Computer simulations of thermo-sensitive microgels: quantitative comparison with experimental swelling data

In this work, a quantitative comparison between experimental swelling data of thermo-sensitive microgels and computer simulation results obtained from a coarse-grained model of polyelectrolyte network and the primitive model of electrolyte is carried out. Polymer-polymer hydrophobic forces are considered in the model through a solvent-mediated interaction potential whose depth increases with temperature. The qualitative agreement between simulation and experiment is very good. In particular, our simulations predict a gradual shrinkage with temperature, which is actually observed for the microgels studied in this survey. In addition, the model can explain the swelling behavior for different contents of ionizable groups without requiring changes in the hydrophobic parameters. Our work also reveals that the abruptness of the shrinkage of charged gels is considerably conditioned by the number of monomeric units per chain. The swelling data are also analyzed with the Flory-Rhener theory, confirming some limitations of this classical formalism.     

Spectroscopic and Electrochemical Study of the Interconversion and Decomplexation of Cobalt(II) Sandwich Polyoxometalates Based on a Dawson-Type Anion

The reaction of the trivacant Dawson polyoxometalate α-[P(2)W(15)O(56)](12-) and the divalent cations Co(2+) is known to form a symmetrically derived sandwich complex of formula ββ-[Co(4)(H(2)O)(2)(P(2)W(15)O(56))(2)](16-) [symbolized as ββ-Co(4)(P(2)W(15))(2)] at low pH (ca. pH 3). We have shown previously that, by a slight modification of the reaction conditions, trinuclear αβ-[(NaOH(2))Co(3)(H(2)O)(P(2)W(15)O(56))(2)](17-) and dinuclear [(NaOH(2))(2)Co(2)(P(2)W(15)O(56))(2)](18-) complexes [symbolized as αβ-NaCo(3)(P(2)W(15))(2) and Na(2)Co(2)(P(2)W(15))(2), respectively] can be synthesized as aqueous-soluble sodium salts. αβ-NaCo(3)(P(2)W(15))(2) is a "lacunary" sandwich complex that can add a Co(2+) cation to form nearly quantitatively an unsymmetrical Dawson tetracobalt sandwich polyoxometalate, αβ-[Co(4)(H(2)O)(2)(P(2)W(15)O(56))(2)](16-) [symbolized as αβ-Co(4)(P(2)W(15))(2)]. Thus, for Co(4)(P(2)W(15))(2), the junctions between the trivacant {P(2)W(15)} subunits and the central tetrameric unit can be either both β type or β and α types. The interconversion between αβ-Co(4)(P(2)W(15))(2) and ββ-Co(4)(P(2)W(15))(2) and the decomplexation process at low pH, leading to the formation of αβ-NaCo(3)(P(2)W(15))(2) and/or Na(2)Co(2)(P(2)W(15))(2), have been followed in aqueous solution at various pH values by electrochemistry, UV-visible absorption spectroscopy, and (31)P NMR spectroscopy.     

Tandem Michael imino–aldol reactions catalyzed by samarium diiodide

Samarium diiodide catalyzes a one-pot procedure allowing to perform sequentially the Michael addition of a ketene silyl acetal on a cyclic ,β-unsaturated ketone, followed by the addition of a glyoxylic or aromatic imine. The presence of a coordinating group on the imine increases the rate of the reaction.     

Synthesis and Anti‐proliferative Activity of N,N′‐bis‐substituted 1,2,4‐Triazolium Salts against Breast Cancer and Prostate Cancer Cell Lines

A series of 1,4‐N,N′‐bis‐substituted 1,2,4‐triazolium bromide salts were synthesized and tested for anti‐proliferative activity. 1,4‐Bis(naphthalen‐2‐ylmethyl)‐1,2,4‐triazolium bromide ( 2 ) showed activity against MDA‐MB‐468 breast cancer and PC‐3 prostate cancer cell lines.     

A practical synthesis of 2,2-difluoro-3-amino-propanoic acid (α,α-difluoro-β-alanine)

Reformatsky reaction of ethyl bromodifluoroacetate with N,N-(dibenzyl)-1H-benzotriazolyl-1-methylamine gave fully protected α,α-difluoro-β-alanine. Hydrogenolysis and hydrolysis furnished α,α-difluoro-β-alanine. Further transformation into N-phthalimido-α,α-difluoro-β-alanine was described.     

The groups related to the smallest non-affine Hall triple system

Every HTS is associated with a M₃-loop, just as every affine space overF ₃ is associated with an elementary abelian 3-group. If E is a M₃-loop, denote by(E) the corresponding HTS. Then ¦ Aut (E) ¦=¦E¦.¦Aut E ¦. When E is free among the M₃-loops which are nilpotent of class 2, the groups Aut E and Aut (E) may be described. The Fischer groups related to the non-affine HTS of order 3⁴ are described and the structure of their automorphism groups is discussed.     

Synthesis of ethyl 2-aminodihydro-5-pyrimidinecar-boxylate derivatives and 3,7-diethoxycarbonyl-4,6-dihydro-2,4,6,8-tetraaryl-1H-pyrimido[1,2-a]pyrimidines

Reactions of ethyl 3-aryl-2-benzoylpropenoates 1 with guanidine and N-alkyl(or benzyl)guanidines have been investigated. Ethyl 2-aminodihydro-5-pyrimidinecarboxylate derivatives 3, 4 or 5, and 3,7-diethoxy-carbonyl-4,6-dihydro-2,4,6,8-tetraaryl-1H-pyrimido[1,2-a]pyrimidines 6 have been synthesized.     

Cut-elimination and interpolation for Ω-logic

In 1978, Girard introduced-logic to generalize-logic. The basic category of-logic is the categoryON of ordinals. For geometric structure reasons, Girard changed the basic categoryON into the more general categoryWF of well-founded orders (1983). The logic he obtained was called-logic. Here, we extend (unpublished) results of-logic to-logic.     

Synthesis of some 2,4-disubstituted tetrahydropyrimido[4,5-b]quinolines as potential antitumor agents

Cyclocondensations of two 2,4-disubstituted 6-aminopyrimidines with 2-chloro-1-cyclohexenecarboxaldehyde afforded in each case a new regiospecific synthesis of tricyclic, linear disubstituted 6,7,8,9-tetrahydro-pyrimido[4,5-b]quinolines 2 and 3 in excellent yields. The linear structures and hence the regiospecificity of the synthesis were established using ¹H nmr and ¹³C nmr. The growth of leukemia L1210 cells in culture was inhibited 50% by 2 at 30 × 10^?6M and 48% by 3 at 100 × 10^?6M.