Hybrid fluorescent liquid crystalline composites: directed assembly of quantum dots in liquid crystalline block copolymer matrices

Hybrid fluorescent liquid crystalline (LC) composites containing inorganic quantum dots (QDs) are promising materials for many applications in optics, nanophotonics and display technology, combining the superior emission capability of QDs with the externally controllable optical properties of LCs. In this work, we propose the hybrid LC composites that were obtained by embedding CdSe/ZnS QDs into a series of host LC block copolymers of different architectures by means of a two-stage ligand exchange procedure. The ABA/BAB triblock copolymers and AB diblock copolymers with different polymerization degrees are composed of nematogenic phenyl benzoate acrylic monomer units and poly(4-vinylpyridine) blocks, which are capable of binding to the QD surface. Our results clearly show that the spatial distribution of QDs within composite films as well as the formation of QD aggregates can be programed by varying the structure of the host block copolymer. The obtained composites form a nematic LC phase, with isotropization temperatures being close to those of the initial host block copolymers. In addition, the influence of the molecular architecture of the host block copolymers on fluorescence properties of the obtained composites is considered. The described strategy for the QD assembly should provide a robust and conventional route for the design of highly ordered hierarchical hybrid materials for many practical applications.

Spatial distribution of QDs within hybrid composite films was programed by varying the molecular architecture of the host LC block copolymers.     

Design and synthesis of lipid-mimetic cationic iridium complexes and their liposomal formulation for in vitro and in vivo application in luminescent bioimaging

Two iridium [Ir(N^C)₂(N^N)]⁺ complexes with the diimine N^N ligand containing a long polymethylene hydrophobic chain were synthesized and characterized by using NMR and ESI mass-spectrometry: N^N – 2-(1-hexadecyl-1H-imidazol-2-yl)pyridine, N^C – methyl-2-phenylquinoline-4-carboxylate (Ir1) and 2-phenylquinoline-4-carboxylic acid (Ir2). These complexes were used to prepare the luminescent PEGylated DPPC liposomes (DPPC/DSPE-PEG2000/Ir-complex = 95/4.5/1 mol%) using a thin film hydration method. The narrowly dispersed liposomes had diameters of about 110 nm. The photophysics of the complexes and labeled liposomes were carefully studied. Ir1 and Ir2 give red emission (λ_em = 667 and 605 nm) with a lifetime in the microsecond domain and quantum yields of 4.8% and 10.0% in degassed solution. Incorporation of the complexes into the liposome lipid bilayer results in shielding of the emitters from interaction with molecular oxygen and partial suppression of excited state nonradiative relaxation due to the effect of the relatively rigid bilayer matrix. Delivery of labeled liposomes to the cultured ARPE-19 cells demonstrated the usefulness of Ir1 and Ir2 in cellular imaging. Labeled liposomes were then injected intravitreally into rat eyes and imaged successfully with optical coherence tomography and funduscopy. In conclusion, iridium complexes enabled the successful labeling and imaging of liposomes in cells and animals.

Novel lipoidal Ir(iii) phosphorescent labels were embedded into liposomes and used for imaging in cells and animals.     

Gas phase methanol synthesis with Raman spectroscopy for gas composition monitoring

Applicability of Raman spectroscopy for time-resolved gas composition monitoring during direct methanol synthesis via carbon dioxide hydrogenation was investigated. A series of methanol synthesis experiments with varied reactor conditions was conducted and the reactor outlet stream was analyzed with in-line gas Raman spectroscopy. Concentrations of H₂, CO₂ and CO were determined directly from the acquired spectral data. For evaluation of methanol and water content a data reconciliation algorithm was developed. The algorithm involves estimation of the occurring chemical reactions'' extents by iterative minimization of the difference between concentration values acquired from the experimental data and concentration values computed based on the mass conservation principle. The obtained experimental concentrations were compared and validated against the results of the reactor mathematical modeling, which is based upon a well-established kinetic interpretation of the process. The findings indicate good repeatability and accuracy of the developed gas analysis system, which together with the advantageous temporal resolution of the method, make Raman spectroscopy a promising technique for fast response monitoring of the process.

Applicability of Raman spectroscopy for time-resolved gas composition monitoring during direct methanol synthesis via carbon dioxide hydrogenation is investigated.     

Comparison of the short-term and long-term results of the Ponseti method in the treatment of idiopathic pes equinovarus

Purpose

Congenital club foot is one of the most common birth defects involving the musculoskeletal system. At present two methods are used for the treatment of this deformity: French and Ponseti method. The purpose of this study was to compare the short-term (up to three years) and long-term (three to seven years) results of treatment with the Ponseti method.

