a discontinuous batch-type reactor. The
influence of H2O2 concentration on the catalase inactivation was investigated. 相似文献
17.
18.
Arzum Erdem Pagona Papakonstantinou Hayley Murphy Martin McMullan Hakan Karadeniz Surbhi Sharma 《Electroanalysis》2010,22(6):611-617
Disposable graphite pencil electrodes (PGE) modified with multiwalled carbon nanotubes (MWCNTs)‐streptavidin (STR) conjugates were used for electrochemical monitoring of label‐free DNA hybridization. The surface morphology of PGE electrode before and after hybridization was characterized by scanning electron microscopy. Electrochemical impedance spectroscopy was used to monitor each step of the construction of the DNA biosensor. The biosensor was demonstrated to have excellent selectivity, being able to differentiate complementary sequences from a noncomplementary ones and in addition select the target sequence of DNA from a mixture of other DNA without loss in current sensitivity. 相似文献
19.
20.
A. Birkan Seluk N. Tuluolu S. Karadeniz S. Bilge Ocak 《Physica B: Condensed Matter》2007,400(1-2):149-154
In this work, the investigation of the interface state density and series resistance from capacitance–voltage (C–V) and conductance–voltage (G/ω−V) characteristics in In/SiO2/p-Si metal–insulator–semiconductor (MIS) structures with thin interfacial insulator layer have been reported. The thickness of SiO2 film obtained from the measurement of the oxide capacitance corrected for series resistance in the strong accumulation region is 220 Å. The forward and reverse bias C–V and G/ω−V characteristics of MIS structures have been studied at the frequency range 30 kHz–1 MHz at room temperature. The frequency dispersion in capacitance and conductance can be interpreted in terms of the series resistance (Rs) and interface state density (Dit) values. Both the series resistance Rs and density of interface states Dit are strongly frequency-dependent and decrease with increasing frequency. The distribution profile of Rs–V gives a peak at low frequencies in the depletion region and disappears with increasing frequency. Experimental results show that the interfacial polarization contributes to the improvement of the dielectric properties of In/SiO2/p-Si MIS structures. The interface state density value of In/SiO2/p-Si MIS diode calculated at strong accumulation region is 1.11×1012 eV−1 cm−2 at 1 MHz. It is found that the calculated value of Dit (≈1012 eV−1 cm−2) is not high enough to pin the Fermi level of the Si substrate disrupting the device operation. 相似文献