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91.
Shirin Panahi Sajad Jafari Abdul Jalil M. Khalaf Karthikeyan Rajagopal Viet–Thanh Pham Fawaz E. Alsaadi 《Chinese Journal of Physics (Taipei)》2018,56(5):2254-2264
In the last decades, many studies have been done about nervous system from the mathematical and computational point of view. Many mathematical models have been proposed to describe neuron. Most of them have described the membrane potential of a neuron in terms of the leakage current and the synaptic inputs. Very recently, according to the Maxwell electromagnetic induction theorem, researchers proposed a new neuron model which considers inner magnetic fluctuation and external electromagnetic radiation as a significant missing part that can participate in neural activity. In this paper, dynamical properties of this new model, such as equilibria and its stability, phase portraits, bifurcation diagram, Lyapunov exponents, and basin of attraction, are investigated. Moreover, an implementation of electronic circuit and FPGA is also done to verify the feasibility of the theoretical model. 相似文献
92.
The speciation and quantification of sulfur species based on sulfur K-edge x-ray absorption spectroscopy is of wide interest, particularly for biological and petroleum science. These tasks require a firm understanding of the sulfur 1s near-edge x-ray absorption fine structure (NEXAFS) spectra of relevant species. To this end, we have examined the gas phase sulfur 1s NEXAFS spectra of a group of simple thiol and thioether compounds. These high-resolution gas phase spectra are free of solid-state broadening, charging, and saturation effects common in the NEXAFS spectra of solids. These experimental data have been further analyzed with the aid of improved virtual orbital Hartree-Fock ab initio calculations. The experimental sulfur 1s NEXAFS spectra show fine features predicted by calculation, and the combination of experiment and calculation has been used to improve assignment of spectroscopic features relevant for the speciation and quantification of the sulfur compounds. 相似文献
93.
We described Ullmann homocoupling promoted by a Pd/biphenyl-based phosphine system using DMF as solvent. Using Hammett equation it is found that the rate determining step of the reaction depends on the electronic nature of substituents of aryl bromides. Increase the rate of reaction with decreasing the electron donating of the substituent from NH2 to H suggesting an oxidative addition step as the rate determining step. Decrease the rate of reaction with increasing the electron-withdrawing ability of the substituent from H to NO2 indicating a reductive elimination step as the rate determining step. 相似文献
94.
N.F. Zobov S.V. Shirin R.I. Ovsyannikov O.L. Polyansky S.N. Yurchenko R.J. Barber J. Tennyson R.J. Hargreaves P.F. Bernath 《Journal of Molecular Spectroscopy》2011,269(1):104-108
A recently-recorded set [Hargreaves et al., Astrophys. J., in press] of Fourier transform emission spectra of hot ammonia is analyzed using a variational line list. Approximately 3350 lines are newly assigned to mainly hot bands from vibrational states as high as v2 = 2. 431 new energy levels of these states are experimentally determined, considerably extending the range of known rotationally-excited states. Comparisons with a recent study of high J levels in the ground and first vibrational states [Yu et al., J. Chem. Phys., 133 (2010) 174317] suggests that while the line assignments presented in that work are correct, their energy level predictions suffer from problems associated with the use of very high-order perturbation series in the effective Hamiltonian. It is suggested that variational calculations provide a more stable method for analyzing spectra involving highly-excited states of ammonia. 相似文献
95.
I. I. Bubukina N. F. Zobov O. L. Polyansky S. V. Shirin S. N. Yurchenko 《Optics and Spectroscopy》2011,110(2):160-166
A semiempirical potential energy surface is obtained for the major isotopologue of the water molecule H2
16O that allows the vibration-rotation energy levels in the range of 0–26000 cm−1 to be calculated with an accuracy almost equal to the average experimental accuracy of measurements in the infrared and visible
ranges. Variational calculations using this potential energy surface reproduce the experimental energy values of more than
1500 vibration-rotation levels of H2
16O with the total angular momentum quantum number J = 0, 2, and 5 in the indicated range with a standard deviation of 0.022 cm−1. The potential was obtained by optimizing a starting ab initio surface using a combination of two approaches, i.e., (1) the
multiplication of the starting ab initio surface by a morphing function whose parameters were optimized and (2) the optimization
of parameters of the ab initio surface using both the experimental values of energy levels and the results of quantum-chemical
electronic structure calculations. 相似文献
96.
Quantum Chemical Study of the Enzymatic Repair of T(6‐4)C/C(6‐4)T UV‐Photolesions by DNA Photolyases
Several strategies have evolved to repair one of the abundant UV radiation‐induced damages caused to DNA, namely the mutagenic pyrimidine (6‐4) pyrimidone photolesions. DNA (6‐4)‐photolyases are enzymes repairing these lesions by a photoinitiated electron transfer. An important aspect of a possible repair mechanism is its generality and transferability to different (6‐4) lesions. Therefore, previously suggested mechanisms for the repair of the T(6‐4)T lesion are here transferred to the T(6‐4)C and C(6‐4)T lesions and investigated theoretically using quantum chemical methods. Despite the different functional groups of the pyrimidine bases involved, a general valid molecular mechanism was identified, in which the initial step is an electron transfer coupled to a proton transfer from the protonated HIS365 to the N3′ nitrogen of the 3′ pyrimidine, followed by an intramolecular OH/NH2 transfer in one concerted step, which does not require an oxetane/azetidine or isolated water/ammonia intermediate. 相似文献
97.
