Universal Strict General Actors and Actors in Categories of Interest

For any category of interest ℂ we define a general category of groups with operations \mathbbC_G, \mathbbC\hookrightarrow\mathbbC_G\mathbb{C_G}, \mathbb{C}\hookrightarrow\mathbb{C_G}, and a universal strict general actor USGA(A) of an object A in ℂ, which is an object of \mathbbC_G\mathbb{C_G}. The notion of actor is equivalent to the one of split extension classifier defined for an object in more general settings of semi-abelian categories. It is proved that there exists an actor of A in ℂ if and only if the semidirect product \textUSGA(A)\ltimes A{\text{USGA}}(A)\ltimes A is an object of ℂ and if it is the case, then USGA(A) is an actor of A. We give a construction of a universal strict general actor for any A ∈ ℂ, which helps to detect more properties of this object. The cases of groups, Lie, Leibniz, associative, commutative associative, alternative algebras, crossed and precrossed modules are considered. The examples of algebras are given, for which always exist actors.     

Main features of electronic momentum distribution in sodium clusters

We have analyzed the electronic momentum distribution n(k) of sodium clusters using the Kohn-Sham formalism within the Local Density Approximation for the valence electrons. Simple approximations to the Wigner transform have been used to understand the deviation between n(k) in clusters and in the bulk system. Deformation effects have been also analyzed.     

The crystal and molecular structures of cyclohexanone thiosemicarbazone

Cyclohexanone thiosemicarbazone (Hchtsc) crystallizes in the triclinic crystal system with space group P (No. 2) and the following unit cell parameters: a = 6.2989(2), b = 7.9730(3), and c = 9.4118(2) Å = 79.607(3), = 85.519(2), and = 73.50(2)° V = 445.60(2) ų, Z = 2. The lengths of the bonds C(1)–S, C(1)–N(1), C(1)–N(2), and N(2)–N(3) suggest electron delocalization in all four. The S atom is trans to N(3), and this E configuration is stabilized by intramolecular hydrogen bonding between N(3) and the N(1)H₂ group. Two intermolecular hydrogen bonds involving the S atom and the N(1)–H(1b) and N(2)–H(2) groups give rise to a polymeric chain of molecule pairs.     

Dual aperture control on pH- and anion-driven supramolecular nanoscopic hybrid gate-like ensembles

The development of gate-like systems able to perform certain programmed functions is an interesting way of taking chemistry to the frontiers of nanoscience. In relation to this field, we report a complete study of the behavior of a pH-driven and anion-controlled nano-supramolecular gate-like ensemble obtained by anchoring suitable polyamines on the pore outlets of mesoporous materials of the type MCM-41 (solid N3-S). The release of an entrapped dye (Ru(bipy)3(2+)) from the pore voids into the bulk solution allows us to study the gating effect. A pH-driven open/close mechanism was observed that arises from the hydrogen-bonding interaction between amines at neutral pH (open gate) and Coulombic repulsions at acidic pH between closely located polyammoniums at the pore openings (closed gate). Molecular dynamics simulations using force field methods have been carried out to explain the pH-driven open/close mechanism. For this purpose, a mesoporous silica structure was constructed, taking as base the (111) plane of the beta-crystoballite structure on which large hexagonal nanopores and anchored polyamines were included. From these calculations, it was observed how completely unprotonated amines display poor coverage of the pore (fully open gate), whereas completely protonated amines (simulating a pH 2 or lower) result in a clear reduction of the pore aperture, in agreement with the experimental results. In additional to the pH-driven protocol, opening/closing of the gate-like ensemble can also be modulated via an anion-controlled mechanism. This study was carried out by monitoring the dye released from the pore voids of the N3-S solid at a certain pH in the presence of a range of anions with different structural dimensions and charges, including chloride, sulfate, phosphate, and ATP (C(anion) = 1 x 10(-2) mol dm(-3)). The choice of a certain anionic guest results in a different gate-like ensemble behavior, ranging from basically no action (chloride) to complete (ATP) or partial pore blockage, depending on the pH (sulfate and phosphate). The remarkable anion-controllable response of the gate-like ensemble can be explained in terms of anion complex formation with the tethered polyamines. These experimental studies are also in agreement with computational simulations with fluoride, chloride, iodide, and dihydrogen phosphate anions. In the model, larger anions push the tethered polyamines toward the pore openings more efficiently, and therefore the pore aperture decreases. The studies also show that, for anions showing a strong tendency to form hydrogen-bonding networks (e.g., phosphate), complete pore blockage was observed at acidic pH. Finally, selectivity patterns have been discussed in terms of kinetic rates of the liberation of the Ru(bipy)3(2+) dye from the amine-functionalized dye-containing material N3-S.     

