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11.
The synthesis of 6-ethyl-5-(4-pyridinyl)-2,4-pyrimidinediamine ( 2 ), the pyridine analog of pyrimethamine, is described. Condensation of 4-pyridineacetonitrile ( 3 ) with methyl propionate afforded α-(1-oxopropyl)-4-pyridineacetonitrile ( 4 ). Treatment with triethyl orthopropionate gave primarily the undesired N-alkylated material. However reaction of the crude mixture with guanidine afforded 2 in low yield. This material was devoid of significant antimalarial activity. 相似文献
12.
Recently, Ye, Tapia and Zhang (1991) demonstrated that Mizuno—Todd—Ye's predictor—corrector interior-point algorithm for linear programming maintains the O(
L)-iteration complexity while exhibiting superlinear convergence of the duality gap to zero under the assumption that the iteration sequence converges, and quadratic convergence of the duality gap to zero under the assumption of nondegeneracy. In this paper we establish the quadratic convergence result without any assumption concerning the convergence of the iteration sequence or nondegeneracy. This surprising result, to our knowledge, is the first instance of a demonstration of polynomiality and superlinear (or quadratic) convergence for an interior-point algorithm which does not assume the convergence of the iteration sequence or nondegeneracy.Supported in part by NSF Grant DDM-8922636 and NSF Coop. Agr. No. CCR-8809615, the Iowa Business School Summer Grant, and the Interdisciplinary Research Grant of the University of Iowa Center for Advanced Studies.Supported in part by NSF Coop. Agr. No. CCR-8809615, AFOSR 89-0363, DOE DEFG05-86ER25017 and ARO 9DAAL03-90-G-0093.Supported in part by NSF Grant DMS-9102761 and DOE Grant DE-FG05-91ER25100. 相似文献
13.
An ab-initio gaussian lobe function study of the structure and some molecular properties of the HPO molecule is reported. By a partial optimization of the geometrical structure the following equilibrium structure parameters are found: rPO = 1.536 Å; rPH = 1.475 Å; the bond angle is found to be close to 102° with a bending force constant of 0.58 mdyne/Å. The dipole moment, effective charges and quadrupole term components at various bond angles are reported. The wavefunction of the equilibrium geometry is available from the authors upon request. 相似文献
14.
Second order perturbation theory (SOP) has been used to introduce electronic correlation effects on CNDP/2 calculated quantities like stabilization energy, proton potential curves, intermolecular dependence on distance and orientation. The HCHO…H2O' model has been studied. The SOP energy as a function of the RO…O' distance introduces changes in the potential minima which amount to 14% of the CNDO/2 value and in the asymmetry of the potential energy curve. For the proton curve, an extra stabilization energy of 4 kcal/mole at the minimum is found as well as changes in the shape of the potential curve. Effects on orientation dependence are also reported. 相似文献
15.
An extremely sensitive voltammetric method is presented for trace measurement of the cancer chemotherapy drug methotrexate. The method is based on controlled adsorptive preconcentration of methotrexate on the hanging mercury-drop electrode, followed by voltammetric determination of the surface species. Cyclic voltammetry was used to explore the interfacial behaviour. The adsorptive stripping response was evaluated with respect to preconcentration time and potential, pH, concentration dependence, stripping mode, possible interferences, and other variables. The detection limit found was 2 x 10(-9)M (5-min preconcentration), the response was linear, and the relative standard deviation (at the 1.6 x 10(-7)M level) 2.2%. Sensitive adsorptive stripping measurements were also obtained by use of a carbon-paste disk electrode. Applicability to urine analysis is illustrated. 相似文献
16.
A quantum-mechanical reaction field theory of solvent effects is proposed. It contains as a limiting case Onsager's model. It leads to an effective, non-linear, hamiltonian for the molecule in solution and hence to a tool for studying changes in charge distributions and molecular properties. Numerical examples are given. 相似文献
17.
18.
Lucía Tapia Yolanda Prez Michael Bolte Josefina Casas Jordi Sol Roberto Quesada Ignacio Alfonso 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(36):12595-12598
Acidic microenvironments in solid tumors are a hallmark of cancer. Inspired by that, we designed a family of pseudopeptidic cage‐like anionophores displaying pH‐dependent activity. When protonated, they efficiently bind chloride anions. They also transport chloride through lipid bilayers, with their anionophoric properties improving at acidic pH, suggesting an H+/Cl? symport mechanism. NMR studies in DPC micelles demonstrate that the cages bind chloride within the lipid phase. The chloride affinity and the chloride‐exchange rate with the aqueous bulk solution are improved when the pH is lowered. This increases cytotoxicity towards lung adenocarcinoma cells at the pH of the microenvironment of a solid tumor. These properties depend on the nature of the amino‐acid side chains of the cages, which modulate their lipophilicity and interactions with the cell membrane. This paves the way towards using pH as a parameter to control the selectivity of cytotoxic ionophores as anticancer drugs. 相似文献
19.
Diederik Aerts Sandro Sozzo Jocelyn Tapia 《International Journal of Theoretical Physics》2014,53(10):3666-3682
Empirical evidence has confirmed that quantum effects occur frequently also outside the microscopic domain, while quantum structures satisfactorily model various situations in several areas of science, including biological, cognitive and social processes. In this paper, we elaborate a quantum mechanical model which faithfully describes the Ellsberg paradox in economics, showing that the mathematical formalism of quantum mechanics is capable to represent the ambiguity present in this kind of situations, because of the presence of contextuality. Then, we analyze the data collected in a concrete experiment we performed on the Ellsberg paradox and work out a complete representation of them in complex Hilbert space. We prove that the presence of quantum structure is genuine, that is, interference and superposition in a complex Hilbert space are really necessary to describe the conceptual situation presented by Ellsberg. Moreover, our approach sheds light on ‘ambiguity laden’ decision processes in economics and decision theory, and allows to deal with different Ellsberg-type generalizations, e.g., the Machina paradox. 相似文献
20.
Optical Emission Spectroscopy Study of Plasma-Precursor Interactions in TiO2 Suspension Plasma Spray
Plasma Chemistry and Plasma Processing - The influence of plasma power on liquid precursor decomposition in suspension plasma spray (SPS) is studied with optical emission spectroscopy (OES). The... 相似文献