Artificial intelligence in simulation

The aims are to clarify some basic concepts on cognizant simulation as well as on the similarity and the relationships of AI and simulation; provide an inventory and a taxonomy of AI-based (cognizant) simulation and AI-assisted simulation (cognizant simulation environments); and to indicate some desirable research directions.     

Syntheses and structural characterizations of a new benzyl(4-methoxyphenyl)dithiophosphinic acid and its Ni(II), Co(II), Zn(II), Cd(II), and Ni–pyridine complexes

Benzyl(4-methoxyphenyl)dithiophosphinic acid (HL) was obtained as solid and was treated with the NiCl₂6H₂O, CoCl₂6H₂O, ZnCl_2, and CdCl₂ to prepare its Ni(II), Co(II), Zn(II), and Cd(II) complexes. The nickel complex was further treated with pyridine which led to the formation of octahedral dipyridine derivative. HL was obtained through the addition reaction of the perthiophosphonic acid anhydride Lawesson reagent, (LR), [2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane-2,4-disulfide], with the corresponding Grignard compound (benzylmagnesium bromide) in diethyl ether medium.

The complexes were all of the stoichiometry of [M(L)₂]_x, with x = 1 for M = Ni²⁺ and x = 2 for M = Co²⁺, Cd²⁺ and Zn²⁺. The coordination geometry was square planar in the nickel(II) complex and tetrahedral in the others. Similar to many other nickel(II) complexes, the Ni(L)₂ reacts reversibly with pyridine to yield the octahedral complex ({(Py)₂Ni(L)₂}).

The compounds were characterized by elemental analysis; MS, FTIR, and Raman spectroscopies. The magnetic susceptibilities of the complexes were measured to confirm the hybridization patterns and the geometries. Single-crystal X-ray analyses of Ni(L)₂ and [Co(L)₂]₂ complexes were also carried out to prove the molecular topologies.     

Phosphorus–nitrogen compounds part 33: in vitro cytotoxic and antimicrobial activities,DNA interactions,syntheses, and structural investigations of new mono(4-nitrobenzyl)spirocyclotriphosphazenes

The condensation reactions of hexachlorocyclotriphosphazene, N₃P₃Cl₆, with N-alkyl-N′-mono(4-nitrobenzyl)diamines (1–3), NO₂PhCH₂NH(CH₂) _n NHR₁ (R₁ = CH₃ or C₂H₅), led to the formation of the mono(4-nitrobenzyl)spirocyclotriphosphazenes (4–6). The tetra-pyrrolidino (4a–6a), piperidino (4b–6b), and 1,4-dioxa-8-azaspiro[4,5]decaphosphazenes (4c–6c) were prepared from(for) the reactions of partly substituted compounds (4, 5, and 6) with excess pyrrolidine, piperidine, and 1,4-dioxa-8-azaspiro[4,5]decane (DASD), respectively. The partly substituted geminal (4d and 5d) and cis-morpholino (6d) phosphazenes were isolated from the reactions of excess morpholine in boiling THF and o-xylene, but the expected fully substituted compounds were not obtained. The structures of all the phosphazene derivatives were determined by elemental analyses, MS, FTIR, ¹H, ¹³C{¹H}, ³¹P{¹H} NMR, HSQC, and HMBC techniques. The crystal structures of 4, 6, 4a, and 5a were verified by X-ray diffraction analysis. In addition, in vitro cytotoxic activities of fully substituted phosphazenes (4a–6c) against HeLa cervical cancer cell lines (ATCC CCL-2) and the compounds 4a and 4c against breast cancer cell lines (MDA-MB-231) and L929 fibroblast cells were evaluated, respectively. Apoptosis effect was determined by MDA-MB-231 cancer cell lines and fibroblast cells. The MIC values of the compounds were in the ranges of 9.8–19.5 µM. The compounds 6, 5a, 6a, 5b, and 6d have greater MIC activity against bacterial and yeast strain. The investigation of DNA binding with the phosphazenes was studied using plasmid DNA. The phosphazene derivatives inhibit the restriction endonuclease cleavage of plasmid DNA by BamHI and HindIII enzymes. BamHI and HindIII digestion results demonstrate that the compounds bind with G/G and A/A nucleotides.     

