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991.
Aminzadeh S Naderi-Manesh H Khajeh K Naderi-Manesh M 《Applied biochemistry and biotechnology》2006,135(3):193-208
For the first time, a polygalacturonase from the culture broth of Tetracoccosporium sp. was isolated and incubated at 30°C in an orbital shaker at 160 rpm for 48h. The enzyme was purified by ammonium sulfate
precipitation and two-step ion-exchange chromatography and had an apparent molecular mass of 36 kDa, as shown by sodium dodecyl
sulfate (SDS)-polyacrylamide gel electrophoresis. Its optimum activity was at pH 4.3 and 40°C, and the K
m
and V
max values of this enzyme (for polygalacturonic acid) were 3.23 mg/mL and 0.15 μmol/min, respectively. Ag+, Co2+, EDTA, Tween-20, Tween-80, and Triton X-100 stimulated polygalacturonase activity whereas Al3+, Ba2+, Ca2+, Fe2+, Fe3+, Ni2+, Mg2+, Mn2+, and SDS inhibited it. In addition, iodoacetamide and iodoacetic acid did not inhibit enzyme activity at a concentration
of 1 mM, indicating that cysteine residues are not part of the catalytic site of polygalacturonase. We studied the kinetic properties
and thermal inactivation of polygalacturonase. This enzyme exhibited a t
1/2 of 63 min at 60°C and its specific activity, turnover number, and catalytic efficiency were 6.17 U/mg, 113.64 min−1, and 35.18 mL/(min·mg), respectively. The activation energy (ΔE
#) for heat inactivation was 5.341 kJ/mol, and the thermodynamic activation parameters ΔG
#, ΔH
#, and ΔS
# were also calculated, revealing a potential application for the industry. 相似文献
992.
Seyyed Javad Sabounchei Parisa Shahriary Zabiholla Bolboli Nojini Hamid Reza Khavasi Cengiz Arici Hakan Dal 《Heteroatom Chemistry》2010,21(7):475-485
Stable phosphoranes, Ar3P = CHCOR (R = C6H5, C6H4NO2, C6H4OCH3, CH3, OCH2C6H5; Ar = p‐tolyl or phenyl), have been C‐acylated by acetic anhydride to obtain new types of phosphorus ylides. Synthesis and characterization of six phosphorus ylides of the type Ar3PC(COCH3)(COR) are reported. The reaction of {(p‐tolyl)3PCHCOC6H5} ( I ), {(p‐ tolyl)3PCHCOC6H4NO2} ( II ), {Ph3PCHCOC6H4NO2} ( III ), {Ph3PCHCOC6H4OCH3} ( IV ), {(p‐tolyl)3PCHCOCH3} ( V ), and {Ph3PCHCOOCH2C6H5} ( VI ) with acetic anhydride in dry chloroform as solvent gives (p‐tolyl)3PC(COMe)(COC6H5), α‐acetyl‐α‐benzoylmethy‐lenetriphenylphosphorane ( 1 ), {(p‐tolyl)3PC(COMe) (COC6H4NO2)} ( 2 ), {Ph3PC(COMe)(COC6H4NO2)} ( 3 ), {Ph3PC(COMe)(COC6H4OCH3)} ( 4 ), {(p‐tolyl)3 PC(COCH3)2} ( 5 ), and {Ph3PC(COMe)(COOCH2 C6H5)} ( 6 ). Single crystal X‐ray analyses for ylides 2 , 5 , and 6 reveal the monoclinic ( 2, 5 ) and triclinic ( 6 ) crystal systems. Characterization of the obtained compounds was also performed by elemental analysis, IR, 1H, 31P, and 13C NMR. The geometries of these compounds have been investigated using density functional theory (DFT). In addition, electronic parameters of these compounds such as HOMO and LUMO energy, Mulliken partial charge, and dipole moment were obtained. In this paper, the reactivity of these ylides is discussed in regard to the aforementioned data. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:475–485, 2010; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20633 相似文献
993.
Mohammad Mehdi Barzegari Morteza Dardel Alireza Fathi 《Acta Mechanica Solida Sinica》2013,26(5):536-550
In this study, analytical relations for evaluating the exact solution of natural fre- quency and mode shape of beams with embedded shape memory alloy (SMA) wires are presented. Beams are modeled according to Euler-Bernoulli, Timoshenko and third order beam (Reddy) the- ories. A relation is obtained for determining the effect of axial load generated by the recovery action of pre-strained SMA wires. By defining some dimensionless quantities~ the effect of different me- chanical properties on the frequencies and mode shapes of the system are carefully examined. The effect of axial load generated by SMA wires with buckling load and frequency jump is accurately studied. 相似文献
994.
