Dual Light and Temperature Responsive Micrometer‐Sized Structural Color Actuators

Externally induced color‐ and shape‐changes in micrometer‐sized objects are of great interest in novel application fields such as optofluidics and microrobotics. In this work, light and temperature responsive micrometer‐sized structural color actuators based on cholesteric liquid‐crystalline (CLC) polymer particles are presented. The particles are synthesized by suspension polymerization using a reactive CLC monomer mixture having a light responsive azobenzene dye. The particles exhibit anisotropic spot‐like and arc‐like reflective colored domains ranging from red to blue. Electron microscopy reveals a multidirectional asymmetric arrangement of the cholesteric layers in the particles and numerical simulations elucidate the anisotropic optical properties. Upon light exposure, the particles show reversible asymmetric shape deformations combined with structural color changes. When the temperature is increased above the liquid crystal‐isotropic phase transition temperature of the particles, the deformation is followed by a reduction or disappearance of the reflection. Such dual light and temperature responsive structural color actuators are interesting for a variety of micrometer‐sized devices.     

Near‐UV activated,photostable nanophosphors for in vitro dosimetry and dynamic bioimaging

Luminescent rare earth nanoparticles exhibit superior optical stability over commonly‐used organic dyes and higher biocompatibility over quantum dots, rendering them advantageous as bioimaging nanoprobes. However, their typical excitation inhibits their broad employment with conventional fluorescence microscopes and, thus, solutions are sought to shift their activation in the long‐wavelength (near‐UV) spectral region. Here, we synthesize YVO₄:Eu³⁺ nanophosphors by flame aerosol technology to systematically study the effect of Bi³⁺ codoping on their luminescence. That way, we identify an optimal Bi‐content for sufficient near‐UV activation. These nanophosphors are highly crystalline and appeared bright red under a conventional fluorescence microscope, facilitating bioimaging with HeLa cells and in vitro dosimetry correlations in the presence and absence of serum. The nanophosphor superiority over organic‐dye‐labeled silica nanoparticles is shown during dynamic imaging for 4 h without photobleaching for the former. These YVO₄:Eu³⁺/Bi³⁺ nanophosphors can provide a non‐photobleaching tool for further dynamic nanoparticle‐cell interaction studies with conventional fluorescence microscopes. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2947–2957, 2018     

Influence of high-pressure–low-temperature treatments on fruit and vegetable quality related enzymes

Recently, high-pressure–low-temperature (HP-LT) treatments, succeeding a regular freezing unit operation, have been shown to inactivate micro-organisms. In this study, we have evaluated the influence of these treatments on the inactivation of quality-related enzymes. The effect of different pressure/temperature combinations (range 0.1–500 MPa/20 to −26 °C) on the activity of pectinmethylesterase, polygalacturonase, lipoxygenase, peroxidase and polyphenoloxidase in model systems, crude extracts and real-food systems was investigated.Present results show that under these HP-LT processing conditions, no or limited enzyme inactivation is obtained for all enzyme systems studied, except for lipoxygenase which can be completely inactivated at high pressure in combination with low temperature. These data suggest that HP-LT treatments, although inactivating micro-organisms, fail to inactivate most food quality related enzymes. Therefore, a blanching unit operation (e.g. a conventional thermal blanching process prior to freezing) is required to prevent enzyme related quality degradation during frozen storage and cannot be replaced by an integrated freezing-HP-LT treatment.     

'Lifestyle' and cancer rates in former East and West Germany: the possible contribution of diagnostic radiation exposures

Breast and prostatic cancer as well as leukaemia in childhood have remarkably increased over some decades in the Federal Republic of Germany as well as in several other highly developed industrial nations. Such increase was much less or not observable in East Germany between 1960 and 1989 where diagnostic exposures were applied to a lesser extent. Low-level radiation can cause these diseases and the difference of cancer rates gives rise to renewed evaluation of current risk estimates. Risk factors for radiation-induced childhood leukaemia and breast cancer are derived from the literature, considering a higher relative biological effectiveness of diagnostic X rays in comparison to the A-bomb gamma rays in Hiroshima and Nagasaki. The prostate is not considered as radiation sensitive by the ICRP. But following a variety of low-level findings in the last two decades it was shown by Myles et al. in the UK that prostatic cancer is inducible by diagnostic X-ray procedures. From their study in men below the age of 60, a doubling dose of about 20 mSv can be estimated. Medical exposures of the considered tissues are taken from published data for East and West Germany. The difference in breast cancer mortality can be explained by diagnostic exposures. The contribution of these to prostatic cancer and childhood leukaemia must be regarded as relevant in current incidences. Reduction of diagnostic exposures would be an important measure for preventing several prominent cancer diseases.     