Characterization of PDPA-b-PDMA-b-PDPA triblock copolymer Langmuir-Blodgett films for organic vapor sensing application

This study reports the synthesis, characterization, and gas sensing applications of the PDPA-b-PDMA-b-PDPA triblock copolymer material using NMR, UV-visible spectroscopy, atomic force microscopy (AFM), quartz crystal microbalance (QCM), and Langmuir-Blodgett (LB) thin film deposition techniques. The thin film deposition conditions of the copolymer material, which are prepared by LB film technique, are characterized by UV-visible spectroscopy, AFM, and QCM system. In this study, the swelling behaviors of the PDPA-b-PDMA-b-PDPA triblock copolymer Langmuir-Blodgett (LB) films were investigated with respect to volatile organic compounds (VOCs) at room temperature. The sensing responses of the films against VOCs were measured by QCM method. The swelling processes could be investigated using the early-time Fick's law of diffusion.     

Association constants of dibenzo[3n + 2]crown-n ethers using steady-state fluorescence spectroscopy

The steady-state fluorescence spectra of cation complexes of fluorophore macrocyclic ethers have been studied for the estimation of 1:1 association constants, and perchlorate salts of Li⁺, Na⁺, K⁺ Rb⁺ and Pb²⁺ complexing with dibenzo[23]crown-9, dibenzo[26]crown-10, and sym-dibenzo[26]crown-10, were investigated. The fluorescence emission maximum of the free and the various ligand/cation mixtures of complexed crown ethers were measured at room temperature in AN. The concentrations of chromophore crown ether were obtained from nonlinear calibration plots. The 1:1 stoichiometry of association constants (K_ass) were calculated using the equation, 1/K_ass [L_o] = (1 − nP)ⁿ(1 − m)^m/P with linear best fit of plots depending on 1/[L_o] where P = P_C/[1 + (m − 1)P_C] and P_C is the mole fraction of n/m ratio of the complexed ligand. The association constants of cations, K_ass, displayed the cation selectivities depending on the cation radii and the macrocyclic ether size, and Pb⁺ was found to give the strongest association with such crown ethers.     

6‐Propylamino‐2,6‐propylepimino‐2,4,4,8,8‐pentakis(pyrrolidin‐1‐yl)‐1,3,5,7,2λ5,4λ5,6λ5,8λ5‐tetraazatetraphosphorocine

The title compound, C₂₆H₅₅N₁₁P₄, consists of a bicyclic phosphazene ring with five bulky pyrrolidino and one propyl­amino group, together with a second propyl­amino group bridging the two P atoms. The asymmetric unit contains two mol­ecules with very similar conformations. The bulky substituents are instrumental in determining the bicyclic P₄N₅ ring conformation. Each of the fused six‐membered N₃P₃ rings is in a sofa conformation. The P—N distances in the bridge are non‐equivalent and one of them is the longest P—N bond in the mol­ecule. The hybridization of the bridging N atom is pyramidal. The single and double P—N bonds cannot easily be distinguished, since they retain their phosphazenic character in the phosphazene macro‐rings.     

Reentrant phase transition and network parameters of hydrophobically modified poly[2-(diethylamino)ethylmethacrylate-co-N-vinyl-2-pyrrolidone/octadecyl acrylate] hydrogels

Hydrophobically modified poly[2-(diethylamino)ethylmethacrylate-co-N-vinyl-2-pyrrolidone/octadecyl acrylate] [P(DEAEMA-NVP/OA)] hydrogels with different OA content were prepared by free-radical crosslinking copolymerization of corresponding monomers in tert-butanol. The swelling equilibrium of the hydrogels was investigated as a function of temperature and hydrophobic comonomer content in pure water. An interesting feature of the swelling behavior of the P(DEAEMA-NVP/OA) hydrogels was the reentrant phase transition where the hydrogels collapse once and reswell as temperature increased. The average molecular mass between crosslinks and polymer-solvent interaction parameter (χ) of the hydrogels were calculated from equilibrium swelling values. The enthalpy (ΔH) and entropy (ΔS) changes appearing in the χ parameter for the hydrogels were determined by using the Flory-Rehner theory. It was observed that the experimental swelling data of the hydrophobic hydrogels at different temperature agreed with the Flory-Rehner theory, that provided that the sensitive dependence of χ parameter on both temperature and polymer concentration is taken into account.     

