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951.
Mehdi Shakourian-Fard Mohammadreza Nasiri Alireza Fattahi Majid Vafaeezadeh 《Structural chemistry》2012,23(3):857-865
Influence of the addition of water molecules (n = 1–6) on the interaction energy between Li+, Na+, K+ cations and indole molecule as tryptophan amino acid residue is considered at MP2(FULL)/6-311++G(d,p)//B3LYP/6-311++G(d,p)
levels of theory. The calculations suggest that the size of cation and the number of water molecules are two important factors
that affect the interaction energy between the hydrated metal cation and indole molecule. The strength of cation–π interactions
get substantially reduced when the metal ion is solvated or the size of metal cation increases. Quantum theory of atoms in
molecules analysis of cation–π interaction indicates that there is a correlation between the electron density (ρ(r)) in the cage critical points generated upon complexation and the distance between metal cation and centroid of phenyl ring
in indole molecule. 相似文献
952.
Synthesis and Characterization of Secondary Nitrosamines from Secondary Amines Using Sodium Nitrite and p‐Toluenesulfonic Acid 下载免费PDF全文
We synthesized nitrosamines (R2N? NO) with R=iPr ( 1 ), nPr ( 2 ), nBu ( 3 ), and hydroxyethyl ( 4 ) from the amine using sodium nitrite/p‐toluenesulfonic acid in CH2Cl2. The rate of formation of 1 – 4 increases in the direction iPr<nPr<nBu2CH2OH. Compounds 1 – 3 were obtained as colorless solids, whereas 4 is a bright yellow liquid. Compounds 1 – 4 were characterized by elemental analysis, MS, IR, and multinuclear NMR (1H, 13C, and 15N) spectroscopies. Additionally, we measured the UV/Vis spectra of all compounds, which show maxima of absorption at approximately 221 nm and molar extinction coefficients between 3043 and 4859 L mol?1 cm?1. We calculated the optimized structures of 1 – 4 (B3LYP/6‐311+G(d,p)) and computed the NMR spectroscopic chemical shifts and infrared frequencies. Furthermore, we carried out a natural bond orbital (NBO) analysis of the nitrosamine moiety. Lastly, the compounds described in this work are valuable starting materials for the synthesis of 2‐tetrazenes with potential interest to replace highly toxic hydrazines in rocket propulsion. 相似文献
953.
Salabat A Eastoe J Vesperinas A Tabor RF Mutch KJ 《Langmuir : the ACS journal of surfaces and colloids》2008,24(5):1829-1832
Commercial silica nanoparticles were dispersed in toluene, stabilized by a mixture of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and a photolyzable anionic surfactant sodium hexylphenylazosulfonate (C6PAS). Selective photolysis of the interfacial C6PAS component induces colloid instability, resulting in flocculation and eventual phase separation of the silica nanoparticles. UV-vis spectroscopy was used to follow the photochemical breakdown of C6PAS; diffusion coefficient measurements by dynamic light scattering were employed to monitor the photoinduced flocculation; and silica contents in the toluene, before and after UV light irradiation, were determined gravimetrically. The results show that light can be used to trigger separation and recovery of nanoparticles stabilized by photolabile interfacial layers. 相似文献
954.
Alireza Mahjub Seyed Hassan Jafari Hossein Ali Khonakdar Udo Wagenknecht Gert Heinrich 《Macromolecular theory and simulations》2013,22(3):207-216
Monte–Carlo kinetic simulations are performed to study exchange reactions in PET/PEN blends. Chain distribution of the blend is simulated at various mixing conditions. The average length of PET and PEN repeating units decreases with increasing exchange reactions. Derivative of heat flow is modeled at Tg region during mixing. Two peaks are observed on the derivative of heat flow curve at the early stages of mixing, indicating formation of an immiscible blend. With increasing mixing time, miscibility between two phases increasea and the peaks converge toward each other and finally form a single peak. The Monte–Carlo simulation results are in fine agreement with experimental data obtained from different systems.
955.
A method to calculate an optimum Erbium distribution to enhance the gain efficiency in EDFA is proposed. This method calculates
Erbium distribution based on optical pump envelop, pump power and optical properties of Erbium ion. The intensity-based Erbium
distribution is obtained for single-mode fiber and dispersion-shifted fiber types EDFA for pump power from 10 to 40 mW. All
of the profiles have a Gaussian-like shape. For single-mode fiber type EDFA, high gain enhancement is obtained in a relatively
short optimal length of fiber. Optimal length of EDFA, using intensity-based Erbium distribution, is increased by a factor
of 1.5–3 with respect to the one using stepwise. This optimal length increasing factor is considerably smaller than that of
the EDFA, using the one-fourth confinement Erbium profile. 相似文献
956.
We present a semidefinite program optimization approach to quantum error correction that yields codes and recovery procedures that are robust against significant variations in the noise channel. Our approach allows us to optimize the encoding, recovery, or both, and is amenable to approximations that significantly improve computational cost while retaining fidelity. We illustrate our theory numerically for optimized 5-qubit codes, using the standard [5,1,3] code as a benchmark. Our optimized encoding and recovery yields fidelities that are uniformly higher by 1-2 orders of magnitude against random unitary weight-2 errors compared to the [5,1,3] code with standard recovery. 相似文献
957.
