Highly sensitive dynamic strain measurements by locking lasers to fiber Bragg gratings

A novel, sensitive, simple, and robust strain interrogation technique is analyzed and experimentally tested. By locking a laser wavelength to the midreflection wavelength of a standard fiber Bragg grating and measuring the error signal, we achieve high dynamic strain sensitivity of 45 picostrain/ radicalHz rms at 3 kHz, where the dominant noise in the experiment is the laser frequency noise.     

Internal structure of a thin film of mixed polymeric micelles on a solid/liquid interface

The adsorption of mixed micelles of poly(4-(2-amino hydrochloride-ethylthio)-butylene)- block-poly(ethylene oxide), PAETB 49- b-PEO 212 and poly(4-(2-sodium carboxylate-ethylthio)-butylene)- block-poly(ethylene oxide), PCETB 47- b-PEO 212 on solid/liquid interfaces has been studied with light, X-ray, and neutron reflectometry. The structure of the adsorbed layer can be described with a two-layer model consisting of an inner layer formed by the coacervate of the polyelectrolyte blocks PAETB 49 and PCETB 47 ( approximately 1 nm) and an outer layer of PEO 212 blocks ( approximately 6 nm). The micelles unfold upon adsorption forming a rather homogeneous flat layer that exposes its polyethylene oxide chains into the solution, thus rendering the surface antifouling after modification with the micelles.     

Finiteness Principles for Smooth Selection

In this paper we prove finiteness principles for \({C^m{({\mathbb{R}^n},{\mathbb{R}^D)}}}\) and \({C^{m-1,1}(\mathbb{R}^n,\mathbb{R}^D)}\) selections. In particular, we provide a proof for a conjecture of Brudnyi-Shvartsman (1994) on Lipschitz selections for the case when the domain is \({X=\mathbb{R}^n}\).     

Wormlike aggregates from a supramolecular coordination polymer and a diblock copolymer

The formation of wormlike micelles in mixed systems of a supramolecular coordination polymer Zn-L2EO4 and a diblock copolymer P2MVP41-b-PEO205 is investigated by light scattering and Cryo-TEM. By direct mixing at a stoichiometric charge ratio, the above mixtures proved to be capable of formation of spherical micelles with a radius of about 25 nm (Yan et al. Angew. Chem., Int. Ed.; 2007, 46, 1807-1809). Lately, we find wormlike micelles with a hydrodynamic radius >150 nm in a mixture with excess positive charge, that is, a negative charge fraction f- < 0.5. The transformation between wormlike and spherical micelles can be realized by variation of the mixing ratio through different protocols. Upon addition of negatively charged Zn-L2EO4 to a mixture with excess positively charged P2MVP41-b-PEO205, most of the wormlike micelles are transformed into spherical ones; upon addition of positively charged P2MVP41-b-PEO205 to a mixture of pure spherical micelles, wormlike micelles can be produced again. The effect of sample preparation protocol, sample history, and concentration on this transformation process is systematically reported in this article. A possible mechanism for the formation of wormlike micelles is proposed.     

Measuring location, size, distribution, and loading of NiO crystallites in individual SBA-15 pores by electron tomography

By the combination of electron tomography with image segmentation, the properties of 299 NiO crystallites contained in 6 SBA-15 pores were studied. A statistical analysis of the particle size showed that crystallites between 2 and 6 nm were present with a distribution maximum at 3 and 4 nm, for the number-weighted and volume-weighted curves, respectively. Interparticle distances between nearest neighbors were 1-3 nm with very few isolated crystallites. In the examined pores, a local loading twice the applied average of 24 wt % NiO was found. This suggests that a very high local loading combined with a high dispersion is achievable.     

Molecular assemblies from imidazolyl-containing haloalkenes and haloalkynes: competition between halogen and hydrogen bonding

The structural characterization of molecular assemblies constructed from imidazolyl-containing haloalkenes and haloalkynes is reported. 1-(3-Iodopropargyl)imidazole (2) and 1-(2,3,3-triiodoallyl)imidazole (5) were synthesized from 1-propargylimidazole (1). In the solid state, these wholly organic modules self-assemble through N...I halogen-bonding interactions, thus giving rise to polymeric chains. The N...I interaction observed in 2 (d(N...I)=2.717 A, angle-spherical C(sp)-I...N=175.8 degrees) is quite strong relative to previously reported data. The N...I interaction in 5 (d(N...I)=2.901 A, angle-spherical C(sp2)-I...N=173.6 degrees) is weaker, in accordance with the order C(sp)-X<--base>C(sp2)-X<--base. Compound 5 was found to give a 1:1 cocrystal 4 with morpholinium iodide (6). In the X-ray crystal studies of 4, N...I halogen-bonding interactions similar to those observed in 5 were shown not to be present, as the arrangement of the molecules is governed by two interwoven hydrogen-bonding networks. The first network involves N-H...O interactions between nearby morpholinium cations, and the second network is based on N-H...N hydrogen bonding between morpholinium cations and imidazolyl groups. Both hydrogen-bonding schemes are charge-assisted. Halogen bonding is not completely wiped out, however, as the triiodoalkene fragment forms a halogen bond with an iodide anion in its vicinity (d(I...I)=3.470 A, angle-spherical C(sp2)-I...I=170.7 degrees). X-ray crystal studies of 6 show a completely different arrangement from that observed in 4, namely, N-H...O interactions are not present. In crystalline 6, morpholinium cations are interconnected through C-H...O bridges (d(H...O)=2.521 and 2.676 A), and the NH2+ groups interact with nearby iodide anions (d(H...I)=2.633 and 2.698 A).     

Application of microwave superheating for the synthesis of TiO2 rods

A simple microwave irradiation method for the large-scale synthesis of submicrometer-sized TiO2 rods at normal atmospheric pressure and the boiling temperature of the solvent is demonstrated. It is emphasized that only 1-3 min of microwave irradiation is adequate to react tetra-isopropyl orthotitanate with ethylene glycol to produce rods of titanium glycolate [TG] with diameters of approximately 0.4 microm and lengths up to 5 microm. The as-formed TG rods, followed by calcination under air for 2 h, fabricated anatase (500 degrees C) and rutile (900 degrees C) titania without changing their rod-shaped morphology. The crystallinity, structure, morphology, and thermal analysis are carried out by several techniques. A mechanism based on microwave superheating phenomena is presented with the support of previous reports and several control experiments.     

Enzymatic condensation and polycondensation reactions in organic solvents

Lipases in organic solvents catalyse lactonisation or polymerisation of ω-hydroxyesters. Under these conditions the enzymes exhibit both enantioselectivity and prochiral selectivity. This approach was used to develop the synthesis of chiral γ-lactones and A-B type polyesters from racemic or prochiral hydroxyester substrate.