Topological representation for monadic implication algebras

In this paper, every monadic implication algebra is represented as a union of a unique family of monadic filters of a suitable monadic Boolean algebra. Inspired by this representation, we introduce the notion of a monadic implication space, we give a topological representation for monadic implication algebras and we prove a dual equivalence between the category of monadic implication algebras and the category of monadic implication spaces.      

Are the mixtures of homologous surfactants ideal?

The interaction between homologous surfactants in mixed micelles was studied by the Regular Solution Theory of mixed micelles. The interaction is independent of the nature of the polar head groups and attractive and the interaction parameter betaM depends linearly on the difference in chain length DeltanC. The interaction becomes ideal at DeltanC=0.75+/-0.06. Above DeltanC approximately 5, the dependence remains linear but the slope increased 2.7 times. The phenomenon is explained as the effect of the reduction of the hydrocarbon/water micelle interface and a better packing of the chains in the micelle core, caused by the inclusion of a shorter homologous surfactants. This reduction can be more effective when DeltanC>or=5.     

Gold(I) and silver(I) mixed-metal trinuclear complexes: dimeric products from the reaction of gold(I) carbeniates or benzylimidazolates with silver(I) 3,5-diphenylpyrazolate

Trinuclear mixed-metal gold-silver compounds are obtained by the reaction of gold(I) carbeniate [Au(mu-C(OEt)=NC6H4-p-CH3)]3, TR(carb), or gold(I) imidazolate [Au-mu-C,N-1-benzyl-2-imidazolate]3, TR(bzim), with silver(I) pyrazolate [Ag(mu-3,5-Ph2pz)]3. The crystalline products are mixed-ligand, mixed-metal dimeric products [Au(carb)Ag2(mu-3,5-Ph2pz)2], [Au2(carb)2Ag(mu-3,5-Ph2pz)].CH2Cl2, [Au(bzim)2Ag2(mu-3,5-Ph2pz)], and [Au2(bzim)2Ag(mu-3,5-Ph2pz)]. They have been characterized by elemental analysis and 1H NMR and mass spectrometry. The X-ray structure of [Au(carb)Ag2(mu-3,5-Ph2pz)2] shows it to be a dimer with two Ag...Au contacts between the trinuclear units of 3.083(2) and 3.310(2) A and with average intramolecular Ag...Ag and Au...Ag distances of approximately 3.3 and 3.2 A, respectively. The structure of [Au2(carb)2Ag(mu-3,5-Ph2pz)].CH2Cl2 is a dimer with one intermolecular Au...Au attraction of 3.3354(10) A and a short Ag...Au distance of approximately 3.42 A and intramolecular Ag...Au and Au...Au contacts of approximately 3.2 and approximately 3.3 A, respectively. Packing diagrams of both complexes show that the dimeric units are independent, similar to their parent molecules. The dimers of trinuclear [Au(carb)Ag2(mu-3,5-Ph2pz)2] and [Au2(carb)2Ag(mu-3,5-Ph2pz)].CH2Cl2 crystallize in the triclinic space group P (Z = 2), a = 9.688(3) A, b = 15.542(4) A, c = 23.689(6) A, alpha = 82.560(5) degrees , beta = 87.887(6) degrees , gamma = 78.060(5) degrees , and the orthorhombic space group Pca2(1) (Z = 4), a = 29.644(4) A, b = 7.4582(10) A, c = 30.473(4) A, respectively. The structure of [Au(bzim)Ag2(mu-3,5-Ph2pz)2] is a dimer with two metallophilic Ag...Au interactions of 3.14 A. The complex crystallizes in the monoclinic space group C2/c (Z = 4), a = 26.368(5) A, b = 15.672(3) A, c = 17.010(3) A, beta = 102.206(3) degrees .     

3D Printing of Poly(3-hydroxybutyrate) Porous Structures Using Selective Laser Sintering

Summary: Poly(3-hydroxybutyrate) (PHB) 3D porous cubes were successfully built with Selective Laser Sintering (SLS), one of the many existing 3D printing technologies. The resulting cubes presented shape and dimensions very close to the corresponding virtual model. Moreover, they were resistant to handling without presenting any visible damage. The PHB powder did not present variation in thermal properties and chemical composition after 32.15 hours of SLS process as observed by proton nuclear resonance (¹H NMR) and differential scanning calorimetry (DSC) analysis, indicating that it can be re-utilized to print additional structures without affecting the reproducibility of the process.     

