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131.
New amino acid—1,2,3-triazolium conjugates were synthesized by establishing a 1,2,3-triazolium unit to the amino acid through Cu-catalyzed alkyne-azide cycloaddition and subsequent N-methylation. These products were applied as ionic-liquid-tagged organocatalysts in asymmetric direct aldol reactions. Remarkably, a lysine-derived conjugate performed better than proline derivatives. Evidence was found that IL-tagging improved the catalytic performance. Recycling of the organocatalyst was easily possible by extraction of products. 相似文献
132.
133.
Mori M Tanaka K Helaleh MI Xu Q Ikedo M Ogura Y Sato S Hu W Hasebe K Haddad PR 《Journal of chromatography. A》2003,997(1-2):219-224
The simultaneous ion-exclusion/cation-exchange separation column packed with a polymethacrylate-based weakly acidic cation-exchange resin of 3 microm particle size was used to achieve the simultaneous high-speed separation of anions and cations (Cl(-), NO3(-), SO4(2-), Na(+), K(+), NH4(+), Ca(2+) and Mg(2+)) commonly found in environmental samples. The high-speed simultaneous separation is based on a combination of the ion-exclusion mechanism for the anions and the cation-exchange mechanism for cations. The complete separation of the anions and cations was achieved in 5 min by elution with 15 mM tartaric acid-2.5 mM 18-crown-6 at a flow-rate of 1.5 ml/min. Detection limits at S/N=3 ranged from 0.36 to 0.68 microM for anions and 0.63-0.99 microM for cations. This method has been applied to the simultaneous determination of anions and cations in several environmental waters with satisfactory results. 相似文献
134.
Estimating the Heavy Tail Index from Scaling Properties 总被引:4,自引:0,他引:4
This paper deals with the estimation of the tail index for empirical heavy-tailed distributions, such as have been encountered in telecommunication systems. We present a method (called the scaling estimator) based on the scaling properties of sums of heavy-tailed random variables. It has the advantages of being nonparametric, of being easy to apply, of yielding a single value, and of being relatively accurate on synthetic datasets. Since the method relies on the scaling of sums, it measures a property that is often one of the most important effects of heavy-tailed behavior. Most importantly, we present evidence that the scaling estimator appears to increase in accuracy as the size of the dataset grows. It is thus particularly suited for large datasets, as are increasingly encountered in measurements of telecommunications and computing systems. 相似文献
135.
Let α? (1,2) and X
α
be a symmetric α-stable (S α S) process with stationary increments given by the mixed moving average
where is a standard Lebesgue space, is some measurable function and M
α
is a SαS random measure on X ×ℝ with the control measure m
α
(dx, du) = μ(dx)du. We show that if X
α
is self-similar, then it is determined by a nonsingular flow, a related cocycle and a semi-additive functional. By using
the Hopf decomposition of the flow into its dissipative and conservative components, we establish a unique decomposition in
distribution of X
α
into two independent processes
where the process X
α
D
is determined by a nonsingular dissipative flow and the process X
α
C
is determined by a nonsingular conservative flow. In this decomposition, the linear fractional stable motion, for example,
is determined by a conservative flow.
Received: 20 June 2000 / Revised version: 6 September 2001 / Published online: 14 June 2002 相似文献
136.
Convergence of integrated processes of arbitrary Hermite rank 总被引:5,自引:0,他引:5
Murad S. Taqqu 《Probability Theory and Related Fields》1979,50(1):53-83
Summary Let {X(s), –<s<} be a normalized stationary Gaussian process with a long-range correlation. The weak limit in C[0,1] of the integrated process
, is investigated. Here d(x) = x
H
L(x) with
<H<1 and L(x) is a slowly varying function at infinity. The function G satisfies EG(X(s))=0, EG
2
(X(s))< and has arbitrary Hermite rank m1. (The Hermite rank of G is the index of the first non-zero coefficient in the expansion of G in Hermite polynomials.) It is shown thatZ
x
(t) converges for all m1 to some process ¯Z
m
(t) that depends essentially on m. The limiting process ¯Z
m
(t) is characterized through various representations involving multiple Itô integrals. These representations are all equivalent in the finite-dimensional distributions sense. The processes ¯Z
m
(t) are non-Gaussian when m2. They are self-similar, that is,¯Z
m
(at) and a
H
¯Z
m
(t) have the same finite-dimensional distributions for all a>0.Research supported by the National Science Foundation grants MCS 77-03543 and ENG 78-11454.This paper contains results closely connected to those of the paper by Dobrushin and Major, Z. Wahrscheinlichkeitstheorie verw. Gebiete 50, 27–52 (1979). The investigations were done independently and at about the same time. Different methods were usedDedicated to Professor Leopold Schmetterer on occasion of his 60th Birthday 相似文献
137.