Mostafa Keshavarz Moraveji Mona Ebrahimi Fakhari Elmira Mohsenzadeh Reza Davarnejad 《Heat and Mass Transfer》2013,49(1):11-19
In this article, the influences of alcohols on the hydrodynamics and oxygen mass transfer characteristics in an airlift reactor equipped with packing were investigated. The hydrodynamic parameters and mass transfer coefficient in 1 % (v/v) aqueous solutions of four aliphatic alcohols were tested. It was concluded that alcohols addition increased gas holdup and gas–liquid mass transfer coefficient. The packing installation increased mass transfer coefficient, gas holdup and liquid circulation velocity, as well. 相似文献
995.
996.
Morteza Yavari 《理论物理通讯》2013,60(3):323-327
The study of the energy localization in f(R) theories of gravity has attracted much interest in recent years. In this paper, the vacuum solutions of the modified field equations for a power model of plane symmetric metric are studied in metric f(R) gravity with the assumption of constant Ricci scalar. Next, we determine the energy-momentum complexes in f(R) theories of gravity for this spacetime for some important models. We also show that these models satisfy the stability and constant curvature conditions. 相似文献
997.
Hamid Reza Shaker 《Nonlinear dynamics》2012,70(2):999-1005
The filtering problem is among the fundamental issues in control and signal processing. Several approaches such as H 2 optimal filtering and H ?? optimal filtering have been developed to address this issue. While the optimal H 2 filtering problem has been extensively studied in the past for linear systems, to the best of our knowledge, it has not been studied for bilinear systems. This is indeed surprising, since bilinear systems are important class of nonlinear systems with well-established theories and applications in various fields. The problem of H 2 optimal filtering for both discrete-time and continuous bilinear systems is addressed in this paper. The filter design problem is formulated in the optimization framework. The problem for the discrete-time case is expressed in terms of linear matrix inequalities which can be efficiently solved. The results are used for the optimal filtering of a bilinear model of an electro-hydraulic drive. 相似文献
998.
This paper deals with the synchronization of uncertain unified chaotic system in the presence of two kinds of disturbances,
white noise and bounded power signal. A sliding mode controller (SMC) is established to guarantee the sliding motion. Moreover,
a proportional-integral (PI) switching surface is used to determine the performance of the system in the sliding motion. Also,
by using a mixed H
2/H
∞ approach, the effect of external disturbances on the sliding motion is reduced. The necessary parameters of constructing
controller and switching surface are found via semidefinite programming (SDP) which can be solved effectively by a standard
software. Finally, a numerical simulation is presented to show the effectiveness of the proposed method. 相似文献
999.
In this paper, a new simple 4D smooth autonomous system is proposed, which illustrates two interesting rare phenomena: first,
this system can generate a four-wing hyperchaotic and a four-wing chaotic attractor and second, this generation occurs under
condition that the system has only one equilibrium point at the origin. The dynamic analysis approach in the paper involves
time series, phase portraits, Lyapunov exponents, bifurcation diagram, and Poincaré maps, to investigate some basic dynamical
behaviors of the proposed 4D system. The physical existence of the four-wing hyperchaotic attractor is verified by an electronic
circuit. Finally, it is shown that the fractional-order form of the system can also generate a chaotic four-wing attractor. 相似文献
1000.
Mosayeb Naseri Mona Abdolmaleky Fariborz Parandin Negin Fatahi Ahmed Farouk Reza Nazari 《理论物理通讯》2018,69(2):215-226
In this paper, a new quantum images encoding scheme is proposed. The proposed scheme mainly consists of four different encoding algorithms. The idea behind of the scheme is a binary key generated randomly for each pixel of the original image. Afterwards, the employed encoding algorithm is selected corresponding to the qubit pair of the generated randomized binary key. The security analysis of the proposed scheme proved its enhancement through both randomization of the generated binary image key and altering the gray-scale value of the image pixels using the qubits of randomized binary key. The simulation of the proposed scheme assures that the final encoded image could not be recognized visually. Moreover, the histogram diagram of encoded image is flatter than the original one. The Shannon entropies of the final encoded images are significantly higher than the original one, which indicates that the attacker can not gain any information about the encoded images. 相似文献