Synthesis,IR spectrum,thermal property and crystal structure of cyano-bridged heteronuclear polymeric complex, [Cd(teta)Ni(μ-CN)<Subscript>2</Subscript>(CN)<Subscript>2</Subscript>] · 2H<Subscript>2</Subscript>O

The cyano-bridged heteronuclear polymeric complex, [Cd(teta)Ni(μ-CN)₂(CN)₂] · 2H₂O (1), (teta = triethylenetetraamine) was synthesized and characterized by FT-IR spectroscopy, thermal analysis and single crystal X-ray diffraction techniques. It crystallizes in the orthorhombic system, space group Pccn. The asymmetric unit also contains two uncoordinated water molecules. The coordination geometry around the Cd(II) centre is a highly distorted octahedral. In the crystal structure, intramolecular N–H···O and intermolecular N–H···O, O–H···O and O–H···N hydrogen bonds, beside the cyano-bridged chains made up of tetracyanonickelate ions coordinated to Cd(II) ions, where the Ni(II) ion is coordinated by four cyanoligands in a square-planar arrangement, link the molecules into polymeric networks parallel to (001) plane, where the hydrogen bonded water molecules occupy the cavities between the layers. The FT-IR spectrum was reported in the 4,000–400 cm⁻¹ region. Vibration assignments were given for all the observed bands and the spectral feature also supported the structure of the polymeric complex. The decomposition reaction takes place in the temperature range 20–1,000 °C in the static air atmosphere.     

How does within‐host dynamics affect population‐level dynamics? Insights from an immuno‐epidemiological model of malaria

Malaria is one of the most common mosquito‐borne diseases widespread in the tropical and subtropical regions. Few models coupling the within‐host malaria dynamics with the between‐host mosquito‐human dynamics have been developed. In this paper, by adopting the nested approach, a malaria transmission model with immune response of the host is formulated. Applying age‐structured partial differential equations for the between‐host dynamics, we describe the asymptomatic and symptomatic infectious host population for malaria transmission. The basic reproduction numbers for the within‐host model and for the coupled system are derived, respectively. The existence and stability of the equilibria of the coupled model are analyzed. We show numerically that the within‐host model can exhibit complex dynamical behavior, possibly even chaos. In contrast, equilibria in the immuno‐epidemiological model are globally stable and their stabilities are determined by the reproduction number. Increasing the activation rate of the within‐host immune response “dampens” the sensitivity of the population level reproduction number and prevalence to the increase of the within‐host reproduction of the pathogen. From public health perspective this means that treatment in a population with higher immunity has less impact on the population‐level reproduction number and prevalence than in a population with less immunity.     

1,1′,3,3′‐Tetraalkyl‐2,2′‐biperimidinylidenes: Unexpected substituent effects on the reactivity of carbon–carbon double bond

C₂ deprotonation of 1,3‐dibutylperimidinium bromide ( 1a ) with sodium hydride and a catalytic amount of potassium tert‐butoxide in dry THF led to the formation of the exceptionally inert tetraaminoalkene 2a . In contrast, isostructural tetrakis(2‐methoxyethyl)‐tetraaminoalkene ( 2b ) instantaneously reacted with O₂ to yield urea 3b , and silver nitrate was readily reduced with 2b to form a silver mirror. Compound 2a has been characterized by X‐ray diffraction studies; the naphtho‐pyrimidine skeleton imposes structural constraints and some rigidity to the CC bonding. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:82–87, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10088