Methods

A total of 195 consecutive infants (143 boys and 52 girls) with idiopathic club foot treated with the Ponseti method in the period of 2005–2012 were included in this study; the total number of feet was 303. The severity of the foot deformity was classified according to Diméglio. When relapse occurred up until three years of age, we started with the casting again. If conservative treatment was unsuccessful we proceeded to surgical treatment.

Results

Primary correction was attained in all cases. Surgical correction of relapses was performed in 30 % of patients according to the Ponseti method (re-tenotomy of the Achilles tendon and transposition of the tibialis anterior) and in 70 % by alternative techniques. The number of relapses indicated for surgery increased with increasing period of follow-up: whereas in patients where the treatment started already in 2005 relapses occurred in 72 %, in patients included in 2011 the number of recurrences only reached 3 %.

Conclusions

It follows from our results that it is impossible to cure all club feet with casting, tenotomy of the Achilles tendon and transposition of the tibialis anterior only.     

Dysprosium magnesium silicate apatite featuring field and temperature stable slow magnetization relaxation

Dy–Mg silicate Dy₈Mg₂(SiO₄)₆O₂ has been prepared by high-temperature solid state reaction. It has an apatite type structure (P6₃/m) with the Dy atoms fully occupying the 6h site and being in random distribution with the Mg atoms at the 4f site. The compound reveals dual magnetization relaxation with widely varying contributions from fast (FR) and slow (SR) relaxation paths controlled by field and temperature. The SR path is stabilized by a strong magnetic field, exhibits a weak dependence of relaxation time τ on field and temperature, and sustains large τ of a few seconds up to a temperature of 40 K and under a field of 50 kOe. The analysis of the electronic structure and comparison with the known Dy-doped phosphate apatites suggests that the Orbach and Raman processes are suppressed.

The compound reveals dual magnetization relaxation with largely varying contributions from fast and slow relaxation paths controlled by field and temperature. The relaxation times retain values of a few seconds up to 40 K.     

fMRI evaluation of hemispheric language dominance using various methods of laterality index calculation

Several functional MR imaging studies evaluating the lateralisation of linguistic functions in patients who underwent Wada testing have been reported. There is extensive variance in the Laterality index (LI) calculation across the studies, and the optimal calculation method remains unclear. We attempted to calculate the LI in different ways in the same subjects, in order to find the LI calculation method with the highest correlation to the Wada test. Fifteen patients (10 females, 5 males) suffering from medically intractable temporal lobe epilepsy (TLE) (12 left, 3 right) were admitted for the study. The patients underwent a standardized bilateral intracarotid short-acting barbiturate test. Language testing included spontaneous speech, oral comprehension, reading, object and picture naming, and repetition. All the tasks were scored separately in order to increase the possibility of correlation between Wada and LI. A silent phonemic verbal fluency task (VFT) was used as a language paradigm for functional measurement. Regions of interest (ROIs), with a known association with language function (Broca’s area, the lateral prefrontal cortex, etc.), were defined. First, the LIs were calculated from the ROIs using a previously reported method (simple suprathreshold count). Next, we used several new methods of LI calculation (t–weighting of voxels, methods independent of the choice of the statistical threshold, etc.) The most significant correlation with Wada was proven in the LIs that were evaluated from Broca’s area (up to R = 0.94, P = 1 × 10⁻⁷). However, the new LI calculation methods used in the present study did not produce a statistically significant benefit in comparison to previously reported methods.     

Topography of signaling molecules as detected by electron microscopy on plasma membrane sheets isolated from non-adherent mast cells

Immunolabeling of isolated plasma membrane (PM) sheets combined with high-resolution electron microscopy is a powerful technique for understanding the topography of PM-bound signaling molecules. However, this technique has been mostly confined to analysis of membrane sheets from adherent cells. Here we present a rapid, simple and versatile method for isolation of PM sheets from non-adherent cells, and show its use for examination of the topography of Fcepsilon receptor I (FcepsilonRI) and transmembrane adaptors, LAT (linker for activation of T cells) and NTAL (non-T cell activation linker), in murine bone marrow-derived mast cells (BMMC). The data were compared with those obtained from widely used but tumor-derived rat basophilic leukemia (RBL) cells. In non-activated cells, FcepsilonRI was distributed either individually or in small clusters of comparable size in both cell types. In multivalent antigen-activated BMMC as well as RBL cells, FcepsilonRI was internalized to a similar extent, but, strikingly, internalization in BMMC was not preceded by formation of large (~200 nm) aggregates of FcepsilonRI, described previously in activated RBL cells. On the other hand, downstream adaptor proteins, LAT and NTAL, were localized in independent domains in both BMMC and RBL cells before and after FcepsilonRI triggering. The combined data demonstrate unexpected properties of FcepsilonRI signaling assemblies in BMMC and emphasize the importance of studies of PM sheets isolated from non-tumor cells.