Abdel‐Sattar S. Hamad Elgazwy 《Journal of heterocyclic chemistry》2004,41(5):755-759
Stille coupling under standard conditions proceeds in low yield when using hindered organostannanes (1) or (2) and aryl bromide partners. The inclusion of aryl iodide instead of aryl bromide with the same organostannanes, significantly improves the efficiency of the coupling, providing a variety of desired products in good to excellent yield. The yields of Stille coupling are compared to the different reactivity of aryl halides. This study of Stille coupling with different aryl halides are documented and rationalized. 相似文献
138.
S. Murad 《Adsorption》1996,2(1):95-101
Computer simulation studies using the method of molecular dynamics have been carried out to investigate osmosis and reverse osmosis in solutions separated by semi-permeable membranes. The method has been used to study the dynamic approach to equilibrium in such systems from their initial nonequilibrium state. In addition density profiles of both the solute and solvent molecules have been investigated, especially near the walls for adsorption effects. Finally the diffusion coefficients and osmotic pressure have also been measured.Our results show both osmosis and reverse osmosis, as well as a smooth transition between the two when either the solution concentration is changed, or the density (pressure) difference between the solvent and solution compartments is varied. We believe this new method can be used to improve our understanding of these two important phenomena at the molecular level. 相似文献
139.
Sattar R. Majeed Mina A. Amin Fawzy A. Attaby Marta E. Alberto Ahmed A. Soliman 《Molecules (Basel, Switzerland)》2022,27(3)
Three new palladium complexes ([Pd(DABA)Cl2], [Pd(CPDA)Cl2], and [Pd(HZPY)Cl2]) bearing dinitrogen ligands (DABA: 3,4-diaminobenzoic acid; CPDA: 4-chloro–o-phenylenediamine; HZPY: 2-hydraziniopyridine) were synthesized, characterized, and tested against breast cancer (MCF-7), prostate carcinoma cell line (PC3) and liver carcinoma cell line (HEPG2). [Pd(DABA)Cl2] complex exhibited the highest inhibition percentage, lying between 68–71%. The hydrolysis mechanism of each palladium complex, the key step preceding the binding to the biological target, as well as their photophysical properties were explored by means of DFT and TDDFT computations. Results indicate a faster hydrolysis process for the Pd(DABA)Cl2 complex. The computed activation energies for the first and second hydrolysis processes suggest that all the compounds could reach DNA in their monohydrated form. 相似文献
140.
Shehla Sattar Samina Siddiqui Asim Shahzad Asghari Bano Muhammad Naeem Rahib Hussain Naeem Khan Basit Latief Jan Humaira Yasmin 《Molecules (Basel, Switzerland)》2022,27(6)
Nano-bioremediation application is an ecologically and environmentally friendly technique to overcome the catastrophic situation in soil because of petroleum waste contamination. We evaluated the efficiency of oil-degrading bacterial consortium and silver nanoparticles (AgNPs) with or without fertilizer to remediate soils collected from petroleum waste contaminated oil fields. Physicochemical characteristics of control soil and petroleum contaminated soils were assessed. Four oil-degrading strains, namely Bacillus pumilus (), Exiguobacteriaum aurantiacum ( KY010576), Lysinibacillus fusiformis ( KY010578), and Pseudomonas putida ( KY010586), were selected based on their in vitrohydrocarbon-degrading efficiency. In a lab experiment, contaminated soils were treated alone and with combined amendments of the bacterial consortium, AgNPs, and fertilizers (ammonium nitrate and diammonium phosphate). We detected the degradation rate of total petroleum hydrocarbons (TPHs) of the soil samples with GC-FID at different intervals of the incubation period (0, 5, 20, 60, 240 days). The bacterial population (CFU/g) was also monitored during the entire period of incubation. The results showed that 70% more TPH was degraded with a consortium with their sole application in 20 days of incubation. There was a positive correlation between TPH degradation and the 100-fold increase in bacterial population in contaminated soils. This study revealed that bacterial consortiums alone showed the maximum increase in the degradation of TPHs at 20 days. The application of nanoparticles and fertilizer has non-significant effects on the consortium degradation potential. Moreover, fertilizer alone or in combination with AgNPs and consortium slows the rate of degradation of TPHs over a short period. Still, it subsequently accelerates the rate of degradation of TPHs, and a negligible amount remains at the end of the incubation period. KX580766相似文献