Aubert B Barate R Boutigny D Couderc F Gaillard JM Hicheur A Karyotakis Y Lees JP Tisserand V Zghiche A Palano A Pompili A Chen JC Qi ND Rong G Wang P Zhu YS Eigen G Ofte I Stugu B Abrams GS Borgland AW Breon AB Brown DN Button-Shafer J Cahn RN Charles E Day CT Gill MS Gritsan AV Groysman Y Jacobsen RG Kadel RW Kadyk J Kerth LT Kolomensky YG Kukartsev G LeClerc C Levi ME Lynch G Mir LM Oddone PJ Orimoto TJ Pripstein M Roe NA Ronan MT Shelkov VG Telnov AV Wenzel WA Ford K Harrison TJ Hawkes CM 《Physical review letters》2004,92(6):061801
We present measurements of branching fractions and charge asymmetries for seven B-meson decays with an eta, eta', or omega meson in the final state. The data sample corresponds to 89x10(6) BB pairs produced from e(+)e(-) annihilation at the Upsilon(4S) resonance. We measure the following branching fractions in units of 10(-6): B(B+-->eta pi(+))=5.3+/-1.0+/-0.3, B(B+-->eta K+)=3.4+/-0.8+/-0.2, B(B0-->eta K0)=2.9+/-1.0+/-0.2 (<5.2, 90% C.L.), B(B+-->eta(')pi(+))=2.7+/-1.2+/-0.3 (<4.5, 90% C.L.), B(B+-->omega pi(+))=5.5+/-0.9+/-0.5, B(B+-->omega K+)=4.8+/-0.8+/-0.4, and B(B0-->omega K0)=5.9(+1.6)(-1.3)+/-0.5. The charge asymmetries are A(ch)(B+-->eta pi(+))=-0.44+/-0.18+/-0.01, A(ch)(B+-->eta K+)=-0.52+/-0.24+/-0.01, A(ch)(B+-->omega pi(+))=0.03+/-0.16+/-0.01, and A(ch)(B+-->omega K+)=-0.09+/-0.17+/-0.01. 相似文献
958.
The present study reports the magnetizations and magneto-transport properties of PrFel_xNixO3 thin films grown by pulsed laser ablation technique on LaA103 snbstrates. From DC M/H plots of these films, weak ferromagnetism or ferrimagnetism behaviors are observed. With Ni substitution, reduction in saturation magnetization is also seen. With Ni doping, variations in saturation field (Hs), coercive field (Hc), Weiss temperature (0), and effective magnetic moment (Pelf) are seen. A small change of magnetoresitance with application of higher field is observed. Various essential parameters like density of state (Nf) at Fermi level, Mott's characteristic temperature (To), and activation energy (Ea) in the presence of and in the absence of magnetic field are calculated. The present observed magnetic properties are related to the change of Fe-O bond length (causing an overlap between the oxygen p orbital and iron d orbital) and the deviation of the Fe-O-Fe angle from 180~. Reduction of magnetic domain after Ni doping is also explored to explain the present observed magnetic behavior of the system. The influence of doping on various transport properties in these thin films indicates a distortion in the lattice structure and single particle band width, owing to stress-induced reduction in unit cell volume. 相似文献
959.
In data envelopment analysis (DEA), identification of the strong defining hyperplanes of the empirical production possibility set (PPS) is important, because they can be used for determining rates of change of outputs with change in inputs. Also, efficient hyperplanes determine the nature of returns to scale. The present work proposes a method for generating all linearly independent strong defining hyperplanes (LISDHs) of the PPS passing through a specific decision making unit (DMU). To this end, corresponding to each efficient unit, a perturbed inefficient unit will be defined and, using at most m+s linear programs, all LISDHs passing through the DMU will be determined, where m and s are the numbers of inputs and outputs, respectively. 相似文献
960.
Ali Nakhaei Pour Mohammad Reza Housaindokht Alireza Behroozsarand Mohammad Ali Khodagholi 《Applied Physics A: Materials Science & Processing》2014,116(2):789-797
The kinetic parameters of the Fischer–Tropsch synthesis (FTS) on iron catalyst are analyzed by size-dependent thermodynamic method. A Langmuir–Hinshelwood kinetic equation is considered for evaluation of catalytic activity of lanthanum promoted iron catalyst. A series of unsupported iron catalysts with different particle sizes were prepared via microemulsion method. The experimental results showed that catalyst activity pass from a maximum value by increasing the iron particle size. Also, data presented that iron particle size has considerable effects on adsorption parameters and FTS rates. The ratio of surface tension (σ) to nanoparticle radius (r) is important in FTS reaction on iron catalyst. Finally, the results showed that by increasing of iron particle size from 18 to 45 nm the activation energies of catalysts and heats of adsorption of catalysts as two main parameters of FTS reaction increased from 89 to 114 kJ/mol and from 51 to 71 kJ/mol, respectively. 相似文献