The cluster state is a special, highly entangled quantum state that forms the universal resource, on which measurement-based quantum computation can be performed. In this study, a new scheme is presented for creating four-ions cluster state in ion-trap system. This scheme is based on resonant sideband excitation in which the population is transferred to target states by precise control of pulse area. Meanwhile, the scheme is consist of combination of elementary stages belonging to a universal set whereby cluster state has been created in five interaction stages by individually addressed ions with red- or blue-sideband resonance laser pulses. The paper studies the population transfer of the system by numerical solutions of the master equation, considering the effect of decoherence channels due to dissipation in the phonon modes. The presented scheme does not require control of the turn-off ratio and time delay among pulses. 相似文献
98.
Seyed Majid Hashemianzadeh Shirin Faraji Amir Hossein Amin Sepideh Ketabi 《Monatshefte für Chemie / Chemical Monthly》2008,139(2):89-100
Summary. Interactions of the DNA bases adenine (A), guanine (G), cytosine (C), and thymine (T) with various metal ions (M) of groups IA and IIA of the periodic table of the elements were studied at the HF, MP2, and DFT levels of theory. The structures and thermodynamic stabilities of these species were studied at the gas phase. The calculations
uphold that there exist two active sites in G and one in A, C, and T. The calculations also show that the O2 atom in T is a more active site for metal ion bindings than that in C. The stability energies for G … M complexes are larger than those for A … M complexes and the stability energies for T … M complexes are larger than those for C … M complexes. As z/r ratio for the metal ion increases, the interaction energy for the complex increases systematically. Thermodynamic quantities
such as ΔH, ΔG, ΔS, and ln K were determined for each complexation reaction, [Base+M
n+ →(Base … M)
n+]. A, G, and C complexation reactions except for C … Rb+ are exothermic. The situation is quite different for T complexation reactions and all except for T … Be2+ and T … Mg2+ are endothermic. 相似文献
99.
Shirin Changizi Mahyar Sameti Gabrielle L. Bazemore Hong Chen Chris A. Bashur 《Macromolecular bioscience》2023,23(9):2300073
Endothelialization of engineered vascular grafts for replacement of small-diameter coronary arteries remains a critical challenge. The ability for an acellular vascular graft to promote endothelial cell (EC) recruitment in the body would be very beneficial. This study investigated epsins as a target since they are involved in internalization of vascular endothelial growth factor receptor 2. Specifically, epsin-mimetic UPI peptides are delivered locally from vascular grafts to block epsin activity and promote endothelialization. The peptide delivery from fibrin coatings allowed for controlled loading and provided a significant improvement in EC attachment, migration, and growth in vitro. The peptides have even more important impacts after grafting into rat abdominal aortae. The peptides prevented graft thrombosis and failure that is observed with a fibrin coating alone. They also modulated the in vivo remodeling. The grafts are able to remodel without the formation of a thick fibrous capsule on the adventitia with the 100 µg mL−1 peptide-loaded condition, and this condition enabled the formation of a functional EC monolayer in the graft lumen after only 1 week. Overall, this study demonstrated that the local delivery of UPI peptides is a promising strategy to improve the performance of vascular grafts. 相似文献
100.
Extraction of phenolic compounds from water samples by dispersive micro‐solid‐phase extraction
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In this article, the use of magnetically separable sorbent polyaniline/silica‐coated nickel nanoparticles is evaluated under a dispersive micro‐solid‐phase extraction approach for the extraction of phenolic compounds from water samples. The sorbent was prepared by in situ chemical polymerization of aniline on the surface of silica‐modified nickel nanoparticles and was characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, X‐ray powder diffraction, scanning electron microscopy, energy‐dispersive X‐ray spectrometry, and vibrating sample magnetometry. Effective variables such as amount of sorbent (milligrams), pH and ionic strength of sample solution, volume of eluent solvent (microliters), vortex, and ultrasonic times (minutes) were investigated by fractional factorial design. The significant variables optimized by a Box–Behnken design were combined by a desirability function. Under the optimized conditions, the calibration graphs of analytes were linear in a concentration range of 0.02–100 μg/mL, and with correlation coefficients more than 0.999. The limits of detection and quantification were in the ranges of 10–23 and 33–77 μg/L, respectively. This procedure was successfully employed in the determination of target analytes in spiked water samples; the relative mean recoveries ranged from 96 to 105%. 相似文献