Synthesis, structural characterization, and antiinflammatory activity of triethylphosphinegold(I) sulfanylpropenoates of the type [(AuPEt3)2xspa] [H2xspa = 3-(aryl)-2-sulfanylpropenoic acid]: an (H2O)6 cluster in the lattice of the complexes [(AuPEt3)2xspa] x 3 H2O

Gold complexes of the type [(AuPEt3)2xspa] were prepared by reacting AuPEt3Cl in basic media with the 3-(aryl)-2-sulfanylpropenoic acids H2xspa [x = p, Clp, -o-mp, -p-mp, -o-hp, -p-hp, diBr-o-hp, f, t, -o-py; p = 3-phenyl, Clp = 3-(2-chlorophenyl)-, -o-mp = 3-(2-methoxyphenyl)-, -p-mp = 3-(4-methoxyphenyl)-, -o-hp = 3-(2-hydroxyphenyl)-, -p-hp = 3-(4-hydroxyphenyl)-, diBr-o-hp = 3-(3,5- dibromo-2-hydroxyphenyl)-, f = 3-(2-furyl)-, t = 3-(2-thienyl)-, -o-py = 3-(2-pyridyl); spa = 2-sulfanylpropenoato], and 2-cyclopentylidene-2-sulfanylacetic acid (H2cpa). The complexes were characterized by spectroscopic methods (IR, (1)H, (13)C and (31)P NMR) and mass spectrometry, and the complexes [(AuPEt3)2pspa] x 3 H2O, [(AuPEt3)2-p-hpspa] x 3 H2O, [(AuPEt3)2tspa)] x 3 H2O, and [(AuPEt3)2-o-hpspa] by X-ray diffractometry. The crystals of the first three complexes contain (H2O)6 clusters hydrogen bonded to [(AuPEt3)2xspa]2 dimer units, whereas in the -o-hpspa derivative the hydrogen bonds are between the monomer [(AuPEt3)2-o-hpspa] units. The antiinflammatory activity of the complexes against plantar edema induced by carrageenan in rats is generally significant, with the values for the o-hpspa and tspa derivatives being particularly high.     

Combinatorial approach to N-substituted aminocyclitol libraries by solution-phase parallel synthesis and preliminary evaluation as glucocerebrosidase inhibitors

Libraries of N-substituted aminocyclitol derivatives of the scyllo and racemic chiro series by means of parallel solution-phase methodology with the help of robotic technology are described. Chemical diversity has been introduced by reaction of selected scaffolds with a set of aldehydes, acyl chlorides, sulfonyl chlorides, chloroformates, and amines to afford the corresponding amines, amides, sulfonamides, carbamates and ureas, respectively. The optimized methodology has proven excellent, in terms of overall purities of the resulting libraries, for the production of amides. Sulfonamides and carbamates have been obtained in slightly lower purities, while amines afforded modest results. Selected library members have been evaluated as inhibitors of recombinant glucocerebrosidase with K(i) values ranging in the low micromolar scale for the most active members.     

Second-Order Necessary Optimality Conditions for Some State-Constrained Control Problems of Semilinear Elliptic Equations

In this paper we are concerned with some optimal control problems governed by semilinear elliptic equations. The case of a boundary control is studied. We consider pointwise constraints on the control and a finite number of equality and inequality constraints on the state. The goal is to derive first- and second-order optimality conditions satisfied by locally optimal solutions of the problem. Accepted 6 May 1997     

Kinetics of corrosion and dissolution of uranium dioxide as a function of pH

A continuous flow-through reactor with a thin layer of solid particles (size ranging from 100 to 300 μm) was used to obtain a deeper knowledge on the mechanism of dissolution of UO₂ under oxidizing conditions. Using this methodology the dissolution rate of uranium dioxide was determined at three different oxygen partial pressures (5, 21, and 100% in nitrogen) and as a function of pH (between 3 and 12) in a noncomplexing medium. From the results of these experiments the following rate equation was derived: In addition, XPS characterizations were performed to determine the U(IV)/U(VI) ratio on the solid surface at different experimental times and conditions. These results showed that at acidic conditions (pH below 6.7) the final solid surface presents a stoichiometry close to UO₂, while at alkaline conditions the final solid surface average composition is close to UO_2.25. This information was integrated with the results of the leaching experiments to present a model for the mechanism of dissolution of uranium dioxide under the experimental conditions. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 261–267, 1997.