Synthesis of hydrogels based on poly(NIPAM) inserted into collagen sponge

The study presents the preparation of a semi-synthetic hydrogel based on poly(N-isopropyl acrylamide-co-diethylene glycol diacrylate) inserted onto the collagen porous membrane. The synthesis of the hydrogels was performed through radical copolymerization of N-isopropyl acrylamide (NIPAM) with diethylene glycol diacrylate (DEGDA) also as crosslinking agent, using ammonium persulfate as initiator and N,N,N',N'-tetramethylethylene diamine as activator, and it was achieved in the presence of the collagen matrix. The prepared hydrogels were characterized by Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy. The swelling behaviour of the semi-interpenetrated polymer network related on the hydrogel composition, it was also evaluated. The pore sizes of the synthesized hydrogels, much larger than the typical mesh size of a conventional hydrogel, allow to consider the hybrid hydrogel based on the inserted poly(NIPAM-co-DEGDA) onto collagen fibrils as a super-porous hydrogel.     

Synthesis and conformation of chiral biheteroaryls

Bridging 2,3 and 2',3' positions in 2,2'-dihydroxy-1,1'-binaphthyl and 2,2'-diamino-1,1'-binaphthyl, respectively, resulted in formation of chiral O- and N-bis-tricyclic compounds accessible in 4 steps from known 3,3'-diiodo precursors. In both cases, 2-fold ring closing metathesis of tetraallyl intermediates proceeded regioselectively to give tetrahydrobinaphtho[2,3-b]oxepine and -azepine, respectively. In case of the N-mesyl-N-allyl precursor, three, at room temperature separable, rotamers were isolated and characterized by NMR spectroscopy and X-ray structure determination. Their interconversion (process I) was followed by NMR, yielding rate constants and thermodynamic parameters. The rotamers with either C(1) or C(2) symmetry were stereospecifically cyclized to conformatively moderately stable bis-sulfonamides. Also in this case, the kinetics of their interconversion (process II) was investigated and from two of them the crystal structure was determined. Processes I and II were investigated by a DFT method, M06-2X, to gain insight into electronic and steric peculiarities responsible for the remarkable conformative stabilities. Transition state geometries and energies were calculated and compared with empirical data.     

An abstract setting for hamiltonian actions

In this paper we develop an abstract setup for hamiltonian group actions as follows: Starting with a continuous 2-cochain ω on a Lie algebra ${\mathfrak h}$ with values in an ${\mathfrak h}$ -module V, we associate subalgebras ${\mathfrak {sp}(\mathfrak h,\omega) \supseteq \mathfrak {ham}(\mathfrak h,\omega)}$ of symplectic, resp., hamiltonian elements. Then ${\mathfrak {ham}(\mathfrak h,\omega)}$ has a natural central extension which in turn is contained in a larger abelian extension of ${\mathfrak {sp}(\mathfrak h,\omega)}$ . In this setting, we study linear actions of a Lie group G on V which are compatible with a homomorphism ${\mathfrak g \to \mathfrak {ham}(\mathfrak h,\omega)}$ , i.e., abstract hamiltonian actions, corresponding central and abelian extensions of G and momentum maps ${J : \mathfrak g \to V}$ .     

Filling in solvable groups and in lattices in semisimple groups

We prove that the filling order is quadratic for a large class of solvable groups and asymptotically quadratic for all -rank one lattices in semisimple groups of -rank at least 3. As a byproduct of auxiliary results we give a shorter proof of the theorem on the nondistorsion of horospheres providing also an estimate of a nondistorsion constant.     

Thermoxidative degradation of poly(vinyl alcohol) under dynamic thermogravimetric conditions. II. Influence of the hydrolysis degree

The influence of the degree of hydrolysis on thermoxidative degradation of the poly(vinyl alcohol) was studied. The thermoxidative degradation was carried out under dynamic thermal conditions. Taking into account the dependence of the activation energy values on the heating rate, molecular weight, degree of conversion, and degree of hydrolysis, some conclusions were drawn about the decomposition mechanism and the variation of the thermal stability.     

Solid phase synthesis of 3,4,7-trisubstituted 4,5,8,9-tetrahydro-3H-imidazo[1,2-a][1,3,5]triazepin-2(7H)-thiones and N-alkyl-4,5,7,8-tetrahydro-3H-imidazo[1,2-a][1,3,5]triazepin-2-amines

The solid-phase parallel synthesis of 3,4,7-trisubstituted 4,5,8,9-tetrahydro-3H-imidazo[1,2-a][1,3,5]triazepin-2(7H)-thiones and N-alkyl-4,5,7,8-tetrahydro-3H-imidazo[1,2-a][1,3,5]triazepin-2-amines starting from resin-bound dipeptides is described. The key synthetic steps involve the cylization of an amino and a guanidino functionality using thiocarbonyldiimidazole and the subsequent transformation of the resulting thiourea moiety to a substituted guanidine group using HgCl(2) and various amines. Following cleavage from the resin, the desired products were obtained in good yields and good to moderate purities, depending on the building blocks employed.     

Progress in silica polypeptide composite colloidal hybrids: from silica cores to fuzzy shells

Core–shell particles have attracted increased interest in the past two decades. The properties of these composite materials are a symbiosis between the core and shell features which neither can exhibit separately. Polypeptide composite particles (PCPs) are a newly expanding field of hybrid materials with potential future impact in a broad variety of applications. In this review, we present an overview about the progress made on designing PCPs. Past and present limitations in the fabrication of the cores and shells alone will be outlined. A special emphasis will be placed on the future challenges directed to design better materials by expanding the architectural repertoire which will benefit their functionality and their range of applications. The review also presents possible future trends and challenges in engineering polypeptide-based materials as platforms for targeted applications.     

Synthese von 3,3-Bis(alkylthio)-2-(2-thioxo-benzo-2H-1,3-thiazol-3-yl)-acrylsäure-Derivaten und Kristallstruktur des entsprechenden Ethyl 3,3-Bis(methylthio)acrylats

Summary The 3,3-bis(alkylthio)-2-(2-thioxo-benzo-2H-1,3-thiazole-3-yl)acrylonitriles3a–e, the methyl and ethyl acrylates4 and5a–d, respectively, are prepared by dithiocarboxylation of the corresponding derivatives of acetic acid1a–c. The crystal structure of ethyl 3,3-bis(methylthio)-2-(2-thioxo-benzo-2H-1,3-thiazole-3-yl)acrylate5a has been determined by X-ray analysis.

     

Intense laser effects on the optical properties of asymmetric GaAs double quantum dots under applied electric field

We investigated the combined effects of a non-resonant intense laser field and a static electric field on the electronic structure and the nonlinear optical properties (absorption, optical rectification) of a GaAs asymmetric double quantum dot under a strong probe field excitation. The calculations were performed within the compact density-matrix formalism under steady state conditions using the effective mass approximation. Our results show that: (i) the electronic structure and optical properties are sensitive to the dressed potential; (ii) under applied electric fields, an increase of the laser intensity induces a redshift of the optical absorption and rectification spectra; (iii) the augment of the electric field strength leads to a blueshift of the spectra; (iv) for high electric fields the optical spectra show a shoulder-like feature, related with the occurrence of an anti-crossing between the two first excited levels.     

Incoherent vector vortex-mode solitons in self-focusing nonlinear media

We suggest a novel type of composite spatial optical soliton created by a coherent vortex beam guiding a partially incoherent light beam in a self-focusing nonlinear medium. We show that the incoherence of the guided mode may enhance, rather than suppress, the vortex azimuthal instability, and we also demonstrate strong destabilization of dipole-mode solitons by partially incoherent light.