From red cells to snowboarding: a new concept for a train track

Feng and Weinbaum [J. Fluid Mech. 422, 282 (2000)]] have shown that there is a remarkable dynamic similarity between a red cell gliding on the endothelial surface glycocalyx and a human snowboarding on fresh powder although they differ in mass by 10(15). The lift forces in each case are 4 orders of magnitude greater than classical lubrication theory. Herein we report the first measurements of the pore pressures generated on the time scale of snowboarding and show a feasibility of designing a train that can glide on a track whose permeability and elastic properties are similar to goose down.     

Structure-catalytic function relationship of SiO2-immobilized mononuclear Cu complexes: an EPR study

Mononuclear CuL and Cu(2L) complexes, where L is propyl-thiazol-2-ylmethylene-amine, covalently immobilized onto SiO2, can catalyze efficiently the oxidation of 3,5-di-t-butylcatechol (DTBC) to 3,5-di-t-butylquinone (DTBQ) by utilizing ambient O2 as oxidant. By increasing the loading of L on SiO2, the DTBQ formation can be improved up to 400% vs the homogeneous catalyst. Equally important is however that grafting per se at low loading is not adequate for an improved catalytic activity. Appropriate loadings have to be achieved, which then may result in significant catalytic performance. Based on EPR spectroscopy a theoretical method is developed, eq A12, for spin-spin distance estimation in heterogeneously dispersed surface complexes. Practical rules including error estimates are provided. By applying this method to the [SiO2-CuL] catalysts it is shown that mononuclear copper complexes fixed on SiO2 with Cu...Cu distances as short as 4.9 +/- 0.3 A are responsible for the improved catalytic activity. The present results demonstrate that mononuclear Cu complexes can have considerable catecholase activity, if the proper geometrical proximity can be fixed. Grafting on SiO2 may be an efficient method for engineering catalysts with improved performance.     

Model block copolymers with complex architecture

The synthesis of non linear block copolymers of the type (BA)₂B (3-miktoarm star copolymer), (BA)₃B (4-miktoarm star copolymer), (BA)₃B(AB)₃ (super H-shaped), B₂AB₂ (H-shaped) and (B,A)A(B,A) (π-shaped), where A is polyisoprene 1,4 and B is polystyrene was performed using anionic polymerization techniques and suitable chlorosilane chemistry. Characterization data showed that the samples are molecularly and compositionally homogeneous. TEM, SAXS and SANS were used to study the microphase behavior of the copolymers. For all samples, the results were analyzed in the frame of the theoretical predictions given by Milner and taking into account the results from previous studies on the A₂B and A₃B miktoarm star copolymers.     

A novel sensitive analytical method for the simultaneous analysis of vancomycin and teicoplanin in human urine via single high-performance liquid chromatography coupled with photodiode array and mass spectrometry in series

Analysis of vancomycin and teicoplanin in biological fluids is vital since they are used in the treatment of hospital infections. For the determination of both glycopeptides in urine, a sensitive and accurate analytical method using high-performance liquid chromatography coupled with photodiode array and mass spectrometry was developed and validated. This research work is the first attempt to develop a chromatographic method for the determination of two glycopeptides with structural similarities. Moreover, the used non-invasive sampling method is an advantage of this research effort, especially when the blood sampling is difficult. Urine was treated with acetonitrile and 5% trichloroacetic acid, followed by solid-phase extraction. The chromatographic separation was established at a C18 column (4.6 × 150 mm, 5 μm), using a gradient method and an electrospray ionization source in a positive mode. The linearity of the method was R²≥ 0.9900. The precision was estimated with a maximum coefficient of variation below 15%, while the accuracy ranged from 64 to 121%. The limit of detection and quantification of both glycopeptides ranged from 0.076 up to 0.33 mg/L and 0.33 up to 2.1 mg/L, respectively, showing the same sensitivity as the triple quadrupole mass spectrometry, which is the most frequently used method.     

Microstructure identification during crystallization of charged colloidal suspensions

We use a polarized light microscope in its orthoscopic and conoscopic arrangements and laser light diffraction to study the effect of particle volume fraction and cell thickness on the microstructure of crystallizing suspensions of negatively charged polystyrene microspheres. Deionized suspensions of these particles nucleate at random sites in the bulk of the suspension to give a variety of structures, orientations and sizes. Orthoscopic observation of the Bragg diffraction colors between crossed polars and conoscopic inspection of the interference figures reveal structural details. We find that the crystallites grow by parallel stacking of the (111) layers to single and twin fcc structures. At moderate volume fractions, Φ ≈ 0.09, the structures are essentially “frozen” in space by their neighbors. At lower concentrations, Φ ≈ 0.05, the crystallites are larger with smoother boundaries and exhibit a range of colors. In thick cells, L ≥ 200 μm, and Φ ≤ 0.05, the colored crystallites become dark with time as they align with the (111) planes parallel to the cell walls. In thin, 50μm cells and Φ ≤ 0.05, this alignment is enhanced. We demonstrate that striated crystallites with lamellae of alternating colors and varying width are polysynthetic fcc twins with (111) twin plane. The number density of twin crystals and the frequency of striations decrease with decreasing volume fraction.     