Intramolecular Diels-Alder reactions with furan: The gem-dialkyl effect revisited

Remote substituents that influence ground state state rotamer populations were found to be important controlling factors in the intramolecular Diels-Alder reaction with furan.     

Structural Features of Phosphate and Sulfate Modified Zirconia Prepared by Sol–Gel Route

This paper describes the effect of sulfate, phosphate and nitrate complexing ligands on the structural features of amorphous xerogels and on the crystallization of metastable zirconia phases during the xerogel-ceramic conversion. Powdered samples were prepared by a sol–gel route using zirconyl chloride precursors chemically modified by complexing ligands. The structural evolution of ZrO₂ phases as function of firing temperature was analyzed by XRPD, EXAFS and ³¹P NMR/MAS. The experimental results show the formation of metastable t-ZrO₂ during the low firing temperature of xerogels modified by sulfate or phosphate groups. The martensitic tetragonal-monoclinic transformation occurs during desorption of sulfate groups. The largest temperature interval of stability of metastable tetragonal zirconia was observed for phosphate-modified xerogels.     

Characterization of poly[(R)-3-hydroxybutyrate-co-epsilon-caprolactone] copolymers by matrix-assisted laser desorption/ionization time-of-flight and electrospray ionization mass spectrometry

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) of narrowly dispersed molecular weight gel permeation chromatography (GPC) fractions was used to characterize random and microblock poly[(R)-3-hydroxybutyrate-co-epsilon-caprolactone] [P(HB-co-CL)] copolymers obtained via the acid-catalyzed transesterification of the corresponding homopolymers, poly([(R)-3-hydroxybutyrate] (PHB) and poly(epsilon-caprolactone) (PCL). High-quality mass spectra were obtained, which made it possible to establish the nature of the polymer end groups. Besides the carboxylic termination, two other moieties were found: alcoholic and tosyl end groups. MALDI mass spectra of CL-rich samples possessed mostly tosyl end groups, while HB-rich samples possessed mostly alcoholic end groups, showing that the tosyl moiety is linked prevalently to CL terminal units. The higher resolution of electrospray ionization (ESI) mass spectra of lower molecular weight GPC fractions permitted the identification of the different oligomer species hypothesized in the assignment of the corresponding MALDI mass spectra. Partial methanolysis of these copolymers was explored as a method of producing mixed HB-CL oligomers to be utilized as new synthons, possessing a minor number of chiral centers from those obtained from hydrolysis of biotechnologically synthesized poly(hydroxyalkanoates) (PHAs).     

Crystal structure of a novel Hg(II) complex, [Hg(tri-2-furylphosphine)2(tri-2-furylphosphinoxide)3] [ClO4]2

The Hg(II) complex [Hg(TFP)₂(OTFP)₃][ClO₄]₂ with TFP=tri-2-furyl-phosphine and OTFP=tri-2-furylphosphinoxide has been prepared and characterised. It crystallises in the hexagonal P6₃/m space group with Z=2, a=13.308(3), c=21.092 (4) Å, V=3235(1) Å³. The structure of the complex cation consists of independent molecules with Hg pentacoordinated in exact trigonal bipyramidal geometry.     

Polyethersulfone‐epoxy terminated materials as thermosetting resins for microelectronic devices

A totally aromatic polyether/sulfone resin (PES‐E) was synthesized and tested as an insulating glue in the construction of a Chip‐on‐Chip (CoC) device. PES‐E, essentially constituted of open‐chain macromolecules of low molecular mass (M _n of about 3000 Da) with hydroxy and/or epoxy end‐groups, has a glass transition temperature of about 150 °C and is subject to crosslinking at temperatures higher than 320 °C. A CoC device was assembled using a five‐step process by interposing a layer of PES‐E between two chips. After curing, SEM cross section images showed a homogeneous crosslinked resin layer well stuck (flick and shear tests) to both chips. The chemical structure of the chains and the hydroxy/epoxy end‐groups ratio were optimized to obtain a crosslinked material with good adhesion and sufficient flexibility to avoid cracking during assembly and use. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5682–5689, 2009     

Highly diastereoselective allylic azide formation and isomerization. Synthesis of 3(2'-amino)-beta-lactams

The stereoselective anti SN2' attack of NaN3 to 3-alkenyl-3-bromo-azetidin-2-ones gave a mixture of diastereomeric azides in fast equilibrium. The [3,3]-sigmatropic rearrangement of allylic azides occurred with complete stereocontrol, allowing the equilibrium to be directed preferentially toward the (E)- or (Z)-isomer, useful precursors of 3(2'-amino)-beta-lactams. [reaction: see text]