Corrections for diffuse irradiance measured with shadowbands

The reduction of measured diffuse irradiance due to the use of a shadowband is evaluated. For cloudless sky, an exact mathematical model was developed. Measurements throughout the year confirm the model results. The values are close to the semiempirical model developed by Drummond only during noon hours. Towards morning and afternoon a contribution from reflected direct solar irradiance from inside the shadowband reduces the loss and, at very low sun angle, can even provide a gain in the measured diffuse irradiance. The albedo of the inner band surface is of importance for the amount of this gain.During overcast sky the loss of measured diffuse irradiance varies with the season: During the winter months when only a small section of the sky is obstructed by band, 3 per cent are lost, during summer this value is between 8 and 10 per cent.     

Dimethyl sulfide removal from synthetic waste gas using a flat poly(dimethylsiloxane)-coated composite membrane bioreactor

The reduction of volatile organic sulfur emissions should be completely as they cause odor nuisance, even when they are emitted in very small amounts. In general, biofilters are applied for odor reduction, but their operational control is limited. A new biotechnique for the treatment of complex emissions is the use of membranes integrated within bioreactors (MBRs). In this study, the reactor performance of MBRs for removal of dimethyl sulfide (DMS) as a model compound is presented. Composite membranes with a poly(dimethylsiloxane) (PDMS)-coating layer were used. The MBRs were inoculated with the sulfur-degrading culture Hyphomicrobium VS or a suspension of Hyphomicrobium VS, ammonium-oxidizing bacteria (AOB), and nitrite-oxidizing bacteria (NOB) to colonize the PDMS-coating layer. Although inoculation with AOB and NOB might give rise to competition for space on the membrane, their presence in the MBRs appeared to be positive as they co-oxidize DMS. Dimethyl sulfide elimination depended on the inoculum type, DMS inlet concentration, gas residence time, and membrane polymer. For equal loading rates, the elimination capacity (EC) increased at larger gas residence times and inlet concentrations. The maximum EC obtained with the MBRs was 4.8 kg of DMS x m(-3) x d(-1). This value is higher than any reported figure for biofilters and biotrickling filters.     

Outdoor weathering performance parameters of exterior wood coating systems on tropical hardwood substrates

Wood coating research almost exclusively focuses on softwood as substrate despite the fact that coatings applied on tropical hardwoods show a different weathering behaviour. The objective of this study was to quantify the impact of wood substrate and coating type on the weathering behaviour of finished wooden joinery in outdoor exposure using a set of statistical methods. Therefore, a broad range of white opaque paints and mid-oak semi-transparent stains were used. The coatings were industrially applied on window frames made of frequently used commercial tropical hardwood species. The general appearance of the wood/coating systems was assessed visually using a rating scale that takes into account the anatomical characteristics of hardwood. For the evaluation, a required minimum exposure time of 2.5 years outdoor weathering for joinery in vertical position and facing south-west was determined. At 30 months best performances were recorded for waterborne alkyd primers with an acrylic topcoat when dry coating film was sufficiently thick. The dry layer thickness also affected the impact of the hiding power on the performance of the wood/coating system. Within hardwood species the degradation rate of coatings on species with a fine texture was the lowest. The significant influence of the substrate’s texture on the weathering behaviour of coated hardwood stressed the need to evaluate the wood/coating system in total.     

Cloning, characterization and functionality of the orotidine-5'-phosphate decarboxylase gene (URA3) of the glycolipid-producing yeast Candida bombicola

Candida bombicola is a yeast species known to synthesize glycolipids. Although these glycolipids find several industrial, cosmetic and pharmaceutical applications, very little is known about the genetics of C. bombicola. A basic tool for genetic study and modification is the availability of an efficient transformation and selection system. In order to develop such a system, the URA3 gene of Candida bombicola was isolated using degenerate PCR and genomic walking. The gene encodes for an enzyme of 262 amino acids and shows high homology with the known orotidine-5'-phosphate decarboxylases of several other yeast species. The functionality of the gene was proved by complementation of a URA3-negative Saccharomyces cerevisiae strain.     

Influence of Low-temperature Blanching Combined with High-pressure Shift Freezing on the Texture of Frozen Carrots

ABSTRACT: Freezing causes texture loss of tissue-based systems such as fruits and vegetables. To evaluate the potentials of high-pressure freezing for minimizing freezing damage, the effects of high-pressure shift freezing and regular freezing conditions on the texture of carrot cylinders were investigated. To improve the strength of the plant material by a pectin-based network, carrot cylinders were submitted to different pretreatment conditions before freezing. The reduced freezing time of high-pressure shift freezing compared with conventional freezing results in a limited positive effect on the hardness of non-pretreated carrots. A pronounced hardness improvement was obtained when calcium soaking followed by thermal (30 min at 60°C) or high-pressure (15 min at 60°C and 300 MPa) pretreatment was combined with high-pressure shift freezing. During subsequent frozen storage at -18°C, the increased hardness values of pretreated, high-pressure frozen carrots could not be maintained.