Acoustic particle manipulation in a 40 kHz quarter-wavelength standing wave with an air boundary

An implementation of a quarter-wavelength standing wave separator that exploits an air drum to achieve the pressure node is presented and characterized experimentally. The air drum configuration was implemented and tested in a set-up with a 40 kHz transducer immersed in a water tank with the quarter-wavelength gap being approximately 9 mm wide. Injection of suspensions of 5 μm and 45 μm diameter polystyrene particles at flow rates of 30 ml/h and 60 ml/h was studied and particle deflection towards the pressure node at the air drum surface was observed for a range of acoustic pressures. Computational results on single particle trajectories show good agreement with the experimental findings for the 45 μm particles, but not for the 5 μm particles. These were considered to behave as aggregates of higher effective dimension, due to their much higher number density relative to the 45 μm particles in the suspensions used. The set-up developed in this study includes a robust method for achieving a pressure node in a quarter-wavelength system and can represent the first step toward the development of an alternative separator configuration in respect to small channel MHz range operated systems for the manipulation of particles streams.     

Dry Red Wine Making Using Yeast Immobilized on Cork Pieces

The commercial Saccharomyces cerevisiae Uvaferme 299 wine yeast was immobilized on cork pieces to produce a biocatalyst for use in dry red wine making. The immobilized biocatalyst was suitable for clarified and non-clarified grape must fermentation at ambient and low temperatures (0–25 °C). Fermentation times were low and very low amounts of residual sugar were detected, showing suitability for dry wine production. The presence of suspended solids in the non-clarified must did not affect the activity of the immobilized cells. Complete fermentation of sugars at 0 °C was possible with immobilized Uvaferme 299, although not a cryotolerant strain, indicating a cryoprotective effect of cork. The presence of cork did not affect the composition of major volatiles with methanol and acetaldehyde kept at low levels. Reduction of amyl alcohols on total volatiles was also observed in wines fermented at low temperatures. Differences in the headspace aroma profile in wines produced by immobilized and free cells were found by GC–MS analysis, but no cork taint compounds were detected.     

A New Process for Wine Production by Penetration of Yeast in Uncrushed Frozen Grapes

Different types of red and white wines were prepared by fermentation of the juice which was naturally separated from uncrushed frozen grapes during thawing (A) and from the residual juice by fermentation inside the berries (B). Yeast penetrated the skin of uncrushed grapes and fermented the content completely. The new types of wines were compared with wines prepared conventionally from the whole material of frozen grapes. Chemical and chromatographic analysis (gas chromatography (GC) and solid-phase microextraction–GC/mass spectrometry) showed similar profiles of the aroma volatiles but with significant quantitative differences among the new types of wines, which reflected to the differences observed during the sensory evaluations. The majority of identified compounds were esters, with higher amounts found in (A) wines due to the higher concentration of the must which was separated during thawing. The proposed process is new and of industrial interest for the production of different types of wines from the same raw material in one fermentation batch.     

Optical,electrochemical, and sensing properties of polyfluorenes bearing thiazole or oxazole and triphenylamine in the main chain

Polyfluorenes bearing thiazole (PFTH) or oxazole (PFOX) heterocyclic units as well as triphenylamine (TPA) in the main chain were synthesized. The ratio of thiazole or oxazole/TPA in the polymer chain varies from 100/0 to 25/75. The optical properties of polymers depend on thiazole or oxazole contents. Cyclic voltammetry reveals that thiazole or oxazole hinder the oxidation of polymers and only polymers with TPA show reversible oxidation. The Electron Affinities do not practically depend on composition of the polymer chain. The sensing properties of polymers PFTH100 and PFOX100 are investigated toward several cations and anions. Polymers detect two analytes, Fe²⁺ and Hg²⁺. PL quenching shows linear response to Fe²⁺ in wide concentration region 1–800 μΜ. I^? anions quench the emission of polymers. Hg²⁺ turns on the emission of the polymer/I^? complex at concentrations as low as 1 μM. Enhancement of polymer/I^? emission exhibits linear response to Hg²⁺ concentration. PFTH100 is able to detect Fe²⁺ and Hg²⁺ that coexist in a solution. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 243–254